NEMATIC BEND-SPLAY ELASTICITY OF CYANOPHENYL COMPOUNDS WITH DIFFERENTTERMINAL GROUPS

The elastic properties of nematic compounds with terminal cyanoaromati c and containing cycles alyphatic groups were investigated. The termin al group structure has essential influence on the bend K-3 and splay K -1 elastic constants and their temperature dependences. The ninth and tenth members of 4-cyanophenyl 4'-n-alkyloxybenzoate series (nCPh) and cyanobiphenyl ether with ethylene-butylcyclohexane terminal group sho w pretransitional divergence of K-3 in the vicinity of the nematic-sme ctic phase transition Outside pretransitional temperature region the a lternatation from odd to even n in nCPh series is accompanied by posit ive jumps of the ratio K-3/K-1 and change of the character of its temp erature dependence. A striking unmonotonous temperature dependence of the elastic splay constant K-1 was founded for cyanobiphenyl ether wit h butylcyclohexane terminal group. The occurrence of frozen striped te xture in a smectic phase after the nematic-smectic transition in the p resence of magnetic field was found for all nematics with the temperat ure divergence of K-3. Distance between stripes was the less, the more magnetic induction.