Research Of Sythesis & Character On Ter-Polymer Hydrogel HEMA-NVP-NIPAm

N-isopropyl acrylamide(NIPAm)is the highlight in the fields of drug-delivery system as a sensitive monomer to temperature.N-vinyl-2-pyrrolidone(NVP)and 2-hydroxyethyl methacrylate(HEMA),both are better biology monomer and the copolymer of HEMA-NVP is the main composition of soft contact lenses.In this paper,the innovation is that sensitive monomer to temperature-NIPAm- was introduced into HEMA-NVP soft contact lensess based on the studying on HEMA-NVP copolymer.HEMA-NVP and HEMA-NVP-NIPAm hydrogel were individually synthesized under 500W ultraviolet lamp with the reaction monomer mixture that was composed of HEMA,NVP,NIPAm monomer,and photo initiator and cross-linker.A series of experiments have been conducted to investigate the preparation of hydrogel,copolymers swelling and their dependence on temperature, oxygen gas and Na~+ solution penetration through the copolymer and hydrogel materials surface character.The contents and related origin conclusions are as follows:1.Using 0.2%(wt)2-hydroxy-2,2dimethyl acetophenone(1173)as photo-initiator and 0.5%(wt)ethylene glycol dimethacrylate(EGDMA)as cross-linker,copolymer of HEMA-NVP and ter-polymer of HEMA-NVP-NIPAm hydrogel were synthesized with NIPAm,HEMA and NVP under 500W UV lamp at room temperature for 2hrs. All samples have good transparence,with 86%average transparency in visible light wave range,and anti-causticity.The pH value of dipping samples liquid is 7.1～7.7, approach to 7.20 that belong to human-being tears.2.The dependence of monomer total conversion on NIPAm content,monomer mass ratio(MMR)and 1173 photo initiator,and the dependence of hydrogel structure and equilibrium water content(EWC)on the MMR and NIPAm content were investigated.The experiments result revealed that the MMR,NIPAm and 1173 influenced copolymerization speed and didn't change the total conversion.TG test result revealed that the hydrogels initial charring temperature,the maximum charring temperature falls as HEMA/NVP ratio reduce,the hydrogel charring temperature rise as NIPAm mass increases. 3.The swelling experiments disclosed that EWC of HEMA-NVP increases with NVP increases,and falls with the cross-linker of EGDMA increases.For the HEMA-NVP-NIPAm,the hydrogel EWC increases with NVP/NIPAm increases when keep HEMA unchanged,EWC increases as NIPAm content increases when keep HEMA/NVP ratio unchanged.4.Hydrogel sensitivity to temperature and the dependence of hydrogel swelling kinetics on MMR were investigated by measuring hydrogel mass,the results showed that the EWC depence on temperature falls as the EGDMA increases and it increases as the NVP increases for HEMA-NVP copolyme.At room temperature,the copolymer swelling character index increases with the NVP mass increases,the swelling behavior was changed into the Case-Ⅲfrom FICK.With the temperature increases, the hydrogel materials swelling are dominative by water diffusion and the swelling model tend to FICK.For those hydrogel with high NVP mass,temperature is prone to improve the polymer network relaxation and change materials swelling behavior model.For the ter-polymer of HEMA-NVP-NIPAm,hydrogel EWC increases with NIPAm mass increases and the sensitivity to temperatureof terpolymer improved.At room temperature,the ter-polymer swelling behavior follows non-Fick model.As swelling temperature increases,for the ter-polymer from HEMA/NVP/NIPAm =68/16/16 or 40/10/50,the swelling kinetics curve revealed that water diffusion become dominate process,for the ter-polymer from HEMA/NVP/NIPAm=34/33/33, which swell dynamic curve dependence on temperature was complicated and needed to get much more information.5.The oxygen and Na~+ penetration through eopolymer hydrogel has benn investigated and the experiments result showed that the penetration performance was improved as the thickness of the hydrogel film be waken or the EWC increased.In the ter-polymer of HEMA-NVP-NIPAm,the dependence of hydrogel penetration on the three monomer take turns as:NVP＞NIPAm＞HEMA.6.Surface character of HEMA-NVP and HEMA-NVP-NIPAm was measured including surface wetting,the absorbency of bovine serum albumin(BSA)and surface dehydration.For HEMA-NVP copolymer surface wetting experiments,the result showed that the copolymer surface was more hydrophilic as the NVP content increased,at the same time,contact angle shrink between copolymer surface and drip as contact time extend.The absorbency of BSA revealed that the absorb time of HEMA-NVP was over 40mins and release BSA time was over 80mins.For different hydrogel copolymer,it was found that the absorption of pHEMA was dominated by physical absorb process,the ter-polymer absorption capacity increases with NIPAm content increases,and the copolymer absorption capacity increases with NVP mass increases.The dehydration tests revealed that the copolymer dehydration speed falls as the NVP or EGDMA cross-linker increases,however,the NIPAm was reverse.