Development of Novel Biodegradable Polymers with High Melting Temperature

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In this year, we have examined some properties and biodegradation of the polymers synthesized last year. Then, we have fed back the obtained results to polymer synthesis, and developed the polymers with good properties and biodegradability.We have prepared the following copolymers with melting temperature higher than 100ﾟC ; (R)-beta-butyrolactone [(R)-beta-BLupsilonepsilon-caprolactone (CL) copolymers ((R)-beta-BL/CL>75/25 ), _L-lactide (_LLA)/CL copolymers(_L-LA/CL>85/15) , and the copolymers of _L-LA with _L-DMO (_L-3, _<DL>6-dimethyl-2,5-morpholinedione ; one of cyclic depsipeptides) (_L-LA/_L-DMO>85/15) etc. The _L-LA/_L-DMO copolymers were degraded most by enzymes such as proteases.Subsequently, we have measured the thermal and mechanical properties of the _L-LA/_L-DMO (=92/8) copolymer. As a result, the thermal and tensile properties of this copolymer were kept at much the same levels as those of poly(_L-LA), however, the brittleness (the lack of flexibility) of poly(_L-LA) could not be improved Thus, we have prepared the _L-LA/_L-DMO/CL terpolymers ; the introduction of CL unit can be expected for improving the brittleness of poly(_L-LA) ; and examined some properties and biodegradability of the terpolymers. It has become apparent that the terpolymers containing ca 10mol% of CL unit, e.g., _L-LA/_L-DMO/CL (=88/4/8) copolymer shows a relatively high elongation, keeping good tensile strength and biodegradation. Henceforth, we will prepare these types of terpolymers, using various depsipeptides and lactones, and develop novel biodegradable polymers having both good properties and biodegradability.