Study On Synthesis, Structures And Properties Of Glycolide/Lactide And The Copolymers

In this thesis, high purified glycolide(GA) and L-lactide (L-LA) monomers were firstly synthesized through orthogonal experiments. Then PLGA copolymers were obtained by co-polymerization of the two monomers. The processing of the co-polymerization for controlling the microstructure and macro-performance of the materials were optimized, which established primary basis for practical use of PLGA.At first, orthogonal experiments were used to optimize the synthesis conditions for GA. Effects on the yield of the product, include the type and dosage of catalyst, reaction time, polymerization temperature were evaluated. The structure of GA were characterized by infrared spectroscopy (FTIR), thermal analysis (DSC), wide angle x-ray diffraction (WAXD) and nuclear magnetic resonant (¹H-NMR) techniques. The results indicated that relatively high yield can be obtained under the conditions of adding 0.8g Sn₂O₃, dewatering at 110～130℃/2h, polymerization at 180℃/4h and decomposition at 260～280℃. High purity GA can be prepared by re-crystallization for three times.Besides, by using lactic acid as monomer, L-lactide (L-LA) is synthesized by condensation polymerization and consequent de-polymerization steps. Effects of synthesis parameters on the yield were also investigated by orthogonal experiments, such as catalyst types and dosage, dewater temperature and decomposition temperature. The purification method on the yield and content of impurities (lactic acid and water) was studied. The molecular structure of prepared L-LA was characterized by FTIR, DSC and ¹H-NMR techniques in detail. Results indicated that the yield of L-LA can reach 80% when dewater and decomposition temperature are 130℃ and 190℃ respectively. After four times re-crystallization in ethyl acetate, high purity product can be obtained successfully.Finally, the open-ring polymerization method was used to synthesis a series of PLGA with various dosage ratios of GA and L-LA. The structure of the copolymers were analyzed by FTIR, DSC, WAXD, ¹H-NMR and gel permeation chromatogram (GPC). The relationships of polymerization temperature/time, monomer ratios between relative...