PROTON MASS-NMR - A NEW TOOL TO STUDY THERMOREVERSIBLE TRANSITION IN HYDROGELS

The lower critical solution temperature (LCST) phenomenon in equilibrium swollen poly(N-isopropylacrylamide) gel has been studied by solid-state H-1 NMR spectroscopy. H-1 MASS-NMR provides considerable insight into the study of thermoreversible transition in hydrogels. It is observed that the proton resonances are inhomogeneously broadened. As a result, MASS studies even at moderate spinning speeds (2 kHz) lead to valuable information to be discerned from the NMR spectra. A clear picture of the LCST is manifested by a transition in the H-1 static line-width measurements. The changes in the molecular mobility within the polymeric gel are primarily governed by polymer-solvent interactions. The suppression of LCST in the presence of a surfactant, sodium dodecyl sulfate, is also demonstrated.