Odd-even effect in the smectic A-cholesteric tricritical pressure of the cholesteryl n-alkanoates. High pressure studies on nine homologues

Abstract

The tricritical pressure, Ptcp, for the smectic A-cholesteric phase transition was determined by optical measurements for nine members of the homologous series of the cholesteryl n-alkanoates. Ptcp shows a clear odd-even effect with the length of the n-alkyl chain. The dependence of Ptcp on the length of the chain is not the same as that of the total smectic A-cholesteric transitional enthalpy, ΔH, at 1 bar. A comparison of both dependences gives hints to a different influence of the chain length on the pretransitional and discontinuous part of ΔH.