Long-range Casimir interactions between impurities in nematic liquid crystals and the collapse of polymer chains in such solvents
Laboratoire de Physico-Chimie Théorique
Ecole Supérieure de Physique et de Chimie Industrielles de la Ville
de Paris 10 rue Vauquelin, F-75231 Paris Cédex 05, France
Accepted: 14 January 2000
The elastic interactions between objects embedded in a nematic liquid crystal are usually caused by the average distortion —rather than by the fluctuations— of the nematic orientational field. We argue that for sufficiently small particles, the nematic-mediated interaction originates purely from the fluctuations of the nematic director. This Casimir interaction decays as d-6, d being the distance between the particles, and it dominates van der Waals interactions close to the isotropic-to-nematic transition. Considering the nematic as a polymer solvent, we show that the onset of this Casimir interaction at the isotropic-to-nematic transition can discontinuously induce the collapse of a flexible polymer chain from the swollen state to the globular state, without crossing the Θ-point.
PACS: 61.30.-v – Liquid crystals / 36.20.-r – Macromolecules and polymer molecules / 83.70.Hq – Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc
© EDP Sciences, 2000