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Two-Dimensional Correlation Analysis of Time-Resolved Step-Scan FT-IR Spectra of a Liquid Crystalline Guest-Host System in an Electric Field

Volume 51, Number 11 (Nov. 1997) Page 1698-1702

Czarnecki, Miroslaw A.; Jordanov, Bojidar; Okretic, Stefano; Siesler, Heinz W.


The time-resolved step-scan FT-IR spectra of a solution of 2-naphthaldehyde in a nematic solvent were recorded during switching of an electric field. The mesogen of the nematic solvent consisted of a nitrile-substituted bicyclohexyl unit and had a flexible aliphatic chain attached to it. Two-dimensional (2D) correlation analysis of the dynamic spectra was undertaken in order to investigate the details of the molecular orientation and relaxation of the sample under the influence of this electric field. In addition, from the time-resolved spectra the relaxation times of selected functionalities were estimated. The results yield strong evidence that both the nematic solvent and the solute reorient in phase at similar rates. However, the movement of the hydrocarbon chain of the nematic solvent seems to be slightly delayed with respect to the mesogen and the solute. It has been shown that the rigidity of the mesogen plays an important role in the mechanism of the electric-field-induced reorientation of the aliphatic chain.