Incorporation of l-lactide random copolymers with Japanese cypress oil (-pinene) using supercritical carbon dioxide

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 -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 -valerolactone (VL), -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 -pinene from Japanese cypress oil and synthetic random copolymers of l -LA with cyclic monomers as base materials under supercritical carbon dioxide (scCO 2 ). Poly( l -LA- ran -VL), poly( l -LA- ran -CL), poly( l -LA- ran -TEMC), and poly( l -LA- ran -DXO), which have lower T m and H m 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%. This study involved the incorporation of useful compounds, such as repellents and antibacterial agents, at high concentrations in l -lactide ( l -LA) random copolymers.