Study On Silk Fibroin/Polyvinyl Pyrrolidone IPN Hydrogel

Polyvinyl pyrrolidone（PVP） and Silk fibroin（SF） are both high polymers with excellent biocompatibility, they are widely used in the field of medical polymer materials. In this article, the polymerization of NVP has occurred in the SF solution and formed a kind of IPN hydrogel, with high resilience and transparency, it dedicates to be applied in the area of artificial vitreous and cornea repairment. This paper mainly studys the structure and properties of the hydrogel to explore the gelation mechanism, the influence of mixture ratio and initiator concentration have also been discussed.IPN structure can greatly shorten the gelation time compared to the polymer blends and pure silk, which would be streched for more than a week with SF conformation turned to β-sheet. Moreover, the light transmittance of IPN hydrogel could be as high as more than 97% and maintain a level of 90% within a week, fully meet the national standard of the contact lens materials. The hydrogel, which mainly consists of random coil, the apertures inside can be up to 200 μm. Elastic modulus increases during the process of gelation, and the gel has nealy 95% resilience under the compression of 70% eventually, much higher than that of SF gel.The gelation time turns to be the shortest（about 11 min） when the ratio is 8:2（SF:NVP）, meanwhile, the hydrogel has a light transmittance of 97%, a resilience of 95% and the highest compression strength. As the content of NVP increases, the gelation time extends and apertures inside are enlarged. But the light transmittance increases at first and then decreases, so do the compression strength and resilience. When the concentration of H₂O₂ is 1 mM/L, with compact apertures, the hydrogel has a light transmittance of 97%, a resilience of 95% and the highest compression strength. But the light transmittance and compression strength would be reduced if the concentration of H₂O₂ is too high or too low.The mechanism of gelation shows that, when the content of NVP accounts for 1.5% that of H₂O₂, the gel has a more regular structure of network, leading to a optimal result in compression strength, light transmittance and resilience. When the ratio turns to be too high or too low, the content of Free Water elevates and the degree of polymerization decreases, which would loose the structure of network and get an inferior material. In addition, the incident light may cause scattering phenomenon which weakens the transmission light intensity would lead to a decrease of the transparency.