Water vapor adsorption on poly(N-isopropylacrylamide) gel cross-linked with N, N′-methylenebisacrylamide

Abstract

Water vapor adsorption characteristics and the thermosensitivity for vapor adsorption of poly(N-isopropylacrylamide) gel (NIPA gel) cross-linked with N, N′-methylenebisacrylamide (MBAA) (cross-linked NIPA gel) were investigated for application in desiccant humidity control systems. The cross-linked NIPA gels were prepared via copolymerization of NIPA monomers and MBAA monomers, which were used as crosslinkers, at various reagent concentrations and polymerization temperatures in the range of 283–323 K. The water vapor adsorption isotherms of NIPA homopolymer, MBAA homopolymer, and cross-linked NIPA gels were obtained at adsorption temperatures in the range of 298–323 K using a volumetric gas adsorption apparatus. The water vapor adsorptivity of the cross-linked NIPA gel increased with increasing MBAA monomer concentration and decreasing NIPA monomer concentration. NIPA homopolymer under dry conditions showed weak thermosensitivity for water vapor adsorption between 298 and 313 K. Meanwhile, MBAA homopolymer showed almost no change in water vapor adsorptivity above adsorption temperatures of 298 K. The cross-linked NIPA gels had a similar thermosensitivity to NIPA homopolymer, but its sensitivity might be shifted to higher temperature than NIPA homopolymer. Thermosensitivity of the cross-linked NIPA gel was effective in improving polymer water adsorptivity, necessary for desiccant humidity control systems; however, the adsorption performance of the polymer gel systems investigated require further improvements before practical application will be possible.