Impregnation of poly(L-lactide-ran-cyclic carbonate) copolymers with useful compounds with supercritical carbon dioxide

In this article, we cover the development of L‐lactide (L‐LA) random copolymers into which useful compounds, such as repellents and antibacterial agents, were impregnated by high concentration. Outstanding controlled release materials were developed with statistical random copolymers of L‐LA with cyclic carbonate (CC) [2,2‐dimethyltrimethylene carbonate (2,2‐DTMC) or tetramethylene carbonate (TEMC)] with tin 2‐ethyL‐hexanoate as a catalyst at 150°C (2,2‐DTMC) or 120°C (TEMC) for 24 h without solvent. The preparation of improved controlled release materials was performed with useful organic compounds with low boiling points and synthetic L‐LA random copolymers containing CCs as base materials under supercritical carbon dioxide (scCO2). Low‐boiling‐point compounds, such as d‐limonene and hinokitiol, were used. In impregnation experiments with scCO2, the amounts of low‐boiling‐point compounds increased with increasings L‐LA content. The compound content impregnated into poly(L‐lactide‐ran‐cyclic carbonate) [poly(L‐LA‐ran‐CC)] was greater than that of the experiment with poly(L‐lactide‐ran‐ε‐caprolactone) previously studied. When the enzymatic degradation of poly(L‐LA‐ran‐CC) was performed with proteinase K, copolymers with a greater L‐LA content degraded more rapidly than did copolymers with a greater CC content. In a controlled release experiment with poly(L‐lactide‐ran‐2,2‐dimethyltrimethylene carbonate) (76/24) or poly(L‐lactide‐ran‐tetramethylene carbonate) (81/19), the rate of polymer degradation and the rate of impregnated compound release were almost the same. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011