Microphase separation in dehydrated N-isopropylacrylamide/sodium acrylate gel

The first small-angle X-ray scattering (SAXS) measurements were carried out in order to examine the mesoscopic structure in the N-isopropylacrylamide/sodium acrylate (NIPA/SA) gel. By the SAXS measurements, a prominent peak was found in the dehydrated gel around 0.026 angstroms^-1. Taking into account of the cross section magnitude against X-ray, the concentration fluctuation of Na⁺ ions was a probable candidate for making contrast for the SAXS profile, which depends on the distribution of the hydrophilic group. Therefore, it was concluded that the mesoscopic structure found in the present study is due to the hydrophilic domains in the dehydrated gel which capture the Na⁺ ions and the remnant water inside the gel.