Heat capacity measurements have been made on a liquid-crystal mixture system formed from bent-shaped molecule 1,3-phenylene bis[4-(4-8-alkoxyphenyliminomethyl)benzoates] (P-8-O-PIMB) and rod-shaped molecule $n$-pentyl-cyanobiphenyl (5CB). The obtained results can be understood assuming that the addition of P-8-O-PIMB molecules to the 5CB system affects as a field conjugate to the nematic order parameter. The $B_X\mathrm{\text{−}}{B}_4$ transition can be viewed as the nematic-isotropic transition of 5CB, which is embedded in a framework of the $B_4$ structure of P-8-O-PIMB molecules. The present mixture system offers a rare example of the nematic-isotropic critical point, whose critical behavior has not been studied yet in detail.

• Received 27 April 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.197801