Copolyesters Made from 1,4-Butanediol, Sebacic Acid, and d-Glucose by Melt and Enzymatic Polycondensation

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 (PBxGluxySeb and PBSebxGluxy) 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 Tg and Tm 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.