Poly (N-Isopropylacrylamide-Stearyl Acrylate) Hydrophobic Association Hydrogels:Synthesis,Characterization And Application

Hydrogels are hydrophilic polymer with three-dimensional networks which are able to swell in aqueous solutions without losing integrity of their structure. Because of the similar environment of swollen hydrogels and body fluid, hydrogels could be used as biological materials. For the application of biological materials, hydrogels should have good biocompatibility and biodegradability. Gelatin, a natural polymer with good biocompatibility, was chose as an emulsifier. Stearyl acrylate was used as a hydrophobic monomer to provide hydrophobic interaction. The main works were listed as follow:1. Poly (n-isopropylacrylamide-stearyl acrylate) hydrogels were successfully prepared by free radical micellar copolymerization of hydrophilic n-isopropylacrylamide (NIPAM) with the hydrophobic stearyl acrylate (C18) by using macro molecular gelatin as emulsifier and APS as initiator. Fourier transform infrared spectra and DSC measurement demonstrated the formation of the copolymer.2.The influences of C18 content on the swelling abilities, the phase transition and the mechanical properties of hydrogels were discussed. With the increasing of C18, the swelling ratio and the lower critical solution temperature (LCST) of hydrogels decreased and the tensile strength of hydrogels increased. The MC3T3 mouse cells were used to study the cytotoxicity of hydrogels. The results of the test showed that the hydrophobic association hydrogels were of low toxicity. The cell proliferation test of samples was researched. According to the results, the materials promoted the growth of cells. And samples with a higher C18 content than others showed a better behavior on cell proliferation. The cell proliferation test showed the present hydrogels good candidates for developing novel tissue regeneration materials.3. The network structure of P(NIPAM-C18) hydrogels was observed by SEM. The SEM micrographs showed two kinds of network in the structure of the hydrogels, hydrogen bonding interactions network of gelatin and hydrophobic interactions network.4.Because of the different two kinds of network of the hydrogels structure, the influences of different ratio of the two networks changing by the amount of gelatin on hydrophobic association hydrogels were discussed. The tensile test showed samples had good mechanical properties when the ratio of two kinds of network was equal, and the tensile strength was above 60 kPa. Furthermore, with the increasing of hydrogen bonding interactions network of gelatin, LCST of samples increased and the swelling ratio of samples decreased. Finally, a kind of natural crosslinker, genipin was added to crosslink the gelatin. Samples cross-linked by genipin were used to study the drug delivery of hydrogels, with ibuprofen as a model drug. Under body's temperature (37?), the release ratio of samples could reach around 50% within 6 hours.