Enzymatic hydrolysis studies on novel eco-friendly aliphatic thiocopolyesters

Copolymers of poly(butylene succinate) (PBS) containing thiodiethylene succinate sequences with different molecular architectures (PBSPTDGS) were prepared via reactive blending in the presence of a Ti-based catalyst. In particular, a block copolymer with long sequences and a random one have been investigated for their biodegradability. The parent homopolymer PBS has been also synthesized via the usual two-stage melt polycondensation and used as reference polymer in the study.The hydrolitic treatment carried out using lipase from Candida cylindracea ([E] = 50 U/ml, T = 30 °C and pH = 7.0), showed that copolymers biodegraded more rapidly and extensively than PBS.ATRIR analysis and DSC measurements also performed on the resulting samples showed that the enzyme simultaneously attacks the amorphous phase and the PTDGS crystalline phase, which is characterized by lower packing density and degree of perfection with respect to the PBS one. This result suggested that the higher degradability of the copolymers under study can be correlated both to the crystallinity degree and to the nature of the crystalline phase. NMR analysis, performed to detect changes in composition of the copolymers during the degradation, demonstrated that enzyme hydrolysis preferentially targeted ester groups of TDGS sequences because of their higher hydrophilicity.