Design of stimuli-responsive materials consisting of the rigid cylindrical inorganic polymer 'imogolite'

In this focused review, various stimuli-responsive materials that are prepared from the rigid rod-like polyelectrolyte 'imogolite' and constructed in accordance with its structural characteristics are described. The combination of imogolite and dicarboxylic acids yields hydrogels that exhibit thixotropy in response to mechanical shocks and physical anisotropy via the orientation of the imogolite during flowing and subsequent standing. Robust hydrogels have also been obtained by in situ polymerization of vinyl monomers in aqueous imogolite dispersions that show reversible isotropic-anisotropic structural transitions in response to strain. Furthermore, an electrorheological effect of the aqueous imogolite dispersions at extremely low voltage has been discovered that should permit the design of imogolite-based architectures as electro-stimulus-responsive materials.