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Abstract

We present deuterium NMR spectra of a series of hexaalkoxytriphenylene solutes (THEn, where n = 5,6,7, and 8 is the number of carbons in the labeled alkoxy chains) dissolved in the calamitic solvent phase V. The observed methylene quadrupolar splitting patterns (segmental order profiles) are markedly different from those obtained in the neat columnar discotic phases of the THEn mesogens; they also differ significantly from order profiles of alkoxy chains attached to calamitic mesogens. Theoretical simulations of the spectra give the assignment of the splittings and, moreover, enable studies of the accommodation of the oblate THEn solute in the calamitic solvent's orientationally biased mean field. The chord model with the rotational isomeric state description of the THEn's six alkoxy chains quantitatively describes this unusual mixture of oblate and prolate molecules. The model shows that the accommodation of the THEn mesogenic core in the calamitic solvent's mean field does not favor maximum extension of the chains: The oblate THEn disk is tangent to the solvent director, and consequently, the radial disposition of extended chain contours on the periphery of the THEn disk is frustrated by the excluded volume interactions that constitute the solvent's mean field