Supercritical Fluid Impregnation of Essential Bark Oil in Copolymers of L-Lactide with 7-Membered Cyclic Compounds

Abstract

In order to develop a novel controlled-release material, we previously attempted to impregnate poly(L-lactide) (poly(L-LA)), poly(L-LA- ran -CL) (CL: ε -caprolactone) or poly(L-LA- ran -TEMC) (TEMC: tetramethylene carbonate) with low boiling point, organic useful compounds using supercritical carbon dioxide (scCO 2 ) as the solvent. In this work, the factors influencing impregnation of poly (L-LA) random copolymers with useful compounds were investigated under scCO 2 using the copolymers previously used. The influence of temperature, pressure, and time on the impregnation contents of the useful compounds on the copolymers was evaluated. The polymer used, which is a base of this material, was poly(L-LA- ran -CL), poly(L-LA- ran -TEMC), or poly(L-LA- ran -DXO) (DXO: 1,5-dioxepan-2-one). Statistical random copolymers of L-LA with CL, TEMC, or DXO were synthesized using Sn(oct) 2 as a catalyst at 150 ° C for 24 h without solvent. Preparation of the controlled-release materials was carried out using essential bark oil from Thujopsis dolabrata var. hondae and synthetic L-LA random copolymers as a base material under scCO 2 . The impregnation experiment, which investigated the influence of pressure, was conducted in the range of 10 to 20 MPa. The influence of temperature on impregnation was carried out at 40 ° C to 100 ° C. Impregnation time was varied from 1 to 5 h. The pressure of essential oil impregnated into poly(L-LA) random copolymers was the highest at 14 MPa. In the influence of temperature on impregnation, the amount of essential oil increased with increasing temperature.