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Influence of Hydrolysis on Non-Isothermal Crystallization of Poly(Butylene Succinate-Co-Adipate) (PBSA)
Summary
This study examines how hydrolytic degradation in phosphate-buffered saline alters the crystallization behavior of biodegradable polyester PBSA, finding that progressive molecular weight reduction drives a structural shift from spherulitic to dendritic crystal morphologies and changes in thermal properties.
This study investigates the impact of hydrolysis on the crystallization behavior of poly(butylene succinate-co-adipate) (PBSA), a biodegradable polyester. Hydrolysis was conducted in a controlled environment using phosphate-buffered saline at 70 °C to isolate the impact of hydrolytic degradation on the polymer's properties. The consequent changes in molecular weight characteristics were tracked using gel permeation chromatography (GPC), revealing a decrease in both weight average molecular weight (Mw) and an increase in polydispersity index (PDI) as hydrolysis progressed. The thermal behavior of PBSA during hydrolysis was thoroughly investigated using differential scanning calorimetry (DSC), which demonstrated significant changes in melting temperature (Tm), glass transition temperature (Tg), and crystallinity (X). These changes in Tm and Tg suggest a change in copolymer composition, likely due to the greater susceptibility of the adipic acid unit to hydrolysis compared to the succinic acid unit. Furthermore, polarized optical microscopy (POM) was employed to observe the morphological evolution of PBSA, showing a transition from spherulitic structures in the early stages of hydrolysis to dendritic structures with prolonged hydrolysis time. The decrease in nucleation activity led to a reduction in the number of spherulites, which in turn allowed the remaining spherulites to grow larger.