WATER IN HYDROGELS .3. POLY(HYDROXYETHYL METHACRYLATE) SALINE SOLUTION SYSTEMS

High-resolution23Na NMR is used in conjunction with broad-line1H resonance and DSC to investigate the nature of water in poly(hydroxyethyl methacrylate) (PHEMA)/saline systems. The introduction of sodium ions into the hydrated polymer system increases the nonfreezable water content and depresses devitrification. The Na+ ions also decrease water mobility below 250 K, confirming sodium as a water-coordinating ion. T2L data indicate a low-temperature (≈220 K) glass transition with Tg(heating) < Tg(cooling). A phase transition in hydrated PHEMA at ≈250 K is indicated. The behavior of the23Na line width and chemical shift are broadly consistent with similar studies in the literature that reveal the sensitivity of23Na to its local environment. © 1990, American Chemical Society. All rights reserved.