(704d) Amphiphile-Induced Reorganization of Liquid Crystals at Aqueous Interfaces

It is well-known that monolayer assemblies of amphiphiles at planar interfaces between thermotropic liquid crystals (LCs) and aqueous phases give rise to configurational transitions of the liquid crystals. The general assumption is that hydrophobic tails of surfactants interdigitate into the liquid crystal molecules at the interface to trigger reconfiguration of LC films. A different mechanism is introduced here, whereby a monolayer decoration of surfactants disturbs antiparallel orientation of 4-cyano-4′-pentylbiphenyl (5CB) molecules to cause a nematic-to-isotropic phase transition of LC within a ~2 nm layer at the interface. Upon formation of this isotropic layer, the anchoring strength of 5CB at the aqueous interface reaches zero to spawn a transition of a hybrid configuration to a uniform configuration. This configuration transition releases the stored elastic energy of the system. These results present a previously unknown mechanism that can be exploited for rational design of biological sensors, and drug delivery systems.