Formation of Mesomorphic Polymorph, Thermal-Induced Phase Transition, and Crystalline Structure-Dependent Degradable and Mechanical Properties of Poly(p-dioxanone)
writer：Zheng, Y.; Zhou, J.; Du, F.; Bao, Y.; Shan, G.; Zhang, L.; Dong, H.; Pan, P.
keywords：Poly(p?dioxanone), Thermal-induced phase transition, Mechanical properties
source：期刊
specific source：Cryst. Growth Des.
Issue time：2018年
Polymorphic crystalline structure has been a key factor determining the mechanical property and degradation behavior of biodegradable polymers. Herein, we report on the polymorphic crystalline structure, phase transition, and their effects on the mechanical property and degradation behavior of poly(p-dioxanone) (PPDO), a typical biodegradable and bioabsorbable semicrystalline polymer for biomedical applications. Both the polymorphic crystalline structure and crystallization kinetics of PPDO depend on crystallization temperature (Tc) drastically. Melting enthalpy and degree of crystallinity of PPDO first decrease and then increase with increasing Tc. PPDO forms a new mesomorphic polymorph (denoted as the α′-form) during crystallization at low Tc (≤10 °C), in contrast to the common α crystals generated at high Tc
(≥60 °C). The α′ crystals have weaker interchain interactions and a shorter long period than the common α crystals, indicating the looser chain packing of α′ crystals. The α′ crystals are metastable, and they transform into the thermodynamically stable α crystals during heating. The α′-form PPDO possesses a slower degradation rate, higher flexibility, but lower strength and modulus than its α counterpart. This would provide a feasible way to tailor the degradation and mechanical properties of PPDO by varying crystal modification.