Director configuration transitions of polyelectrolyte coated liquid-crystal droplets

Liquid-crystal droplets are of great interest because of their large surface areas, rich phases, and tunable optical properties. The director configuration of liquid-crystal droplets provides a unique optical sign to detect the events occurring at the droplet surface. In this article, we report the alternating bipolar/radial configuration transitions of 4-n-pentyl-4'-cyanobiphenyl (5CB) droplets triggered by the layer-by-layer coating of negatively charged poly(styrenesulfonate sodium (PSS) and positively charged poly(diallyldimethylammonium chloride) (PDADMAC) on the droplet surface. The alternating configuration transitions are due to the interactions of the 5CB with polar versus nonpolar PDADMAC/PSS multilayer coatings. Furthermore, we find that the coating of PDADMAC/PSS multilayers makes the director configuration of the 5CB in the droplets sensitive to environmental salt concentrations.