1H NMR studies of poly(N-isopropylacrylamide) gels near the phase transition

摘要: Abstract The phase transition and critical phenomenon of equilibrium swollen poly( N -isopropylacrylamide) (NIPA) hydrogels were studied by 1 H NMR spectroscopy in liquid solution mode. quantitative observation shows that the peak height line width polymer proton HOD proton, relaxation times all transitionally change as temperature approaches temperature. water protons are also measured quantitatively, which dependence on before is not consistent with theory based assumption dominated dipolar interaction between like-spin nuclei isotropic rotational motion. To explain surprising behavior HOD, we suggest amount bound gels increases gradually at approach transition. pulsed-gradient spin-echo experiments NIPA gel confirm this suggestion. We believe these results have important implications concerning mechanism hydrogels.