Preparation And Characterization Of Photocrosslinking Poly (L-lactic Acid)-Poly (Ethylene Glycol) Hydrogel Network

The biodegradable polymer materials have been widely investigated and applied in material science and biomedical filed at recent years. Poly(lactic acid) has been attached much attention in biomedical applications owing to their innocuity, biodegradability, bioenvironmental compatibility and so on. However, their clinical applications are sometimes interfered with hydrophobic property, which in turn decreasing their biocompatibility. Another potential disadvantage is the complications resulting from the accumulation of lactic acid produced in the process of degradation. Poly(ethylene glycol) (PEG) is also an excellent biomaterial with favorable hydrophilic ability, biocompatibility and resistibility to protein adsorption and cell adhesion. If combining the advantages of PLA and PEG, better biomaterials will be attained.In this dissertation, at first poly (L-lactic acid) with two hydroxyl groups in the end (PLLA-OH) were prepared using SnCl2·2H2O as catalyst from L-lactic acid and 1,6-hexanediol by direct polycondensation. Afterward, poly (L-lactic acid) diacrylated macromer (PLLA-DA) was gained through the reaction of PLLA-OH and acryloyl chloride. Furthermore, a series of PLLA-PEG networks were formed upon UV-initiated free-radical polymerization using 2,2-dimethoxy- 2-phenylacetophenone (DMPA) as initiator. The both preparation process of PLLA-DA and PLLA-PEG hydrogel were studied in detail.The structures of PLLA-OH and PLLA-DA were characterized by IR, 1H-NMR, DSC, X-ray and GPC. The crystability of them were studied. In addition, the morphology, thermal properties, crystability, surface properties, hydrophilicity of PLLA-PEG hydrogels were measured by DSC, X-ray, DMA, SEM, XPS and Contact Angle Measurement. Control drug release performance was also studied in detail.The results showed that inserting PEG soft chains resulted in the obvious improvement of flexibility, hydrophilicity, thermal performance of PLLA-PEG hydrogels, and foretelled that these biomaterials with good control drug release performance will be widely applied in biomedical filed in the future.