Temperature and pressure studies of the isotropic - Mesophase transition discontinuity by static nonlinear dielectric effect

Results of studies of static nonlinear dielectric effect (NDE) in the isotr opic phase in the homologous series of nDBT: (5-n-alkyl-2-(4-isothio-cyanat ophenyl)-1.3-dioxane) for n= 4, 6 and 8 exhibiting the I-SmA transition are presented, The strong pretransitional anomaly in the isotropic phase is si milar to the one observed in nematogens. It has been found that the discont inuity of the I-N transition increases from 10.8 K to 18.8 K when moving fr om 4DBT to 8DBT, It has been also shown that pressure reduces the discontin uity of the I-SmA transitions. Results obtained are compared with similar s tudies in two other homologous series.