(State Key Laboratory for Modification of Chemical Fiber and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China)
Polyhydroxyalkanoates (PHAs) is the only bio-based polyester directly synthesized by microorganisms, which can achieve a full green ecological cycle from raw material preparation, product processing to material degradation. With the advantages of being green and environment-friendly, PHAs have potential applications in textile fibers, packaging materials, and biomedical materials. However, PHAs also have unfavorable structural factors such as slow crystallization rate, large spherulite size and secondary crystallization, which limit their application. Therefore, this paper mainly focuses on the research progress of modification of the crystal structure and mechanical properties of PHAs from three aspects: the heterogeneous nucleation effect, the longchain branching structure design and the external field induction. First, inorganic nanomaterials with high heat resistance (tungsten sulfide) can be used to significantly improve the heterogeneous nucleation ability of PHAs. Secondly, the long-chain branched structure can be used to compensate for the lack of PHA melt strength. Furthermore, the crystal form of PHAs can be changed by the synergistic effect between heterogeneous nucleation, long-chain branching and drawing process. Finally, further research directions and applications of PHAs have also been presented.