Effect of Polymer Matrix and Divalent Metal Salts on Spectral Characteristics of Interfacial Water

In the present study, the influence of the polymer matrix and divalent metal salts on the electrochemical and spectroscopic characteristics of interfacial water in Nafion- and carboxymethyl cellulose-based systems was investigated. The aim of the study was to establish the regularities governing the restructuring of the interfacial aqueous environment under the combined effect of the polymer surface and the ionic composition of the solution. As model electrolytes, ۱ M solutions of BaCl۲, CuSO۴, Mg(NO۳)۲, and CoCl۲ were employed. The state of water was evaluated from changes in pH and oxidation-reduction potential, as well as from FTIR and Raman spectroscopic data. It was shown that the structuring of interfacial water is governed by the combined influence of the chemical nature of the polymer and the hydration-coordination characteristics of the divalent cations. In the presence of Nafion, a more pronounced decrease in pH and an increase in oxidation-reduction potential were observed, indicating the formation of a more acidic and electrochemically stressed interfacial region. In CMC-based systems, the changes were less pronounced and were accompanied by a greater contribution of coordination interactions between the ions and the hydroxyl and carboxyl groups of the polymer. Analysis of the O-H bands in the FTIR and Raman spectra revealed a redistribution of more strongly and more weakly hydrogen-bonded water species, as well as changes in the degree of local heterogeneity of the interfacial medium. The most pronounced structuring effect was observed for Mg(NO۳)۲, whereas CuSO۴ exhibited a more distinct intrinsic coordination and ion-association contribution. The obtained results expand current understanding of the nature of interfacial water in ion-conducting and hydrophilic polymer systems and may be of interest for the development of membrane materials, sorbents, and functional aqueous media.

کلیدواژه ها:

interface water ، Nafion ، Carboxymethylcellulose ، Divalent metal salts ، Raman spectroscopy