Effect of different lengths of side groups on the thermal, crystallization and mechanical properties of novel biodegradable poly(ethylene succinate) copolymers

Abstract

To explore the effect of different lengths of side groups, the thermal, crystallization, and mechanical properties were systematically investigated for three novel poly(ethylene succinate) (PES) based copolyesters containing methyl, butyl, and octyl as side groups, respectively, in this research. Relative to linear PES, the presence of side groups did not modify the crystal structure, while increasing the length of side groups slightly decreased the crystallinity of the copolymers. Despite the length of side groups, they all displayed high thermal decomposition temperatures. Increasing the length of side groups gradually decreased the melting point temperatures of PES copolymers. The glass transition temperature of poly(ethylene succinate-co-1,2-propylene succinate) slightly increased; however, those of poly(ethylene succinate-co-1,2-hexamethylene succinate) and poly(ethylene succinate-co-1,2-decamethylene succinate) gradually decreased with an increase in the length of side groups. PES and its copolymers displayed the same crystallization mechanism; however, the crystallization time increased as the length of side groups increased at the same degree of supercooling. The elongation at break increased while the Young's modulus decreased with increasing the length of side groups. The dynamic mechanical analysis results revealed that the storage modulus and tan δ gradually decreased as the length of side groups increased. In brief, the length of side groups significantly influenced the thermal, crystallization, and mechanical properties of PES based copolymers.