CRYSTAL GROWTH FROM SUPERSATURATED AQUEOUS SALT SOLUTIONS ON A POLYMER NAFION SUBSTRATE

Bunkin, N.F.; Novakovskaya, Y.V.; Bolotskova, P.N.; Voronov, V.V.; Kozlov, V.A.; Timchenko, S.L.; Khoung, M.T.; Baranova, E.N.

Авторы: Bunkin N.F., Novakovskaya Y.V., Bolotskova P.N., Voronov V.V., Kozlov V.A., Timchenko S.L., Khoung M.T., Baranova E.N.
Журнал: Journal of Structural Chemistry
Том: 65
Номер: 7
Год издания: 2024
Издательство: Maik Nauka/Interperiodica Publishing
Местоположение издательства: Russian Federation
Первая страница: 1292
Последняя страница: 1304
DOI: 10.1134/S0022476624070023
Аннотация: Features of the crystallization of various compounds on the Nafion polymer substrate from supersaturatedaqueous solutions is studied by XRD. The solutions are prepared from natural deionized and deuteriumdepleted water. It was earlier established that the swelling of Nafion in natural deionized water clearly demonstrates effects caused by the partial uncoiling of polymer fibers into the liquid volume, but no such effects were observed in deuterium-depleted water. The ab initio calculations performed in the present work show that the uncoiling of lateral Nafion chains with terminal –SO3H groups and the dissociation of these groups with subsequent formation of hydronium ions and SO3− structural anionic residues are energetically favorable in the case of the contact with a sufficient amount of water molecules. The influence of these factors on the process of crystal formation on polymer substrates is studied. It is established that the effect of partial uncoiling of polymer chains indeed affects the crystallization, and does it in different ways, depending on the crystal structure. Thus, no differences between XRD patterns of crystals grown onsmooth and polymer substrates are observed for the monoclinic lattice of sodium acetate trihydrate. In the case of copper sulfate (with either CuSO4⋅5H2O pentahydrate crystals (triclinic crystal system) orCuSO4⋅3H2O trihydrate crystals (monoclinic crystal system)), copper sulfate trihydrate and pentahydrateare formed on the polymer and smooth substrates, respectively. None of the studied crystals exhibiteddifferences between smooth and polymer substrates for the supersaturated solutions based on deuteriumdepleted water, and in both cases a triclinic crystal system of the CuSO4⋅5H2O pentahydrate precipitate is identified for the CuSO4 aqueous solution. For sucrose, the precipitate amorphization upon the deposition onto the Nafion plate is detected. A theoretical model is proposed to explain the effect of partial polymer chain uncoiling on the growth of crystals, depending on their crystal system, unit cell parameters, and the volumetric ratio of hydrophilic and hydrophobic fragments in the molecular structure.
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CRYSTAL GROWTH FROM SUPERSATURATED AQUEOUS SALT SOLUTIONS ON A POLYMER NAFION SUBSTRATEстатья

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