Synthesis And Properties Of Polymer Hydrogels With Photoresponsive Deformation

Photoresponsive hydrogels,with the properties of softness and wetness,is expected to be the novel materials for producing parts of micro-apparatus,such as switch,valve,sensor and so on.Compared to other intelligent polymers, photoresponsive hydrogels will have very brighter prospect in industrial and biomedical cycles because of its safe,clean and easy to be controlled and to be used light source-UV.Now,the research on the photoresponsive hydrogels is just on the primary phase.To achieve the photoresponse to the UV,the functional groups of photoisomerization of azobenzene were copolymerized into the structure of the hydrogels in this study.Through the design of molecular,the reactive intermediate of acrylamido azobenzene(AAAB)was first synthesized,afterwards the copolymers of AAAB and AAm,NIPAAm and AA were synthesized by the approach of copolymerization and three kinds of photoresponsive hydrogels were synthesized for the first time.The structures,molecular weight and thermal properties of the copolymers and their hydrogels were characterized by the FT-IR,¹H NMR,¹³C NMR, XRD,GPC,DSC ect.,and the properties of the photoresponse to UV were studied.In this paper,we demonstrated the first example of the synthesis of the eopolymer and its hydrogels of Poly(acryl amide-co-acrylamido azobenzene) (P(AAm-co-AAAB))which contains groups of azobenzene in the side chains.The effects of the molar ratio of AAm to AAAB and the time of UV irradiation on the photoresponse of the copolymer,and the properties of swelling,photoresponse to UV and strength were studied.The results indicated that the copolymer and its hydrogels had the photoresponse to UV.The copolymer hydrogels of P(NIPAAm-co-AAAB)with the properties of thermo-sensitivity and UV response was synthesized for the first time.The effects of the molar ratio of AAAB to NIPAAm and the concentrations of NIPAAm and MBAA on the properties of swelling,photoresponse to UV,thermo-sensitivity and strength were studied.The effects of the intensity of UV and the time of the irridation on the photoresponse were also studied.The results showed that the thermo-sensitivity of the copolymer hydrogels was affected by the molar ratio of AAAB to NIPAAm and the concentration of MBAA.The volume of the hydrogels shrinked under the UV irradiation,and the higher intensity of the UV irradiation is,the faster of the photoresponse speed is.The copolymer and its hydrogels of P(AA-co-AAAB)with the properties of pH and UV response were also synthesized for the first time.The properties of UV and pH response were studied,and the results showed that the absorption were affected by the pH value and the UV irradiation.The volume of the hydrogels shrinked obviously under the UV irradiation,but resumed gradually when the UV irradiation was stopped, which means the copolymer hydrogels has excellent reversibility of photoresponse.