Texture control strategies for flow-aligning liquid crystal polymers

Abstract

The Landau-de Gennes nematodynamics equations for flow-aligning liquid crystal polymers are used to: (i) perform a simulation study of shear-induced textural transformation and defect nucleation and (ii) to integrate and characterize the combined effects of flow and temperature on defect densities in sheared flow-aligning LCPs. The results are summarized into texture scaling laws and texture diagrams given in terms of shear rates and temperature. The simulations, based on low dimensionality and imposed hydrodynamics, are in qualitative agreement with a wide range of previous scaling and experimental results. The results indicate that pronounced texturing with high defect densities occur at Deborah number close to unity and that decreasing temperature enhances texturing. The simulations capture a number of well known defect coarsening and defect nucleation processes including: (1) defect–defect annihilation, (2) defect pinching and (3) defect–wall interactions. The results are integrated into a texture control phased diagram that indicates the flow and temperature fields needed to achieve defect-free monodomain melts. This work provides the necessary foundation for higher dimensional modeling with coupled hydrodynamics and texturing.