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.Peer ReviewedPostprint (published version
The diacetalized diol 2,4:3,5-di-O-methylene-D-glucitol (Glux), a bicyclic compound derived from D-glucose, was used as a comonomer of 1,6-hexanediol in polycondensation in the melt with dimethyl terephthalate to produce a set of aromatic copolyesters (PHxGluxyT) with Glux contents ranging from 5 to 32%-mole. These sustainable copolyesters had molecular weights within the 12,000 to 45,000 g mol-1 range, and polydispersities between 2.0 and 2.5. They all had a random microstructure and displayed slight optical activity. PHxGluxyT showed a good thermal stability and were semicrystalline with both crystallinity degree and crystallization rate decreasing as the content in Glux increased. Conversely, Tg increased with the incorporation of Glux going from 8 oC in PHT to near 60 oC in the copolyester containing 32%-mole Glux. Compared to PHT, PHxGluxyT copolyesters showed not only an enhanced susceptibility to hydrolysis but also an appreciable biodegradability in the presence of lipases.Ministerio de Economía y Competitividad MAT2009-14053-C02AGAUR 2009SGR146
Biotechnologically accessible 1,4-butanediol and vegetal oil-based diethyl sebacate were copolymerized with bicyclic acetalized D-glucose derivatives (Glux) by polycondensation both in the melt at high temperature and in solution at mild temperature mediated by polymer-supported Candida antarctica lipase B (CALB). Two series of random copolyesters (PB x Glux y Seb and PBSeb x Glux y ) were prepared differing in which D-glucose derivative (Glux diol or Glux diester) was used as comonomer. The three parent homopolyesters PBSeb, PBGlux and PGluxSeb were prepared as well. Both methods were found to be effective for polymerization although significant higher molecular weights were achieved by melt polycondensation. The thermal properties displayed by the copolyesters were largely dependent on composition and also on the functionality of the replacing Glux unit. The thermal stability of PBSeb was retained or even slightly increased after copolymerization with Glux whereas crystallinity and melting temperature were largely depressed. On the contrary, the glass-transition temperature noticeably increased with the content in Glux units. PGluxSeb distinguished in displaying both T g and T m higher than PBSeb because a different crystal structure is adopted by this homopolyester. The hydrolytic degradability of PBSeb in water was enhanced by copolymerization, in particular when biodegradation was assisted by lipases.2
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