Synthesis and properties of poly(butylene succinate) with N-hexenyl side branches

N-hexenyl side branches were introduced into poly(butylene succinate) (PBS) by polymerization of succinic acid (SA) with 1,4-butanediol (BD) in the presence of 7-octene-1,2-diol (OD). Thermal properties and biodegradability of the aliphatic polyesters were investigated before and after epoxidation of the pendant double bonds. The glass-transition temperature (T_g) decreased with the branching density to give a minimum at 0.03 mol of branching units per mole of structural units. Thereafter, T_g increased due to the in situ crosslinking of the unsaturated groups during the differential scanning calorimetry (DSC) measurements. N-Hexenyl side branches decreased melting temperature (T_m) more significantly than ethyl side branches, but the effect was on par with that by n-octyl branches. Epoxidation of the double bonds decreased T_m and melting enthalpy (ΔH_m), but increased T_g of the aliphatic polyester. Biodegradability was enhanced to some extent by the presence of N-hexenyl side branches. However, the epoxidation of the unsaturated groups did not notably affect the biodegradability.