Structure of nematic liquid crystalline elastomers under uniaxial deformation.

We have used in situ x-ray diffraction and calorimetry to study liquid crystalline elastomers prepared using a one-step photopolymerization method. We used suspended weights to stretch free-standing crystalline elastomer films. With the mechanical stress parallel to the initial director, we observed a gradual nematic to isotropic transition with increasing temperature. The thermal evolution of the nematic order parameter on cooling, together with the observation of isotropic-nematic coexistence over a broad temperature range, suggests that the heterogeneity in the samples introduces a distribution of transition temperatures. With the mechanical stress perpendicular to the initial director, we observed both uniform director rotation and stripe formation, depending on the details of sample preparation.