Diamagnetism and orientational order of nematic liquid crystals

Abstract

Measurements are presented for the diamagnetic anisotropy of thirteen nematic liquid crystals. As any bias in the rotation around the long molecular axis is most probably small, the results probe accurately the temperature variations of S, the degree of orientational order. The critical behaviour of S near the nematic-isotropic phase transition can be described by an exponent 03B2 of the order of 0.25. Procedures are considered to obtain the molecular magnetic anisotropy. By a systematic variation of the structure of the molecules an impression of the contributions of the various molecular groups can be obtained It turns out to be rather difficult to obtain accurate data for the molecular magnetic anisotropy. As a consequence the absolute scale of S can only be fixed with an accuracy of the order of 10 %. J. Physique 43 (1982) 361-367 FTVRIER 1982,