2ND-ORDER FLEXOELECTRIC EFFECT IN CHIRAL NEMATIC LIQUID-CRYSTALS

A molecular-statistical model for the second-order flexoelectric effec t in chiral nematics is developed, accounting for additional chiral te rms in the pair intermolecular potential U(1,2). It is shown by symmet ry analysis, that there are four independent chiral terms in the flexo electric polarization, proportional to the square of director gradient s, P approximately lambdadelndeln. A molecular-statistical theory is d eveloped for the second-order chiral flexoelectric constants lambda. T heir values, obtained in the mean-field approximation, depend on molec ular dimensions, interaction parameters, and the degree of molecular c hirality. Possible experimental situations are discussed where this ef fect can be observed.