2,4:3,5-Di-O-methylene-D-mannitol, abbreviated as Manx, is a D-mannitol-derived compound with the secondary hydroxyl groups acetalized with formaldehyde. The bicyclic structure of Manx consists of two fused 1,3-dioxane rings, with two primary hydroxyl groups standing free for reaction. A homopolyester made of Manx and dimethyl terephthalate as well as a set of copolyesters of poly(butylene terephthalate) (PBT) in which 1,4-butanediol was replaced by Manx up to 50% were synthesized and characterized. The polyesters had M w in the 30 000−52 000 g mol −1 range and a random microstructure and were thermally stable up to nearly 370°C. They displayed outstanding high T g with values from 55 to 137°C which steadily increased with the content in Manx. Copolyesters containing up to 40% of Manx were semicrystalline and adopted the crystal structure of PBT. Their stress− strain parameters were sensitively affected by the presence of carbohydrate-based units with elongation at break decreasing but tensile strength and elastic moduli steadily increasing with the degree of replacement.

The preparation of cyclic ethylene and butylene 2,5-furandicarboxylate oligoesters and their conversion to furan-based polyesters poly(ethylene furanoate) (PEF) and poly(butylene furanoate) (PBF) by ring-opening polymerization (ROP) are described. The cyclic oligoesters were obtained in high yields by both high dilution condensation and thermal cyclodepolymerization methods, and they consisted of mixtures of small size species. Cyclic dimer, trimer and tetramer oligoesters were isolated by semipreparative chromatography and found to be crystalline compounds melting within the 140–200 °C range. ROP catalyzed by Sn(Oct)2 of both mixtures and individual species afforded PEF and PBF with weight-average molecular weights between 50,000 and 60,000 g mol-1. Polymerization rate was found to be higher for butylene than for ethylene cyclic oligofuranoates, and also to increase slightly as cycle size decreased. The thermal properties of PEF and PBF prepared by ROP were in full agreement with those reported for these polyesters obtained by melt polycondensation.Peer ReviewedPostprint (author's final draft

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 carbohydrate-based diol 2,4:3,5-di-O-methylene-d-mannitol (Manx) has been used to obtain aliphatic polyesters. Manx is a symmetric bicyclic compound consisting of two fused 1,3-dioxane rings and bearing two primary hydroxyl groups. In terms of stiffness, it is comparable to the widely known isosorbide, but it affords the additional advantages of being much more reactive in polycondensation and capable of producing stereoregular polymers with fairly high molecular weights. A fully bio-based homopolyester (PManxS) has been synthesized by polycondensation in the melt from dimethyl succinate and Manx. The high thermal stability of PManxS, its relatively high glass transition temperature (Tg = 68 °C) and elastic modulus, and its enhanced sensitivity to the action of lipases point to PManxS as a polyester of exceptional interest for those applications where biodegradability and molecular stiffness are priority requirements. In addition, random copolyesters (PBxManxyS) covering a broad range of compositions have been obtained using mixtures of Manx and 1,4-butanediol in the reaction with dimethyl succinate. All PBxManxyS were semicrystalline and displayed Tg values from -29 to +51 °C steadily increasing with the content in Manx units. The stress-strain behavior of these copolyesters largely depended on their content in Manx and they were enzymatically degraded faster than PBS.

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Two bicyclic carbohydrate-based diols, 2,3:4,5di-O-methylene-galactitol (Galx) or 2,4:3,5-di-O-methylene-Dmannitol (Manx), were introduced into the backbone of poly(butylene terephthalate) using the solid-state modification technique (SSM). The resulting copolyesters had a unique block-like chemical microstructure that endows them with superior thermal properties when compared with their random counterparts obtained by melt copolymerization. The materials prepared by SSM displayed higher melting points, crystallization temperatures, and crystallinity due to the presence of long PBT sequences in the copolyester. The glass-transition temperatures also increased upon incorporation of the bicyclic comonomers, this effect being more pronounced for Manx units. The melting points of these block-like copolyesters decreased after melting due to the occurrence of randomization, but they remained higher than those of copolyesters prepared from the melt. SSM was demonstrated to be a very suitable technique for the incorporation of rigid monomers into the amorphous phase of PBT, leading to bio-based non-random copolyesters with remarkable thermal properties.

Tuning the thermal properties and morphology of isodimorphic poly[(butylene succinate)-ran-(ɛ-caprolactone)] copolyesters by changing composition, molecular weight and thermal history

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