<jats:title>Abstract</jats:title><jats:p>This work studied the incorporation of essential bark oil from <jats:italic>Thujopsis dolabrata</jats:italic> var. <jats:italic>hondae</jats:italic>, which is known to repel various insects, in poly(L-lactide-<jats:italic>ran</jats:italic>-<jats:italic>δ</jats:italic>-valerolactone) [poly(L-LA-<jats:italic>ran</jats:italic>-VL)] using supercritical carbon dioxide (scCO<jats:sub>2</jats:sub>). The poly(L-LA-<jats:italic>ran</jats:italic>-VL) was synthesized by first purifying the monomers by azeotropic distillation with benzene, followed by polymerization with Sn(oct)<jats:sub>2</jats:sub> using the same equipment, representing an efficient one-pot process. The copolymerization of L-LA with VL using this technique at a feed ratio of 90/10 mol/mol gave poly(L-LA-<jats:italic>ran</jats:italic>-VL) (91/9) with a molecular weight of 6.48 × 10<jats:sup>4</jats:sup> g/mol and a high yield of 74.9%. Products with molecular weights over 5.0 × 10<jats:sup>4</jats:sup> g/mol were obtained at L-LA feed proportions of 70 to 90%. Impregnation trials were conducted between 40 and 120 °C at 14 MPa for 3 h. The oil content of a 73/27 specimen was found to increase significantly during processing at 100 or 120 °C. During enzymatic degradation with proteinase K, the 91/9 specimen showed the fastest degradation rate. Although the 71/29 sample was slowly hydrolyzed in a phosphate buffer at pH 7.0, the release of oil vapor from this material was slightly higher than that from the 91/9 specimen, and the vapor release rate continuously increased throughout the hydrolysis process.</jats:p>