Relaxation Mössbauer spectra of two57Fe3+-exchanged acrylate cation-exchangers (SGK-7 and SG-1M, USSR) with various cross-linkage concentrations 2.5–16 mol.% were observed in windows of observation up to 250 mm/s. The frequencies of slow (ω≲10 s−1) intramolecular motions (displayed in Mössbauer lineshape) and the values of high frequency (ω≳10 s−1) atomic displacements (reflected in thef’ factor) decrease with the increase of cross-linkage concentration.

The transition from solid-like (glassy) state into the (elastic) state with high intramolecular mobility under hydration was investigated for two57Fe3+-substituted cation exchangers (SGK −7 and SG −1 m with acrylic and methacrylic nature of chains). The transition was observed as sharp change of Mössbauer lineshape (appearance of quasielastic components) and decrease of Mössbauer effect probability. The region of hydration degrees in which the transition occurs in both systems varies from 1 to 3–4 H2O molecules per −COOH group depending on cross-linkage concentration in a nonmonotonous way.