The shrunken and swollen matrices coexisting in the volume phase transition gel segregate from each other and form macroscopic domain structures. In this study, we investigated the mechanism of formation of the patterns found in transition. Ionic gels undergo shrinkage as a result of the hydrophobic counterion binding, which makes the gel chain hydrophobic. We have recently observed various patterns forming in rod-like ionic gels during shrinkage of volume phase transition. The observed patterns were rings around the rod, wrinkled stripes along the rod and bubble-like patches on the surface. A strong correlation was found between type of pattern and type of deformation in the shrinking gel. In elongating gel in the direction of the long axis, stripes developed in the gel. In compressing gel in the same direction, rings formed. When the gel shrunk almost homogeneously, bubbles formed on the gel surface. The patterns observed were strongly affected by mechanical perturbation. In this respect, they were considered to be mechano-chemical coupling patterns.
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