A series of ionic complexes with a comb-like architecture and a nearly stoichiometric composition were prepared from bacterial poly(gamma,dl-glutamic acid) (PGGA) and alkyltrimethyl phosphonium bromides (nATMP·Br) bearing long linear alkyl chains with even numbers of carbon atoms (n) ranging from 12 to 22. The nATMP·PGGA complexes were non-water soluble but readily soluble in organic solvents, and they displayed a high thermal stability. Combined DSC and XRD studies revealed that these complexes adopted an amphiphilic layered structure with the polypeptide chain and the alkyl chain separated in two differentiated phases with a nanoperiodicity that increased steadily with the length of the alkyl chain. The paraffinic phase was found to be partially crystallized in an extent that decreased with n, so that complexes with n = 12 and 14 did not show any sign of crystallinity whereas those with n from 16 to 22 showed crystalline melting in the ~30–70 °C range. The structural transitions taking place by temperature effects were characterized by simultaneous SAXS/WAXS using synchrotron radiation at real time. In all cases, a shortening of the layer periodicity occurred upon heating with recovering of the initial structure after cooling. nATMP·PGGA with n = 16 showed strong antimicrobial activity against both E. coli and S. aureus, a property that could be related to the weak dissociation of the complexes happening upon incubation in water. The structure and properties of these complexes where comparatively discussed taking as reference their analog complexes made from PGGA and alkyltrimethylammonium bromides already studied by us.
Quaternary organophosphonium salts bearing long alkyl chains are cationic surfactants of interest owing to their physical and biological properties. In the present work, the crystal structure and thermotropic behavior of the homologous series of alkyltrimethylphosphonium bromides (nATMP·Br), with the alkyl chain containing an even number (n) of carbon atoms from 12 to 22, have been examined within the 0–300 °C range of temperatures. These compounds were shown to be resistant to heat up to ~390 °C. The phases adopted at different temperatures were detected by DSC, and the structural changes involved in the phase transitions have been characterized by simultaneous WAXS and SAXS carried out in real-time, and by polarizing optical microscopy as well. Three or four phases were identified for n = 12 and 14 or n = 16, respectively, in agreement with the heat exchange peaks observed by DSC. The phase existing at room temperature (Ph-I) was found to be fully crystalline and its crystal lattice was determined by single-crystal X-ray diffraction methods. Ph-II consisted of a semicrystalline structure that can be categorized as Smectic-B with the crystallized ionic pairs hexagonally arranged in layers and the molten alkyl chain confined in the interlayer space. Ph-II of 12ATMP·Br and 14ATMP·Br directly isotropicized upon heating at ~220 °C, whereas for n = 16, it converted into a Smectic-A phase (Ph-III) that needed to be heated above ~240 °C to become isotropic (Ph-Is). The correlation existing between the thermal behavior, phase structure and length of the alkyl side chain has been demonstrated.
Gamarra, A.; Alla, A.; Martinez de Ilarduya, A.; Casas, M.; Muñoz, S. Reunión del Grupo Especializado de Polímeros (GEP) de la RSEQ y RSEF p. 89-91 Data de presentació: 2016-09-06 Presentació treball a congrés
In this communication we wish to report on HyA ionic complexes prepared by coupling with a) choline-based surfactants (nACh·HyA complexes), and b) alkylphosphonium surfactants (nATMP·HyA complexes) with n being the number of carbons of the alkanoyl or alkyl side chain. nACh surfactants are synthesized from choline and fatty acids, and distinguished because they are fully biobased and biocompatible. The nATMP surfactants have been scarcely studied as counterions of polyacids in spite of being more stable to heat and less harmful than their alkylammonium analogs.
A series of alkyltrimethylphosphonium bromides (nATMP·Br, n being the number of carbon atoms contained in the linear alkyl chain)
has been synthesized for the first time, and their thermal properties examined by DSC and polarizing optical microscopy. The crystal
structure of representative examples was elucidated using XRDmonocrystal direct methods. Several thermal transitions involving
crystalline, semicrystalline and liquid-crystal phases were characterized for these soaps by WAXS-SAXS at temperatures increasing with thevalue of n.
Ionic complexes nATMP·PGGA were prepared from the these phosphonium soaps and both poly(gamma glutamic acid)
and hyaluronic acid (Scheme Ic) sodium salts. Their stoichiometry was depending on n and they were non soluble in water although display remarkable hydrophylicity. The structure and thermal behavior of these complexes have been examined on the basis of the behavior observed for the nATMP·Br salts and compared with those reported for analogous alkyltrimethylammonium complexes recently described by us.