Interpretation of Mesophase Transitions

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Abstract
New data have provided a means for quantitatively testing the statistical theory of Frenkel for explaining the pretransitional effects adjacent to first‐order transitions in mesophase systems. This theory has been frequently suggested as a qualitative explanation for pretransitional changes in physical properties that occur within 10°C of mesophase–isotropic transitions. The one previous quantitative test used compressibility and volume expansion data on p‐azoxyanisole, which forms a single mesophase of the nematic type. It was concluded that the Frankel theory was of limited applicability; that (a) the equations did not apply closely, within about l°C of the transition, and (b) did not apply to pretransition effects below the transition. Calculations made here using new data on p‐azoxyanisole show, in contrast, that the Frenkel theory (a) applies well near the nematic–isotropic transition, (b) the theory may be applied equally well on both sides of the transition, (c) that asymmetrical pretransitional effects are accurately treated, and (d) in contrast to an earlier result, specific‐heat anomalies near the transition are accurately predicted and differ by a factor of 2 from previous estimates.