The effect of steady flow fields on the isotropic–nematic phase transition of rigid rod-like polymers

Abstract

In this paper we study the stability of steady state solutions to Doi’s kinetic equation for rigid rod-like polymers in an arbitrary flow field. It is found that for a certain range of concentration, the addition of flow to an isotropic phase can induce a transition to the nematic phase, if the flow rate exceeds a certain critical value. This critical flow rate decreases as concentration is increased. For phase transitions occurring in weak flow, exact solutions to this problem are calculated. Unlike the ‘‘free energy’’ approach, these calculations are not restricted to potential flows.

Suspensions of prolate spheroids in Stokes flow. Part 2. Statistically homogeneous dispersions

“…('Nematic' is the liquid crystalline phase favoured thermodynamically by systems of hard spheroids at sufficiently high densities (Frenkel, Mulder & McTague 1984).) Although external fields -either electromagnetic (for susceptible particles) or mechanical (an imposed continuous deformation for example -can induce orientational order, in effect lowering the isotropic-to-nematic boundary (Thirumalai 1986;See, Doi & Larson 1990), we shall focus on equilibrium microstructures only. The effect of the flow on the configuration is not accounted for.…”

Isotropic-nematic spinodals of rigid long thin rodlike colloids by event-driven Brownian dynamics simulations

“…Under shear the rods have a propensity to align along the flow direction, both in the isotropic and in the nematic phase, thus decreasing the spinodal concentrations. 23,[26][27][28][29][30][31][32] At sufficiently high shear rates the spinodals are predicted to terminate at a coalescence point, eliminating the phase transition between ordered and disordered states. This paper is organized as follows: The event-driven Brownian dynamics algorithm is described in detail in the next section, followed by a validation against a traditional BD program at the dilute and semidilute concentrations accessible to the latter.…”

Rheo-Optical Evidence of a Flow-Induced Isotropic−Nematic Transition in a Thermotropic Liquid-Crystalline Polymer

“…45 Some theoretical treatments of lyotropic LCPs show that elongational flow 46 will promote isotropic-nematic (I-N) transition at a concentration below that predicted by the Flory theory 47 of rodlike molecules in the absence of a flow field; others predict that the nematic phase is more stable than the disordered isotropic one 48 or that the I-N transition can be induced by imposing a flow, if the shear rate exceeds a certain critical value, and the critical shear rate (γ c ) will decrease with increasing concentration. 49 Despite this background, no reports exist of a flow-induced I-N transition in lyotropic LCPs.…”