Kazuhiro Kuwabara

Solid-state structures and thermal properties of aliphatic–aromatic poly(butylene adipate-co-butylene terephthalate) copolyesters

Abstract Aliphatic–aromatic copolyesters of poly(butylene adipate-co-butylene terephthalate) [P(BA-co-BT)] with wide copolymer compositions were synthesized by melt polycondensation. Solution 13 C NMR analyses show that the copolyesters are statistically random copolymers of BA and BT units. Their solid-state microstructures and thermal properties were investigated by wide-angle X-ray diffraction (WAXD), solid-state 13 C NMR, differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The WAXD shows that the copolyesters with 10–25 mol% BT contain PBA crystals, while those with 27.5–80 mol% BT contain PBT crystals. In contrast, solid-state 13 C NMR analyses demonstrate that the copolyesters with 20–30 mol% BT units contain both PBA and PBT crystals, but the minor one cannot be detected by X-ray diffraction due to the small sizes and amounts. Both the melting temperature and crystallinity of copolyesters show minimum values at around 25 mol% BT content which is the transition point from PBA crystal structure to PBT crystal structure. The composition dependences of melting temperature, crystallinity, crystallization rate and spherulite morphology are discussed and correlated to the biodegradability of the P(BA-co-BT) copolyesters.

The Solid-State Structure, Thermal and Crystalline Properties of Bacterial Copolyesters of (R)-3-Hydroxybutyric Acid with (R)-3-Hydroxyhexanoic Acid

Bacterial poly(3-hydroxyalkanoic acid)s (PHAs) are interesting biodegradable and biocompatible thermoplastics produced by a wide variety of microorganisms from various carbon sources.1,2 The PHAs are known to accumulate inside bacterial body as intracellular storage materials for biological carbon and energy sources1–4. Until now PHAs with more than 100 different monomeric units as constituents have been found5. These biodegradable PHA thermoplastics have attracted much attention in the recent two decades as they are environmentally friendly materials which can be degraded to carbon dioxide, water and biomass by a wide of microorganisms. Therefore the bacterial PHAs are a prospective candidate to replace the normally used plastics, which result in serious environmental pollution by waste polymers.