PATTERN-FORMATION OF CONSTRAINED ACRYLAMIDE SODIUM ACRYLATE COPOLYMERGELS IN ACETONE WATER MIXTURE/

Pattern formation and evolution in constrained acrylamide/sodium acryl ate (PAAM/SA) gels have been investigated in acetone/water mixture. Th e constraint is achieved by, cross linking the gel slabs onto a rigid substrate. All samples are initially kept in water with the hexagonal pattern develop on the surface before being immersed in the acetone/wa ter mixture. Depending on the solvent composition and ionic strength o f the sample, different patterns, i.e., hexagonal, grains, and bubbles , have been observed. These patterns are formed at acetone concentrati on below, near, and above the concentration at which the gel volume ph ase transition occurs. The wavelengths of hexagonal and bubble pattern s are found to be the same, while that of the grain pattern is four ti mes smaller. It is suggested that the shrinking patterns are formed du e to the dense gel surface produced during the shrinking process.