Effects of Network Inhomogeneity in Poly($N$-isopropylacrylamide) Gel on its Surface Structure

概要

論文の詳細を見る
Atomic force microscopy (AFM) was used to investigate the effect of the bulk network inhomogeneity on the surface structure of poly($N$-isopropylacrylamide) (NIPA) gels in water. The spongelike domains were found to be strongly related to the bulk inhomogeneity that is introduced during gelation. With increasing gelation temperature, the bulk structure became more inhomogeneous, and accordingly the number of large-size domains increased on the surface. When the gelation temperature exceeded the cloud point of the NIPA polymer, large domains became dominant. The surface structure was strongly affected not only by the gelation temperature (permanent network inhomogeneity) but also by the measurement temperature (temporary network fluctuation). When the bulk polymer network entered into the collapsed phase with increasing temperature, the conformation of the spongelike domains on the surface changed evidently, but it was restored when the gel swelled again through the volume phase transition. The surface roughness and its change in response to temperature were discussed on the basis of results of the roughness analysis performed by calculating the auto-correlation function from the AFM images.
2003-05-15