Measurements of the dielectric and viscoelastic constants in mixtures of 4,4'-n-octyl-cyanobiphenyl and biphenyl
We performed measurements of the dielectric constants, splay elastic constant, and rotational viscosity of the nematic phase of mixtures of 4,4'-n-octyl-cyanobiphenyl (8CB) and biphenyl (BP). In contrast with previous results of DasGupta et al. [Phys. Rev. E 63, 041703 (2001), 10.1103/PhysRevE.63.041703; Phys. Lett. A 288, 323 (2001), 10.1016/S0375-9601(01)00537-0], we do not find any anomaly of these constants when the smectic-A phase is approached at all concentrations of BP. These results are compatible with recent calorimetric measurements of Denolf et al. [Phys. Rev. Lett. 97, 107801 (2006), 10.1103/PhysRevLett.97.107801; Phys. Rev. E 76, 051702 (2007), 10.1103/PhysRevE.76.051702] and the absence of a tricritical point in the phase diagram. The origin of the anomalies observed by DasGupta et al. at large concentration of BP is also briefly discussed and a likely explanation in terms of biphenyl evaporation is proposed.