RELATION BETWEEN MOLECULAR-STRUCTURES OF DICHROIC DYES AND THEIR SOLUBILITIES IN FLUORINATED LIQUID-CRYSTALS

A molecular design rule for dichroic dyes with a high solubility in fl uorinated liquid crystals has been investigated. Molecular interaction s and a concept of motional segments proportional to molecular weight were introduced to explain the deviation from an ideal solution. A sem i-empirical equation was obtained: log C = -20.75(Sigma Delta H-f/T - Sigma Delta S-f) - 0.013(E-h - E-p) + 2.32, where C represents a satur ated solubility in wt% at T (K). Sigma Delta H-f(kJ kg(-1)) represents the sum of the enthalpies of fusion and of phase-transitions from T t o melting point. Sigma Delta S-f represents the sum of the entropies. Calculated E-h represents a hydration energy. E-p is the hydrophobic e nergy determined from calculated 1-octanol log P. Log C is mainly dete rmined by the interaction between dye molecules. Bulky, rigid and asym metric structures give a high solubility, Large electrostatic interact ion between a dye molecule and liquid crystal molecules increases solu bility.