Studies On The Syntheses And Properties Of Graft Copolymers Based On PVA As The Main Chains And PLA、PLGA As The Side Chains

Polylactic acid (PLA) and its copolymer of lactic acid and glycolic acid (PLGA) haveattracted growing attention of scientists due to their advantages such as biocompatibility,biodegradability and avirulence. They were used widely in medicine, food, agriculture andindustry, and many areas of life. High molecular weight PLA and PLGA are usually made oflactide, glycolide and some other monomers by ring opening polymerization orcopolymerization, but these two methods have the shortcomings of expensive monomers,harsh conditions and high large scale applications cost. At the same time, poor hydrophilicityand toughness degradation are major drawback with pure PLA, so its application range waslimited. In order to overcome these defects, the study designed two comb-like polymers inwhich hydrophilic polyvinyl alcohol was used as main chain, PLA and PLGA were used asside chain. And both of these two grafting polymers were synthesized by meltingpolycondensation using1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(EDC HCl) as a catalyst. A series of copolymers were synthesized by adjusting the molarratio of monomers, and the effects of different reaction conditions on properties of productwere also studied. We also determined the molecular weight of the copolymers, contact Angle,permeability, and various structural performances by using nuclear magnetic resonance(NMR), infrared spectroscopy, dynamic thermogravimetric analysis, differential thermalanalysis and X-ray diffraction. The results showed that the molecular weights of thecopolymers synthesized by direct polycondensation can reach up to some cetain values.According to the results, we found that with the increase in LA content, the property oftoughness had been greatly increased, crystallinity degree decreased and the hydrophileincreased, and also with the increase in GA content, its hydrophilicity and adhesive abilitieshad been improved dramatically. The copolymers’ degeneration speeds can be adjusted bychanging the raw material’s formulae. The results suggest that PVA-g-PLGA has theproperties of good hydrophilicity, toughness and controllable degradability.In order to inspect applications of the products in medicine field, I made two kinds ofmedical anti-sticking films from grafting copolymer PVA-g-PLA and PVA-g-PLGA, andimplanted these films into the back of SD rats to observe the biocompatibility and degradationof these comb copolymers. The preliminary studies revealed that PVA-g-PLA andPVA-g-PLGA could prevent the wound tissue adhesion, and both of them had a goodhistocompatibility and appropriate mechanical properties. PVA-g-PLGA films werebiodegraded completely in the back of SD rats6weeks later, which was faster thanPVA-g-PLA that degraded in8weeks. Cytotoxic activities experiments in vivo suggest thatthese polymers exhibited good activities(its cytotoxicity less than grade1). The implantexperiments in the body of animals and the cytotoxic activities experiments show that thecomposite material has good biological compatibility and biosafety, so the materials areexpected to be used for prevention of post surgical adhesion membrane in the future. The twotypes of grafting copolymers PVA-g-PLA and PVA-g-PLGA can be prepared by using cheapraw materials under suitable technological conditions, therefore this products has good application prospects.