Abstract
The heat of mixing ΔH M has been obtained as a function of composition for nematic p-methoxybenzylidine-p-n-butylaniline (MBBA) at 25°C with two pairs of normal and branched alkane isomers (n-octane and 2,2,4-trimethylpentane (TMP), n-hexadecane and 2,2,4,4,6,8,8-heptamethylnonane (HMN)) and with cyclohexane, toluene, and carbon tetrachloride. Heats of mixing were also obtained at 55°C for isotropic MBBA with n-hexadecane, HMN, and toluene. The composition dependence of ΔH M is strongly skewed toward high MBBA concentration for systems containing nematic MBBA, and less so for those containing MBBA in the isotropic state. Heats of solution ΔH S at a low volume fraction (0.08) of MBBA were measured between 25°C and 75°C in the above seven solvents. The ΔH S values change rapidly with temperature in both the nematic and isotropic temperature ranges with a small discontinuity at 43°C, the nematic-isotropic transition temperature. The data indicate: (1) a strongly temperature-dependent orientational order in pure MBBA, of long range in the nematic phase and of short range in the isotropic phase, (2) a correlation of orientations of MBBA molecules with n-alkane chains and with toluene, but not with the branched alkane molecules or cyclohexane.
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Croucher, M.D., Patterson, D. Temperature and composition dependences of the heat of mixing of MBBA with hydrocarbon. J Solution Chem 9, 771–784 (1980). https://doi.org/10.1007/BF00646796
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DOI: https://doi.org/10.1007/BF00646796