Pretransitional behavior of dielectric permittivity on approaching a clearing point in a mixture of nematogens with antagonistic configurations of dipoles - art. no. 051701

The results of studies of static dielectric permittivity epsilon (T) in the isotropic phase of 4-cyano-4-pentylalkylbiphenyl and n-p-methoxybenzyliden e-p'-butylaniline (5CB-MBBA) mixtures are presented. 5CB and MBBA are nemat ogens with antagonistic permanent dipole moments configurations. An increas e in MBBA concentration strongly decreases the pretransitional effect. Howe ver, a derivative analysis detected the existence of a pretransitional anom aly even if its weakness, made a straightforward epsilon (T) fit impossible . The obtained anomalies can be well portrayed by,fluidlike equations, isom orphic to that applied in critical binary mixtures. Every time the same val ue of the specific heat critical exponent alpha approximate to0.5 was obtai ned. A preliminary discussion of the influence of the permanent dipole conf iguration on the pretransitional behavior of dielectric permittivity was al so possible.