Mid‐ and low‐frequency Raman spectra of stable and metastable crystalline states of the 4‐n‐alkyl‐4′‐cyanobiphenyl (n = 9, 11, 12) liquid crystals

Abstract

Metastable crystalline states of each of the title compounds were reproducihly generated by rapid low-temperature quenching of the corresponding liquids, as judged by the phonon-like appearance of their low-frequency Raman spectra (5-200 cm-') and by a splitting of the mid-Raman (ca. 2220 cm-') CN stretch. Their observed aspects of peak frequencies, peak multiplicities and hand widths differ markedly from those of the corresponding spectra of the stable crystals. We propose that the solid metastable configurations consist of packings or stacks of immobilized smectic-like structures with significant long-range positional order within each, but with disordered director orientations between them.

Molecular behaviors in thin film lubrication—Part two: Direct observation of the molecular orientation near the solid surface

“…As indicated in Fig. 5(a), the peak at 2,230 cm −1 in the Raman spectra recorded on the SERS substrates was broadened, which shows that the cyano group (C-N) was influenced by Ag [48]. According to previous studies, 6CB molecules are inclined to be adsorbed vertically on the Ag surface via C-N bonds as depicted in the inset panel in Fig.…”