A series of hydrophobically modified poly(acrylic acid) gels were prepared by the radical copolymerization of acrylic acid and small amounts of hydrophobic comonomers, 2-(N-ethylperfluorooctane-sulfoamido)ethyl methacrylate and lauryl acrylate, in tert-butanol. The effects of the fractions and species of hydrophobes on hydrophobic association were determined. The hydrophobic association within the hydrophobically modified gels was proven with measurements of swelling and fluorescence as well as Fourier transform infrared spectroscopy. Fluorocarbon-modified hydrogels showed stronger hydrophobicity than hydrocarbon-modified hydrogels.