Control of mesogen configuration in colloids of liquid crystalline polymers

Abstract

We report on a method to chemically predetermine the surface anchoring of mesogens in liquid crystalline colloids formed by different types of dispersion polymerization, and hence to achieve control over the mesogen configuration in such colloids. The surface anchoring is controlled by the chemical linkage of the polymers forming the colloids to the surfactants stabilizing the colloids towards the dispergent. We find that the hydroxypropyl cellulose used in conventional dispersion poylmerization induces parallel mesogen surface anchoring that in turn leads to bipolar director-field configurations, while a methacrylate terminated polysiloxane stabilizer, which is used in nonpolar dispersion polymerization, induces perpendicular anchoring and because of that to radial or axial configurations, depending on the size of the synthesized colloid. These differences in surface anchoring tendencies are due to differences in the molecular structure of the LC/non-LC block copolymers formed by the mesogens and the stabilizers. Based on these observations we synthesized a novel macroinitiator able to induce bipolar director-field configurations in the nonpolar dispersion polymerization.