In this study, a novel temperature-sensitive polymer, poly(N-2-methoxyisopropylacrylamide), PNMIPA, in the crosslinked hydrogel form was obtained. The monomer, N-2-methoxyisopropylacrylamide (NMIPA) was synthesized by the nucleophilic substitution reactions of acryloyl chloride with 2-methoxyisopropylamine. Hydrogel matrix of PNMIPA was obtained by the bulk polymerization method. The bulk polymerization experiments were performed at +4 degrees C, by using N,N-methylenebisacrylamide (MBA) as crosslinker, polyethyleneglycol (PEG) 4000 as diluent, and potassium persulfate (KPS) and tetramethylethylenediamine (TEMED) as the initiator and accelerator, respectively. The same polymerization procedures were applied by changing monomer, initiator, crosslinker and diluent concentrations in order to obtain crosslinked gel structures having different temperature-sensitivity properties. The equilibrium swelling ratio of PNIMPA gel matrices at constant temperature increased with increasing initiator concentration and decreasing monomer concentration. The use of PEG 4000 as diluent in the gel synthesis resulted in about two times increase in equilibrium swelling ratios in the low temperature region. A decrease in the equilibrium swelling ratios of gel matrices started at 30 degrees C and the decrease became insignificant at 55 degrees C. Temperature-sensitivities were determined in two different media. Distilled water medium was used in order to observe the temperature-sensitivity of the gel clearly and the phosphate buffer medium was used in order to represent the temperature-sensitive swelling behavior of the gel when it is used in biological media. Step effect was applied on ambient temperature in two opposite directions in order to examine the dynamic swelling and shrinking behaviors of the gels. (C) 2008 Wiley Periodicals, Inc.