Liquid-crystalline polymers: interfacial properties

Abstract

Main-chain liquid-crystalline polymers (LCPs) in nematic media are ellipsoid-like objects. Long LCPs support hairpin defects. The elasticity of the major axis is then significantly weaker than that of the minor axis. Furthermore, the major axis is aligned with the nematic direction. These two traits give rise to novel interfacial behaviour of solutions of LCPs in nematic solvents. A family of second-order tilting phase transitions is expected for the appropriate combination of deformations and anchoring conditions. These occur in a variety of situations involving a solid/solution interface: confinement, grafting and adsorption. A different family of effects are associated with domain boundaries in mesophases of block copolymers incorporating an LCP block. The first-order isotropic–nematic phase transition results in an abrupt change in the elastic behaviour of the LCP block. This, in turn, results in qualitative changes in the phase diagram of the block copolymers.