Mixing Effects on the Cotton-Mouton Constant of 3OCB and 5OCB in Isotropic Phase

概要

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To find a material with large magnetic-field-induced birefringence ?n/H^2, we have studied the mixing effects on K_C and (?n/H^2)_<T=T_c> of 4'-n-propyloxy-4-cyanobiphenyl (3OCB), which has the largest value of K_C, and 4'-n-pentyloxy-4-cyanobiphenyl (5OCB), which has the largest value of (?n/H^2)_<T=T_c> among the cyanobiphenyls so far investigated. Here K_C is the proportionality constant in the relation ?n/H^2=K_C/(T-T^*_c) ; (?n/H^2)_<T=T_c> is necessary because the relation may not hold as the temperature approaches the clearing point T_c. The mixing is effective and both K_C and (?n/H^2)_<T=T_c> attain the maxima at x=0.2 and 0.6, respectively, where x=[5OCB]/([3OCB]+[5OCB]). The phase field in which the isotropic and nematic phases coexist appears to be less than 0.07℃. The K_C(x) and T_c(x) curves have mirror symmetry with respect to a line parallel to the abscissa ; larger K_C corresponds to lower T_c. To understand their dependence on x, we have also discussed what phenomenological parameters in the Landau-de Gennes theory are responsible for K_C and (?n/H^2)_<T=T_c>.
社団法人応用物理学会の論文
1981-03-05