The phase behaviors of N-alkylacrylamide hydrogels was studied with the help of Cu(II) spin probe, in this paper. The changes of the anisotropy ESR spectra of the Cu(II) spin probes are different at the different temperature- hydrogels. Because of this interaction between the substituent and Cu(II) is different mainly. The anisotropy inverted spectra will be determine, when the temperature reaches and goes beyond the temperature of phase transition for the NNPA and NIPA hydrogels that exhibit a LCST phase behaviors. The network is collapsed and the hydrated Cu(II) ion is bound by network chains. We believe it feasible method to study the phase structure and microscopic phase behaviors of gels, using he Cu(II) spin probes.

Key words: PROPENAMIDE, ELECTRON SPIN RESONANCE, PHASE STRUCTURE, HYDROGEL