Study of impregnation of poly(l-lactide-ran-ε-caprolactone) copolymers with useful compounds in supercritical carbon dioxide
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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 (scCO2). Low-boiling-point compounds such as d-limonene, hinokitiol, and trans-2-hexenal were used. In impregnation experiments using scCO2, 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%.
KeywordsSupercritical Carbon Dioxide Feed Ratio Impregnation Experiment Disodium Hydrogen Phosphate Solvent Casting Method
The authors are grateful to the head of the College and the Research Institute for permitting publication of this work.