Abstract
Hydrophobically modified polyacrylamide hydrogels were prepared by polymerizing acrylamide, using n‐butyl acrylate and 2‐ethyl hexyl acrylate as comonomers and dimethyl formamide as a solvent. We report here for the first time that the Alfred Q‐e reactivity ratios are matching with the experimental value (elemental analysis result) for the terpolymer hydrogel systems. Differential scanning calorimetry (DSC) thermograms of the hydrogel samples revealed two endothermic transitions, one near 0°C, corresponding to the melting transition of ice and another above ambient temperature. This high temperature transition is due to the rearrangement of water molecules engaged in hydrophobic hydration surrounding the hydrophobic groups (alkyl side chains). This depends on the type of hydrophobic groups and the gel compositions. Swelling and deswelling studies of the gels were performed using various solvents such as water and isopropyl alcohol. An abnormally high swelling and deswelling behavior was observed in the homopolymer gels and the gels with low amount of hydrophobic comonomers. This could be attributed to the more intramolecular cross‐linked structure formed during synthesis in organic solvent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010