Far-Infrared and Raman Spectra of the Solid Phases of CBOOA

Publisher Website
Google Scholar
Abstract
The far-infrared and the Raman spectra of crystalline CBOOA (N-p-cyanobenzilidene-p-n-octyloxyaniline) have been studied above 30 cm−1. The temperature dependence of the farinfrared spectrum reveals the existence of a solid-solid transition at 65°C. The two solid modifications can be obtained, respectively, from solvent crystalization (Phase II) and solidification from the mesophase (Phase I). Differential scanning calorimetric results confirm that an endothermic change from Phase II to Phase I occurs at 65°C with an associated heat of transition of 2030 cal/mole. X-ray powder diffraction patterns establish that the structures of the two phases are different. Tentative vibrational assignments are made for the far-infrared and the Raman lines observed in the internal mode region. At frequencies below 120 cm−1, both the far-infrared and the Raman spectra of Phase II exhibit distinct modes whereas, Phase I exhibits nearly quasicontinuous spectra. The possible implications of this result for the structure of Phase I and the formation of the mesophase are discussed.