Anomalous Effects Owing to Electric Fields in the Nematic Phase of 4,4prime;hyphen;dihyphen;nhyphen;heptyloxyazoxybenzene

摘要

The nematic phase of 4, 4prime;hyphen;dihyphen;nhyphen;heptyloxyazoxybenzene exhibits a negative low frequency dielectric anisotropy, therefore, one would expect an anomalous alignment in a dc electric field with the long molecular axes preferring a direction parallel to the electric field. If the sample becomes slightly decomposed this is what is observed. In the very pure sample the preferred direction is perpendicular to the field for both dc and ac fields and it does not appear to exhibit domains or dynamic scattering. When a pure sample is doped to increase its conductivity, a dc or 25 Hz electric field appears to be more effective than a field of higher frequency in producing an ordering with the long molecular axes preferring a direction perpendicular to the field. The existence of another anomalous behavior with the long molecular axes preferring a direction perpendicular to the field is suggested. Since the dc conductivity for this particular sample was greatest in a direction perpendicular to the long molecular axes, when ordered by a high magnetic field, a mechanism similar to that suggested earlier for anomalous alignment is proposed.