The Synthesis And Responsive Behaviors Of Thermo-and PH-sensitive IPN Hydrogels

Responsive hydrogels are sensitive to the external stimulus such astemperature, pH, composition of solution, light, ionic strength, magnetic field,electric field, and some biochemical molecules. Especially the temperature andpH responsive hydrogels whose swelling and deswelling behaviors are controlledby temperature and pH, have promising potential application in the field of drugdelivery system, biomaterial culture, separation and enzyme immobilization, andso on. At the same time, excellent biocompatibility is necessary to them.PVP(Poly N-vinyl pyrrolidone) is a kind of polymer with excellentbiocompatibility and it has the ability to bind reversibly to various molecules(dyes, metals, and some polymer, for example, Poly acidic acid). By introducingNVP-based structure into responsive hydrogel, its application will has brilliantprospects. In this paper, new IPN hydrogels Poly(N-vinyl pyrrolidone-co-β-hydropropyl acrylate)/ Poly(acidic acid ) P(NVP-co-HPAT)/PAA andPoly(N-vinyl pyrrolidone-co- acidic acid)/ Poly(β-hydropropyl acrylate)P(NVP-co-AA)/PHPAT were prepared, their temperature and pH sensitivebehaviors and the association between networks were studied.Random copolymer of P(NVP-co-HPAT) was prepared by radicalcopolymerization. The hydrogels of P(NVP-co-HPAT) obtained by changing theinitial NVP/HPAT mol ratio, total monomer, and cross linker concentration havedifferent thermoresponsive properties. The copolymers with wide range ofNVP/HPAT mol ratio have sensitivity thermoresponsive character. The resultshows that cross linker concentration has greater effect on the swelling ratio(SR),the tOtal monomer conceIhaion has greatCr effect on the sensitivity tOtemPeratUre, and the LCST of copolyIner were decided by the HPAWP molratio.IPN hydrogel PpeVP-co-HPAThaA was synthsized by usinginterpenetrating polymer nerworks(IPN) technique. The resultS of DSC andSEM show that in acidic medium, the association betwCen the two netwOrks exists,while in alkaline medium it doesn't exiSt. Its temPerAn and pH sensitivebehaviors were studied. In acidic meditun, the swelling ratio(SR) of this hydrogelslWs sudderily and drops quickly with the temPeratUre raised due to thehyduogen bond formation betWeen PNVP and PAA. In alkaline medium, the SRof the IPN hydrogel rises as the temPeratUre is raised.P(NVP-co-AA)NHPAT IPN hydrogel was prepared. The results of DSCshOw that in distilled waer, there is hydrogen bond formed between PNVP andM, and in buffer solUtion, the hydrogen bond doesn't exist, while even indistilled Waer, there isn't hydrogen bond formed between PHPAT and PNVP ItstemPeratUr and pH sensitive behaviors were stUdied. In distilled Watef, theswelling ratio(SR) of this hydrogel slUrnPs suddenly and drops quickly with thetemPeratUre raised due to the hyduogen bond formation between PHPAT and PAA,In alkaline medium, the SR of the IPN hydrogel rises as the temPeratUre is raised.