Crosslinked poly [2-(tert-butylamino)ethyl methacrylate] (PtBAEMA) hydrogels were synthesized by Co-60-gamma-radiation-initiated simultaneous polymerization and crosslinking of 2- (tert-butylamino) ethyl methacrylate in bulk and in aqueous solutions. The results showed that the gelation percentage decreased with increasing water content. The structural and thermal characterizations of the hydrogels were accomplished with several techniques, including Fourier transform infrared spectroscopy, swelling measurements, thermogravimetry, and differential scanning calorimetry. The effects of time, pH, temperature, and ionic strength on the swelling behavior were also investigated. Swelling equilibrium was attained in 2-3 days. PtBAEMA hydrogels originally swelled to 350% (by volume) in deionized water, but this value reached 3000% around pH 2.0. PtBAEMA hydrogels were reversibly affected by the change in temperature within the temperature range of 4-70 degrees C. The swelling ratios of the gels decreased with increasing ionic strength. As a result, PtBAEMA hydrogels show stimuli-responsive properties depending on the characteristics of the environment, and they are being considered for adoption as some kind of carrying material for separation. (c) 2008 Wiley Periodicals, Inc.