Investigation On Radiation Polymerization And Application Of Hydrogels Containing N-isopropylacrylamide

Poly(N-isopropylacrylamide) (PNIPA) hydrogel is a typical temperature sensitive hydrogel. Around a certain temperature (LCST), there is an abrupt change of swelling ratio up to several hundreds. It swells in water below LCST, and shrinks above LCST. Due to its proper gel transition temperature and swelling property, PNIPA hydrogel is used in medicine separation and controlled drug delivery.In this paper, radiation polymerization was used without any initiator and cross linker. This method was especially attractive for synthesis of hydrogel with potential biomedical application.In order to meet the requirement of various applications, a series of hydrogels were prepared by four monomers forming copolymers or interpenetrating polymer networkers (IPN) with NIPA.Poly (N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) hydrogels (P (NIPA-HEMA )) and P(NIPA)/P(HEMA) IPN hydrogels were synthesized at different molar ratios in various media. Small differences of solubility parameters between P( NIPA-HEMA ) and reaction media were in favor of producing homogeneous hydrogels with higher swelling ratios. The transition temperatures of these hydrogels were enhanced as HEMA contents in the gels increased. These hydrogels were fit for macromolecule drug release.Poly(N-isopropylacrylamide-co-N-vinylpyrolidone) hydrogels were prepared. The gel transition temperatures and swelling ratios of these hydrogels were enhanced as NVP contents in the gels increased. The swelling ratios of P(NIPA-co-NVP) hydrogels were less decreased in aqueous electrolyte solutions. Due to the ability of forming associationcomplex with biological molecules, these hydrogels made drug easily todissolve.Poly(N-isopropylacrylamide-co-2-methpropyl sulfonate) hydrogels were manufactured. They had extremely high swelling ratios and improved transition temperatures; and could be used in concentration of macromolecule drug.Temperature and pH sensitive hydrogels were produced by NIPA with sodium acrylate (SA) or sodium methacrylate (SMA). Drug releasing rate was nearly zero in the buffer solution of pH 1, while the releasing rate increased in the buffer solution of pH 7.4.Finally, states of water were investigated by DSC. There were three type of water in the hydrogel, and the gel transition temperature was obtained.