Liquid Crystals from Polymer-Functionalized TiO2 Nanorod Mesogens

In this work, we functionalized TiO2 nanorods with dopamine-functionalized diblock copolymers. After functionalization, they are well dispersible in organic solvents. Light scattering proves that the nanorods are dispersed as single objects, and we could use AFM (tapping mode) to visualize the homogeneous polymer shell around the nanorods. When using a LCST polymer such as poly(diethylene glycol monomethyl ether) methacrylate (PDEGMEMA), the functionalized nanorods showed a temperature-dependent dispersion stability. The dispersions became microscopically (light scattering) and macroscopically (turbidity measurement) unstable when reaching the LCST of PDEGMEMA. After investigation of the nanorod mesogens, we investigated their liquid crystalline behavior. The phase diagram of PMMA-functionalized nanorods in PEG 400 as the mobile matrix was explored, and we found a rising clearing temperature with increasing volume fractions of nanorods. On the other hand, we investigated PDEGMEMA-functionalized nanorods in excess PDEGMEMA polymer as the matrix and found again liquid crystalline phases.