Synthesis and Characterization of Novel Poly(N-vinylcaprolactam-co-itaconic Acid) Gels and Analysis of pH and Temperature Sensitivity

Poly(N-vinylcaprolactam-co-itaconic acid), P(VC-co-IA), gels were synthesized in ethanol by using the free radical cross-linking polymerization method at 60 degrees C for 24 h in the presence of azobis(isobutyronitrile) (AIBN) and ally] methacrylate (AMA) as the initiator and the cross-linking agent, respectively. In order to determine the effect of the synthesis medium on the percentage of gelation (PG) and equilibrium swelling value (ESV), an ethanol/distilled water mixture (80:20, v/v) was also used as the synthesis medium for poly(N-vinylcaprolactam) (PVC) and P(VC-co-IA) gels. The swelling behaviors of the gels were investigated in distilled water at various temperatures and in different pH buffer solutions. Structural, morphologic, and thermal characterization studies of the gels were carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA), respectively. The lowest PG and highest ESV were obtained for the gel including 5 mol % IA, which was the gel synthesized in the ethanol/distilled water mixture. PVC synthesized in ethanol/water mixture had the highest percentage of gelation. All the gels displayed pH- and temperature-sensitive swelling behavior. The swelling kinetics of the copolymer gels synthesized in ethanol was investigated at pH 10.0, and it was determined that gels containing 5 and 10 mol % of IA indicated non-Fickian and case II swelling behavior, respectively.