Mechanical/Optical Behaviors Of Imogolite Hydrogels Depending On Their Compositions And Oriented Structures

A robust acrylamide (AAm) hydrogel reinforced by imogolite (IG), a perfect rigid nanotubular clay mineral, exhibited distinct tensile stress-strain characteristics and strain-induced birefringence in accordance with the compositions of the gels. The gel showed a reversible anisotropic/isotropic structural transition in response to stretching/releasing before the breakdown strain. The strain-induced birefringence of the IG-reinforced gels could be fixed by the in situ interpenetrating polymerization of other AAm monomers that were impregnated into the gels in the stretched states. This resulted in gels with nonvolatile anisotropic birefringence, and therefore, the fixed anisotropic IG ordering showed specific stress-strain characteristics depending on the orientation of IG. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41691.