Effects of hydrophilic and hydrophobic gold nanoclusters on the stability and ordering of bolaamphiphilic liquid crystals

Abstract

Electron microscopy, optical microscopy, and X-ray diffraction studies of dispersions of hydrophilic and hydrophobic thiolate-capped gold nanoclusters in bolaamphiphilic liquid crystals (LCs) indicate random inclusion of the nanoclusters in the LC matrix with a concentration- and monolayer-type-dependent effect on the mesophase stability of the LC host. Both types of nanoclusters show no effect on the thermal properties of the smectic A phase of 1. In contrast, the rectangular columnar phase of 2 is gradually destabilized with an increasing concentration of the hydrophobic hexane thiolate gold clusters Au1, and gradually stabilized with an increasing concentration of the hydrophilic ethyleneglycol protected gold nanoclusters Au2. In addition, structural characterization using SAXS indicated no change in the lattice of the rectangular columnar phase of 2 in mixtures with both nanoclusters (c2mm), but provided evidence for a macroscopic phase separation into particle-rich and particle-poor domains with the same rectangular lattice but slightly different lattice parameters for mixtures with higher concentrations of Au2 in 2.