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 degrees 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 similar to 24 degrees 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 An, 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.