Mutual relation between microstructure and properties of bacterial copolyesters

聚[（R）-3-羟基丁酸酯] [PHB]及其共聚物是由可再生资源经细菌发酵而成的可生物降解的热塑性塑料，引起了广泛的关注。本课题分析了细菌共聚酯的微观结构与性能之间的相互关系。聚合物材料的性能与从原子到宏观尺度的不同层次的结构相关，该项目旨在深入分析一种聚合物，聚（3-羟基丁酸酯-co-3-羟基戊酸酯）（PHB-HV），而不是各种共聚酯的浅之一。我们取得了以下成果。1.在约100 ℃时发现了一种特殊的结构转变。10mol%HV的PHB-HV具有窄的化学组成分布。对于具有双峰化学组成分布的PHB-HV，随着组成分布峰位差的增大和/或结晶温度的降低，其相结构从所有PHB-HV链的完全共结晶，经高HV含量的PHB-HV结晶，转变为结晶前的相分离。PHB-HV的各种性质发生了显著变化.通过FTIR显微镜对具有双峰组成分布的PHB-HV结晶过程的原位观察，证实了上述相的形成机理。

Poly [(R)-3-hydroxybutyrate] [PHB] and its copolymers, which are produced from renewable resources by bacterial fermentation, attract widespread interest as biodegradable thermoplastics. In this project, mutual relation between microstructure and properties of bacterial copolyesters were analyzed. Properties of Polymeric materials are correlated with structures of diverse levels from atomic to macroscopic scales, this project was directed toward deep analysis of a copolyester, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-HV), rather than shallow one of various coplyesters. We have achieved the following results.1. A speculer structural transition was found at ca. 10 mol% HV for PHB-HV with narrow chemical composition distribution.2. For PHB-HV with bimodal chemical composition distribution, the phase structure changes from perfect cocrystallization of all the PHB-HV chains, via crystallization of the PHB-HV with high HV content, to phase segregation preceding crystallization with the increase of the difference in the peak positions in composition distribution and/or the decrease of the crystallization temperature. Coincidentally various properties of PHB-HV remarkably changes.3. Through in situ observation of crystallization of PHB-HV with bimodal composition distribution by FTIR microscopy, the formation mechanism of the phases described above was demonstrated.