Nanoparticle-Promoted Thermal Stabilization of Room Temperature Cholesteric Blue Phase Mixtures

A blue phase (BP*) liquid crystal mixture was stabilised via doping with three different types of colloidal particles, smaller hexane thiolate-capped gold nanoparticles (NP1) with a size around 2.2 nm, larger oleylamine capped gold nanoparticles (NP2) with an average size of 13.2 nm, and manganese oxide nanoparticles (NP3) capped with oleic acid (10 nm in core diameter). We have experimentally studied the thermal stability of the blue phases by varying the core material of the nanoparticle additives (metal vs. metal oxide), the nature of the capping agents, and the core size. We have used polarized optical microscopy (POM) and the selective reflection of blue phases to identify the type of blue phase as well as the mesomorphic range. For the doped colloidal mixtures, POM and UV-vis spectrophotometry results confirmed the thermal stabilisation of the used BP* mixtures.