Solubility of thioindigo dopants in a smectic liquid crystal host evaluated by2H NMR spectroscopy

Kenneth E. Maly, Gang Wu, Robert P. Lemieux
2001 Liquid crystals (Print)  
The solubility of two partially deuterated thioindigo dopants in a smectic liquid crystal host was evaluated by variable temperature 2H NMR spectroscopy and polarized microscopy. 2H NMR spectra showed that the dopant ( Ô )-6,6¾ -bis(2-octyloxy)-5,5¾ -dinitrothioindigo-d 6 forms a homogeneous solution with the smectic phases of the liquid crystal host ( Ô )-4-(4-methylhexyloxy) phenyl 4-decyloxybenzoate (PhB) up to its saturation point of 3 mol %. These results are consistent with polarized
more » ... scopy observations of the dopant crystallizing out of solution upon reaching a concentration of 3 mol %. On the other hand, 2H NMR spectra of ( Ô )-5,5¾ -dichloro-6,6¾ -bis(2-octyloxy)thioindigo-d 6 dissolved in PhB showed evidence of a partitioning of the solution between smectic and isotropic microdomains, which increases with increasing dopant concentration-from 1.2 to 9.1 mol %. To a large extent, this smectic/isotropic microphase separation could not be detected by polarized microscopy. These results suggest that 2H NMR spectroscopy can provide a more accurate determination of the occurrence and extent of microphase separation in doped liquid crystal samples.
doi:10.1080/02678290010005613 fatcat:sp4ysvjl2zf5batanevfvdgim4