Synthesis and characterization of poly(N-isopropyl acrylamide) gels prepared by using (NH₄)₂Ce(NO₃)₆-Tegomer H-Si 2111 redox pair

Hydrogels have been prepared by free radical solution polymerizations in acetone and acetonitrile of N-isopropyl acrylamide (NIPAAM). The redox pair composed of ceric ammonium nitrate ((NH₄)₂Ce(NO₃)₆, Ce(IV)) as an catalyst and •,• -dihydroxy poly(dimethylsiloxane) (Tegomer H-Si 2111, H-Si) as an activator and hydrophobic constituent was used to initiate the polymerizations. The equilibrium swelling degrees against the temperature and lower critical solution temperatures (LCSTs) in water were investigated for the gels produced by changing the initial [Ce(IV)] / [H-Si] ratios and monomer concentrations in the reaction media. Results showed that type of synthesis-solvent had an important effect on the stability and concentration of Ce (IV)-H-Si complexes, which had been used to synthesize the PNIPAAM gels having hydrophobic Tegomer H-Si end groups.