Enhancing Liquid-Crystalline Order and Fluidity of a Hydrophobic Host with Trace Hydrophilic Solvent

An impurity usually degrades the crystalline order of the host material. Here, we investigate an intriguing counterexample where an impurity strongly enhances the ordering of a thermotropic liquid crystal while increasing its fluidity. At 5 wt %, glycerol enhances the smectic layering of the hydrophobic host itraconazole by reducing the random molecular offsets in each layer, creating more compact layers with nearly zero thermal expansion. We attribute glycerol’s effect to its cross-linking of itraconazole by hydrogen bonds within a monolayer. This system suggests the intriguing prospect of enhancing the structural order of a hydrophobic thermotropic liquid crystal with a small dose of protic solvent. This effect is potentially related to the dual role of glycerol in a bioprotective glass, namely, plasticizer for global mobility and antiplasticizer for local mobility.