The effect of a high electric field on a solution of a lyotropic liquid-crystalline polymer, poly(n-hexyl isocyanate) in p-xylene, was studied. The application of a high-voltage alternating-current electric field to the biphasic solution resulted in an elongation of the nematic domains in the field direction, the degree of elongation varying approximately with the square of the electric field. At a constant field, the extent of elongation decreased, varying inversely with the frequency in an exponential fashion. The domain structure and thus the molecular orientation were examined to explain these electric field effects. (c) 2005 Wiley Periodicals, Inc.