| In this paper, copolymer hydrogel for contact lens having high water content and high mechanical strength were prepared by copolymerization of non-ion, hydrophilic monomers N-Vinylpyrrolidone (NVP), Hydroxyethylmethacrylate (HEMA) and hydrophobic monomer methylmethacrylate (MMA), ethylmethacrylate (EMA) or butylmethacrylate (BMA), technical conditions were studied, and influence of the monomers on properties of the hydrogel material were investigated as well.During preparation of the copolymer hydrogel for contact lens, BenzoylPeroxide (BPO) was used as initiator, the dosage was 0.1% (Wt%), the dosage of NVP was no more than 40%(v/v), and the dosage of methacrylate was no more than 15%(v/v), reacting at 80℃ for 20 hours, when the product being swollen with water, colorless and transparent, odorless, glassy hydrogels membrane can be obtained, suitable for contact lens material. During copolymerization of NVP and HEMA, it was found that the reactivity ratio of NVP was 0.296, and the reactivity ratio for HEMA was 3.64, the total reaction index of the monomers was 2, the reaction index of BPO was 0.41, and the activity energy was 22.04kJ/mol. For the copolymerization of NVP, HEMA and MMA/EMA/BMA, the reaction index of BPO was 0.519, 0.523, 0.583 respectively, and the activity energy was 19.28kJ/mol, 20.11kJ/mol, 19.69kJ/mol respectively.It was found that monomers had no influence on transparency, stability and pH value of the hydrogel, and the properties comply with National Standard. The mechanical strength of the hydrogel increases with decrease in NVP and increase in methacrylate. The toxicity of the copolymer hydrogel was investigated by cell-toxicity experiments; it was found that the toxicity reaction index is 1, having no toxicity on organism.The swelling behaviors of the copolymer hydrogel were investigated. It was found that the water content and the linear swelling ratio increase with increase in NVP and decrease in methacrylate. When fully swollen, the water content of the copolymer hydrogel was 40-75%, and the linear swelling ratio of the copolymer hydrogel was 3-22%. Excessively swelling was investigated, and the reason for deviation different, from Fick's Model was given: the time that the molecular chain stretch can't be neglected.Theoretical model for dehydration of free water in hydrogel was established. It was thought that the difference of vapor pressure between the surface of hydrogel and atmosphere was the reason leading to dehydration of hydrogel; the dehydration speed of the hydrogel depends on diffusion speed of water in the capillary of hydrogel. The dehydration speed increases with increase in NVP and decrease in matharcylate. It is lower than evaporation rate of human tear under common conditions. The dehydration kinetics index is 1 for free water of the copolymer hydrogel.A kind of device to measure oxygen permeability of the copolymer hydrogel membrane was designed, and oxygen permeability of the copolymer hydrogel were measured by this device as well. It was found that the Dk/L value of the copolymer hydrogel membrane increases with increase in NVP, and decreases with increase in methacrylate. The Dk/L value of the copolymer hydrogel was much greater than that of the Poly-HEMA hydrogel. The mechanism for oxygen permeability of hydrogelmembrane was thought to be dissolution-diffussion-release of oxygen, and itwas thought that permeability of oxygen in hydrogel membrane is influenced by movements of molecular chain and water, and the methods of improving the oxygen permeability of the hydrogel membrane include decreasing the cross-linking density, increasing the water content.Affinities of the copolymer hydrogel for contact, lens with BSA and triolein were investigated. It was found that the deposition of BSA and triolein increases with increase in NVP, and decreases with increase in methacrylate in the copolymer hydrogel. When temperature increases, time becomes longer, and the concentration of BSA or triolein increases, the deposition of BSA and triolein incr...
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