3-(4-Hydroxyphenyl)propanoic acid, so-called phloretic acid (PA), is a naturally occurring phenolic compound which can be produced by the hydrogenation of p-coumaric acid or synthesized from phloretin, a by-product of apple tree leaves. It is explored herein as a renewable building block for enhancing the reactivity of –OH bearing molecules towards benzoxazine (Bz) ring formation instead of phenol. PA is used to bring phenolic functionalities by its reaction with model molecules (ethylene glycol, as well as two polyethylene glycol molecules with molar masses corresponding to 400 g·mol-1 and 2000 g·mol-1) via solvent-free Fischer esterification. These phenolic groups are further reacted with a bio-based amine (furfurylamine) to form almost 100% bio-based benzoxazine end-capped molecules. Very interestingly, the whole synthesis of Bz monomers from PEG400 and PEG2000 does not require a solvent or purification, and their polymerization led to a set of materials with thermal and thermo-mechanical properties suitable for a wide range of applications. These results show that renewable phloretic acid is a sustainable alternative to phenol to provide easily the specific properties of benzoxazine to aliphatic –OH bearing molecules or macromolecules. This novel approach paves the way towards a multitude of applications given the large number of –OH bearing compounds in materials science.
In recent years, significant research has aimed at developing environmentally friendly supercapacitors by introducing biopolymeric materials, such as polysaccharides or proteins. In addition to the sustainability and recyclability of such novel energy storage devices, these polymers also provide flexibility, lightweight nature and stable cycling performance, which are of tremendous importance for applications related to wearable electronics. Among the different sustainable natural polymers, cellulose deserves special consideration since it is the most abundant and is extensively recycled. Consequently, research on electrically active cellulose-based supercapacitors has noticeably increased since 2012, which makes this review on the field timely. Specifically, recent advances in preparing high performance cellulose supercapacitors are summarized. Moreover, the key roles of cellulose in improving the specific capacitance and cycling stability of cellulose-based devices are compiled to offer important fundamental guidelines for designing the next generation of all-cellulose energy storage devices that are to come. Finally, challenges and perspectives in this exciting area of study are also discussed.
Poly(alkylene terephthalate)s, PET and PBT in particular, are materials of great relevance and growing projection in the thermoplastic field but are today almost totally produced from fossil resources. The current huge consumption of these polyesters necessitates urgent actions addressed to make them renewable by using naturally-occurring raw materials. Among the different approaches that are being followed to develop bio-based poly(terephthalate)s, the use of bicyclic carbohydrate-derived difunctional compounds as building-blocks is receiving much attention in the last few years because partially renewable polyesters with high Tg may be thus obtained. This review presents a critical account of the terephthalate homopolymers and copolymers that have been synthesized using the two types of carbohydrate-based bicyclic monomers, isohexides and diacetals, explored to date. The properties displayed by the novel bio-based poly(terephthalate)s in relation to the bicyclic structure of the used monomers are comparatively reviewed and their potential as emergent materials for thermoplastic applications is evaluated.
Lavilla, C.; Gubbels, E.; Alla, A.; Martinez de Ilarduya, A.; Noordover, B.; Koning, Cornelis Eme; Muñoz, S. Green chemistry Vol. 16, num. 4, p. 1789-1798 DOI: 10.1039/C3GC41759J Data de publicació: 2014-04-01 Article en revista
2,3-O-Methylene-L-threitol (Thx) is a cyclic carbohydrate-based diol prepared by acetalization and subsequent reduction of the naturally occurring tartaric acid. The structure of Thx consists of a 1,3-dioxolane ring with two attached primary hydroxyl groups. Two series of partially bio-based poly(butylene terephthalate) (PBT) copolyesters were prepared using Thx as a comonomer by melt polycondensation (MP) and solid-state modification (SSM). Fully random copolyesters were obtained after MP using mixtures of Thx and 1,4-butanediol in combination with dimethyl terephthalate. Copolyesters with a unique block-like chemical microstructure were prepared by the incorporation of Thx into the amorphous phase of PBT by SSM. The partial replacement of the 1,4-butanediol units by Thx resulted in satisfactory thermal stabilities and gave rise to an increase of the Tg values, this effect was comparable for copolyesters prepared by MP and SSM. The partially bio-based materials prepared by SSM displayed higher melting points and easier crystallization from the melt, due to the presence of long PBT sequences in the backbone of the copolyester. The incorporation of Thx in the copolyester backbone enhanced the hydrolytic degradation of the materials with respect to the degradation of pure PBT.
This work describes a novel enzymatic approach to develop a lignin-based adhesive aimed at replacing synthetic latex in wool floor coverings. The adhesive production consisted of a lignin pre-activation step to oxidise it by a laccase-enhancer system followed by a phenolation step where natural phenolic compounds were copolymerised with lignin in order to increase its content of quinone structures reactive towards wool. The electrochemical behaviour of the adhesive precursors and the influence of process conditions on the adhesive characteristics suggested that the phenolic compounds were able to autopolymerise and copolymerise between themselves and with lignin during the enzymatic reaction. Consequently, the flexibility and bonding strength of the adhesive increased. The latter showed strength performance similar to that of the traditional latex-based adhesive. Satisfactory level of flexibility was obtained using polyethylene glycol as an external plasticizer of lignin.
Commercial Beta, ZSM-5 and mordenite zeolites and commercial montmorillonite K-10 were successfully
sulfonated by a one-step simple method using microwaves. Different amounts of the sulfonating agent
were required to maximize the incorporation of sulfonic groups for each structure. This has been related
to the different dealumination degree suffered by the starting samples during sulfonation together with
the different accessibility of the silanols to the sulfonic groups depending on the arrangement and size
of their pores. All optimised sulfonated catalysts showed total conversion and very high selectivity
(79–91%) to h-GTBE (glycerol di- and tri-ethers), in spite of their microporosity, due to the incorporation
of the sulfonic groups that led to a higher number and strength of Brønsted acid sites. Pore size and
arrangement together with the external surface area of the catalysts affected the accessibility of the acid
sites to the reactants, explaining the evolution of the catalytic results with time for each structure.