NIPA Monomer Intercalation into Several Clay Minerals and Characterization of Clay-PNIPA Hydrogels Prepared by Photopolymerization

Abstract

In this paper we summarized intercalation behavior of N-isopropylacrylamide (NIPA) monomer into cation-exchanged clays and characterization of photosynthesized clay-poly(NIPA) nanocomposites with several clay minerals. The monomer intercalation was possible by both solid-liquid and solid-solid reactions with Na-saponite, Na-montmorillonite, Na-hectorite and various cation-exchanged saponites. Hydrogels of clay-poly(NIPA) (clay: saponite, hectorite and fluorohectorite) were formed by photopolymerization. The appearance of the obtained hydrogels for the composite of saponite was translucent and relatively stiff, whereas that for fluorohectorite was highly transparent and soft. DSC measurements showed an endothermic anomaly at the volume phase transition in each hydrogel upon increasing temperature. The transition heat decreased with increasing clay content. Swelling behaviors were significantly different between the composites of saponite and fluorohectorite. The amounts of absorbed water in the fluorohectorite-composites were 2-4 times greater than that in the saponite- and hectorite-composites at the same clay content. The equilibrium water content in the hydrogel decreased with increasing amount of saponite and hectorite, however, almost no correlation between the clay and water contents in the composite of fluorohectorite was observed.