Raman and NMR Spectroscopic Studies on Hydrolytic Degradation of d,l-Lactide−δ-Valerolactone–d,l-Lactide Copolymer

Hydrolytic degradation of BAB terpolymers with δ-valerolactone as the central (A) block and d,l-lactide as the terminal (B) block was studied by 1H NMR and Raman spectroscopic techniques. The following variations were investigated: (i) the ratio of δ-valerolactone to d,l-lactide, (ii) replacement of d,l-lactide with cis-lactide or glycolide, keeping A constant, and (iii) replacement of δ-valerolactone with e-caprolactone, keeping B constant. The intensity of the characteristic peaks for the d,l-lactide segment almost disappeared, and the intensity of the characteristic signals for δ-valerolactone decreased after 30 days. As evident from quantitative analysis of 1H NMR, 97% of the d,l-lactide segment degraded within 30 days, and the value was 35% for the δ-valerolactone block (both based on the initial value). Upon degradation of the triblock, a significant increase in water uptake and decrease in molecular weight and bulk weight were observed. Crystallinity of the triblock increased after degradation due ...