Dual Localization of Paramagnetic Probe Molecules in Smectic Liquid Crystals

Molecular localization of nitroxide stable radicals in three smectic liquid crystals (4-n-octyl-4'-cyanobiphenyl (8CB), p-hexyloxyphenyl ester of p-octyloxybenzoic acid (HOPOOB) and p-hexyloxyphenyl ester of p-decyloxybenzoic acid (HOPDOB)) was analyzed by means of numerical simulation of electron paramagnetic resonance spectra. It was shown that admixture molecule can be localized in the structure of smectic LC in several different ways. The studied nitroxide molecules demonstrated dual localization in HOPOOB and HOPDOB but unique localization in 8CB. The radical molecules with different localization are distinguished by the values of rotation diffusion coefficients and by the direction of the main rotation axis.