Kerr response of nematic liquids

The Kerr response of seven nematic substances has been measured just above their nematic‐isotropic transition temperature, in their isotropic state. If the reciprocal of the Kerr constant B is plotted against temperature, a linear relationship analogous to the Curie‐Weiss dielectric relationship in ferroelectrics is found in all cases. The transient Kerr response—that is, the variation of induced birefringence with time in response to a field step—was also measured in three of the compounds. In p‐(p‐ethoxybenzylidene) amino benzonitrile (EBAB), a maximum Kerr constant of 175×10⁻¹⁰ cm² V⁻¹ was observed, together with a response time of 13 nsec. The extremely short response time indicates that molecular association does not take place. On the other hand, n‐(p‐methoxybenzylidene)‐p‐butylaniline (MBBA) under similar conditions showed a response time of 3 μsec, indicating that a high degree of association does take place in the isotropic phase.