In this study, thermosensitive oligo(N-isopropylacrylamide) [oligo(NIPAM)] chains were grafted to amphiphilic N,N-dimethylacrylamide (DMAA) gel networks to form DMAA-graft-oligo(NIPAM) gels. The gels were prepared by copolymerizing oligo(NIPAM) macromonomers with DMAA. On heating, the gel caused structural changes in the gel network without causing a large volume change. The effects of the molecular weights and copolymerization ratios of oligo(NIPAM) on the temperature dependence of the swelling properties of the gel were investigated. Furthermore, to confirm the structural changes in the gel network, the temperature dependence of the diffusivity of rhodamine B through the gel membrane was investigated. Oligo(NIPAM) monomers with different molecular weights (M-n) of 2300, 7000, and 13,000 were prepared. The transition from hydrophilic to hydrophobic for oligo(NIPAM) of M-n 7000 and 13,000 was observed at about 32 degrees C, while that of M-n 2300 was observed between 32 and 45 degrees C. The gels grafted with oligo(NIPAM)s of M-n 7000 and 13,000 shrank above 32 degrees C; in other words, thermosensitivity was clearly observed. On the other hand, the swelling behavior of the gel grafted with oligo(NIPAM) of M-n 2300 was similar to that of the DMAA gel; that is, negligible shrinkage of the gel was observed on heating. The diffusivity of rhodamine B through the gel membrane grafted with oligo(NIPAM) of M-n 2300 increased stepwise between 40 and 45 degrees C. These results suggest that by selecting the molecular weights and copolymerization ratios of oligo(NIPAM), structural changes in the gel network occur without an overall volume change. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012