|Budget Amount *help
¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1996 : ¥1,200,000 (Direct Cost : ¥1,200,000)
The structure-property relationships of one-and two-component aliphatic polyesters have been studied for developing new biodegradable polymers that can be readily synthesized by chemical synthesis. The following results have come out of this study. (1) Poly (L-lactic acid) (PLLA) with high degree of polymerization could successfully be prepared by direct melt-polycondensation of L-lactic acid. In this polycondensation, an oligomer with Mw=1,000-5,000 was first made from L-lactic acid and then subjected to thermal condensation at reduced pressure in the presence of silica-alumina heterogeneous catalyst system to from high polymers with molecular weight higher than 100,000. (2) PLLA with Mw=10,000-30,000 was prepared by similar direct polycondensation of methyl L-lactate, when special tin catalysts were used. With these successes low-cost manufacturing of PLLA should be performed in the near future. (3) Both gamma-valerolactone and gamma-butyrolactone, having no polymerizability, were co
polymerized with beta-butyrolactone to form bacterially synthesized copolyalkanoates. (4) A-B-A block coply (ester-ethers) comprising PLLA as A and polyether (poly (oxyethlene/propylene) : Puluronic^<TM>) as B were synthesized, melt-spun to obtain biodegradable fibers. It was shown that the fibers have increased hydrolyzability and flexibility. (5) Solid state post-polymerization of L-lactide has been found to be effective for decreasing remaining monomer in the final polymerization product. This methos will contribute the practical manufacturing of PLLA based on the ring-opening polymerization of L-lactide. (6) It has been demonstrated that a two-component aliphatic polyester, poly (butylene succinate) (PBS), can be processed to high-strength fibers if its molecular weight is enough high. Enzymatic degradation of the PBS fibers was also studied by use of various lipases.
These synthetic methods should give new tools for manufacturing the biodegradable polyesters, whose applications covers not only commodity goods, but also biomedical materials. Less