Understanding the properties of liquid-crystalline polymers by computational modeling

Abstract A topical review of recent theoretical work on the properties of lyotropic solutions and melts containing semiflexible polymers in thermal equilibrium is given, with a focus on the liquid-crystalline and smectic order of these systems in the bulk and under confinement. Starting with a discussion of single chain properties in terms of the Kratky-Porod worm-like chain model and its limitations, extensions along the lines of Onsager’s theory for the isotropic-nematic transition of solutions of hard rods are briefly reviewed. This discussion is followed by a review of recent Molecular Dynamics simulations and classical Density Functional Theory calculations. It is argued that, even in the simplest case of athermal solutions, coarse-grained polymer models must include three lengths: the contour length L, the persistence length {ℓ}_p, and the effective chain thickness D. The discussion is then extended to semiflexible polymers in solutions with thermally driven transitions, where the isotropic-isotropic phase separation competes with the isotropic-nematic transition. Basic physical phenomena due to confinement of these systems in thin films with either repulsive or attractive walls are briefly reviewed, and conditions for the formation of strongly ordered surface layers are identified.