Chiral Polymeric Nanocapsules and Their Use for Conformational Deracemization of Liquid Crystals

Abstract

We present the first preparation and properties of chiral nanocapsules. The chiral shell, a polyurea derivative, was obtained by interfacial emulsion polymerization of l-lysine with polymethylene polyphenyl isocyanate. The chirality of these nanocapsules was manifested by its ability to induce conformational deracemization of a liquid crystal. This induced chirality was measured using the “Raynes’ experiment”, in which the boundary conditions of cells impose a ±90° rotation of the liquid crystal director from one surface to the other. Both left- and right-handed director twist domains appear on cooling from the isotropic to the nematic phase. Owing to the weak induced chirality of the liquid crystal, one sense of director rotation is energetically more favorable and its domain size expands, resulting in curvature of the domain walls. The curvature was measured as a function of capsule concentration and serves as a metric of the induction of chirality in the surrounding liquid crystal.