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  • Molecular characterization of L-phenylalanine terminated poly(L-lactide) conjugates

     Murase Fernandez, Sara Keiko; Haspel, Nurit; Del Valle Mendoza, Luis Javier; Perpete, Eric; Nussinov, Ruth; Michaux, Catherine; Puiggali Bellalta, Jorge; Aleman Llanso, Carlos Enrique
    RSC Advances
    num. 44, p. 23231-23241
    DOI: 10.1039/C4RA01534G
    Date of publication: 2014-05-15
    Journal article

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    Peptide¿polymer conjugates made of poly(L-lactide) and L-phenylalanine or L,L-diphenylalanine (F¿PLA and FF¿PLA, respectively) have been synthesized by the ring-opening polymerization of L-lactide using the peptide fragment as an initiator. The structure of the conjugates was confirmed by 1H NMR, FT-IR, GPC, UV-Vis and CD. Molecular dynamics simulations have been used to identify both the conformational preferences of the FF¿PLA conjugate in solution and the potential intramolecular interactions between the peptide and polymer blocks, while TD-DFT calculations have been applied to model the electronic transitions observed by the UV-Vis absorption spectroscopy. Results show that the polymer fragment prefers a random coil or a mix of helix/strand while the peptide fragment tends to have folded and helical conformations. Although the degree of interaction between the two fragments is slightly higher than that reported for other peptide¿polymer conjugates, it is small enough to suggest that FF¿PLA is a potential candidate to aggregate forming peptide-guided organizations via self-assembly. On the other hand, quantum mechanical calculations have allowed us to identify the p ¿ p* transition, which is typically observed in helical peptides and proteins, as well as the n ¿ p* transition along the N¿C¿O backbone.

  • Influence of the temperature on the proton transport in poly(styrene-co-divinylbenzene) membranes from molecular dynamics simulations

     Cordova Mateo, Ester; Bertran Cànovas, Oscar; Aleman Llanso, Carlos Enrique
    The journal of physical chemistry. Part C, nanomaterials and interfaces
    Vol. 118, num. 31, p. 17643-17654
    DOI: 10.1021/jp503908u
    Date of publication: 2014-08-07
    Journal article

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    The effect of the temperature on the properties of sulfonated poly(styrene-co-divinylbenzene), P(S-DVB), cation exchange membranes has been examined in the absence and presence of an external electric field of 0.7 V.nm(-1). Results indicate that the temperature provokes local structural deformations around the sulfonate groups, which are manifested by the distortions at the C S bonds (random and preferential in the absence and presence of the electric field, respectively). These distortions affect both the density and porosity of the membranes, even though the effects of the electric field decrease with increasing temperature. The electric field dominates over the thermal energy in the motion of the hydronium ions, while the external field does not affect the motion of water molecules, which follow a Brownian behavior similar to that observed for the two species in the absence of an electric field. The calculated electro-osmotic drag coefficient indicates that the hydronium flow is several times higher than the water flow in the presence of the electric field, and this effect increases the temperature. The diffusion of hydronium ions in the absence of the external field increases slowly and isotropically with the temperature, this behavior being preserved in the presence of the external electric field once the component associated with the drift velocity is discounted. Finally, the structure and dynamics of hydration shells at hydronium and sulfonate ions have been examined. Interestingly, the shells associated with two such ions as well as their response toward the temperature and electric field are significantly different, which has been attributed to the fact that sulfonate-water interactions are stronger than hydronium water interactions.

  • Restricted puckering of mineralized RNA-like riboses

     Casanovas Salas, Jordi; Revilla López, Guillem; Bertran Cànovas, Oscar; Del Valle Mendoza, Luis Javier; Turon Dols, Pau; Puiggali Bellalta, Jorge; Aleman Llanso, Carlos Enrique
    Journal of physical chemistry B
    Vol. 118, num. 19, p. 5075-5081
    DOI: 10.1021/jp501714q
    Date of publication: 2014-05-15
    Journal article

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    The pseudorotational motions of highly hydroxylated pentafuranose sugars in the free state and tethered to hydroxyapatite have been compared. The conformation pentafuranose ring remains restricted at the North region of the pseudorotational wheel, which is the one typically observed for nucleosides and nucleotides in the double helix A-RNA, when the phosphate-bearing sugar is anchored to the mineral surface. Results indicate that the severe restrictions imposed by the mineral are responsible of the double helix preservation when DNA and RNA are encapsulated in crystalline nanorods.

  • Electro-biocompatibility of conjugates designed by chemical similarity

     Maione, Silvana; Fabregat Jove, Georgina; Del Valle Mendoza, Luis Javier; Ballano Ballano, María Gema; Cativiela, Carlos; Aleman Llanso, Carlos Enrique
    Journal of peptide science
    Vol. 20, num. 7, p. 537-546
    DOI: 10.1002/psc.2660
    Date of publication: 2014-07-01
    Journal article

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    The roughness and thickness of films formed by hybrid conjugates prepared by coupling poly(3,4-ethylenedioxythiophene) and synthetic amino acids bearing a 3,4-ethylenedioxythiophene group in the side chain have been significantly increased using a new synthetic approach. This procedure also provoked a more effective incorporation of the amino acid at the end of the polymer chains, as has been reflected by the electronic and electrochemical properties. Although the surface polarity of all these materials is similar to that of formamide, the hydrophilicity of the conjugates is higher than that of the conducting polymer. The surface energy of all the investigated systems is dominated by the dispersive component, even though the role played by the polar contribution is more important for the conjugates than for the conducting polymer. On the other hand, all the prepared materials behave as bioactive matrices. The electrochemical response of the conjugates coated with cells reflects the electro-compatibility of these two-component substrates. Thus, the ability to exchange charge reversibly of all conjugates increases considerably when they are coated with cellular monolayers, which has attributed to favorable interactions at the interface formed by the conjugate surface and the cellular monolayer. Copyright (c) 2014 European Peptide Society and John Wiley & Sons, Ltd.

    The roughness and thickness of films formed by hybrid conjugates prepared by coupling poly(3,4-ethylenedioxythiophene) and synthetic amino acids bearing a 3,4-ethylenedioxythiophene group in the side chain have been significantly increased using a new synthetic approach. This procedure also provoked a more effective incorporation of the amino acid at the end of the polymer chains, as has been reflected by the electronic and electrochemical properties. Although the surface polarity of all these materials is similar to that of formamide, the hydrophilicity of the conjugates is higher than that of the conducting polymer. The surface energy of all the investigated systems is dominated by the dispersive component, even though the role played by the polar contribution is more important for the conjugates than for the conducting polymer. On the other hand, all the prepared materials behave as bioactive matrices. The electrochemical response of the conjugates coated with cells reflects the electro-compatibility of these two-component substrates. Thus, the ability to exchange charge reversibly of all conjugates increases considerably when they are coated with cellular monolayers, which has attributed to favorable interactions at the interface formed by the conjugate surface and the cellular monolayer. Copyright (c) 2014 European Peptide Society and John Wiley & Sons, Ltd.

  • Molecular dynamics simulation study of methanesulfonic acid

     Canales Gabriel, Manel; Aleman Llanso, Carlos Enrique
    Journal of physical chemistry B
    Vol. 118, num. 12, p. 3423-3430
    DOI: 10.1021/jp500817s
    Date of publication: 2014-03-04
    Journal article

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    A molecular dynamics simulation study of methanesulfonic acid has been carried out using a reliable force field in a large range of temperatures. Several thermodynamic, structural, and dynamical properties have been calculated and compared with the available experimental data. The density, the shear viscosity, the heat of vaporization, and the melting temperature results, calculated from this force field, are in a good agreement with the experimental data. Analysis of the influence of the hydrogen bonds in structural and dynamical properties has also been performed. The continuous and interrupted methodologies to compute hydrogen bonding lifetimes have been applied. The interrupted hydrogen bond lifetimes values are consistent with the diffusion and viscosity coefficients. The activation energies of the self-diffusion, the reorientational motions, and the hydrogen bonding lifetimes are coincident.

    A molecular dynamics simulation study of methanesulfonic acid has been carried out using a reliable force field in a large range of temperatures. Several thermodynamic, structural, and dynamical properties have been calculated and compared with the available experimental data. The density, the shear viscosity, the heat of vaporization, and the melting temperature results, calculated from this force field, are in a good agreement with the experimental data. Analysis of the influence of the hydrogen bonds in structural and dynamical properties has also been performed. The continuous and interrupted methodologies to compute hydrogen bonding lifetimes have been applied. The interrupted hydrogen bond lifetimes values are consistent with the diffusion and viscosity coefficients. The activation energies of the self-diffusion, the reorientational motions, and the hydrogen bonding lifetimes are coincident.

  • Incorporation of a clot-binding peptide into polythiophene: properties of composites for biomedical applications

     Fabregat Jove, Georgina; da Cruz Teixeira Dias, Bruno José; Del Valle Mendoza, Luis Javier; Armelin Diggroc, Elaine; Estrany Coda, Francisco; Aleman Llanso, Carlos Enrique
    ACS applied materials and interfaces
    Vol. 6, num. 15, p. 11940-11954
    DOI: 10.1021/am503904h
    Date of publication: 2014-08-13
    Journal article

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    Biocomposites formed by a pentapeptide (CREKA), which recognizes clotted plasma proteins, entrapped into the poly(3,4-ethylenedioxythiophene) (PEDOT) matrix have been prepared using three very different procedures. X-ray photoelectron spectroscopy analyses indicate that PEDOT-CREKA films, prepared by chronoamperometry in basic aqueous solution (pH = 10.3) and deposited onto a PEDOT internal layer, present the higher concentration of peptide: one CREKA molecule per six polymer repeat units. The surface of this bilayered system shows numerous folds homogeneously distributed, which have been exhaustively characterized by scanning electron microscopy and atomic force microscopy. Indeed, the morphology and topography of such bilayered films is completely different from those of biocomposite-prepared acid aqueous and organic solutions as polymerization media. The impact of the entrapped peptide molecules in the electrochemical properties of the conducting polymer has been found to be practically negligible. In contrast, biocompatibility assays with two different cellular lines indicate that PEDOT-CREKA favors cellular proliferation, which has been attributed to the binding of the peptide to the fibrin molecules from the serum used as a supplement in the culture medium. The latter assumption has been corroborated examining the ability of PEDOT-CREKA to bind fibrin. The latter ability has been also used to explore an alternative strategy based on the treatment of PEDOT-CREKA with fibrin to promote cell attachment and growth. Overall, the results suggest that PEDOT-CREKA is appropriated for multiple biomedical applications combining the electrochemical properties of conducting polymer and the ability of the peptide to recognize and bind proteins.

    Biocomposites formed by a pentapeptide (CREKA), which recognizes clotted plasma proteins, entrapped into the poly(3,4-ethylenedioxythiophene) (PEDOT) matrix have been prepared using three very different procedures. X-ray photoelectron spectroscopy analyses indicate that PEDOT-CREKA films, prepared by chronoamperometry in basic aqueous solution (pH = 10.3) and deposited onto a PEDOT internal layer, present the higher concentration of peptide: one CREKA molecule per six polymer repeat units. The surface of this bilayered system shows numerous folds homogeneously distributed, which have been exhaustively characterized by scanning electron microscopy and atomic force microscopy. Indeed, the morphology and topography of such bilayered films is completely different from those of biocomposite-prepared acid aqueous and organic solutions as polymerization media. The impact of the entrapped peptide molecules in the electrochemical properties of the conducting polymer has been found to be practically negligible. In contrast, biocompatibility assays with two different cellular lines indicate that PEDOT-CREKA favors cellular proliferation, which has been attributed to the binding of the peptide to the fibrin molecules from the serum used as a supplement in the culture medium. The latter assumption has been corroborated examining the ability of PEDOT-CREKA to bind fibrin. The latter ability has been also used to explore an alternative strategy based on the treatment of PEDOT-CREKA with fibrin to promote cell attachment and growth. Overall, the results suggest that PEDOT-CREKA is appropriated for multiple biomedical applications combining the electrochemical properties of conducting polymer and the ability of the peptide to recognize and bind proteins.

  • Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024

     Dalmoro, V.; Dos Santos, J.H.Z.; Armelin Diggroc, Elaine; Aleman Llanso, Carlos Enrique; Azambuja, Denise S.
    Journal of colloid and interface science
    Vol. 426, p. 308-313
    DOI: 10.1016/j.jcis.2014.04.021
    Date of publication: 2014-07-15
    Journal article

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    The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sal-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L-1 NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L-1) of embedded clay provide the highest corrosion protection. (C) 2014 Elsevier Inc. All rights reserved.

    The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sal-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L-1 NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L-1) of embedded clay provide the highest corrosion protection. (C) 2014 Elsevier Inc. All rights reserved.

  • Solvent-induced conformational flexibility of a bicyclic proline analogue: Octahydroindole-2-carboxylic acid

     Torras Costa, Juan; Warren, Javier G.; Revilla López, Guillem; Jiménez, Ana I.; Cativiela, Carlos; Aleman Llanso, Carlos Enrique
    Biopolymers
    Vol. 102, num. 2, p. 176-190
    DOI: 10.1002/bip.22465
    Date of publication: 2014-03-21
    Journal article

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    The conformational preferences of the N-acetyl-N'-methylamide derivatives of the four octahydroindole-2-carboxylic acid (Oic) stereoisomers have been investigated in the gas-phase and in aqueous solution using quantum mechanical calculations. In addition to the conformational effects provoked by the stereochemical diversity of Oic, which presents three chiral centers, results provide evidence of interesting and rather unusual features. The conformational preferences of the Oic stereoisomers in solution are only well described by applying a complete and systematic search process, results achieved by simple re-optimization of the gas-phase minima being very imprecise. This is because the conformational rigidity detected in the gas-phase, which is imposed by the chemical restrictions of the fused bicyclic skeleton, disappears in aqueous solution, the four stereoisomers behaving as flexible molecules in this environment. Thus, in general, the ¿-turn is the only minimum energy conformation in the gas-phase while in aqueous solution the helical, polyproline-II and ¿-turn motifs are energetically favored. Molecular dynamics simulations indicate that the conformational flexibility predicted by quantum mechanical calculations for the four Oic stereoisomers in solution is satisfactorily reproduced by classical force-fields

  • Synergistic computational-experimental approach to improve ionene polymer-based functional hydrogels

     Bachl, Jürgen; Zanuy Gomara, David; Lopez Perez, Daniel Ernesto; Revilla Lopez, Guillermo; Cativiela, Carlos; Aleman Llanso, Carlos Enrique; Diaz Diaz, David
    Advanced functional materials
    Vol. 24, num. 31, p. 4893-4904
    DOI: 10.1002/adfm.201304230
    Date of publication: 2014-08-20
    Journal article

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    The manifold applications of ionene-based materials such as hydrogels in daily life, biomedical sciences, and industrial processes are a consequence of their unique physical and chemical properties, which are governed by a judicious balance between multiple non-covalent interactions. However, one of the most critical aspects identified for a broader use of different polyelectrolytes is the need of raising their gelation efficiency. This work focuses on surfactant-free ionene polymers 1-3 containing DABCO and N, N'-(x-phenylene)dibenzamide (x = ortho-/meta-/para-) linkages as model systems to develop a combined computational-experimental approach to improve the hydrogelation through a better understanding of the gelation mechanism. Molecular dynamics simulations of isomeric ionenes 1-3 with explicit water molecules point out remarkable differences in the assembly of the polymeric chains in each case. Interchain regions with high degree of hydration (i.e., polymer water interactions) and zones dominated by polymer polymer interactions are evident in the case of ortho-(1) and meta -(2) isomeric ionenes, whereas domains controlled by polymer polymer interactions are practically inexistent in 3. In excellent agreement, ortho-ionene 1 provides experimentally the best hydrogels with unique features such as thixotropic behavior and dispersion ability for single-walles carbon nanotubes.

    The manifold applications of ionene-based materials such as hydrogels in daily life, biomedical sciences, and industrial processes are a consequence of their unique physical and chemical properties, which are governed by a judicious balance between multiple non-covalent interactions. However, one of the most critical aspects identified for a broader use of different polyelectrolytes is the need of raising their gelation efficiency. This work focuses on surfactant-free ionene polymers 1-3 containing DABCO and N, N'-(x-phenylene)dibenzamide (x = ortho-/meta-/para-) linkages as model systems to develop a combined computational-experimental approach to improve the hydrogelation through a better understanding of the gelation mechanism. Molecular dynamics simulations of isomeric ionenes 1-3 with explicit water molecules point out remarkable differences in the assembly of the polymeric chains in each case. Interchain regions with high degree of hydration (i.e., polymer water interactions) and zones dominated by polymer polymer interactions are evident in the case of ortho-(1) and meta -(2) isomeric ionenes, whereas domains controlled by polymer polymer interactions are practically inexistent in 3. In excellent agreement, ortho-ionene 1 provides experimentally the best hydrogels with unique features such as thixotropic behavior and dispersion ability for single-walles carbon nanotubes.

  • Measuring the proton conductivity of ion-exchange membranes using electrochemical impedance spectroscopy and Through-Plane cell

     Müller, Franciélli; Ferreira, Carlos A.; Azambuja, Denise S.; Aleman Llanso, Carlos Enrique; Armelin Diggroc, Elaine
    Journal of physical chemistry B
    Vol. 118, num. 4, p. 1102-1112
    DOI: 10.1021/jp409675z
    Date of publication: 2014-01-30
    Journal article

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    The role of the incorporation of conducting polymer (CP), doped with different sulfonic acid organic molecules, in polystyrene (PS) and high-impact polystyrene (HIPS) with poly(styrene-ethylene-butylene) (SEBS) triblock copolymer has been investigated. Two factors associated with this model membrane system are addressed: (i) the influence of the presence of a low concentration of doped conducting polymer and (ii) the influence of the membrane preparation method. Membrane characterization and bulk conductivity measurements allowed the conclusion that proton conductivity has been promoted by the addition of CP; the best results were achieved for PAni-CSA, in either PS/SEBS or HIPS/SEBS blends. Additionally, the water uptake only decreased with the addition of PAni-doped molecules compared to the pure copolymer, without loss of ion-exchange capacity (IEC). Electrodialysis efficiency for HIPS/SEBS (before annealing) is higher than that for HIPS/SEBS (after annealing), indicating that membrane preparation method is crucial. Finally, through-plane cell arrangement proved to be an effective, quick, and time-saving tool for studying the main resistance parameters of isolating polymers, which is useful for application in industry and research laboratories working with membranes for electrodialysis or fuel cells.

  • Selective detection of dopamine combining multilayers of conducting polymers with gold nanoparticles

     Fabregat Jove, Georgina; Armelin Diggroc, Elaine; Aleman Llanso, Carlos Enrique
    Journal of physical chemistry B
    Vol. 118, num. 17, p. 4669-4682
    DOI: 10.1021/jp412613g
    Date of publication: 2014-05-01
    Journal article

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    Electrodes based on the combination of three-layered films formed by two different conducting polymers and gold nanoparticles have been developed for the selective voltammetric determination of dopamine in mixtures with ascorbic acid and uric acid and human urine samples with real interferents. Voltammetric studies of solution mixtures indicate that electrodes formed by alternated layers of poly(3,4-ethylenedioxithiophene) (internal and external layer) and poly(N-methylpyrrole) (intermediate layer) show the best performance in terms of sensitivity and resolution. Furthermore, the sensitivity of such three-layered electrodes increases only slightly after coating its surface with gold nanoparticles (AuNPs), indicating that the catalytic effect typically played by AuNPs in the oxidation of dopamine is less effective in this case. Electrochemical pretreatments based on the application of consecutive oxidation-reduction cycles to electrodes before the detection process have been found to improve the selectivity without altering the sensitivity. On the other hand, the flux of dopamine to the three-layered surface increases linearly with the scan rate. The detection limit for these electrodes is around 10 µM DA in mixtures with uric acid, ascorbic acid, and cetaminophen, decreasing to 2-3 µM in the absence of such interferents. The utility of three-layered electrodes as sensors has also been demonstrated by determining DA in human samples with real interferents.

    Electrodes based on the combination of three-layered films formed by two different conducting polymers and gold nanoparticles have been developed for the selective voltammetric determination of dopamine in mixtures with ascorbic acid and uric acid and human urine samples with real interferents. Voltammetric studies of solution mixtures indicate that electrodes formed by alternated layers of poly(3,4-ethylenedioxithiophene) (internal and external layer) and poly(N-methylpyrrole) (intermediate layer) show the best performance in terms of sensitivity and resolution. Furthermore, the sensitivity of such three-layered electrodes increases only slightly after coating its surface with gold nanoparticles (AuNPs), indicating that the catalytic effect typically played by AuNPs in the oxidation of dopamine is less effective in this case. Electrochemical pretreatments based on the application of consecutive oxidation-reduction cycles to electrodes before the detection process have been found to improve the selectivity without altering the sensitivity. On the other hand, the flux of dopamine to the three-layered surface increases linearly with the scan rate. The detection limit for these electrodes is around 10 µM DA in mixtures with uric acid, ascorbic acid, and cetaminophen, decreasing to 2-3 µM in the absence of such interferents. The utility of three-layered electrodes as sensors has also been demonstrated by determining DA in human samples with real interferents.

  • Detection of dopamine using chemically synthesized multilayered hollow microspheres

     Fabregat Jove, Georgina; Estrany Coda, Francisco; Casas Becerra, M. Teresa; Aleman Llanso, Carlos Enrique; Armelin Diggroc, Elaine
    Journal of physical chemistry B
    Vol. 118, num. 17, p. 4702-4709
    DOI: 10.1021/jp500959j
    Date of publication: 2014-05-01
    Journal article

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    Microspheres made of alternating layers of two different conducting polymers, poly(3,4-ethylenedioxythiophene) and poly(N-methylpyrrole), have been found to be sensitive to dopamine (DA) oxidation, presenting a very well-defined and linear response in the range of DA concentrations from 0.5 to 2 mM. The novelty of the present study is the use of doped multilayered hollow microspheres, which are prepared by successive oxidative chemical polymerizations in FeCl3 aqueous solution. The multilayered microspheres were characterized by FTIR and UV-visible spectroscopies, scanning and transmission electron microscopies, and atomic force microscopy. The UV-visible bands confirm that the multilayered system is not well doped with FeCl4 - counterions. Therefore, the doping level was increased by further oxidation with LiClO4 before DA electrochemical detection. Despite that the range of concentration detection was limited from 0.5 mM to 2 mM, doped hollow multilayered microspheres show a very good anodic peak current response compared to single-layer films fabricated with an individual conducting polymer and activated by gold nanoparticles.

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    Mineralization of DNA into nanoparticles of hydroxyapatite  Open access

     Bertran Cànovas, Oscar; Del Valle Mendoza, Luis Javier; Revilla Lopez, Guillermo; Chaves Barboza, Gustavo Adolfo; Cardus Andreu, Lluis; Casas Becerra, M. Teresa; Casanovas Salas, Jordi; Turon Dols, Pau; Puiggali Bellalta, Jorge; Aleman Llanso, Carlos Enrique
    Dalton transactions
    Vol. 43, num. 1, p. 317-327
    DOI: 10.1039/c3dt52112e
    Date of publication: 2014-01-07
    Journal article

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    Encapsulation of DNA into hydroxyapatite (HAp) has been investigated using a rational approach that involves computer simulation and experimental techniques. The temporal evolution of the radial distribution functions derived from atomistic molecular dynamics simulations of Ca2+, PO 4 3- and OH--containing aqueous solutions in the presence and absence of B-DNA has been used to conclude that the backbone of the double helix acts as a template for HAp growth. More specifically, results reveal the formation of calcium phosphate clusters at the first stages of the simulations, which subsequently re-organize to nucleate HAp. This effect is produced in the absence and, especially, presence, of DNA indicating that the biomolecules do not inhibit but even promote mineral growth. Furthermore, computer simulations suggest that the diffusion of the OH- anions through the inorganic solution is the limiting step for the nucleation of the biomineral. Nanocapsules and crystalline nanorods of HAp containing DNA molecules inside have been prepared by mixing solutions containing Ca 2+ and PO4 3- ions with fish sperm DNA at high pH. The dimensions and morphology of such nanostructures have been examined by transmission electron microscopy, while the characterization of the biomineral has been focused on the identification of DNA inside HAp using infrared, X-ray photoelectron and UV-vis spectroscopies, as well as gel electrophoresis. The biominerals reported in this work are important for biomedical applications requiring the protection of DNA from aggressive environmental conditions. © 2014 The Royal Society of Chemistry.

    Encapsulation of DNA into hydroxyapatite (HAp) has been investigated using a rational approach that involves computer simulation and experimental techniques. The temporal evolution of the radial distribution functions derived from atomistic molecular dynamics simulations of Ca2+, PO4 3− and OH−-containing aqueous solutions in the presence and absence of B-DNA has been used to conclude that the backbone of the double helix acts as a template for HAp growth. More specifically, results reveal the formation of calcium phosphate clusters at the first stages of the simulations, which subsequently reorganize to nucleate HAp. This effect is produced in the absence and, especially, presence, of DNA indicating that the biomolecules do not inhibit but even promote mineral growth. Furthermore, computer simulations suggest that the diffusion of the OH− anions through the inorganic solution is the limiting step for the nucleation of the biomineral. Nanocapsules and crystalline nanorods of HAp containing DNA molecules inside have been prepared by mixing solutions containing Ca2+ and PO4 3− ions with fish sperm DNA at high pH. The dimensions and morphology of such nanostructures have been examined by transmission electron microscopy, while the characterization of the biomineral has been focused on the identification of DNA inside HAp using infrared, X-ray photoelectron and UV-vis spectroscopies, as well as gel electrophoresis. The biominerals reported in this work are important for biomedical applications requiring the protection of DNA from aggressive environmental conditions

  • All-polythiophene rechargeable batteries

     Aradilla Zapata, David; Estrany Coda, Francisco; Casellas Beneyto, Francisco; Iribarren Laco, Jose Ignacio; Aleman Llanso, Carlos Enrique
    Organic electronics
    Vol. 15, num. 1, p. 40-46
    DOI: 10.1016/j.orgel.2013.09.044
    Date of publication: 2014-01-01
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  • How organophosphonic acid promotes silane deposition onto aluminum surface: a detailed investigation on adsorption mechanism

     Torras Costa, Juan; Azambuja, Denise S.; Wolf, Johanna M.; Aleman Llanso, Carlos Enrique; Armelin Diggroc, Elaine
    The journal of physical chemistry. Part C, nanomaterials and interfaces
    Vol. 118, num. 31, p. 17724-17736
    DOI: 10.1021/jp5046707
    Date of publication: 2014-08-07
    Journal article

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    Many research works have evidenced the importance in using inorganic organic hybrid materials to protect metal surface or to serve as intermediate adhesion promoter layer for further coating deposition. The main aim of the present work was to elucidate the mechanism of silane deposition onto aluminum surface, in the presence of organophosphonic acid as adhesion promoter and using experimental and theoretical techniques. Transparent thin films of layered inorganic organic composites were prepared by the sol gel synthesis of tetraethylorthosilicate and vinyltrimethoxysilane in the presence of 1,2-diaminoethanetetrakis-methylenephosphonic acid. Aluminum surface was characterized by X-ray diffraction, SEM and XPS techniques. On the other hand, inorganic-organic coating was characterized by FTIR and XPS spectroscopies. Density functional theory was employed to evaluate three simplified molecules, orthosilicic acid (Si(OH)(4)), methylphosphonic acid (MePA), and Si(OH)(3)OMePA, by using different coordination modes, in order to approach the most stable chemical bonding between silane-phosphonic groups with modified aluminum surface (i.e., with boehmite as oxidized layer).

  • Hybrid nanofibers from biodegradable polylactide and polythiophene for scaffolds

     Llorens Domenjo, Elena; Perez Madrigal, Maria Del Mar; Armelin Diggroc, Elaine; Del Valle Mendoza, Luis Javier; Puiggali Bellalta, Jorge; Aleman Llanso, Carlos Enrique
    RSC Advances
    Vol. 4, num. 29, p. 15245-15255
    DOI: 10.1039/c3ra42829j
    Date of publication: 2014-01-01
    Journal article

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    Hybrid scaffolds constituted of polylactide (PLA) as a biodegradable polymer and poly(3-thiophene methyl acetate) (P3TMA) as an electroactive polymer were prepared and studied. Both polymers had a similar solubility and consequently could be easily electrospun using a common solvent. Electrospinning operational parameters were optimized to get continuous micro/nanofibers with a homogeneous diameter that ranged between 600 and 900 nm depending on the PLA-P3TMA ratio. Electrospinning was only effective when the P3TMA content was at maximum 50 wt%. The incorporation of P3TMA slightly decreased the fibre diameter, led to smoother fibre surfaces and gave rise to some heterogeneous clusters inside the fibers. PLA was highly oriented inside the electrospun fibers and able to easily cold crystallize by heating. Thermal degradation was not highly influenced by the presence of P3TMA, although the onset temperature slightly increased since the first decomposition step of PLA was prevented. New scaffolds had promising electrochemical properties and even provided a good substrate for cell adhesion and cell proliferation. Therefore, these hybrid materials are suitable to improve the cellular response towards physiological processes.

  • Exploiting molecular self-assembly: from urea-based organocatalysts to multifunctional supramolecular gels

     Schoen, Eva Maria; Marques Lopez, Eugenia; Herrera, Raquel P.; Aleman Llanso, Carlos Enrique; Diaz Diaz, David
    Chemistry: a european journal
    Vol. 20, num. 34, p. 10720-10731
    DOI: 10.1002/chem.201402436
    Date of publication: 2014-08-18
    Journal article

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    We describe the self-assembly properties of chiral N,N'-disubstituted urea-based organocatalyst 1 that leads to the formation of hierarchical supramolecular gels in organic solvents at low concentrations. The major driving forces for the gelation are hydrogen bonding and pi-pi interactions according to FTIR and H-1 NMR spectroscopy, as well as quantum-mechanical studies. The gelation scope could be interpreted based on Kamlet-Taft solvatochromic parameters. TEM, SEM, and AFM imaging revealed that a variety of morphologies including helical, laths, porous, and lamellar nanostructures could be obtained by varying the solvent. Experimental gelation tests and computational structural analysis of various structurally related compounds proved the existence of a unique set of molecular interactions and an optimal hydrophilic/hydrophobic balance in 1 that drive the formation of stable gels. Responses to thermal, mechanical, optical, and chemical stimuli, as well as multifunctionality were demonstrated in some model gel materials. Specifically, 1 could be used for the phase-selective gelation of organic solvent/water mixtures. The gel prepared in glycerol was found to be thixotropic and provided a sensitive colorimetric method for the detection of Ag-I ions at millimolar concentrations in aqueous solution. Moreover, the gel matrix obtained in toluene served as a nanoreactor for the Friedel-Crafts alkylation of H-1-indole with trans-beta-nitrostyrene.

    We describe the self-assembly properties of chiral N,N'-disubstituted urea-based organocatalyst 1 that leads to the formation of hierarchical supramolecular gels in organic solvents at low concentrations. The major driving forces for the gelation are hydrogen bonding and pi-pi interactions according to FTIR and H-1 NMR spectroscopy, as well as quantum-mechanical studies. The gelation scope could be interpreted based on Kamlet-Taft solvatochromic parameters. TEM, SEM, and AFM imaging revealed that a variety of morphologies including helical, laths, porous, and lamellar nanostructures could be obtained by varying the solvent. Experimental gelation tests and computational structural analysis of various structurally related compounds proved the existence of a unique set of molecular interactions and an optimal hydrophilic/hydrophobic balance in 1 that drive the formation of stable gels. Responses to thermal, mechanical, optical, and chemical stimuli, as well as multifunctionality were demonstrated in some model gel materials. Specifically, 1 could be used for the phase-selective gelation of organic solvent/water mixtures. The gel prepared in glycerol was found to be thixotropic and provided a sensitive colorimetric method for the detection of Ag-I ions at millimolar concentrations in aqueous solution. Moreover, the gel matrix obtained in toluene served as a nanoreactor for the Friedel-Crafts alkylation of H-1-indole with trans-beta-nitrostyrene.

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    A single-residue substitution inhibits fibrillization of Ala-based pentapeptides. A spectroscopic and molecular dynamics investigation  Open access

     Caruso, M.; Gatto, Emanuela; Placidi, E.; Venanzi, Mariano; Ballano Ballano, María Gema; Formaggio, Fernando; Toniolo, Claudio; Zanuy Gomara, David; Aleman Llanso, Carlos Enrique
    Soft matter
    Vol. 10, num. 15, p. 2508-2519
    DOI: 10.1039/c3sm52831f
    Date of publication: 2014-01-01
    Journal article

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    The aggregation properties of two Ala-based pentapeptides were investigated by spectroscopic techniques and molecular dynamics (MD) simulations. The two peptides, both functionalized at the N-terminus with a pyrenyl group, differ in the insertion of an alpha-aminoisobutyric acid residue at position 4. We showed that this single modification of the homo-peptide sequence inhibits the aggregation of the pentapeptide in aqueous solutions. Atomic force microscopy imaging revealed that the two peptides form mesoscopic aggregates of very different morphologies when deposited on mica. MD experiments showed that the two peptides have a very different propensity to form beta-pleated sheet structures, as confirmed by our spectroscopic measurements. The implications of these findings for our understanding of the mechanism leading to the formation of amyloid structures, primary responsible for numerous neurodegenerative diseases, are also discussed.

    The aggregation properties of two Ala-based pentapeptides were investigated by spectroscopic techniques and molecular dynamics (MD) simulations. The two peptides, both functionalized at the N-terminus with a pyrenyl group, differ in the insertion of an alpha-aminoisobutyric acid residue at position 4. We showed that this single modification of the homo-peptide sequence inhibits the aggregation of the pentapeptide in aqueous solutions. Atomic force microscopy imaging revealed that the two peptides form mesoscopic aggregates of very different morphologies when deposited on mica. MD experiments showed that the two peptides have a very different propensity to form beta-pleated sheet structures, as confirmed by our spectroscopic measurements. The implications of these findings for our understanding of the mechanism leading to the formation of amyloid structures, primary responsible for numerous neurodegenerative diseases, are also discussed.

  • Copper Coordination Study in a Metal-Induced Chiral Polythiophene Aggregate

     Torras Costa, Juan; Aleman Llanso, Carlos Enrique
    The journal of physical chemistry. Part C, nanomaterials and interfaces
    Vol. 118, num. 18, p. 9769-9779
    DOI: 10.1021/jp501118y
    Date of publication: 2014-05-08
    Journal article

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    The chiral regioregular polythiophene, poly[(R)-3-(4-(4-ethyl-2-oxazolin-2-yl)phenyl)-thiophene] (PEOPT), forms chiral aggregates in chloroform under copper salt presence, with chirality disappearing upon the addition of acetonitrile. We report here a comprehensive quantum mechanical study of intermolecular assembly adducts with a copper ion that may be involved in this switching process. Results indicate that copper adducts made of undissociated copper salt in chloroform prefer a syn-(EOPT)(2) disposition of ligands belonging to different polythiophene chains, favoring a double-stranded helical conformation. In contrast, doped polymer with copper ions in acetonitrile prefers an anti-(EOPT)(2) arrangement for the different polythiophene side chains, favoring a nonchiral pi-stacked packing. Furthermore, another cross-linked interaction besides the most stable NN-type has been characterized. Thus, NO-type interactions on the [Cu(EDOT)(2)]Cl-2 adducts in chloroform have been shown to be energetically stable. However, hybrid quantum mechanical/molecular mechanical molecular dynamics (QM/MM MD) simulations indicate that only those adducts that involve helical chains keep structural stability under kinetic considerations.

  • Conducting Polymers Obtained from Quiescent and Stirred Solutions: Effects on the Properties

     Sanchez Jimenez, Margarita; Aleman Llanso, Carlos Enrique; Estrany Coda, Francisco
    Polymer Engineering & Science Journal
    Vol. 54, num. 9, p. 2121-2131
    DOI: 10.1002/pen.23761
    Date of publication: 2014-09-01
    Journal article

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    Poly(3,4-ethylenedioxythiophene), poly(N-methylpyrrole), and three-layered systems made of alternated layers of such two conducting polymers have been prepared by agitating the generation solution through a magnetic bar at a stirring speed of 400 rpm. The influence of these controlled dynamic conditions on both the electrochemical behavior and the superficial morphology has been examined. Results indicate that the increase in transport rate of reactants slightly favors the generation of more polymer weight at equal charge consumed. Consequently, the thickness of the materials prepared under stirring increases considerably with respect to those obtained from quiescent solutions, systems prepared using short (100 s) and large (300 s) polymerization times changing from nanometric to submicrometric and from submicrometric to micrometric length-scales, respectively. Moreover, the porosity of PNMPy and PEDOT films also increases upon agitation. Thus, quiescent solutions produce compact and cavernous morphologies, respectively, for these materials, whereas the PNMPy and PEDOT obtained from agitated solutions are globular and spongy, respectively. Finally, the electroactivity, electrochemical stability, and electrical conductivity of the materials obtained from stirred solutions have been found to be significantly higher than those of the polymers prepared using quiescent solutions. (C) 2013 Society of Plastics Engineers

    Poly(3,4-ethylenedioxythiophene), poly(N-methylpyr- role), and three-layered systems made of alternated layers of such two conducting polymers have been prepared by agitating the generation solution through a magnetic bar at a stirring speed of 400 rpm. The influence of these controlled dynamic conditions on both the electrochemical behavior and the superficial morphology has been examined. Results indicate that the increase in transport rate of reactants slightly favors the generation of more polymer weight at equal charge consumed. Consequently, the thickness of the materials prepared under stirring increases consider- ably with respect to those obtained from quiescent solutions, systems prepared using short (100 s) and large (300 s) polymerization times changing from nano- metric to submicrometric and from submicrometric to micrometric length-scales, respectively. Moreover, the porosity of PNMPy and PEDOT films also increases upon agitation. Thus, quiescent solutions produce compact and cavernous morphologies, respectively, for these materials, whereas the PNMPy and PEDOT obtained from agitated solutions are globular and spongy, respectively. Finally, the electroactivity, elec- trochemical stability, and electrical conductivity of the materials obtained from stirred solutions have been found to be significantly higher than those of the poly- mers prepared using quiescent solutions.

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    A rational design for the selective detection of dopamine using conducting polymers  Open access

     Fabregat Jove, Georgina; Casanovas Salas, Jordi; Redondo Negrete, Edurne; Armelin Diggroc, Elaine; Aleman Llanso, Carlos Enrique
    Physical chemistry chemical physics
    Vol. 16, num. 17, p. 7850-7861
    DOI: 10.1039/c4cp00234b
    Date of publication: 2014-02-25
    Journal article

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    Poly(N-methylpyrrole) (PNMPy), poly(N-cyanoethylpyrrole) (PNCPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared using both single and two polymerization steps for the selective determination of low concentrations of dopamine, ascorbic acid and uric acid in tertiary mixtures. Analysis of the sensitivity and resolution parameters derived from the electrochemical response of such films indicates that PEDOT is the most appropriate for the unambiguous detection of the three species. Indeed, the performance of PEDOT is practically independent of the presence of both gold nanoparticles at the surface of the film and interphases inside the film, even though these two factors are known to improve the electroactivity of conducting polymers. Quantum mechanical calculations on model complexes have been used to examine the intermolecular interaction involved in complexes formed by PEDOT chains and oxidized dopamine, ascorbic acid and uric acid. Results show that such complexes are mainly stabilized by C-H¿O interactions rather than by conventional hydrogen bonds. In order to improve the sensitivity of PEDOT through the formation of specific hydrogen bonds, a derivative bearing a hydroxymethyl group attached to the dioxane ring of each repeat unit has been designed. Poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeDOT) has been prepared and characterized by FTIR, UV-vis spectroscopy, cyclic voltammetry, scanning electron microscopy and atomic force microscopy. Finally, the performance of PHMeDOT and PEDOT for the selective detection of the species mentioned above has been compared. © 2014 the Partner Organisations.

    Poly(N-methylpyrrole) (PNMPy), poly(N-cyanoethylpyrrole) (PNCPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared using both single and two polymerization steps for the selective determination of low concentrations of dopamine, ascorbic acid and uric acid in tertiary mixtures. Analysis of the sensitivity and resolution parameters derived from the electrochemical response of such films indicates that PEDOT is the most appropriate for the unambiguous detection of the three species. Indeed, the performance of PEDOT is practically independent of the presence of both gold nanoparticles at the surface of the film and interphases inside the film, even though these two factors are known to improve the electroactivity of conducting polymers. Quantum mechanical calculations on model complexes have been used to examine the intermolecular interaction involved in complexes formed by PEDOT chains and oxidized dopamine, ascorbic acid and uric acid. Results show that such complexes are mainly stabilized by C-H¿O interactions rather than by conventional hydrogen bonds. In order to improve the sensitivity of PEDOT through the formation of specific hydrogen bonds, a derivative bearing a hydroxymethyl group attached to the dioxane ring of each repeat unit has been designed. Poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeDOT) has been prepared and characterized by FTIR, UV-vis spectroscopy, cyclic voltammetry, scanning electron microscopy and atomic force microscopy. Finally, the performance of PHMeDOT and PEDOT for the selective detection of the species mentioned above has been compared. © 2014 the Partner Organisations.

  • Electronic, electric and electrochemical properties of bioactive nanomembranes made of polythiophene:thermoplastic polyurethane

     Perez Madrigal, Maria Del Mar; Giannotti, Marina I.; Armelin Diggroc, Elaine; Sanz Carrasco, Fausto; Aleman Llanso, Carlos Enrique
    Polymer Chemistry
    Vol. 5, num. 4, p. 1248-1257
    DOI: 10.1039/c3py01313h
    Date of publication: 2014-02-21
    Journal article

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    The electronic, electric and electrochemical response of nanomembranes prepared by using spin-coating mixtures of a semiconducting polythiophene derivative (P3TMA) and thermoplastic polyurethane (TPU) has been exhaustively examined by UV-vis spectroscopy, conductive AFM, current/voltage measurements and cyclic voltammetry. TPU:P3TMA nanomembranes were reported to be good substrates for applications related to tissue engineering, acting as a cellular matrix for cell adhesion and proliferation. Both TPU:P3TMA and P3TMA nanomembranes show semiconductor behavior with very similar band gap energy (2.35 and 2.32 eV, respectively), which has been attributed to the influence of the fabrication process on the pi-conjugation length and packing interactions of P3TMA chains. This behavior is in opposition to the observations in THF solution, which indicates that the band gap energy of P3TMA is clearly lower than that of the mixture, independently of the concentration. The current and conductivity values determined for the nanomembranes, which range from 0.43 to 1.85 pA and from 2.23 x 10(-5) to 5.19 x 10(-6) S cm(-1), respectively, evidence inhomogeneity in the P3TMA-rich domains. This has been associated with the irregular distribution of the doped chains and the presence of insulating TPU chains. The voltammetric response of TPU:P3TMA and P3TMA nanomembranes is similar in terms of ability to store charge and electrochemical stability. Overall results indicate that TPU:P3TMA nanomembranes are potential candidates for the fabrication of bioactive substrates able to promote cell regeneration through electrical or electrochemical stimulation.

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    Synthesis and evaluation of a PVDF-PT3MA-Zn2SiO4:Mn hybrid polymeric composite for optical device applications  Open access

     Gomes, Alex Linardi; Lang, Rossano; Armelin Diggroc, Elaine; Aleman Llanso, Carlos Enrique; Sinezio De Carvalho Campos, Joao
    Journal of materials chemistry C
    Vol. 2, num. 14, p. 2502-2509
    DOI: 10.1039/c3tc32116a
    Date of publication: 2014-01-01
    Journal article

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    A new hybrid organic/inorganic composite consisting of poly(3-thiophene methyl acetate) (PT3MA), poly(vinylidene fluoride) (PVDF) and manganese-doped zinc silicate (Zn2SiO4:Mn) has been synthesized and applied for the fabrication of an optical device. Recrystallized PVDF was used as a host matrix for the PT3MA polymer and Zn2SiO4:Mn inorganic compound. The active layer was deposited on an indium-tin-oxide (ITO)-coated glass substrate by the drop casting technique. A spin-coating method was also used for morphological comparison purposes. The synthesized material as well as the device (aluminium electrodes/PVDF-PT3MA-Zn2SiO4:Mn/ITO/glass) was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), dark current-voltage (I-V) characteristic curves, absorbance and photoluminescence (PL) spectroscopy. The results show spherical-and irregular-shaped microparticles both dispersed on and within the PVDF matrix, which correspond to PT3MA and Zn2SiO4:Mn, respectively. The hybrid composite shows strong luminescence at approximate to 525 nm superimposed by a broadband between 600 and 800 nm, originating from the Zn2SiO4:Mn radiative transitions and from the recombination of photogenerated carriers at PT3MA. At room temperature, the device presented semiconductor behaviour typically observed for photodetectors and a DC electrical conductivity of approximate to 0.37 mu S cm(-1).

    A new hybrid organic/inorganic composite consisting of poly(3-thiophene methyl acetate) (PT3MA), poly(vinylidene fluoride) (PVDF) and manganese-doped zinc silicate (Zn2SiO4:Mn) has been synthesized and applied for the fabrication of an optical device. Recrystallized PVDF was used as a host matrix for the PT3MA polymer and Zn2SiO4:Mn inorganic compound. The active layer was deposited on an indium-tin-oxide (ITO)-coated glass substrate by the drop casting technique. A spin-coating method was also used for morphological comparison purposes. The synthesized material as well as the device (aluminium electrodes/PVDF-PT3MA-Zn2SiO4:Mn/ITO/glass) was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), dark current-voltage (I-V) characteristic curves, absorbance and photoluminescence (PL) spectroscopy. The results show spherical-and irregular-shaped microparticles both dispersed on and within the PVDF matrix, which correspond to PT3MA and Zn2SiO4:Mn, respectively. The hybrid composite shows strong luminescence at approximate to 525 nm superimposed by a broadband between 600 and 800 nm, originating from the Zn2SiO4:Mn radiative transitions and from the recombination of photogenerated carriers at PT3MA. At room temperature, the device presented semiconductor behaviour typically observed for photodetectors and a DC electrical conductivity of approximate to 0.37 mu S cm(-1).

  • Interactions in dendronized polymers: intramolecular dominates intermolecular

     Cordova Mateo, Ester; Bertran Cànovas, Oscar; Zhang, Baozhong; Vlassopoulos, Dimitris; Pasquino, Rossana; Schlüter, A. Dieter; Kröger, Martin; Aleman Llanso, Carlos Enrique
    Soft matter
    Vol. 10, num. 7, p. 1032-1044
    DOI: 10.1039/c3sm52343h
    Date of publication: 2014
    Journal article

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    In an attempt to relate atomistic information to the rheological response of a large dendritic object, inter- and intramolecular hydrogen bonds and pi,pi-interactions have been characterized in a dendronized polymer (DP) that consists of a polymethylmethacrylate backbone with tree-like branches of generation four (PG4) and contains both amide and aromatic groups. Extensive atomistic molecular dynamics simulations have been carried out on (i) an isolated PG4 chain and (ii) ten dimers formed by two PG4 chains associated with different degrees of interpenetration. Results indicate that the amount of nitrogen atoms involved in hydrogen bonding is similar to 11% while similar to 15% of aromatic groups participate in pi,pi-interactions. Furthermore, in both cases intramolecular interactions clearly dominate over intermolecular ones, while exhibiting markedly different behaviors. Specifically, the amount of intramolecular hydrogen bonds increases when the interpenetration of the two chains decreases, whereas intramolecular pi,pi-interactions remain practically insensitive to the amount of interpenetration. In contrast, the strength of the corresponding two types of intermolecular interactions decreases with interpenetration. Although the influence of complexation on the density and cross-sectional radius is relatively small, interpenetration affects significantly the molecular length of the DP. These results support the idea of treating DPs as long colloidal molecules.

  • Conducting polymers and hybrid derivates with specific applications as sensors and bioactive platforms

     Fabregat Jove, Georgina
    Universitat Politècnica de Catalunya
    Theses

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    El propósito de la presente tesis es el desarrollo y diseño de nanocompuestos híbridos basados ??en polímeros conductores para su posterior aplicación en el campo de la biotecnología y la biomedicina. Las principales líneas de investigación se resumen de la siguiente manera; 1) Preparación , caracterización y evaluación de derivados N-sustituidos de polipirrol y poli(3,4-etilendioxitiofeno ) (PEDOT) para la detección electroquímica de la dopamina, uno de los neurotransmisores asociados a trastornos neurológicos. Para examinar este propósito, diferentes estrategias han sido consideradas, tales como; el método de polimerización empleando polímeros individuales o combinados, la incorporación de nanopartículas de oro, la utilización de templates, etc. 2) Diseño de aminoácidos sintéticos unidos covalentemente con un grupo EDOT y posterior desarrollo de materiales híbridos (péptido - PEDOT). Los materiales híbridos han demostrado conservar las propiedades eléctricas y electroquímicas del polímero base, siendo posibles candidatos para el desarrollo de plataformas bioactivas y bioelectrocompatible. 3) Preparación y caracterización de materiales híbridos orgánicos formados por una cadena principal de politiofeno y cadenas injertadas de polietilenglicol (PEG), los cuales tienen una elevada aplicabilidad como superficies activas para la adsorción selectiva de proteínas y como plataformas bioactivas. 4) Preparación y caracterización de nuevos bionanocomposites formados por PEDOT y CREKA, el cual es un pentapéptido lineal biológicamente activo. La incorporación de CREKA en una matriz de PEDOT se ha llevado a cabo en diferentes condiciones experimentales, y ha demostrado tener un efecto positivo sobre las propiedades electroquímicas del polímero conductor como también proporcionar una mejora en la proliferación celular debido a la capacidad de éste para unirse a la fibrina. Algunos resultados obtenidos en la presente Tesis han sido publicados o aceptados para su publicación en revistas científicas: 1.An electroactive and biologically responsive hybrid conjugate based on chemical similarity. G. Fabregat, G. Ballano, E. Armelin, L. J. del Valle, C. Cativiela and C. Alemán, Polym. Chem., 2013, 4, 1412.2.Hybrid materials consisting of an all-conjugated polythiophene backbone and grafted hydrophilic poly(ethylene glycol) chains. A.-D. Bendrea, G. Fabregat, L. Cianga, F. Estrany, L. J. del Valle, I. Cianga and C. Alemán, Polym. Chem., 2013,4, 2709.3.Polythiophene-g-poly(ethylene glycol) graft copolymers for electroactive scaffolds.A.-D. Bendrea, G. Fabregat, J. Torras, S. Maione, L. Cianga, L. J. del Valle, I. Cianga and C. Alemán, J. Mater. Chem. B, 2013,1, 4135.4.Design of hybrid conjugates based on chemical similarity.G. Fabregat, G. Ballano, J. Casanovas, A. D. Laurent, E. Armelin, Luis J. del Valle, C. Cativiela, D. Jacquemin and C. Alemán, RSC Adv., 2013, 3, 21069.5.Controlling the morphology of poly(N -cyanoethylpyrrole).G. Fabregat, M. T. Casas, C. Alemán and E. Armelin, J. Phys. Chem. B, 2012, 116, 5064.7.Ultrathin Films of Polypyrrole Derivatives for Dopamine Detection. G. Fabregat, E. Córdova-Mateo, E. Armelin, O. Bertran and C. Alemán. J. Phys. Chem. C, 2011, 115,14933.8.Nanostructured conducting polymer for dopamine detection.M. Martí, G. Fabregat, F. Estrany, C. Alemán and E. Armelin, J. Mater. Chem., 2010, 20, 10652.

  • Peptide and Protein-Polymer: Sudy of their applications in Nanoengineering and Bioengineering

     Lopez Perez, Daniel Ernesto
    Universitat Politècnica de Catalunya
    Theses

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    El tema principal de esta tesis es el desarrollo y diseño de nanocompuestos hibridos basados en polimeros conductores y peptidos-proteinas. Con aplicaciones en el campo de la nanoingenieria y bioingenieria. Las lineas principales de esta investigación se pueden resumir de la siguiente manera:1) Estudio de ensamble de Fmoc-tretrapeptidos basados en secuencias bioactiva RGD. Más específicamente, esta Thesis esta enfocada en la adhesión de la secuencia Fmoc-RGDS y su homologo Fmoc-GRDS, el cual contiene los mismos residuos pero en diferente secuencia. 2) Examinar el mecanismo en la transferencia de electron en un peptido con conformación alpha-helice, Cys-Ala-Lys-(Glu-Ala-Ala-Ala-Lys)2-Ala, en oro como función de la elongación molecular entendiendo el papel que juega las interacciones intermoleculares.3) Contrucción de una platadorma bioactivas con propiedades capacitivas para ser usadas como biocondensador mediante el aprovechamiento de las propiedades electroquimicas del PEDOT y las propiedades bactericidas y biocopatibles de la Lisozima.4) Fabricación de plataformas electro compatibles bioactivas mediante la combinacion de dos materiales relativamente incompatibles: Polimero conductor soluble y collageno, la mayor proteina estructural en los animales.Algunos resultados de las investigaciones previstas en esta Tesis han sido publicados o aceptados para su publicación en revistas científicas:1.Self-assembly of Fmoc-tetrapeptides based on the RGDS cell adhesion motif . V. Castelleto, C.M. Moulton, G. Cheng, I.W. Hamley, M.R. Hicks, A. Rodger, D.E. López-Pérez, G. Revilla-López and C. Alemán, Soft Matter, 2011, 24, 11405.2. Intermolecular interactions in electron transfer through stretched helical peptides. D.E. López-Pérez, G. Revilla-López D. Jacquemin, D. Zanuy and C. Alemán, Phys. Chem. Chem. Phys., 2012,14, 10332.3. Molecular insights into aggregates made of amphiphilic Fmoc-tetrapeptides. D.E. López-Pérez, G. Revilla-López D., I.W. Hamley and C. Alemán, Soft Matter, 2013, 9, 11021 4.Capacitive Composites Made of Conducting polymer and Lysozyme: Toward the biocondenser. D.E. López-Pérez, D. Aradilla, L. J. del Valle and C. Alemán, J.Phys. Chem., 2013, 117, 6607. * .Fabrication of Collagen-Polythiophene Composites as Bioactive Platforms with Cellular Electrocompatibility D.E. López-Pérez, C. Illera and C. Alemán . * enviada en espera de aceptación

  • Thermally-induced irreversible increasing conductivity in polythiophene

     Estrany Coda, Francisco; Peres, Rafael; Sanchez Jimenez, Margarita; Ferreira, Carlos A.; Aleman Llanso, Carlos Enrique
    Meeting of electrochemistry of the Spanish Royal Society of Chemistry; E3 Mediterranean Symposium Electrochemistry for Environment and Energy
    p. 222
    Presentation's date: 2014-07-14
    Presentation of work at congresses

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    In this work we examine thermal effects on the conductivity of poly(3,4-ethylenedioxythiophene) (PEDOT) in the absence of light. Polymer films were electrogenerated at 1.40 V in an electrolytic cell using a 10 mM EDOT solution with 0.1 M LiClO4 electrolyte and dopant. Furthermore, PEDOT films were prepared considering two different solvents, acetonitrile and deionized water. The temperature was reversibly increased from 20 °C to 70 °C, an electric resistance being used as heater. The rate of heating and cooling did not exceed 1.5 ºC/min. Electrical resistance measurements were carried out continuously for the whole test in the same heating device. ( a ) ( b ) Fig.1. AFM images of PEDOT films prepared in water before (a) and after (b) termal treatment. Although the conductivity of PEDOT obtained in acetonitrile is about 200 times higher than that of PEDOT electrogenerated in water, the two materials show the same behavior upon thermal treatment. Their conductivity increase significantly with temperature, reached values remaining irreversibly in the cooling stage. This effect has been attributed to permanent structural changes provoked during the heating. These changes have been examined at the surface of the films using AFM (Fig. 1) and SEM. Acknowledgements: This work has been supported by MICINN and FEDER funds (project MAT2012-34498).

  • Transport of hydronium ions inside poly(styrene-co-divinyl benzene) cation exchange membranes

     Cordova Mateo, Ester; Bertran Cànovas, Oscar; Ferreira, Carlos Arthur; Aleman Llanso, Carlos Enrique
    Journal of membrane science
    Vol. 428, p. 393-402
    DOI: 10.1016/j.memsci.2012.10.048
    Date of publication: 2013-02-01
    Journal article

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  • Determination of new Cu+, Cu2+, and Zn2+ Lennard-Jones ion parameters in acetonitrile

     Torras Costa, Juan; Aleman Llanso, Carlos Enrique
    Journal of physical chemistry B
    Vol. 117, num. 36, p. 10513-10522
    DOI: 10.1021/jp402545g
    Date of publication: 2013-08-14
    Journal article

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    We present new Lennard-Jones (LJ) parameters for Cu+, Cu2+, and Zn2+ ion-acetonitrile interactions. The adjustment of ion parameters is made to reproduce simultaneously experimental solvation free energy and structural properties, namely ion¿N distance and coordination numbers. Initially, the methodology has been validated deriving parameters for well-studied Na+ and Cl¿ ions in acetonitrile being compared with experimental and theoretical data. The transferability of parameters is checked by the calculation of thermodynamic and structural properties with three different acetonitrile models. The results obtained for transition metal ions show an overall agreement with reference values. The solvation free energy calculated with new LJ trained parameters using a six-site acetonitrile model, and two older three- and six-site acetonitrile models presents, respectively, percent differences of 0.4, 4.8, and 7.3% when compared with experimental values.

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    Polythiophene-g-poly(ethylene glycol) graft copolymers for electroactive scaffolds  Open access

     Bendrea, Anca Dana; Fabregat Jove, Georgina; Torras Costa, Juan; Maione, Silvana; Cianga, Ioan; Del Valle Mendoza, Luis Javier; Cianga, Luminita; Aleman Llanso, Carlos Enrique
    Journal of materials chemistry B
    p. 4135-4145
    DOI: 10.1039/C3TB20679C
    Date of publication: 2013
    Journal article

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    The properties, microscopic organization and behavior as the cellular matrix of an all-conjugated polythiophene backbone (PTh) and well-defined poly(ethylene glycol) (PEG) grafted chains have been investigated using different experimental techniques and molecular dynamic simulations. UV-vis spectroscopy has been used to determine the optical band gap, which has been found to vary between 2.25 and 2.9 eV depending on the length of the PEG chains and the chemical nature of the dopant anion, and to detect polaron ¿ bipolaron transitions between band gap states. The two graft copolymers have been found to be excellent cellular matrices, their behavior being remarkably better than that found for other biocompatible polythiophene derivatives [e.g. poly(3,4-ethylenedioxythiophene)]. This is fully consistent with the hydrophilicity of the copolymers, which increases with the molecular weight of the PEG chains, and the molecular organization predicted by atomistic molecular dynamics simulations. Graft copolymers tethered to the surface tend to form biphasic structures in solvated environments (i.e. extended PTh and PEG fragments are perpendicular and parallel to the surface, respectively) while they collapse onto the surface in desolvated environments. Furthermore, the electrochemical activity and the maximum of current density are remarkably higher for samples coated with cells than for uncoated samples, suggesting multiple biotechnological applications in which the transmission with cells is carried out at the electrochemical level.

    The properties, microscopic organization and behavior as the cellular matrix of an all-conjugated polythiophene backbone (PTh) and well-de fi ned poly(ethylene glycol) (PEG) grafted chains have been investigated using di ff erent experimental techniques and molecular dynamic simulations. UV-vis spectroscopy has been used to determine the optical band gap, which has been found to vary between 2.25 and 2.9 eV depending on the length of the PEG chains and the chemical nature of the dopant anion, and to detect polaron / bipolaron transitions between band gap states. The two graft copolymers have been found to be excellent cellular matrices, their behavior being remarkably better than that found for other biocompatible polythiophene derivatives [ e.g. poly(3,4- ethylenedioxythiophene)]. This is fully consistent with the hydrophilicity of the copolymers, which increases with the molecular weight of the PEG chains, and the molecular organization predicted by atomistic molecular dynamics simulations. Graft copolymers tethered to the surface tend to form biphasic structures in solvated environments ( i.e. extended PTh and PEG fragments are perpendicular and parallel to the surface, respectively) while they collapse onto the surface in desolvated environments. Furthermore, the electrochemical activity and the maximum of current density are remarkably higher for samples coated with cells than for uncoated samples, suggesting multiple biotechnological applications in which the transmission with cells is carried out at the electrochemical leve

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    Resolving the subnanometric structure of ultrathin films of poly(3,4-ethylenedioxythiophene) on steel surfaces: A molecular modeling approach  Open access

     Zanuy Gomara, David; Aleman Llanso, Carlos Enrique
    Soft matter
    Vol. 9, num. 48, p. 11634-11644
    DOI: 10.1039/c3sm52477a
    Date of publication: 2013-12-28
    Journal article

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    Poly(3,4-ethylenedioxythiophene), abbreviated PEDOT, is one of the most outstanding electroactive polymers, whose applications cover a wide range of fields from biomedicine to electronic components. In this work the physicochemical properties of nanoconstructs obtained by growing PEDOT chains over steel surfaces are investigated. The structural features of such nanostructures, which had successfully been used to build supercapacitors, are investigated, revealing that the polymeric phase plays a key role in the charge accumulation process. The ultra-structure organization and dynamics of these constructs are explored by molecular simulations and the results are compared with the available experimental data. The outcome of this investigation has offered a detailed vision of the structural features that lead to an extraordinarily efficient charge accumulation. Atomistic models generated using stochastic methods had provided different distributions of polymer chains over a metallic surface. Molecular dynamics simulations performed on such models have demonstrated that the extraordinary capacity for charge accumulation stems from a thin balance between the electrostatic repulsion that polymer chains exercise to each other and the attraction that the counterions present in the electropolymerization exert on those oxidized PEDOT chains. This situation favors the aggregation of the PEDOT chains mediated by the perchlorate ions, which act over them as inter-chain cement and which leads to regular three dimensional organization of chains, regardless of their initial distribution over the metallic surface. At the same time, such inner proximity of the polymer chains when growing upwards forces the capture of perchlorate ions, acting as accumulated charges that could be further released if the PEDOT oxidation state is externally reversed.

    Poly(3,4-ethylenedioxythiophene), abbreviated PEDOT, is one of the most outstanding electroactive polymers, whose applications cover a wide range of fields from biomedicine to electronic components. In this work the physicochemical properties of nanoconstructs obtained by growing PEDOT chains over steel surfaces are investigated. The structural features of such nanostructures, which had successfully been used to build supercapacitors, are investigated, revealing that the polymeric phase plays a key role in the charge accumulation process. The ultra-structure organization and dynamics of these constructs are explored by molecular simulations and the results are compared with the available experimental data. The outcome of this investigation has offered a detailed vision of the structural features that lead to an extraordinarily efficient charge accumulation. Atomistic models generated using stochastic methods had provided different distributions of polymer chains over a metallic surface. Molecular dynamics simulations performed on such models have demonstrated that the extraordinary capacity for charge accumulation stems from a thin balance between the electrostatic repulsion that polymer chains exercise to each other and the attraction that the counterions present in the electropolymerization exert on those oxidized PEDOT chains. This situation favors the aggregation of the PEDOT chains mediated by the perchlorate ions, which act over them as inter-chain cement and which leads to regular three dimensional organization of chains, regardless of their initial distribution over the metallic surface. At the same time, such inner proximity of the polymer chains when growing upwards forces the capture of perchlorate ions, acting as accumulated charges that could be further released if the PEDOT oxidation state is externally reversed.

  • Novel epoxy coating based on DMSO as a green solvent, reducing drastically the volatile organic compound content and using conducting polymers as a nontoxic anticorrosive pigment

     Martí Barroso, Mireia; Molina Pérez, Laura; Aleman Llanso, Carlos Enrique; Armelin Diggroc, Elaine
    ACS Sustainable Chemistry & Engineering
    Vol. 1, num. 12, p. 1609-1618
    DOI: 10.1021/sc400271k
    Date of publication: 2013-12-02
    Journal article

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    This work reports novel anticorrosive epoxy coatings based on safer dimethyl sulfoxide solvent and free of zinc anticorrosive pigment. The latter was replaced by conducting polymers, as nontoxic anticorrosive pigments. The procedure used for their formulation, spectroscopic characterization, thermal and mechanical properties have been discussed and compared with those of conventional epoxy coatings. Furthermore, accelerated and long-term corrosion assays have evidenced that the new epoxy coatings protect steel from chlorine aggressive medium for 2880 h and for 2 years in atmospheric corrosive medium. Therefore, the results evidenced an excellent corrosion resistance, excellent application, and aesthetic appearance of the new coatings. © 2013 American Chemical Society.

    This work reports novel anticorrosive epoxy coatings based on safer dimethyl sulfoxide solvent and free of zinc anticorrosive pigment. The latter was replaced by conducting polymers, as nontoxic anticorrosive pigments. The procedure used for their formulation, spectroscopic characterization, thermal and mechanical properties have been discussed and compared with those of conventional epoxy coatings. Furthermore, accelerated and long- term corrosion assays have evidenced that the new epoxy coatings protect steel from chlorine aggressive medium for 2880 h and for 2 years in atmospheric corrosive medium. Therefore, the results evidenced an excellent corrosion resistance, excellent application, and aesthetic appearance of the new coatings.

  • Nanometric ultracapacitors fabricated using multilayer of conducting polymers on self-assembled octanethiol monolayers

     Aradilla Zapata, David; Perez Madrigal, Maria Del Mar; Estrany Coda, Francisco; Azambuja, Denise S.; Iribarren Laco, Jose Ignacio; Aleman Llanso, Carlos Enrique
    Organic electronics
    Vol. 14, num. 6, p. 1483-1495
    DOI: 10.1016/j.orgel.2013.03.010
    Date of publication: 2013-06
    Journal article

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    Symmetric ultracapacitors have been fabricated considering nanometric 3-layered films made of alternated layers of poly(3,4-ethylenedioxythiophene) (external and internal layers) and polypyrrole (intermediate layer) deposited on steel uncoated and coated with octanethiol self-assembled monolayer. The highest electrochemical and capacitance parameters (i.e. electroactivity, doping level, stored charge, specific capacitance, Coulomb efficiency, energy density and power density) correspond to the ultracapacitor derived from the assembly of 3-layered films deposited on pre-treated steel. Thus, the interface separating the octanethiol monolayer and the most internal layer of the 3-layered film produces a very favorable interaction, which promotes important electrochemical benefits similar to those found for the interfaces in conventional multilayered films. Moreover, the pre-treatment of the steel electrode enhances the roughness and porosity of the film deposited on it, transmitting this effect layer-by-layer. Structural and morphological characteristics, which have been characterized using scanning electron microscopy and atomic force microscopy, have been related with the electrochemical and capacitance properties of the ultracapacitors.

    Symmetric ultracapacitors have been fabricated considering nanometric 3-layered films made of alternated layers of poly(3,4-ethylenedioxythiophene) (external and internal layers) and polypyrrole (intermediate layer) deposited on steel uncoated and coated with octanethiol self-assembled monolayer. The highest electrochemical and capacitance parameters (i.e. electroactivity, doping level, stored charge, specific capacitance, Coulomb efficiency, energy density and power density) correspond to the ultracapacitor derived from the assembly of 3-layered films deposited on pre-treated steel. Thus, the interface separating the octanethiol monolayer and the most internal layer of the 3-layered film produces a very favorable interaction, which promotes important electrochemical benefits similar to those found for the interfaces in conventional multilayered films. Moreover, the pre-treatment of the steel electrode enhances the roughness and porosity of the film deposited on it, transmitting this effect layer-by-layer. Structural and morphological characteristics, which have been characterized using scanning electron microscopy and atomic force microscopy, have been related with the electrochemical and capacitance properties of the ultracapacitors.

  • Engineering strategy to improve peptide analogs: from structure-based computational design to tumor homing

     Zanuy Gomara, David; Sayago García, Francisco Javier; Revilla Lopez, Guillermo; Ballano Ballano, María Gema; Agemy, Lilach; Kotamraju, Venkata Ramana; Jimenez, Ana I.; Cativiela, Carlos; Nussinov, Ruth; Sawvel, April M.; Ruoslahti, Erkki; Stucky, Galen; Aleman Llanso, Carlos Enrique
    Journal of computer-aided molecular design
    Vol. 27, num. 1, p. 31-43
    DOI: 10.1007/s10822-012-9623-5
    Date of publication: 2013-01
    Journal article

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    We present a chemical strategy to engineer analogs of the tumor-homing peptide CREKA (Cys-Arg-Glu-Lys-Ala), which binds to fibrin and fibrin-associated clotted plasma proteins in tumor vessels (Simberg et al. in Proc Natl Acad Sci USA 104:932-936, 2007) with improved ability to inhibit tumor growth. Computer modeling using a combination of simulated annealing and molecular dynamics were carried out to design targeted replacements aimed at enhancing the stability of the bioactive conformation of CREKA. Because this conformation presents a pocket-like shape with the charged groups of Arg, Glu and Lys pointing outward, non-proteinogenic amino acids alpha-methyl and N-methyl derivatives of Arg, Glu and Lys were selected, rationally designed and incorporated into CREKA analogs. The stabilization of the bioactive conformation predicted by the modeling for the different CREKA analogs matched the tumor fluorescence results, with tumor accumulation increasing with stabilization.

    We present a chemical strategy to engineer analogs of the tumor-homing peptide CREKA (Cys-Arg- Glu-Lys-Ala), which binds to fibrin and fibrin-associated clotted plasma proteins in tumor vessels (Simberg et al. in Proc Natl Acad Sci USA 104:932–936, 2007) with improved ability to inhibit tumor growth. Computer mod- eling using a combination of simulated annealing and molecular dynamics were carried out to design targeted replacements aimed at enhancing the stability of the bio- active conformation of CREKA. Because this conforma- tion presents a pocket-like shape with the charged groups of Arg, Glu and Lys pointing outward, non-proteinogenic amino acids a -methyl and N -methyl derivatives of Arg, Glu and Lys were selected, rationally designed and incor- porated into CREKA analogs. The stabilization of the bioactive conformation predicted by the modeling for the different CREKA analogs matched the tumor fluorescence results, with tumor accumulation increasing with stabil- ization. Here we report the modeling, synthetic procedures, and new biological assays used to test the efficacy and utility of the analogs. Combined, our results show how studies based on multi-disciplinary collaboration can con- verge and lead to useful biomedical advances

  • Synergy of the I-/I-3(-) redox pair in the capacitive properties of nanometric poly(3,4-ethylenedioxythiophene)

     Aradilla Zapata, David; Estrany Coda, Francisco; Aleman Llanso, Carlos Enrique
    Organic electronics
    Vol. 14, num. 1, p. 131-142
    DOI: 10.1016/j.orgel.2012.10.026
    Date of publication: 2013-01
    Journal article

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  • Examining the formation of specific interactions between poly(3,4-ethylenedioxythiophene) and nucleotide bases

     Zanuy Gomara, David; Teixeira Dias, Fábio; Del Valle Mendoza, Luis Javier; Poater, Jordi; Solà, Miquel; Aleman Llanso, Carlos Enrique
    RSC Advances
    Vol. 3, num. 8, p. 2639-2649
    DOI: 10.1039/c2ra22640e
    Date of publication: 2013-02-28
    Journal article

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    he formation of specific interaction between poly(3,4-ethylenedioxythiophene) (PEDOT) and adenine (A), cytosine (C) and thymine (T) single stranded homonucleotides has been investigated, complementing our previous investigation on complexes formed by PEDOT and guanine (G) homonucleotide (B. Teixeira-Dias et al, Soft Matter, 2011, 7, 9922¿9932). Results derived from UV-vis and FTIR spectroscopy suggest that A and, especially, C homonucleotides form adducts dominated by non-specific electrostatic interactions, while complexes with T homonucleotides show a behavior that differ from those found for A-, C- and G-containing systems. Results provided by molecular dynamics simulations were consistent with these experimental observations. Thus, specific interactions are much less abundant in A- and C-containing complexes than in those involving G. Moreover, simulations allowed us to detect a structural re-organization in the T-containing complexes, which occurs after their initial formation. This has been attributed to the optimization of electrostatic interactions rather than to the formation of new specific interactions, as was previously found in complexes with G. From the analysis of the interaction of the different nucleotides with an EDOT molecule it is concluded that the most stabilizing specific interaction corresponds to the formation of N-HOEDOT hydrogen bonds. Stabilization comes from electrostatic interactions, although the covalent contribution is non negligible.

  • POLIMEROS CONDUCTORES Y SUS DERIVADOS HIBRIDOS CON APLICACIONES AVANZADAS

     Estrany Coda, Francisco; Armelin Diggroc, Elaine; Zanuy Gomara, David; Iribarren Laco, Jose Ignacio; Sanchez Jimenez, Margarita; Aleman Llanso, Carlos Enrique
    Competitive project

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  • Revestimientos a base de sílica e ácido fosfônico para proteção anticorrosiva da liga de alumínio AA2024-T3  Open access

     Dalmoro, Viviane
    Universitat Politècnica de Catalunya
    Theses

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    La aleación de aluminio AA2024 , que se utiliza ampliamente en la industria aeronáutica, debido a las microestructurasheterogéneos intencionadamente diseñadas para optimizar las propiedades mecánicas . es muy susceptible a la corrosiónlocalizada. Para prevenir la corrosión diversos tratamientos de superficie han sido investigados para reemplazar eltratamiento con cromato, en este sentido las películas a base de sílice constituyen una alternativa prometedora.El objetivo de este trabajo es la obtención, desarrollo y caracterización de películas de viniltrimetoxisilano (VTMS) combinadocon tetraetilortosilicato (TE OS) o y-glicidiloxipropiltrimetoxisilano (GPTMS) en presencia y ausencia de etilendiaminatetrametilenofosfonico (EDTPO) como tratamientos previos contra la corrosión de la aleación de aluminio AA2024-T3 enNaCI 0,05 mol L- 1. Por otro lado, se investigó el efecto de la adición de arcilla en la matriz híbrida y la presencia denanoparticulas de sílice a la matriz sol-gel VfMS/GPTMS que contienen EDTPO. Se evaluaron diferentes proporciones deconcentraciones de sil ice y precursores de ácido fosfónico y arcilla. Las propiedades anticorrosivas de la aleaciónrecubierta con los filmes de sílice modificados se estudiaron mediante espectroscopia de impedancia electroquímica (EIS)después de diferentes tiempos de inmersión. La estructura química de los filmes y de las soluciones de partida secaracterizaron por espectroscopia de infrarrojo (FT-IR), mientras que la morfología y la composición de las películas seexaminaron por microscopía electrónica de barrido (SEM), espectroscopia de energía dispersiva de rayos-X (EDX) y/oespectroscopia de fotoelectrones de rayos-X (XPS). Los resultados obtenidos son positivos para la protección contra lacorrosión del AA2024 con el uso de los recubrimientos preparados con el método sol-gel y modificado con ácido fosfónico.Después de la optimización de los recubrimientos de sílice y sílice/ácido fosfónico, se aplicó los mejores sistemas comotratamientos anticorrosivos y promotores de la adherencia de una pintura epoxi de imprimación. Los ensayos de corrosiónacelerados permitieron comprobar la acción beneficiosa de la capa de sílice como sistema de anclaje de la pintura epoxi.Se encontró que el sistema compuesto por: la silica/ pintura epoxi, silica +ácido fosfónico 1 pintura epoxi y sílica 1 pinturaepoxi modificada con polímero conductor proporcionan una protección eficaz contra la corrosión de la aleación AA2024-T3.Lloc 1 Barcelona Data 02/0912013Signatura iL._.

    Tesi realitzada en co-tutela (Universidade Federal do Rio Grande do Sul -Brasil- i Universtitat Politécnica de Catalunya)

    The aluminum alloy AA2024-T3, u sed extensively in the aerospace industry, dueto the heterogeneous microstructures intentionally designed to optím ize the m echanical properties, is very susceptible to localízed corros ion. In order to preven! the corros ion several surface treatments have been investigated to replace the chromate treatment and, in thís way, sílica based films can be regarded as a promising alternatíve. The aim ofthis work ís the obtaíníng, development and characterízation offilms vinyltrímethoxysilane (VfMS) combíned wíth tetraethylorthosílícate (TEOS) or y-glycídoxypropyltrímethoxysílane in the presence and absence of ethylenedíamíne tetrametílene phosphoníc a cid (EDTPO) as pretreatments agaínst corros ion of alumínum alloy AA2024-T3 in NaCI 0.05 mol L-1. Furthermore, ít was investígated the effect of addíng clayto sol-gel hybríd matríx and sílica nanoparticles to the matrix of VfMS/GPTMS films containing EDTPO. Different ratios of precursor and silica concentrations of phosphonic acid andel ay were evaluated. The anticorrosíve properties ofthe alloycoated with the modífied sílíca films were studied using electrochemical impedance spectroscopy (El S) after different immersion times. The chemical structure ofthe films and the starting solutíons were characterízed by ínfrared spectroscopy (FT-IR), whíle the morphology and com posítion of the film s were examíned on usíng Scanníng Electron Microscopy (SEM), Energy Dispersive Spectroscopy X-Ray (E O X) and 1 or Photoelectron Spectroscopy X-Ray (XPS). The results obtained were posítive for the corros ion protectíon of AA2024 using the coatings obtaíned by the sol-gel method and modífied with phosphonic a cid. Mer optimization ofthe coatings of silica and silica/phosphonic acid we applied !he bes! systems as anticorrosíve pretreatments and adhesion promoters for one epoxy primer paínt. Accelerated corros ion tests allowed check the beneficia! action ofthe silica layer as anchoring system for the epoxy paint. lt was found that the systems composed by: silica/epoxy paint and silica + phosphonic acid/epoxy paint and silica/ epoxy paint modified with conducting polymer provide effective corros ion protection for the alloy AA2024-T3. The results deríved from the present thesis have been accepted or have been sent for publicatíon in ínternational journals and also reported in sorne international congresses, as we point below: [1] V. Dalmoro, J . H. Z. dos Santos, E. Armelin, C. Alemán, O. S. Azambuja, Phosphonic acid/silica-based films: A potential treatm en! for corros ion protection, Corros. Sci. 60 (2012) 173-180. [2] V. Dalmoro, J. H. Z. dos Santos, E. Armelín, C. Alemán, D. S. Azambuja, A synergistic combination oftetraethylorthosilicate and multiphosphonic acid offers excellent corros ion protectíon to AA1100 aluminum alloy, Appl. Surf. Sci . 273 (2013) 758-768. [3] V. Dalmoro, J . H. Z. dos Santos, l. M. I.M. Baibich, E. Armelin, C. Alemán, O. S. Azambuja Cooperatíve effect between VfMS/TEOS and phosphonic acid for corros ion protection of AA2024, Submitted, 2013. [4] V. Dalmoro, J. H. Z. dos Santos, E. Armelín, C. Alemán, D. S. Azambuja, Organosílane and Montmorílloníte-based hybríd films produced by sol-gel: A potencial treatrnent for corros ion of AA2024, Manuscript on preparation, 2013. [5] V. Dalmoro, J. H. Z. dos Santos, E. Armelin, C. Alemán, D. S. Azambuja, Characterization ofTEOS/phosphoníc acíd films, 63rd Annual Meeting of lnternatíonal Socíety of Electrochem ís try 19-24 August 2012, Prague, Chech Republíc

    A liga de alumínio AA2024-T3, extensivamente empregada na indústria aeronáutica, devido as microestruturas heterogêneas intencionalmente desenvolvidas para otimizar as propriedades mecânicas é susceptível a corrosão localizada. Com o intuito de prevenir a corrosão vários tratamentos de superfície têm sido investigados para substituir o tratamento de cromatização, e os filmes a base de sílica podem ser considerados como uma alternativa promissora. O objetivo deste trabalho é a obtenção, desenvolvimento e caracterização de filmes de viniltrimetoxisilano (VTMS) combinado com tetraetilortosilicato (TEOS) ou γ-glicidiloxipropiltrimetoxisilano (GPTMS) na presença e na ausência de ácido 1,2-diaminoetanotetrametileno fosfônico (EDTPO) como pré-tratamentos contra a corrosão da liga de alumínio AA2024-T3 em NaCl 0,05 mol L-1. Além disso, foi investigado o efeito da adição de argila na matriz híbrida sol-gel e de nanopartículas de sílica na matriz VTMS/GPTMS contendo EDTPO. Diferentes razões de precursores de sílica e concentrações de ácido fosfônico e de argila foram avaliadas. As propriedades anticorrosivas da liga com os filmes foram estudadas usando espectroscopia de impedância eletroquímica (EIS) após diferentes tempos de imersão. A estrutura química dos filmes e das soluções de partida foi determinada por espectroscopia de infravermelho (FT-IR), enquanto que a morfologia e composição dos filmes foram examindas através de Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Energia Dispersiva de Raios-X (EDX) e/ou Espectroscopia Fotoeletrônica de Raios-X (XPS). Os resultados alcançados foram satisfatórios para a proteção contra a corrosão da AA2024 utilizando os revestimentos obtidos a partir do processo sol-gel e modificados com ácido fosfônico. Após a otimização dos revestimentos de sílica e de sílica/ácido fosfônicos estes sistemas foram avaliados como pré-tratamentos anticorrosivos e promotores de adesão de pintura epóxi comercial. Ensaios acelerados de corrosão permitiram comprovar a ação benéfica da camada de sílica como sistema de ancoragem da pintura epóxi. Foi verificado que os sistemas constituídos por sílica/pintura epóxi, sílica + ácido fosfônico/pintura epóxi e sílica/pintura epóxi modificada com polímero condutor propiciam uma efetiva proteção contra a corrosão da AA2024-T3.

    La aleación de aluminio AA2024-T3, que se utiliza ampliamente en la industria aeronáutica, debido a las microestructuras heterogéneas intencionadamente diseñadas para optimizar las propiedades mecánicas, es muy susceptible a la corrosión localizada. Para prevenir la corrosión diversos tratamientos de superficie han sido investigados para reemplazar el tratamiento con cromato, en este sentido las películas a base de sílice constituyen una alternativa prometedora. El objetivo de este trabajo es la obtención, desarrollo y caracterización de películas de viniltrimetoxisilano (VTMS) combinado con tetraetilortosilicato (TEOS) o γ-glicidiloxipropiltrimetoxisilano (GPTMS) en presencia y ausencia de ácido etilendiamina tetrametilenofosfônico (EDTPO) como tratamientos previos contra la corrosión de la aleación de aluminio AA2024-T3 en NaCl 0,05 mol L- 1. Por otro lado, se investigó el efecto de la adición de arcilla en la matriz híbrida y la presencia de nanopartículas de sílice a la matriz sol-gel VTMS/GPTMS que contienen EDTPO. Se evaluaron diferentes proporciones de concentraciones de sílice y precursores de ácido fosfónico y arcilla. Las propiedades anticorrosivas de la aleación recubierta con los filmes de sílice modificados se estudiaron mediante espectroscopia de impedancia electroquímica (EIS) después de diferentes tiempos de inmersión. La estructura química de los filmes y de las soluciones de partida se caracterizaron por espectroscopia de infrarrojo (FT-IR), mientras que la morfología y la composición se examinaron por microscopía electrónica de barrido (SEM), espectroscopia de energía dispersiva de rayos-X (EDX) y/o espectroscopia de fotoelectrones de rayos-X (XPS). Los resultados obtenidos son positivos para la protección contra la corrosión del AA2024-T3 con el uso de los recubrimientos preparados con el método sol-gel y modificado con ácido fosfónico. Después de la optimización de los recubrimientos de sílice y sílice/ácido fosfónico, se aplicó los mejores sistemas como tratamientos anticorrosivos y promotores de la adherencia de una pintura epoxi de imprimación. Los ensayos de corrosión acelerados permitieron comprobar la acción beneficiosa de la capa de sílice como sistema de anclaje de la pintura epoxi. Se encontró que los sistemas compuestos por: la sílica/pintura epoxi, sílica + ácido fosfónico/pintura epoxi y sílica/pintura epoxi modificada con polímero conductor proporcionan una protección eficaz contra la corrosión de la aleación AA2024-T3.

  • Formulation of anticorrosive paints employing conducting polymers  Open access

     Martí Barroso, Mireia
    Universitat Politècnica de Catalunya
    Theses

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    El propósito de la presente tesis es preparar una serie de recubrimientos protectores empleando polímeros conductores(CPs) como inhibidores de la corrosión. El uso de pinturas orgánicas es el método más empleado para la prevención de lacorrosión. Los recubrimientos anticorrosivos forman una clase de sistemas de alto rendimiento con una amplia variedad deaplicaciones y pueden ser clasificados en dos grandes grupos: recubrimientos de altas prestaciones y recubrimientos desuaves prestaciones. El primero de ellos es el que se emplea en estructuras expuestas a ambientes muy agresivos, talescomo: plataformas petrolíferas, puentes, plantas industriales químicas, contenedores, barcos, entre otros; y el último es elque se suele emplear en el exterior de ambientes industriales, ambientes urbanos, casas, oficinas, entre otros.La presente tesis consiste en un compendio de las siguientes etapas del trabajo y resultados:1. Preparación de CPs nanoestructurados para inhibición de la corrosión: Estudio de la habilidad del Poli(N-metilpirrol) paraformar estructuras nanoestructuradas y la actuación de éstas como aditivo anticorrosivo en recubrimientos orgánicos.2. Sustitución parcial del zinc metálico en polvo habitualmente empleado en pinturas de altas prestaciones, por unapequeña cantidad de CP: Estudio del uso de pequeñas concentraciones de polianilina sal emeraldina (PAni-EB), comosustituto parcial del zinc metálico en polvo, en pinturas de imprimación epoxi marinas, con el objetivo de mantener lainhibición a la corrosión.3. Evaluación de pigmentos anticorrosivos amigables con el medio ambiente para pinturas de imprimación alquídicas:Estudio de la sustitución de una elevada concentración de fosfato de zinc, generalmente empleado en recubrimientos desuaves prestaciones, por una concentración muy baja de PAni-EB (forma no-dopada), PAni-ES (forma dopada) y un derivadodel politiofeno (parcialmente dopado) en un recubrimiento alquídico, y el estudio de sus capacidades protectorasempleando ensayos de corrosión acelerados.4. Preparación de una nueva pintura epoxi, basada en DMSO como disolvente ecológico y libre de pigmento anticorrosivo dezinc, y su aplicación para la protección de acero al carbono: Formulación y evaluación de una nueva pintura epoxi basada enDMSO como solvente y empleando PAni-EB y poli[2, 2¿-(3-metilacetato)tiofeno] como nuevos pigmentos anticorrosivos.Todos los resultados obtenidos en la presente tesis han sido aceptados o han sido enviados para publicación en revistasinternacionales; además, algunos resultados han sido divulgados recientemente en congresos internacionales, tal y comose describe abajo:1. M. Martí, G. Fabregat, F. Estrany, C. Alemán, E. Armelin, ¿Nanostructured conducting polymer for dopamine detection¿, J.Mater. Chem., 2010, 20, 10652-10660.2. E. Armelin, M. Martí, F. Liesa, J.I. Iribarren, C. Alemán, ¿Partial replacement of metallic zinc dust in heavy duty protectivecoatings by conducting polymer¿, Prog. Org. Coat., 2010, 69, 26-30.3. M. Martí, G. Fabregat, D.S. Azambuja, C. Alemán, E. Armelin, ¿Evaluation of an environmentally friendly anticorrosivepigment for alkyd primer¿, Prog. Org. Coat., 2012, 73, 321¿329.4. M. Martí, L. Molina, C. Alemán, E. Armelin, ¿Replacement of toxic solvents and anticorrosive pigments used in solvent-borneepoxy coatings by safer functional organic compounds¿, enviado para publicación en Journal of Hazardous Materials, 2013.5. M. Martí, E. Armelin, J. Iribarren, C. Alemán. Soluble polythiophenes as anticorrosive additives for marine epoxy paints¿,enviado para publicación en Materials and Corrosion, 2013.6. G. Fabregat, M. Martí, F. Estrany, C. Alemán, E. Armelin, E-MRS 2010 Spring Meeting. 2010, Strasbourg, France.7. E. Armelin, M. Martí, F. Estrany, C. Alemán, 12th Mediterranean Congress of Chemical Engineering: shaping the future ofchemical engineering. 2011, Barcelona, Spain

    The intention and purpose of the present thesis is to prepare a series of protective coatings using some conducting polymers (CPs) as corrosion inhibitors. The use of organic paints is the most common method for corrosion prevention. Anticorrosive coatings form a class of high-performance systems with a very wide range of applications and being classified in two broad groups: heavy-duty coatings, for high performance, and light-duty coatings, for medium performance. The first class being required for highly aggressive medium, like oil platforms, bridges, chemical industry plants, containers, shipping, and others; the late being employed mainly for outside industrial environments, urban environments, houses, offices, and others. This thesis consists of an overview and a compendium of the following work stages and results: 1. Preparation of nanostructured CPs for corrosion inhibition: Study of the ability of poly(N-methylpyrrole) to form nanostructures and the performance of such nanostructures when act as anticorrosive additive of organic coatings. 2. Partial replacement of metallic zinc dust usually employed in heavy duty protective coatings, by a small concentration of CPs: Study of the use of a small amount of polyaniline emeraldine salt as a partial substitute of metallic zinc dust in marine epoxy primers in order to maintain corrosion inhibition. 3. Evaluation of an environmentally friendly anticorrosive pigment for alkyd priming: Study of the substitution of a high concentration of zinc phosphate, commonly employed in light-duty coatings, by a very low concentration of polyaniline emeraldine base (undoped form), polyaniline emeraldine salt (doped form) and an eco-friendly polythiophene derivative (partially oxidized) in an alkyd coatings and the study of their protective performance using accelerated corrosion assays. 4. Preparation of a novel epoxy coating, based on DMSO as green solvent and free of zinc anticorrosive pigment, and its application on carbon steel protection: Formulation and evaluation of a novel anticorrosive epoxy coating based on DMSO solvent and free of zinc, using polyaniline emeraldine base and poly[2,2’-(3-methylacetate)thiophene] as anticorrosive pigments. All the results derived from the present thesis have been accepted or have been sent for publication in international journals and also reported in some international congresses, as we point below: 1. M. Martí, G. Fabregat, F. Estrany, C. Alemán, E. Armelin, “Nanostructured conducting polymer for dopamine detection”, J.Mater. Chem., 2010, 20, 10652-10660. 2. E. Armelin, M. Martí, F. Liesa, J.I. Iribarren, C. Alemán, “Partial replacement of metallic zinc dust in heavy duty protective coatings by conducting polymer”, Prog. Org. Coat., 2010, 69, 26-30. 3. M. Martí, G. Fabregat, D.S. Azambuja, C. Alemán, E. Armelin, “Evaluation of an environmentally friendly anticorrosive pigment for alkyd primer”, Prog. Org. Coat., 2012, 73, 321–329. 4. M. Martí, L. Molina, C. Alemán, E. Armelin, “Replacement of toxic solvents and anticorrosive pigments used in solvent-borne epoxy coatings by safer functional organic compounds”, submitted for publication in Journal of Hazardous Materials, 2013. 5. M. Martí, E. Armelin, J. Iribarren, C. Alemán. Soluble polythiophenes as anticorrosive additives for marine epoxy paints”, submitted for publication in Materials and Corrosion, 2013. 6. G. Fabregat, M. Martí, F. Estrany, C. Alemán, E. Armelin, “Nanostructured Poly(N-Methylpyrrole) and Its Application in Dopamine Detection”, E-MRS 2010 Spring Meeting. 2010, Strasbourg, France. 7. E. Armelin, M. Martí, F. Estrany, C. Alemán, “Environmentally friendly anticorrosive additive to replace zinc and its compounds in alkyd and epoxy primers”, 12th Mediterranean Congress of Chemical Engineering: shaping the future of chemical engineering. 2011, Barcelona, Spain

    El propósito de la presente tesis es preparar una serie de recubrimientos protectores empleando polímeros conductores (CPs) como inhibidores de la corrosión. El uso de pinturas orgánicas es el método más empleado para la prevención de la corrosión. Los recubrimientos anticorrosivos forman una clase de sistemas de alto rendimiento con una amplia variedad de aplicaciones y pueden ser clasificados en dos grandes grupos: recubrimientos de altas prestaciones y recubrimientos de suaves prestaciones. El primero de ellos es el que se emplea en estructuras expuestas a ambientes muy agresivos, tales como: plataformas petrolíferas, puentes, plantas industriales químicas, contenedores, barcos, entre otros; y el último es el que se suele emplear en el exterior de ambientes industriales, ambientes urbanos, casas, oficinas, entre otros. La presente tesis consiste en un compendio de las siguientes etapas del trabajo y resultados: 1. Preparación de CPs nanoestructurados para inhibición de la corrosión: Estudio de la habilidad del Poli(N-metilpirrol) para formar estructuras nanoestructuradas y la actuación de éstas como aditivo anticorrosivo en recubrimientos orgánicos. 2. Sustitución parcial del zinc metálico en polvo habitualmente empleado en pinturas de altas prestaciones, por una pequeña cantidad de CP: Estudio del uso de pequeñas concentraciones de polianilina sal emeraldina (PAni-EB), como sustituto parcial del zinc metálico en polvo, en pinturas de imprimación epoxi marinas, con el objetivo de mantener la inhibición a la corrosión. 3. Evaluación de pigmentos anticorrosivos amigables con el medio ambiente para pinturas de imprimación alquídicas: Estudio de la sustitución de una elevada concentración de fosfato de zinc, generalmente empleado en recubrimientos de suaves prestaciones, por una concentración muy baja de PAni-EB (forma no-dopada), PAni-ES (forma dopada) y un derivado del politiofeno (parcialmente dopado) en un recubrimiento alquídico, y el estudio de sus capacidades protectoras empleando ensayos de corrosión acelerados. 4. Preparación de una nueva pintura epoxi, basada en DMSO como disolvente ecológico y libre de pigmento anticorrosivo de zinc, y su aplicación para la protección de acero al carbono: Formulación y evaluación de una nueva pintura epoxi basada en DMSO como solvente y empleando PAni-EB y poli[2, 2’-(3-metilacetato)tiofeno] como nuevos pigmentos anticorrosivos. Todos los resultados obtenidos en la presente tesis han sido aceptados o han sido enviados para publicación en revistas internacionales; además, algunos resultados han sido divulgados recientemente en congresos internacionales, tal y como se describe abajo: 1. M. Martí, G. Fabregat, F. Estrany, C. Alemán, E. Armelin, “Nanostructured conducting polymer for dopamine detection”, J. Mater. Chem., 2010, 20, 10652-10660. 2. E. Armelin, M. Martí, F. Liesa, J.I. Iribarren, C. Alemán, “Partial replacement of metallic zinc dust in heavy duty protective coatings by conducting polymer”, Prog. Org. Coat., 2010, 69, 26-30. 3. M. Martí, G. Fabregat, D.S. Azambuja, C. Alemán, E. Armelin, “Evaluation of an environmentally friendly anticorrosive pigment for alkyd primer”, Prog. Org. Coat., 2012, 73, 321–329. 4. M. Martí, L. Molina, C. Alemán, E. Armelin, “Replacement of toxic solvents and anticorrosive pigments used in solvent-borne epoxy coatings by safer functional organic compounds”, enviado para publicación en Journal of Hazardous Materials, 2013. 5. M. Martí, E. Armelin, J. Iribarren, C. Alemán. Soluble polythiophenes as anticorrosive additives for marine epoxy paints”, enviado para publicación en Materials and Corrosion, 2013. 6. G. Fabregat, M. Martí, F. Estrany, C. Alemán, E. Armelin, E-MRS 2010 Spring Meeting. 2010, Strasbourg, France. 7. E. Armelin, M. Martí, F. Estrany, C. Alemán, 12th Mediterranean Congress of Chemical Engineering: shaping the future of chemical engineering. 2011, Barcelona, Spain.

  • Atomistic organization and characterization of tube-like assemblies comprising peptide-polymer conjugates: computer simulation studies

     Bertran Cànovas, Oscar; Curcó Cantarell, David; Zanuy Gomara, David; Aleman Llanso, Carlos Enrique
    FARADAY DISCUSSIONS
    Vol. 166, p. 59-82
    DOI: 10.1039/c3fd00079f
    Date of publication: 2013
    Journal article

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    The structure and stability of the nanotube obtained by assembling peptide-polymer conjugates consisting of two poly(n-butyl acrylate) blocks coupled to the cyclic (D-alt-L)-octapeptide cyc[(L-Gln-D-Ala-L-Lys-D-Ala)(2)], have been investigated at the molecular level using atomistic molecular dynamics simulations. The effect of the wrapping polymer shells in the tube-like core, which consists of stacked beta-sheet cyclopeptides, has been examined by simulating assemblies of both unsubstituted cyclopeptides, and conjugates in chloroform and N,N-dimethylformamide solutions. Furthermore, the influence of the environment has been investigated by comparing conjugate assemblies in solution with those deposited on mica. In addition, nanotubes stabilized by beta-sheet-like hydrogen bonds between both parallel and antiparallel oriented cyclopeptides have been considered in all cases. The results, which have been analysed in terms of energy contributions, partial radial distribution functions, inter-subunit distances, shape of the cyclopeptide ring, internal van der Waals diameters, and both height and width of the nanostructures deposited on mica, have provided important microscopic insights. For example, analysis of both the energy terms and the structural dynamics obtained for the different assemblies indicate that the mica surface interacts more favourably with the parallel assembly than with the antiparallel ones, whereas the only configuration that is structurally stable in solution is the latter. Furthermore, adsorption onto the solid substrate produces a small deformation of the cylindrical molecular system.

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    Nanomembranes and nanofibers from biodegradable conducting polymers  Open access

     Llorens Domenjo, Elena; Armelin Diggroc, Elaine; Perez Madrigal, Maria Del Mar; Del Valle Mendoza, Luis Javier; Aleman Llanso, Carlos Enrique; Puiggali Bellalta, Jorge
    Polymers
    Vol. 5, num. 3, p. 1115-1157
    DOI: 10.3390/polym5031115
    Date of publication: 2013-09-01
    Journal article

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    This review provides a current status report of the field concerning preparation of fibrous mats based on biodegradable (e. g., aliphatic polyesters such as polylactide or polycaprolactone) and conducting polymers (e. g., polyaniline, polypirrole or polythiophenes). These materials have potential biomedical applications (e. g., tissue engineering or drug delivery systems) and can be combined to get free-standing nanomembranes and nanofibers that retain the better properties of their corresponding individual components. Systems based on biodegradable and conducting polymers constitute nowadays one of the most promising solutions to develop advanced materials enable to cover aspects like local stimulation of desired tissue, time controlled drug release and stimulation of either the proliferation or differentiation of various cell types. The first sections of the review are focused on a general overview of conducting and biodegradable polymers most usually employed and the explanation of the most suitable techniques for preparing nanofibers and nanomembranes (i.e., electrospinning and spin coating). Following sections are organized according to the base conducting polymer (e. g., Sections 4-6 describe hybrid systems having aniline, pyrrole and thiophene units, respectively). Each one of these sections includes specific subsections dealing with applications in a nanofiber or nanomembrane form. Finally, miscellaneous systems and concluding remarks are given in the two last sections.

    This review provides a current status report of the field concerning preparation of fibrous mats based on biodegradable (e. g., aliphatic polyesters such as polylactide or polycaprolactone) and conducting polymers (e. g., polyaniline, polypirrole or polythiophenes). These materials have potential biomedical applications (e. g., tissue engineering or drug delivery systems) and can be combined to get free-standing nanomembranes and nanofibers that retain the better properties of their corresponding individual components. Systems based on biodegradable and conducting polymers constitute nowadays one of the most promising solutions to develop advanced materials enable to cover aspects like local stimulation of desired tissue, time controlled drug release and stimulation of either the proliferation or differentiation of various cell types. The first sections of the review are focused on a general overview of conducting and biodegradable polymers most usually employed and the explanation of the most suitable techniques for preparing nanofibers and nanomembranes (i.e., electrospinning and spin coating). Following sections are organized according to the base conducting polymer (e. g., Sections 4-6 describe hybrid systems having aniline, pyrrole and thiophene units, respectively). Each one of these sections includes specific subsections dealing with applications in a nanofiber or nanomembrane form. Finally, miscellaneous systems and concluding remarks are given in the two last sections.

  • Computer simulation of fifth generation dendronized polymers: impact of charge on internal organization

     Bertran Cànovas, Oscar; Zhang, Baozhong; Schlüter, A. Dieter; Kröger, Martin; Aleman Llanso, Carlos Enrique
    Journal of physical chemistry B
    Vol. 117, num. 19, p. 6007-6017
    DOI: 10.1021/jp402695g
    Date of publication: 2013-05-16
    Journal article

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    The internal organization of a fifth-generation dendronized polymer (PG5) has been investigated by atomistic molecular dynamics simulations in a vacuum. This study reveals an exceptional behavior of PG5 within the homologous series of g-generation PGg polymers. Three molecular configurations, which present a heterogeneous distribution of dendrons and an amount of backfolding lower than PG4 and PG6, have been obtained for PG5. The highest stability and closest agreement with available experimental data corresponds to a helical conformation characterized by a pitch of about 30 A, thickness of 105 A, and average density of 0.861 g/cm3. While small angle neutron scattering studies of PG5 in solution show a constant radial density distribution around the backbone, we here in our vacuum studies find a cylindrical volume element of sharply reduced density reminiscent of a pore. This neutral PG5 was compared with its charged deprotected analogue, dePG5 in water, to see in as much the positive charges in the periphery of this macromolecule would affect its conformational behavior. During deprotection of PG5, the tert-butyloxycarbonyl protected amine groups are converted into ammonium, mimicking the experimental situation during a divergent synthesis procedure. The repulsive interactions among the positively charged ammonium groups are responsible for a huge (30%) reduction of the average density and a small (1%) increase of elongation of the helical backbone, which results in a structure with a spongy appearance. Also here, we find a reduced dendron density near the backbone which is compensated for by the pore being filled with water. 2013 American Chemical Society

  • Polypyrrole derivatives as solvent vapor sensors

     Aradilla Zapata, David; Estrany Coda, Francisco; Aleman Llanso, Carlos Enrique
    RSC Advances
    Vol. 3, p. 20545-20558
    DOI: 10.1039/c3ra41067f
    Date of publication: 2013-09
    Journal article

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    Quantum mechanical calculations have been carried out to investigate the affinity of polypyrrole (PPy) and poly[N-(2-cyanoethyl)pyrrole] (PNCEPy) towards molecules from vapors of different solvents (i.e. water, methanol, acetonitrile and chloroform). Results show that neutral cyano-containing polymers interact more favorably with both water and methanol than neutral PPy, whereas these affinities are the opposite for materials in the oxidized state. Moreover, addition of the geometric distortion contributions and the thermodynamic corrections to the interaction energies allow us to conclude that the binding affinities between the two neutral polymers and small polar molecules in the vapor phase are similar, in excellent agreement with experimental information. On the other hand, the affinity of the two conducting polymers towards chloroform is relatively poor independently of the oxidation state, while acetonitrile interacts more favorably with the N¿H of PPy than with the cyano group. The influence of both the vapor molecules and the solvent on the geometric parameters (i.e. dihedral angles, inter-ring bond lengths and bond length alternation pattern) and electronic properties (i.e. ionization potential and p¿p* lowest transition energy) have been evaluated using different approaches, which include time-dependent density functional theory calculations.

  • Hybrid materials consisting of an all-conjugated polythiophene backbone and grafted hydrophilic poly(ethylene glycol) chains

     Bendrea, Anca Dana; Fabregat Jove, Georgina; Cianga, Luminita; Estrany Coda, Francisco; Del Valle Mendoza, Luis Javier; Cianga, Ioan; Aleman Llanso, Carlos Enrique
    Polymer Chemistry
    Vol. 4, num. 9, p. 2709-2723
    DOI: 10.1039/C3PY00029J
    Date of publication: 2013-03-01
    Journal article

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    Organic hybrid materials consisting of an all-conjugated polythiophene backbone and well-defined poly(ethylene glycol) (PEG) grafted chains have been prepared by anodic polymerization of chemically synthesized macromonomers. The latter consist of a pentathiophene sequence in which the central ring bears a PEG chain with Mw = 1000 or 2000 at the 3-position. The influence of the polymerization potential, the length of the PEG branches and the dopant agent on the structure and properties of the graft copolymers has been examined. The chemical structure of the grafted materials has been corroborated by FTIR and X-ray photoelectron spectroscopies. Scanning electron microscopy and atomic force microscopy studies reveal that the morphology and topography of these materials are influenced by the above mentioned factors, even though homogeneous films showing a compact distribution of nanoaggregates, very flat surfaces (i.e. roughness < 15 Å) and nanometric thickness (i.e. 100¿500 nm) were obtained in all cases. Cyclic voltammetry assays have been used to determine the presence of charged species, the electroactivity, the electrostability and the formation of cross-links. The electrochemical stability of the copolymer with grafted PEG chains of Mw = 1000 has been found to increase with the number of consecutive oxidation¿reduction cycles (self-electrostabilizing behavior). Finally, a preliminary investigation into the applicability of these hybrid materials as active surfaces for the selective adsorption of proteins is presented.

  • A synergistic combination of tetraethylorthosilicate and multiphosphonic acid offers excellent corrosion protection to AA1100 aluminum alloy

     Dalmoro, Viviane; dos Santos, João Henrique Zimnoch; Armelin Diggroc, Elaine; Aleman Llanso, Carlos Enrique; Azambuja, Denise S.
    Applied surface science
    Vol. 273, p. 758-768
    DOI: 10.1016/j.apsusc.2013.02.131
    Date of publication: 2013-05-15
    Journal article

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    This work describes a new mechanism for the incorporation of organophosphonic acid into silane self-assembly monolayers, which has been used to protect AA1100 aluminum alloy. The protection improvement has been attributed to the fact that phosphonic structures promote the formation of strongly bonded and densely packed monolayer films, which show higher surface coverage and better adhesion than conventional silane systems. In order to evaluate the linking chemistry offered by phosphonic groups, two functionalized organophosphonic groups have been employed, 1,2-diaminoethanetetrakis methylenephosphonic acid (EDTPO) and aminotrimethylenephosphonic acid (ATMP), and combined with tetraethylorthosilicate (TEOS) films prepared by sol¿gel synthesis. Results suggest that phosphonic acids may interact with the surface through a monodentate and bidentate coordination mode and, in addition, form one or more strong and stable linkages with silicon through non-hydrolysable bonds. Therefore, the incorporation of a very low concentration of phosphonic acids on TEOS solutions favors the complete coverage of the aluminum substrate during the silanization process, which is not possible using TEOS alone. The linking capacity of phosphonic acid has been investigated by FTIR-RA spectroscopy, SEM and EDX analysis, X-ray photoelectron spectroscopy (XPS), and quantum mechanical calculations. Finally, electrochemical impedance spectroscopy has been used to study the corrosion protection revealing that EDTPO-containing films afforded more protection to the AA1100 substrate than ATMP-containing films.

    This work describes a new mechanism for the incorporation of organophosphonic acid into silane self-assembly monolayers, which has been used to protect AA1100 aluminum alloy. The protection improvement has been attributed to the fact that phosphonic structures promote the formation of strongly bonded and densely packed monolayer films, which show higher surface coverage and better adhesion than conventional silane systems. In order to evaluate the linking chemistry offered by phosphonic groups, two functionalized organophosphonic groups have been employed, 1,2-diaminoethanetetrakis methylenephosphonic acid (EDTPO) and aminotrimethylenephosphonic acid (ATMP), and combined with tetraethylorthosilicate (TEOS) films prepared by sol–gel synthesis. Results suggest that phosphonic acids may interact with the surface through a monodentate and bidentate coordination mode and, in addition, form one or more strong and stable linkages with silicon through non-hydrolysable bonds. Therefore, the incorporation of a very low concentration of phosphonic acids on TEOS solutions favors the complete coverage of the aluminum substrate during the silanization process, which is not possible using TEOS alone. The linking capacity of phosphonic acid has been investigated by FTIR-RA spectroscopy, SEM and EDX analysis, X-ray photoelectron spectroscopy (XPS), and quantum mechanical calculations. Finally, electrochemical impedance spectroscopy has been used to study the corrosion protection revealing that EDTPO-containing films afforded more protection to the AA1100 substrate than ATMP-containing films

  • Sequence dependence of C-end rule peptides in binding and activation of neuropilin-1 receptor

     Zanuy Gomara, David; Kotla, Rohith; Nussinov, Ruth; Teesalu, Tambet; Sugahara, Kazuki N.; Aleman Llanso, Carlos Enrique; Haspel, Nurit
    Journal of structural biology
    Vol. 182, num. 2, p. 78-86
    DOI: 10.1016/j.jsb.2013.02.006
    Date of publication: 2013-02-24
    Journal article

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    Neuropilin-1 (NRP-1) is a hub receptor that plays an essential role in angiogenesis and vascular permeability. It is over-expressed in the new blood vessels grown by tumor cells and is a target for anti-tumor treatments. Peptides that expose the consensus sequence R/K/XXR/K at the C-terminus (C-end rule or CendR peptides) bind to NRP-1 and are internalized into the cell. We used peptide phage display binding assays and molecular dynamics (MD) simulations to study the potential role of the central residues of CendR peptides in binding and activation of the NRP-1 receptor. The high stability of RPAR-receptor domain complex stems from the formation of a characteristic pattern of three hydrogen bonds between the peptide C-terminus and the residues in the NRP-1 loop III. Any changes in the peptide structure that fail to preserve this triad result in a less-stable complex. We performed a systematic study of RXXR mutants, where X = A/D/S/R/P, in order to test the effect of replacement of A or P on the binding capabilities. Our results, both experimental and computational, show that RRAR, RDAR, RPDR, RPRR and RPPR are capable of binding NRP-1. However, only RPPR and RPRR segments form an optimal organization around loop III with low potential energy. In other analogs, the absence of these stabilizing interactions always results in higher potential energy of the complexes. The binding of RPAR analogs does not guarantee receptor activation; only stable complexes that are properly stabilized via loop III appear able to trigger NRP-1 activation.

    Neuropilin-1 (NRP-1) is a hub receptor that plays an essential role in angiogenesis and vascular perme- ability. It is over-expres sed in the new blood vessels grown by tumor cells and is a target for anti-tumor treatment s. Peptides that expose the consensus sequence R/K/ XX R/K at the C-terminus ( C-end rule or CendR peptides) bind to NRP-1 and are internalized into the cell. We used peptide phage display binding assays and molecular dynamics (MD) simulations to study the potential role of the central residues of CendR peptides in binding and activa tion of the NRP-1 receptor. The high stability of RPAR–receptor domain complex stems from the formation of a characteristic pattern of three hydrogen bonds between the peptide C-terminus and the residues in the NRP-1 loop III. Any changes in the peptide structure that fail to preserve this triad result in a less-stable complex. We performed a systematic study of R XX R mutants, where X = A/D/S/R/P, in order to test the effect of replacement of A or P on the binding capabil- ities. Our results, both experimental and computational, show that RRAR, RDAR, RPDR, RPRR and RPPR are capable of binding NRP-1. However, only RPPR and RPRR segments form an optimal organization around loop III with low potential energy. In other analogs, the absence of these stabilizing interactions always results in higher potential energy of the complexes. The binding of RPAR analogs does not guarantee receptor activation; only stable complexes that are properly stabilized via loop III appear able to trigger NRP-1 activati on

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    Modeling biominerals formed by apatites and DNA  Open access

     Revilla Lopez, Guillermo; Casanovas Salas, Jordi; Bertran Cànovas, Oscar; Turon Dols, Pau; Puiggali Bellalta, Jorge; Aleman Llanso, Carlos Enrique
    Biointerphases: an open access journal for the biomaterials interface community
    Vol. 8, num. 1, p. 1-15
    DOI: 10.1186/1559-4106-8-10
    Date of publication: 2013-04-08
    Journal article

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    Different aspects of biominerals formed by apatite and DNA have been investigated using computer modeling tools. Firstly, the structure and stability of biominerals in which DNA molecules are embedded into hydroxyapatite and fluoroapatite nanopores have been examined by combining different molecular mechanics methods. After this, the early processes in the nucleation of hydroxyapatite at a DNA template have been investigated using molecular dynamics simulations. Results indicate that duplexes of DNA adopting a B double helix can be encapsulated inside nanopores of hydroxyapatite without undergoing significant distortions in the inter-strand hydrogen bonds and the intra-strand stacking. This ability of hydroxyapatite is practically independent of the DNA sequence, which has been attributed to the stabilizing role of the interactions between the calcium atoms of the mineral and the phosphate groups of the biomolecule. In contrast, the fluorine atoms of fluoroapatite induce pronounced structural distortions in the double helix when embedded in a pore of the same dimensions, resulting in the loss of its most relevant characteristics. On the other hand, molecular dynamics simulations have allowed us to observe the formation of calcium phosphate clusters at the surface of the B-DNA template. Electrostatic interactions between the phosphate groups of DNA and Ca 2+ have been found to essential for the formation of stable ion complexes, which were the starting point of calcium phosphate clusters by incorporating PO34 from the solution

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    Sensitive thermal transitions of nanoscale polymer samples using the bimetallic effect: Application to ultra-thin polythiophene  Open access

     Ahumada Heredero, Óscar; Perez Madrigal, Maria Del Mar; Ramírez García, Jorge; Curcó Cantarell, David; Esteves, Carina; Armelin Diggroc, Elaine; Luongo, Giovanni; Puiggali Bellalta, Jorge; Aleman Llanso, Carlos Enrique; Salvador Matar, Antonio
    Review of scientific instruments
    Vol. 84, num. 5, p. 1-8
    DOI: 10.1063/1.4804395
    Date of publication: 2013-06-15
    Journal article

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    A sensitive nanocalorimetric technology based on microcantilever sensors is presented. The tech- nology, which combines very short response times with very small sample consumption, uses the bimetallic effect to detect thermal transitions. Specifically, abrupt variations in the Young¿s modu- lus and the thermal expansion coefficient produced by temperature changes have been employed to detect thermodynamic transitions. The technology has been used to determine the glass transition of poly(3-thiophene methyl acetate), a soluble semiconducting polymer with different nanotechno- logical applications. The glass transition temperature determined using microcantilevers coated with ultra-thin films of mass = 10 - 13 gis5.2 ¿ C higher than that obtained using a conventional differential scanning calorimeter for bulk powder samples of mass = 5 × 10 - 3 g. Atomistic molecular dynamics simulations on models that represent the bulk powder and the ultra-thin films have been carried out to provide understanding and rationalization of this feature. Simulations indicate that the film-air in- terface plays a crucial role in films with very small thickness, affecting both the organization of the molecular chains and the response of the molecules against the temperature.

    A sensitive nanocalorimetric technology based on microcantilever sensors is presented. The tech- nology, which combines very short response times with very small sample consumption, uses the bimetallic effect to detect thermal transitions. Specifically, abrupt variations in the Young’s modu- lus and the thermal expansion coefficient produced by temperature changes have been employed to detect thermodynamic transitions. The technology has been used to determine the glass transition of poly(3-thiophene methyl acetate), a soluble semiconducting polymer with different nanotechno- logical applications. The glass transition temperature determined using microcantilevers coated with ultra-thin films of mass = 10 − 13 gis5.2 ◦ C higher than that obtained using a conventional differential scanning calorimeter for bulk powder samples of mass = 5 × 10 − 3 g. Atomistic molecular dynamics simulations on models that represent the bulk powder and the ultra-thin films have been carried out to provide understanding and rationalization of this feature. Simulations indicate that the film-air in- terface plays a crucial role in films with very small thickness, affecting both the organization of the molecular chains and the response of the molecules against the temperature.

  • Bioactive nanomembranes of semiconductor polythiophene and thermoplastic polyurethane: Thermal, nanostructural and nanomechanical properties

     Perez Madrigal, Maria Del Mar; Giannotti, Marina I.; Oncins Marco, Gerard; Franco Garcia, Maria Lourdes; Armelin Diggroc, Elaine; Puiggali Bellalta, Jorge; Sanz Carrasco, Fausto; Del Valle Mendoza, Luis Javier; Aleman Llanso, Carlos Enrique
    Polymer Chemistry
    Vol. 4, num. 3, p. 568-583
    DOI: 10.1039/c2py20654d
    Date of publication: 2013-02-07
    Journal article

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  • Computer simulation of dendronized polymers: organization and characterization at the atomistic level

     Bertran Cànovas, Oscar; Zhang, Baozhong; Schlüter, A. Dieter; Halperin, Avraham; Kröger, Martin; Aleman Llanso, Carlos Enrique
    RSC Advances
    Vol. 3, num. 1, p. 126-140
    DOI: 10.1039/C2RA22034B
    Date of publication: 2013
    Journal article

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