Effects of director angle anchoring conditions on the dynamic moduli of heterogeneous nematic polymers

Document Type

Conference Proceeding

Publication Date

9-11-2008

Abstract

We examine the linear viscoelastic response of heterogeneous nematic polymers to small amplitude oscillatory shear flow, paying special attention to the macroscopic influence of strong plate anchoring conditions. To predict the dynamic moduli, we model the system with Stokes hydrodynamic equations with viscous and nematic stresses coupled with orientational dynamics driven by the flow, an excluded volume potential, and an elasticity potential. First, we show that for special cases of normal and tangential anchoring, we recover explicitly solvable Leslie-Ericksen-Frank behavior. In this case we observe significant differences between the moduli for normal and tangential anchoring, including a two-to-three order of magnitude enhancement of the storage modulus for normal over tangential anchoring. Then, we turn to a numerical study of oblique anchoring conditions, which are more complicated due to the appearance of order parameter gradients at leading order. When the anchoring angle is near 45 degrees, we observe significantly different scaling behavior in the storage modulus for high frequencies compared to the behavior for normal or tangential anchoring. Furthermore, we find that for low frequencies, normal anchoring gives the largest storage modulus and tangential the smallest; however, we see a brief window of higher frequencies where the maximum storage modulus occurs at an oblique anchoring angle. © 2008 American Institute of Physics.

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