Bent-core liquid crystal (LC) decorated gold nanoclusters: synthesis, self-assembly, and effects in mixtures with bent-core LC hosts

We present the first synthesis of a series of thiol-, thioacetate-, and xanthate-terminated bent-core derivatives, as well as the preparation of gold nanoclusters using the thiol-terminated bent-core compounds. The mesomorphic properties of the bent-core compounds have been investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and electro-optic tests. From this series, the mono-xanthate derivatives form rectangular or hexagonal columnar phases, and the mono-thiol derivative with shorter alkyl chains forms a metastable, likely smectic, phase. All other bent-core compounds and intermediates exclusively form disordered or multi-layer lamellar crystalline solid modifications. High-resolution transmission electron microscopy (HR-TEM) images of the bent-core functionalized gold nanoclusters prepared from the thiol-terminated derivatives, taken after slow evaporation of the solvent, provide evidence for the formation of self-assembled nanocluster arrays. Upon dispersion of these gold nanoclusters in two structurally related bent-core LC hosts (one forming a SmCPA, and the second with a terminal double bond displaying a Col(r) phase), a shift in the surface plasmon resonance was observed indicating a LC host-dependent aggregation of the nanoparticles. Finally, we report initial results on the effects of different concentrations of these nanoclusters on the thermal properties as well as the applied voltage/current response of the parent SmCPA host.