K. Antonova et al., FAR-IR SPECTROSCOPIC INVESTIGATIONS OF NEMATIC LIQUID-CRYSTALS WITH HYDROGEN-BONDED MOLECULES, Journal of molecular structure, 325, 1994, pp. 189-201
Far-IR spectroscopy (200-30 cm-1) was used to study the temperature ev
olution of the hydrogen bonds in the nematic liquid crystal phase of 4
, n-heptyl-, octyl- and nonyl-oxybenzoic acids (HOBA, OOBA and NOBA).
The observed absorption bands (v(OH) = 82, 68, 63 and 42 cm-1) are ass
igned to the four predominant vibrations respectively - stretching, be
nding (out of and in the dimer ring plane) and twisting. From a spectr
al band half-width temperature analysis hydrogen-bond evolution in the
isotropic and nematic phases is investigated. A cyclic reversible ope
n dimer transformation at different vibrational frequencies and polari
zations is indicated.