Synthesis, cocrystallization, and enzymatic degradation of novel poly(butylene-co-propylene succinate) copolymers

A series of poly(butylene-co-propylene succinate) (PBPSu) random copolyesters were synthesized and characterized using (HNMR)-H-1 spectroscopy and viscometry. Tensile properties decreased with increasing propylene succinate (PSu) content. Cocrystallization and multiple melting behaviors were investigated. The copolymers showed a eutectic behavior. The minimum melting point corresponded to 75 mol % PSu. Wide-angle X-ray diffraction (WAXD) patterns showed that the copolymers with up to 60 mol % PSu units formed poly(butylene succinate) crystals. The interplanar spacings slightly differentiated. The copolymer with 11.5 mol % poly(propylene succinate) (PPSu) units formed PPSu crystals. The results indicated isodimorphic cocrystallization. The cocrystallization was thermodynamically analyzed using the Wendling-Suter model. The defect free energy decreased for copolymers with high PPSu content. The banded spherulites of the copolyesters were studied, and growth rates were analyzed using the Lauritzen-Hoffman theory. Enzymatic hydrolysis study, using Rhizopus delemar and Pseudomouas cepacia lipases, showed that degradation was faster for copolymers with high PSu content, compared even to the fast-degrading PPSu.