Infrared spectral change in a zinc salt of an ethylene-methacrylic acid ionomer on water absorption

Abstract

Local structural change in the ion aggregate in a zinc salt of poly(ethylene-co-methacrylic acid) ionomer on water absorption-desorption process was investigated with use of infrared spectral change in the carboxylate antisymmetric stretch region. Three bands were found at 1539, 1560, and 1625 cm−1 in dried state. They collapsed into a singlet at 1587 cm−1 on swelling. The spectral change occurred reversibly with respect to the water content at a constant temperature. Analyzing the ratio of the relative integrated intensities of the dry state to the wet one, we evaluated the hydration number to a Zn2+ ion in the wet state. The difference in molar absorption coefficients of the bands between the dry and wet states can be explained by the vibrational coupling between the va (COO−) and carboxylate rocking P (COO−) modes. © 1993, The Society of Polymer Science, Japan. All rights reserved.