Electrically driven director-rotation of swollen nematic elastomers as revealed by polarized Fourier transform infrared spectroscopy.

We have investigated the director reorientation behavior of unconstrained nematic gels (nematic elastomer swollen by low molecular mass liquid crystals) under electric fields by means of polarized Fourier transform infrared (FTIR) spectroscopy. The polarized FTIR reveals that the director rotates about the (y) axis normal to the original director ( x axis) and field directions ( z axis), and the nematic order remains unchanged in the plane where the director stays confined during rotation. The rotation angle of director (theta) is estimated as a function of imposed voltage amplitude on the basis of the absorbances of the cyano group which is aligned along the long axis of the mesogen for light linearly polarized in the x and y directions. The director-rotation drives a two-dimensional macroscopic deformation which is characterized by a contraction along the x axis, an extension in the z direction, and nonappreciable length change along the y axis. The strain in the x direction is linearly proportional to sin;{2} theta in agreement with the expectation of soft or semisoft elasticity theory for thin nematic elastomer films where the shear contribution becomes negligibly small.