Cation Motion in Anionic Fields of the Polyelectrolytic Salts of Ethylenemethacrylic Copolymers

Abstract

The far‐infrared spectra of the Li+, Na+, K+, Cs+ salts and acid forms of polyelectrolytic ethylene‐methacrylic acidcopolymers have been examined in the 800–33‐cm−1 region at ambient and low temperatures. A broad band, which shifts to lower frequency as the cation mass is increased, is attributed to cation motion in anionic fields, and the appearance of a low frequency band, whose intensity is related to the cation properties, is assigned to perturbed skeletal motions of a neighboring polymer segment. Models are proposed and analyzed for the vibrational modes involving ion motion. The vibrational force constants for aggregate distortion, as calculated from the observed ion‐motion frequencies, are in agreement with such constants computed here employing an ion‐multipole potential energy function which does not use these experimental data. The spectral and theoretical results are considered in terms of the molecular interactions of importance in polyelectrolytes and in the physical properties of these materials.