Fourier transform far-infrared spectroscopy of the hydrogen bond in 4-n-alkoxybenzoic acids

✍ Scribed by K. Antonova; M. Petrov; N. Kirov; T. Tenev; H. Ratajczak

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 372 KB
• Volume: 8
• Category: Article
• ISSN: 0924-2031
• DOI: 10.1016/0924-2031(94)00025-c

✦ Synopsis

Far-infrared transmittance spectra (200-30 cm-1) of the hydrogen bond in cyclic dimers of 4-n-heptyl-, octyl-and nonyloxybenzoi c acids are observed and investigated. The spectral bands at 42, 63, 68 and 82 cm-a are assigned to the four deformation vibrations: twisting, bending (in and out of the dimer ring plane) and stretching by halfwidth spectral band temperature analysis. The hydrogen band evolution in the isotropic and nematic phases is investigated. A cyclic ,--, open dimer transformation at different vibration frequencies and polarizations is shown. The critical character of the temperature T*, defined as the temperature dividing the nematic phase of the nematics with hydrogen-bonded molecules into high-temperature (classical) and low-temperature (smectic-like) subphases, is demonstrated.