Study of impregnation of poly(l-lactide-ran-ε-caprolactone) copolymers with useful compounds in supercritical carbon dioxide

Outstanding controlled release materials were developed using statistically random copolymers of l -lactide ( l -LA) with ε -caprolactone (CL) using Sn(oct) 2 as a catalyst at 150 °C for 24 h without solvent. Preparation of novel controlled release materials was carried out using useful organic compounds with low boiling points and synthetic random copolymers composed of l -LA and CL as base materials under supercritical carbon dioxide (scCO 2 ). Low-boiling-point compounds such as d -limonene, hinokitiol, and trans -2-hexenal were used. In impregnation experiments using scCO 2 , the amounts of low-boiling-point compounds increased with an increase in l -LA content. When enzymatic degradation of poly( l -LA- ran -CL) was performed using lipase PS, copolymers with higher CL contents degraded more rapidly than did copolymers with higher l -LA content. In contrast, enzymatic degradation of copolymers occurred to a higher degree with increased l -LA content in enzymatic degradation by proteinase K. In a controlled release experiment with poly( l -LA- ran -CL) (=73/27), after 400 h of degradation by proteinase K, the remaining weight of the copolymer pellet was 6% and the amount of d -limonene remaining in the pellet was 15%.