The hydrophilicity of silicone hydrogels used as soft corneal contact lens plays an important role in wearing comfort.In order to enhance hydrophilicity and protein resistance,silicone hydrogel membranes were modified by atmospheric pressure glow discharge plasma(APGDP) induced surface graft polymerization of N-vinyl pyrrolidone(NVP) and poly(oligoethylene glycol methyl ether methacrylate)(PEGMA) in this paper.XPS analysis demonstrated the success of graft polymerization of NVP and PEGMA onto the surface of silicone hydrogel membranes.The hydrophilicity of silicone hydrogels was characterized by the measurement of water contact angle(WCA).The result showed that NVP grafted silicone hydrogel has the WCA of about 68°and PEGMA grafted silicone hydrogel has the lowest WCA of about 62°,while the pristine silicone hydrogel is hydrophobic with the WCA of about 103°.Protein resistance of silicone hydrogels was investigated by the method of bicinchoninic acid assay using bovine serum albumin(BSA) as a model.It's found that the grafted silicone hydrogel has a significant improvement of protein resistance,and PEGMA grafting is more efficient for the reduction of protein adsorption than NVP grafting.The silicone hydrogel membranes grafted with NVP and PEGMA are good candidates of soft corneal contact lenses.
Antibacterial poly(D,L-lactide)(PDLLA) fibrous membranes were developed via electrospinning,followed by surface modification which involved plasma pretreatment,UV-induced graft copolymerization of 4-vinylpyridine(4VP) and quaternization of the grafted pyridine groups with hexylbromide.The success of modification with quatemized pyridinium groups on the PDLLA fibrous membranes was ascertained by X-ray photoelectron spectroscopy(XPS).The antibacterial activities of these membranes were assessed against Gram-positive Staphylococcus aureus(S.aureus) and Gram-negative Escherichia coli(E.coli).The PDLLA fibrous membranes modified with quaternized pyridinium groups showed antibacterial efficiency against both bacteria as high as 99.999%.The results demonstrated that the antibacterial activity was based on the interaction of the positive charge of pyridinium group and negatively charged cell membrane of bacteria, resulting in loss of membrane permeability and cell leakage.
Poly(vinylidenefluoride-hexafluoropropylene)(PVDF-HFP) nanofiber membranes with improved hydrophilicity and protein fouling resistance via surface graft copolymerization of hydrophilic monomers were prepared.The surface modification involves atmospheric pressure glow discharge plasma(APGDP) pretreatment followed by graft copolymerization of poly(ethylene glycol) methyl ether methacrylate(PEGMA).The success of the graft modification with PEGMA on the PVDF-HFP fibrous membrane is ascertained by X-ray photoelectron spectroscopy(XPS) and attenuated total reflectance Fourier transform infrared measurements(ATR-FTIR).The hydrophilic property of the nanofiber membranes is assessed by water contact angle measurements.The results show that the PEGMA grafted PVDF-HFP nanofiber membrane has a water contact angle of 0°compared with the pristine value of 132°.The protein adsorption was effectively reduced after PEGMA grafting on the PVDF-HFP nanofiber membrane surface.The PEGMA polymer grafting density on the PVDF-HFP membrane surface is measured by the gravimetric method,and the filtration performance is characterized by the measurement of water flux.The results indicate that the water flux of the grafted PVDF-HFP fibrous membrane increases significantly with the increase of the PEGMA grafting density.
The interpenetrating polymer network(IPN) silicone hydrogels with improved oxygen permeability and mechanical strength were prepared by UV-initiated polymerization of monomers including methacryloxypropyl tris(trimethylsiloxy)silane(TRIS),2-hydroxyethylmethacrylate(HEMA) and N-vinyl pyrrolidone(NVP) in the presence of free radical photoinitiator and cationic photoinitiator.The polymerization mechanism was investigated by the formation of gel network.The structure of IPN hydrogels was characterized by Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC) and transmission electron microscopy(TEM).The results showed that the IPN hydrogels exhibited a heterogeneous morphology.The mechanical properties,surface wettability and oxygen permeability were examined by using a tensile tester,a contact angle goniometer and an oxygen transmission tester,respectively.The equilibrium water content of the hydrogels was measured by the gravimetric method.The results revealed that the IPN hydrogels possessed hydrophilic surface and high water content.They exhibited improved oxygen permeability and mechanical strength because of the incorporation of TRIS.
Zein/chitosan composite fibrous membranes were fabricated from aqueous ethanol solutions by electrospinning. Poly(vinyl pyrrolidone)(PVP) was introduced to facilitate the electrospinning process of zein/chitosan composites.The asspun zein/chitosan/PVP composite fibrous membranes were characterized by scanning electron microscopy(SEM) and tensile tests.SEM images indicated that increasing zein and PVP concentrations led to an increase in average diameters of the composite fibers.In order to improve stability in wet stage and mechanical properties,the composite fibrous membranes were crosslinked by hexamethylene diisocyanate(HDI).The crosslinked composite fibrous membranes showed slight morphological change after immersion in water for 24 h.Mechanical tests revealed that tensile strength and elongation at break of the composite fibrous membranes were increased after crosslinking,whereas Young's modulus was decreased.
