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This study involved the incorporation of useful compounds, such as repellents and antibacterial agents, at high concentrations in l-lactide (l-LA) random copolymers. The amount of α-pinene released in gas from the copolymers was also evaluated. Outstanding controlled release properties were developed using random copolymers of l-lactide (l-LA) with γ-valerolactone (VL), ε-caprolactone (CL), tetramethylene carbonate (TEMC) (1,3-dioxepan-2-one), and 1,5-dioxepan-2-one (DXO) using tin 2-ethyl-hexanoate [Sn(oct)2] as a catalyst at 150 °C for 24 h without solvent. Preparation of controlled release materials was accomplished using α-pinene from Japanese cypress oil and synthetic random copolymers of l-LA with cyclic monomers as base materials under supercritical carbon dioxide (scCO2). Poly(l-LA-ran-VL), poly(l-LA-ran-CL), poly(l-LA-ran-TEMC), and poly(l-LA-ran-DXO), which have lower Tm and ΔHm values than poly(l-LA) were used for the impregnation experiments. The oil content of the copolymers was greater than that in poly(l-LA). The content of oil into poly(l-LA-ran-TEMC) (80 : 20) was 8.1%, 2.1-fold greater than that in poly(l-LA) (Lacea H-100) (H-100), and 1.5-fold greater than that in poly(l-LA) (Lacea H-440) (H-440). Although a previous study showed that 3.2% d-limonene could be incorporated into poly(l-LA-ran-CL) (85 : 15) under the same conditions, results of this experiment showed that 5.8% and 6.6% oil could be incorporated into poly(l-LA-ran-CL) (81 : 19 or 91 : 9), respectively. Results from controlled release experiments demonstrated that the oil content in the polymer decreased upon copolymer degradation for all copolymers. In gas release tests, polymers H-440 and poly(l-LA-ran-VL) (85 : 15) released gas upon hydrolysis. Although the weight loss of H-440 was only 9% at 56 days, the calculated loss of oil in H-440 was 28%. [ABSTRACT FROM AUTHOR]

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 (scCO). Low-boiling-point compounds, such as d-limonene and hinokitiol, were used. In impregnation experiments with scCO, 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 [ABSTRACT FROM AUTHOR]