Environmentally friendly PBS-based copolyesters containing PEG-like subunit: Effect of block length on solid-state properties and enzymatic degradation

The use of biodegradable polymers could contribute to mitigate the huge environmental problems caused by the massive use of conventional non-biodegradable plastics, especially in the case of time-limited applications. In this framework, in the present study we propose a new class of multiblock eco-friendly copolyesters containing butylene succinate (BS) and triethylene succinate (TES) sequences. In particular, four copolyesters with the same chemical composition but different block lengths - P(BS10TES10), P(BS5TES5), P(BS3TES3), and P(BS2TES2) - were synthesized by reactive blending. For sake of comparison, homopolymer PBS was also considered. Physicochemical characterization (DSC, WAXS, tensile tests, WCA) of the copolymers synthesized demonstrated that it is possible to control polymer crystallinity, thermal and mechanical properties and wettability of the final product by simply varying block length. As a matter of fact, melting point, crystallinity degree, elastic modulus and surface wettability decreased with the block length; on the contrary, elongation to break significantly increased. Enzymatic hydrolysis performed with lipase from Candida cylindracea ([E] = 50 U/mL, T = 30 °C and pH = 7.0), showed that copolymers biodegradation is much higher than that of PBS homopolymer. Moreover, copolymers displayed a tunable range of degradation rates, related to their crystallinity degree and hydrophilic/hydrophobic ratio, which render them promising for different time-span applications, ranging from long-term (P(BS10TES10) to very short-term (P(BS2TES2)).