An IR study on ion-specific and solvent-specific swelling of poly(N-vinyl-2-pyrrolidone) gel |
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Authors: | Hajime MutaKoji Ishida Emi TamakiMitsuru Satoh |
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Affiliation: | Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan |
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Abstract: | Swelling degrees of poly(N-vinyl-2-pyrrolidone) (PVP) gel were measured in aqueous salt solutions and in water/organic solvent mixtures to find marked ion- and solvent-specificities. In order to investigate any correlation of those specificities with hydration or solvation of PVP, IR spectra band of the CO group was monitored by means of ATR method both for PVP gel and the relevant solution systems. Dependence of the peak frequency on the swelling ratio suggested that hydration of PVP carbonyl group in deswollen gel systems is different from that in the corresponding solution systems. In the solution systems, PVP carbonyl band showed a high-wavenumber shift for deswollen systems, which can be well correlated with changes in water proton charge through ionic hydration and with Gutmann's acceptor number of organic solvents. In the deswollen gel systems, the CO band showed a low-wavenumber shift, suggesting a strong hydration or doubly hydrated state. This unexpected behavior was interpreted by assuming an intermolecular hydrogen bond of two carbonyl groups intermediated by water molecules. |
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Keywords: | Poly(N-vinyl-2-pyrrolidone) hydrogel Acceptor number Intermolecular hydrogen bond |
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