Thermoresponsive shrinkage triggered by mesophase transition in liquid crystalline physical hydrogels

The hydrogel of poly(11-(4'-cyanobiphenyloxy)undecyl acrylate-co-acrylic acid), poly(11CBA-co-AA), which was comprised of the hydrophobic cross-linking junction zone with the liquid crystalline nature and the hydrated amorphous domain, showed a smectic mesophase transition at 40 degreesC in the body temperature range. X-ray diffraction study suggests the water transfer from the main chain domain of the liquid crystalline junction zone to the amorphous domain through the smectic transition. The oriented hydrogel fiber showed a drastic shrinkage through this transition, keeping the orientation. Moreover, the mesomorphic behavior of LCG depended on the aqueous milieu. Thus, the present LCG physically cross-linked by the mesomorphic junction could be considered to be an open system of new actuators controllable in the change in the aqueous milieu at ambient conditions.