Formation of Mesomorphic Polymorph, Thermal-Induced Phase Transition, and Crystalline Structure-Dependent Degradable and Mechanical Properties of Poly(p-dioxanone)

Abstract

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 metastabl...