Large electroclinic effect in SmA* liquid crystals induced by an atropisomeric biphenyl dopant

Electroclinic coefficients (e(c)) and reduced polarizations (P-o) were measured in the SmA* and SmC* liquid crystal phases formed by 4 mol% mixtures of the chiral dopant (-)-2,2', 6,6'-tetramethyl- 3,3'-dinitro-4,4'-bis[(4-nonyloxybenzoyl) oxy] biphenyl [(-)- 1] in the binary host mixture of 5-(4-butyloxyphenyl)-2-octyloxypyrimidine (5-PhP1) and 2-(4-butyloxyphenyl)-5-octyloxypyrimidine (2-PhP1) over the mole fraction range 0 less than or equal to (x5-PhP1) less than or equal to 0.24. Both e(c) and P-o increase with x(5-PhP1), which is consistent with the assumption that 5- PhP1 should be more effective in propagating chiral perturbations exerted by (-)-1. At x(5-PhP1) = 0.24 and T - T-C = +5 K, the electroclinic coefficient is 0.34degrees mum V-1, which is one order of magnitude greater than the highest e(c) value previously reported for a chiral dopant at the same mole fraction and reduced temperature.