Swelling and Shrinking Dynamics of Monodomain Nematic Elastomers

We demonstrate that the swelling and shrinking of monodomain nematic elastomers in solvents exhibit unusual dynamics because of the presence of shape and volume variation modes with markedly different rates. A variation in the degree of orientational order induced by temperature (T) jumps causes a spontaneous deformation along the director as well as a change in the chemical potential of the solvent inside the gel. The former effect results in an almost instantaneous shape change, whereas the latter drives a slow volume change governed by the diffusion of polymer networks. The markedly different rates of these two modes cause unique dynamics: (i) a pronounced over- or undershoot of the specimen dimensions occurs in the direction where the shape and volume variations act to change the dimensions in the opposite manner, and (ii) a large dimensional change (more than 50 percent of the total change) takes place with almost no delay after the T-jumps in the direction where these two effects on the dimension synchronize.