A kinetic theory and benchmark predictions for polymer-dispersed, semi-flexible macromolecular rods or platelets

The goals of this paper are: to present a mean-field kinetic theory for the hydrodynamics of macromolecular high aspect ratio rods or platelets dispersed in a polymeric solvent; and, to apply the formalism to predict the impact due to a polymeric versus viscous solvent on the classical Onsager isotropic–nematic equilibrium phase diagram and on the monodomain response to imposed steady shear. The kinetic theory coupling between the nanoscale rods or platelets and the polymeric solvent is incorporated through a mean-field potential that reflects the enormous particle–polymer surface area and the particle–polymer interactions across this interfacial area. To determine predictions of this theory on the equilibrium and sheared monodomain phase diagrams, we present a reduction procedure which approximates the coupled Smoluchowski equations for the polymer chain probability distribution function (PDF) and the nano-particle orientational PDF in favor of a coupled system of equations for the rank 2 second-moment tensors for each PDF. The reduced model consists of an 11-dimensional dynamical system, which we solve using continuation software (AUTO) to predict the modified Onsager equilibrium phase diagram and the modified Doi–Hess shear phase diagram due to the physics of polymer–particle surface interactions.

Research highlights► Kinetic theory for polymer nano-rod composites. ► Modified Onsager isotropic–nematic phase diagram due to polymeric solvent. ► Modified sheared responses due to polymeric solvent and particle semi-flexibility.