Dynamics of Backbone Chain and Side Groups in a Nematic Liquid Single Crystal Elastomer Studied by Combined Mechanical and Stress-Optical Measurements

Abstract

Dynamic mechanical and stress-optical measurements on nematic liquid single elastomers have been carried out both in the nematic and in the isotropic phase. In case of shear stress and in case of tensile stress applied parallel to the director the compliances were not affected by the nematic-isotropic transition. For tensile stress oriented perpendicular an increased compliance was observed in the vicinity of the phase transition. The stress-optical coefficients for tensile stresses applied pararallel and perpendicular to the director both increase on approaching the nematic-isotropic transition. In the isotropic phase its temperature dependence is well described by the Landau-de Gennes theory. Far from the transition temperature in the nematic phase other mechanisms superpose this behavior, leading to negative stress-optical coeffients for stress parallel, and positive coefficients perpendicular to the director.

Key Words:

• Nematic
• elastomer
• dynamic mechanical properties
• stress-optical coefficient
• critical phenomena