Temperature-Dependent Raman Spectroscopic Study of the Nematic Liquid Crystal 4-n-Pentyl-4′-Cyanobiphenyl

Abstract

The spectral behaviors of 4- n-pentyl-4′-cyanobiphenyl (5CB) have been studied by means of temperature-dependent Raman spectroscopy in the range between −70 and 70 °C. The v(C≡N) bands in the Raman spectra were found splitting below the transition temperature from the solid to the nematic liquid crystalline phase at ∼24 °C, suggesting the existence of solid crystalline polymorphism. The interfacial structures of 5CB on metal plate surfaces have been reexamined by surface-enhanced Raman scattering (SERS) at different temperatures. On Ag and Au, the asymmetric shapes of the v(C≡N) bands suggest that there should exist different binding schemes for 5CB on metal surfaces. These asymmetric bands in the v(C≡N) stretching region were found to vary in changing temperature.