The lsquo;lsquo;chord modelrsquo;rsquo; of flexible alkane solute ordering in the nematic phase lsqb;D. J. Photinos, E. T. Samulski, and H. Toriumi, J. Phys. Chem.94, 4688 (1990);94, 4694 (1990)rsqb; is extended to prolate mesogen molecules with a single alkyl tail, and the physical properties of two homologous series, 4,4rsquo;hyphen;nhyphen;alkylcyanobiphenyls and 4,4rsquo;hyphen;nhyphen;alkyloxycyanobiphenyls, in neat nematic phases are evaluated. The chord model of the mesogenrsquo;s anisotropic interactions yields a consistent description of the essential features of the chain order profile (derived from deuterium nuclear magnetic resonance) and the evenndash;odd variation of thermodynamic quantities associated with the nematicndash;isotropic transition. Very accurate agreement with experimental observations is obtained using the standard rotational isomeric state description of the tailndash;chainrsquo;s flexibility along with a minimal form of the selfhyphen;consistent anisotropic potential (i.e., only two coupling constants determine the strength of orientation dependent interactions, one for the biphenyl core and one for the aliphatic chord segments). There is remarkable compatibility among the values of optimized coupling constants obtained from modeling the chain segmental order parameters and the mesophase transition temperatures. Moreover, these coupling constants evaluated for aliphatic chord segments in the neat mesogens show quantitative agreement with the values obtained for simple alkane solutes in nematic solvents. These findings suggest that the chord model, which explicitly represents molecular shape anisotropy (excluded volume effects) in conjunction with molecular flexibility, provides a very good description of complex molecules in liquid crystals.
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