RELATION BETWEEN ORIENTATIONAL ORDER PARAMETERS OF MATRIX AND PROBE IN NEMATIC LIQUID-CRYSTALS

The phenomenological relation between the orientational order parameters of matrix (S) and probe (S p) has been obtained and confirmed for a large number of impure nematic liquid cyrstals. The temperature-dependent parts of the parameters S and S p are proportional to one another and have the same critical behaviour over the whole mesophase range, although the absolute values of S and S p as well as their temperature dependences S(T) and S p(T) may be sufficiently different. The relation observed is not the consequence of the known molecular-statistical theories of impure nematic liquid crystals. © 1990 Società Italiana di Fisica.