Flow Alignment of a Colloidal Solution which can Undergo a Transition from the Isotropic to the Nematic Phase (Liquid Crystal)
The flow alignment and the resulting flow birefringence of a colloidal solution of nonspherical particles is studied theoretically. Point of departure is a Fokker-Planck equation (FPE) for the orientational distribution function where torques exerted by the gradient of the flow velocity field and by an internal (molecular) field are taken into account. It is due to this internal field that a transition into an ordered liquid crystal phase of nematic type can occur if the concentration of the molecules exceeds a certain critical value. From the FPE a nonlinear inhomogeneous relaxation equation for the alignment tensor is derived which can be applied to the isotropic and nematic phases. Thus a unified theory is obtained for the pre-transitional behaviour of the flow birefringence in the isotropic phase and for the flow alignment in the nematic phase as well as in the transition region between both phases.
KeywordsLiquid Crystal Colloidal Particle Colloidal Solution Nematic Phase Isotropic Phase
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