Presentations

Chemical recycling of bio-based polymers such as poly(butylene adipate) and poly(butylene succinate), were studied using an enzyme. Chemically recyclable bio-based polymers were prepared via the ring-opening polymerization of cyclic oligomers which were produced by the condensation of diols and dicarboxylates by lipase in a toluene solution. The cyclic oligomer was readily polymerized by the same lipase in more concentrated solution to produce a high-molecular weight polyester. The produced polyester was readily degraded by lipase to produce cyclic oligomers as the chemical recycling. In this report, the effect of ring-size of cyclic oligomer was studied with respect to the repolymerizability.

Aliphatic polythionoesters were prepared by the one-pot thionoesterification of polycaprolactone, polypentadecanolactone, poly (butylene succinate) and poly (butylene adipate) using diphosphorus pentasulfide and hexamethyldisiloxane. And their physico-chemical properties as well as enzymatic degradabilities and chemical recyclabilities were evaluated.

Novel nonionic surfactants containing carbonate linkages were synthesized by the two-step reaction of 1-dodecanol and diphenyl carbonate with the subsequent reaction with tetraethylene glycol using lipase. And their physico-chemical properties and biodegradabilities were measured.

Enzyme-catalyzed synthesis and degradation of a typical diol-diacid type plastic, poly(butylene succinate) (PBS), and diol-diacid type polythioester were studied with respect to the establishment of sustainable polymer production and chemical recycling system. A significantly higher-molecular weight polyester was produced via the ring-opening polymerization of the cyclic oligomer. The cyclic oligomer was produced both by the condensation of monomers and degradation of the polyester. Polymer blends of PBS/poly(L-lactic acid) (PLLA) were degraded into repolymerizable oligomers, first by the lipase-catalyzed degradation of PBS into cyclic BS oligomers followed by the degradation of PLLA into lactic acid oligomers by montmorillonite K-5. By the reprecipitation procedures, the PLLA and BS oligomers were completely separated. Aliphatic dithiol-diacid type polythioesters were enzymatically prepared by the direct polycondensation of dithiol and diacid diesters. A higher molecular weight polythioester was produced using lipase in a two-step procedure, i.e., cyclization with subsequent ring-opening polymerization.

Polythioester was enzymatically synthesized by both polycondensation and ring-opening polymerization. The obtained polythioesters showed a higher melting point compared to the corresponding polyoxyesters.