Dynamic Soft Elasticity in Monodomain Nematic Elastomers.pdf

EPJ manuscript No. (will be inserted by the editor) 2 0 0 2 Dynamic Soft Elasticity in Monodomain Nematic Elastomers g u A. Hotta and E.M. Terentjev A Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, U.K. 8 February 1, 2008 ] i c s Abstract. We study the linear dynamic mechanical response of monodomain nematic liquid crystalline - elastomers under shear in the geometry that allows the director rotation. The aspects of time-temperature l r superposition are discussed at some length and Master Curves are obtained between the glassy state and the t nematic transition temperature Tni . However, the time-temperature superposition did not work through m the clearing point Tni , due to change from the “soft-elasticity” nematic regime to the ordinary isotropic . t rubber response. We focus on the low-frequency region of the Master Curves and establish the power-law a dependence of the modulus G′ ∝ ωa . This law agrees very well with the results of static stress relaxation, m where each relaxation curve obeys the analogous power law G′ ∝ t−a in the corresponding region of long - times and temperatures. d n PACS. 83.80.Dr Elastomeric polymers – 61.30.-v Liquid crystals. – 83.10.Nn Polymer dynamics o c [ 1 Introduction Newtonian. Hanus et al. [3] measured dynamic-mechanical 1 properties of a weakly crosslinked main-chain LCP hav- v For the last two decades, thermotropic liquid crystalline ing crystalline, smectic B, smectic A and isotropic phases. 1 polymers (LCP) have been a subject of increasing activity They only observed a