Linear Viscoelasticity of Leslie-Ericksen Liquid Crystal Polymers Luiz R.P. de Andrade Lima; Alejandro D. Rey Department of Chemical Engineering, McGill University 3610 University Street, Montreal, Quebec, Canada H3A 2B2 e-mail: ldeand@po-box.mcgill.ca; alejandro.rey@mcgill.ca Abstract The linear viscoleasticity of seven lyotropic and thermotropic liquid crystalline polymers is characterized using the Leslie-Ericksen equations of defect-free nematodynamics for small amplitude oscillatory capillary Poiseuille flow, and using analytical, numerical and scaling methods. The experimental data sets used in this study correspond to the six Leslie viscosities coefficients for seven nematics liquid crystal polymers, that include shear flow-aligning and non-aligning materials. The predicted equivalent rheological responses between the shear flow-aligning and shear non-aligning polymers demonstrate the universality of nematodynamics. In this work the principles of superposition are developed, applied, and shown to be accurate in collapsing the data sets for both classes of polymers. The scaled resonance peak in the loss tangent (tan δ=G”/G’) as a function of the oscillation frequency shown to be a universal constant for monodomain nematics. Introduction The Leslie-Ericksen liquid crystal (LELC) is a mathematical material model for rod- or disk-like uniaxial incompressible isothermal nematic liquid crystals widely used to describe anisotropic viscoelastic behavior [1]. A common rheological classification scheme for nematic liquid crystal polymers (LCPs) is based on their shear flow aligning characteristics, which is set by the sign and magnitude of the reactive order parameter λ [1,2,3]. Lyotropic LCPs are usually non-aligning at low shear rates and aligning at high shear rates [3]. On the other hand, main-chain thermotropic LCPs with flexible spacers are likely to be flow-aligning at all shear rates, while main-chain thermotropic LCPs without flexible spacers are apparently non- aligning. A data set of viscoelastic parameters for seven thermotropic and lyotropic LCPs was recently presented [4]; it shows the rheological differentiation between lyotropic and thermotropic LCPs. Small amplitude oscillatory flows (SAOFs) are a main rheological tool used to characterize viscoelasticity in terms of the storage G’(ω,T) and loss G”(ω,T) moduli as a function of frequency (ω) and temperature (T) [5]. This paper uses small-amplitude pressure driven Poiseuille capillary flow, and characterizes the linear viscoelasticity of seven LCPs [4] using the Leslie-Ericksen equations of defect-free nematodynamics that is useful to understand the nematics liquid crystals materials rheology. [1,2,6]. This paper also demonstrates that flow-aligning and non-aligning materials can exhibit identical viscoelastic responses, thus showing features of universality in the nematodynamics of lyotropic and thermotropic materials.