The Solid State Reaction Of Poly(L-lactic Acid) And Preparation The Dimer Of Lactic Acid-Leucine

In a variety of natural polymer and synthetic polymer, polylactic acid (PLA) is the most widely studied synthetic degradable polymer. Not only because of the degradation products of PLA are the non-toxic water and carbon dioxide products, but polylactic acid have better performance and processing properties. Because of its special properties,there are a lot of using in the medical and packaging industries now. Although the PLA are more widely used, the PLA itself has many shortcomings. For example PLA has a high degree of crystallinity, so the brittleness is too large; the high molecular weight polylactic acid are so expensive; lacks of biological activity groups, thus reducing biological compatibility and so on. In order to further expand the using scope of polylactic acid and to improve performance of polylactic acid,modification of the PLA is a hot research in scientists in recent years. This issue first use method of melt polymerization to obtaine polylactic acid. And we use solid phase polymerization andγ-radiation crosslinking methods to improve the molecular weight of polylactic acid at same time reduce the crystallinity of polylactic acid. We use amino acids that containe biologically active groups with lactic acid to copolymerize in order to modify PLA.①Using stannous octoate, stannous octoate and p-toluene sulphonic acid as catalyst to make the polylactic acid, respectively. Using polarized light microscopy found that the more obvious ball crystal.The results of DSC, TG thermal analysis show that the initial decomposition temperature of the synthesis of polylactic acid is above 260℃, melting temperature is above 140℃.②The use of lower molecular weight of polylactic acid by solid phase polymerization to improve the molecular weight. And research the reaction temperature and catalyst content on the molecular weight of solid phase polymerization.③Research the polylactic acid of different TAIC content at low radiation doses of y-Radiation effects, and the results showed that TAIC with poly(lactic acid) have a good cross-linking, the molecular weight has been significantly improved, and with the increasing of TAIC, PLA crystallinity decreased. Moreover, with the increase of radiation dose, the molecular weight of polylactic acid first increased and then decreased. In the study of the low radiation dose when the radiation dose is 10KGy,the highest molecular weight are got;④First preparation the leucine methyl ester salt and threonine methyl ester salt.Second the reaction of lactic acid and leucine methyl ester salt and the reaction of lactic acid and threonine methyl ester salt. Respectively to get lactic-leucine methyl ester dimer and lactic-threonine methyl ester dimer. At same time we try some reaction of the polymerization.