Photochemical Synthesis And Characterization Of Hydrogels Containing Polyacrylamide

Responsive hydrogels are sensitive to the external stimulus such as temperature, pH,composition of solution, light, ionic strength, magnetic field, electric field, and somebiochemical molecules. Especially the temperature and pH responsive hydrogels whoseswelling and deswelling behaviors are controlled by temperature and pH, have promisingpotential application in the field of drug delivery system, biomaterial culture, separation andenzyme immobilization, and so on. At the same time, excellent biocompatibility is necessary tothem. PDMAA(Poly(N,N'-dimethylacrylamide)) is a kind of polymer with excellentbiocompatibility. By introducing DMAA-based structure into responsive hydrogel, itsapplication will has brilliant prospects. In this paper, P(DMAA-co-MMA) copolymerichydrogels,P (DMAA-MMA)/nano-SiO₂ complex hydrogels, P(N,N'-dimethylacrylamide-co-N-isopylacryl amide ) hydrogels, temperature/pH sensitive P(AAc-co-NIPAm) hydrogels andP(AAc-co-NIPAm) INP hydrogels were prepared by the technique of photochemistry, theirtemperature, ionic strength, pH sensitive behaviors and the association between networks werestudied. Obtained conclusions were of high academic and reference value to synthesize andcharacterize intelligent hydrogels. The followings are main conclusions of our work:1. Poly(N,N'-dimethylacrylamid) hydrogels have been prepared by the technique ofphotochemistry. The process of photo-polymerization was completed within conveniently andswift. The best experiment conditions of high Swelling Ratio (SR) and conversion rate wereobtained (the reaction time is 100 s, the dosage of crosslinker is 1.5ï¼…). 1)P(DMAA-co-MMA) copolymeric hydrogels were synthesized by adding a bit of MMA. AddingMMA made higher intensity of the hydrogels network than PDMAA hydrogels, and couldweaken the effect of pH. 2) P(DMAA-MMA)/nano-SiO₂ complex hydrogels were prepared bythe radical graft copolymerization of N,N'-dimethylacrylamide and a bit of MMA onto thesurface of nano-SiO₂ particles whose surface was modified. P(DMAA-co-MMA) copolymerichydrogels exhibit higher swelling ratio, pH-sensitive and ionic strength sensitive than PDMAAhydrogels.2. P(N,N'-dimethylacrylamide-co-N-isopylacrylamide) hydrogels have been prepared by thetechnique of photochemistry in the solvent of H₂O at different temperatures (50℃and 28℃)respectively. The hydrogels synthesized at 50℃(P2) exhibit a looser network and lower swellingratio than the hydrogels synthesized at 28℃(P1), but P2 exhibit faster temperature and betterionic strength (0.1～3.0 mol/L) responsive properties, more excellent water release behavior at high temperature.3. P(AAc-co-NIPAm) hydrogels have been prepared by the technique of photochemistry in thesolvent of H₂O at different temperatures (50℃and 28℃) respectively. The hydrogels exhibit anobvious pH sensitive behavior. In acidic (pH=4.0) solution, the SR of the hydrogels decreasewhile the temperature raised. The hydrogels synthesized at 50℃exhibit a more obvious pH andtemperature responsive properties.4. Poly(acrylicacid)/Poly(N-isopropylacrylamide)(PAAc/PNIP) IPN hydrogels has beensynthesized by the technique of photochemistry. The Swelling Ratio (SR) of this hydrogel inweak alkaline (pH=9.18) solution is much more than that in acidic (pH=4.0) solution.Experimental results showed that in the range of 30～80℃its SR increased as the temperature inacidic solution, and its SR decreased as the temperature in alkaline (pH=9.18) solution.Another approach in this paper is controlled photopolymerization of N,N'-dimethylacryl-amide as a monomer. Obtained conclusions were of high academic and reference value to how tocome true controlled/"living" radical polymerization of N,N'-dimethylacrylamide monomers.After selecting experiment conditions such as the film reactor selection, the kind and dosage ofinitiator, the intensity of light, reaction time, the kinds of controlled systems and so on. Thekinetic performances of the bulk photopolymerization of DMAA in the different systemsmediated by HTEMPO and PMP/HTEMPO, was studied using Irgacure651 as an initiator atambient temperature. The results of the systems controlled by HTEMPO as a mediator wasshown that obtained the DMAA homopolymers exhibited narrow polydispersities (PDI=1.20～1.50), which was characterized by GPC, even until the conversion up to 80ï¼…. When themolar ratio of PMP/HTEMPO was 3.0, the photopolymerization of DMAA was controlled, andthe smallest value of polydispersity index (PDI) was 1.15. It is found that when HTEMPO wasonly used as a mediator, the same results were obtained in the system with the PMP/HTEMPO.The number average molecular weight ((?)_n) of the DMAA homopolymers increased linearlywith conversion, but PDI was higher, indicating that the system with PMP/HTEMPO wassuperior to that with HTEMPO.