The Research On Silk Fibroin Modified Poly(Lactic Acid) By Copolymerization

Poly (lactic acid) (PLA) is one of the most important environmental friendly polymers because of their biodegradability, renewable resources, and excellent properties. But poly(lactic acid) also exists many defects, such as the bad hydrophily, short of the cell identification signal and the bad cell affinity and so on. These defects restrict the PLA's application on the cell's matrixes of organization engineering and the medical postpones explaining system. The silk fibroin of silkworm is not only in rich in our country, but also having good cell affinity to the human cell. It can be used to modify the poly(lactic acid) material to improve the biodegradability of the material. There are many researches on the modification of poly(lactic acid) with aminophenol and synthetical peptide, but there aren't any on modifing the modification of PDLLA by inartificial silk fibroin peptide chain so far.In this paper, silk fibroin/PLA is prepared through ring-opening copolymerization of D,L-lactide with silk fibroin. Viscometry, polarimetry, FT-IR, differential scaning calorimetry, X-ray diffraction, thermogravimetry, scanning electron microscopy and ¹H nuclear magnetic resonance are employed for the characterization of polymers obtained. The effects of reaction time, temperature, weight of catalyst, molar ratio of two catalysts were detected.Segment PSFLA can be prepared through SnCl₂/TSA. The molecular weight, optical activity and compose of PSFLA will change with the six different delivery quality proportion. The catalyst system of D,L-lactide/ silk fibroin 6: 1 and D,L-lactide/ silk fibroin 10:1 can be used to prepare PSFLA with high molecular weight.The molecular weight and compose of PSFLA will change with the reaction conditions. PSFLA with higher viscosity can be prepared with SnCl₂/naphthalene disulfonic acid as catalyst in following conditions: reaction time 10 hours, temperature 170℃, SnCl₂ 0.5wt%, molar ratio of SnCl₂/ naphthalene disulphonic acid 1:1, and vacuum -0.1 MPa. PSFLA with higher viscosity can be prepared with Sn(Oct)₂/naphthalene disulfonic acid as catalyst in following conditions: reaction time 8 hours, reaction temperature 170℃, SnCb 0.5wt%, molar ratio of SnCl₂/ naphthalene disulphonic acid 1:1, and vacuum -0.1 MPa.PLA with high optical activity can be prepared through D, L-lactide catalyzed by Tin salt and proton acid systems, which will deduce PLA cost and lessen the pollution of solvents during its process.