Influence of the chain length on the nematic-to-isotropic phase transition for the odd members of a highly non-symmetric pyrene-based series of liquid crystal dimers

Abstract

This paper describes a detailed study of the nematic (N)-isotropic (I) phase transition in the homologous series of liquid crystal dimers, the a-(4-cyanobiphenyl-4'-oxy)-¿-(1-pyreniminebenzylidene-4'-oxy)alkanes (CBOnO.Py) by means of calorimetric and dielectric measurements as a function of temperature. It is concluded that for this transition, the latent heat or the entropy change decreases as the chain length of the odd dimers decreases, and this decrease is consistent with the observed tricritical behaviour.