Bipolar to Radial Drop Transitions in the Presence of Novel Surfactants*

Liquid crystals (LCs) are a class of molecules that can form a variety of phases that can be influenced by external interactions. We are interested in controlling the phase of a liquid crystal droplet by controlling the interface between the organic liquid crystal (5CB) and the aqueous surfactant medium. This is an interesting physical system because the molecules at the surface can alter the phase of the LC throughout the interior by balancing the elastic energy of splay, twist, and bend against the interfacial tension. Here, we test the effects of novel amphiphiles, in the presence of SDS, on the phase of the LC droplets. We have synthesized molecules with various triggerable stimuli, such as pH, light, and protein binding. To help us understand the dynamics of the phase changes, we compare our experiments to simulations. We find that the phase transition is triggered by the addition of SDS, but not the novel surfactants. The concentration at which the phase transition occurs does not appear to depend on the droplet size, but does depend on the novel surfactant in the solution. Interestingly, we find a hysteresis in the concentration of the phase transition, from bipolar to radial and back again, that depends on the novel surfactant used.