Synthesis, structure and thermal properties of poly(A-block-B-block-A) copolymer based on biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and amorphous polystyrene

A series of poly(A-block-B-block-A) copolymers based on biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and amorphous polystyrene (PS) were synthesised by atom transfer radical polymerisation (ATRP). The chemical structure, molecular weight and distribution were systematically characterised by Fourier transform infrared, H-1 nuclear magnetic resonance (H-1 NMR) and gel permeation chromatography (GPC). The melting and crystallisation behaviours, and thermal stabilities of copolymers were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA); the degradation activation energy was calculated by Horowitz-Metzger method. Results showed that the maximum yield of triblock copolymer was 88%. DSC curves revealed that the triblock copolymers had their cold crystallisation temperature from 50.83 to 65.67 degrees C, and the crystallinity from 55.60 to 12.60. TG curves showed that the thermal stabilities of triblock copolymers were enhanced, and its degradation activation energy decreased from 428 to 197 kJ mol(-1)