Enzymatic hydrolytic degradation of aliphatic polyesters in organic solvents has been examined. The degradation of poly(epsilon-caprolactone) took place using Candida antarctica lipase as catalyst in toluene at 60 degrees C to give oligomers with molecular weight of less than 500. The degradation behavior catalyzed by lipase was quite different than an acid-catalyzed degradation (random bond cleavage of polymer). After the removal of the solvent from the reaction mixture, the residual oligomer was polymerized in the presence of the same catalyst of lipase. These data provide a basic concept that the degradation-polymerization could be controlled by presence or absence of the solvent, providing a new methodology of plastics recycling.

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Synthesis of aliphatic polyesters has been examined using Candidaantarctica lipase in supercritical carbon dioxide (scCO2). The enzymatic ring-opening polymerization of ε-caprolactone (ε-CL) proceeded in scCO2 to give a polymer with molecular weight higher than 104. Effects of reaction parameters such as the monomer concentration, enzyme amount and pressure have been systematically investigated. Copolymerization of ε-CL with 12-docecanolide afforded the random copolymer. The enzymatic polycondensation of divinyl adipate and 1,4-butanediol also proceeded in scCO2 to produce the corresponding polyester.

Hydrolytic degradation of polyurethane has been achieved using lipase as catalyst. The degradation of polyurethane containing an aliphatic polyester chain as soft segment rapidly took place in the presence of Candida antarctica lipase in toluene at 60 °C to give oligomers with molecular weight less than 500.

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