Poly(N-vinylcaprolactam-co-2-(diethylamino)ethyl methacrylate), P(VC-co-DEAEMA), gels were synthesized in ethanol by using free radical cross-linking polymerization method at 60 °C for 24 h in the presence of azobis(isobutyronitrile) (AIBN) as initiator. Homopolymer gels of N-vinylcaprolactam (PVC) and 2-(diethylamino)ethyl methacrylate (PDEAEMA) were also synthesized at the same conditions and used for comparison purposes. In the synthesis of homopolymer and copolymer gels, ethylene glycol dimethacrylate (EGDMA) and allyl methacrylate (AMA) cross-linking agents were employed in order to determine the effects of cross-linker type on the equilibrium swelling value (ESV) and percentage of gelation (PG). pH and temperature sensitivities of gels were investigated for both cross-linkers, and network parameters of gels were also found. In addition, detailed characterization studies were performed by Fourier transform infrared and scanning electron microscopy techniques. It was observed that PVC gel had the lowest PG and highest ESV. Compared to EGDMA, AMA increased thee percentage of gelation and decreased the equilibrium swelling value of gels. pH-sensitive profiles of gels were substantially different from each other and strongly dependent on DEAEMA content. Copolymer gels containing the highest mole percentage of N-vinylcaprolactam (95%) showed non-Fickian and Fickian swelling behavior at pH 7.4 for EGDMA and AMA cross-linkers, respectively. It was found that both monomer concentration and cross-linker type affected the polymer−solvent interaction parameters (χ), mesh size (ζ), and experimental average molecular mass between the cross-links (M c E) of gels.

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 °C for 24 h in the presence of azobis(isobutyronitrile) (AIBN) and allyl 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.

Swelling behaviour of poly(N-vinylcaprolactam) (PVC) and poly(N-vinylcaprolactam-co-itaconic acid) (P(VC-co-IA)) gels was investigated in different solvents (water, ethanol, methanol, isopropyl alcohol (IPA), chloroform, toluene, acetone) and in binary solvent mixtures (ethanol/chloroform, ethanol/methanol, IPA/chloroform, ethanol/water, IPA/water). Gels were synthesised in ethanol by the free radical cross-linking polymerisation method at 60°C for 24 h in the presence of azobis( isobutyronitrile) and allyl methacrylate as the initiator and cross-linker, respectively. And also, ethanol/distilled water mixture (φ

Poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-1-vinyl-2-pyrrolidone), P(AMPS-co-VP), hydrogel was prepared by free radical cross-linking polymerization method. Prepared hydrogel was used in the competitive removal of Cd(II), Pb(II) and Cu(II) ions from aqueous solution. The characterization of P(AMPS-co-VP) before and after sorption was carried out by the Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Atomic absorption spectrometer was used to found the concentration of metal ions in the aqueous solution. The selectivity of P(AMPS-co-VP) was as follows: Cd(II)>Pb(II)>Cu(II). Kinetic study showed that competitive removal of heavy metal ions on poly(AMPS-co-VP) was in accordance with a pseudosecond-order model.

In this study, poly(2-acrylamido-2-methyl-1-propane sulfonic acid-co-1-vinyl-2-pyrrolidone), P(AMPS-co-VP), hydrogels were prepared by free radical cross-linking polymerization method in deionized water at 60 • C for 24 hours with different molar percentages of AMPS and VP. In the preparation of hydrogels, ammonium persulphate (APS), N,N'-methylenebisacrylamide (NMBA) and N,N,N',N'-tetramethylethylenediamine (TEMED) were used as initiator, cross-linking agent and accelerator, respectively. NMBA was used in amounts of 5, 6 and 8% with respect to total monomer concentration in the feed. The equilibrium swelling value (ESV) of P(AMPS-co-VP) hydrogels was determined in deionized water and in buffers with different pH values. ESV of P(AMPS-co-VP) hydrogels prepared with 5% NMBA is higher than that of the counterparts with 6 and 8%. Swelling behavior of hydrogels was strongly dependent on AMPS content and ESV decreased with increase in AMPS amount. An evident pHsensitivity was not observed for the P(AMPS-co-VP) hydrogels. The characterization study was performed using Fourier transform infrared spectroscopy and thermogravimetric analysis.