TEMPERATURE EFFECTS ON THE FTIR SPECTRA OF NEMATIC LIQUID CRYSTALS

We have investigated the FT-IR of the n(CN) and n(C=O) groups of the nematic liquid crystal CP6B (4-cyanophenyl-4’hexylbenzoate) at different temperatures (solid, liquid crystalline and isotropic phase). Whenthe temperature of CP6B changes in the range 45 - 80 °C the absorption bands of in the IR spectradecreases and the bands are shifted. Even at the highest temperature reached in this study 80°C above thenematic–isotropic transition, the liquid has not yet achieved the structure of the simple liquid. Thevibrational and orientational relaxations occur in very different time scales. Experimental results show thatdissipative processes are the least intense in liquid crystal state, so the intensity of absorption band ishighest in this state.