Magnetic field induced alignment of the directors of a smectic-A liquid crystal

Deuterium NMR is used to monitor the magnetic field induced alignment of th e directors in the smectic A phase of 4-octyl-4'-cyanobiphenyl. The experim ents consist of first preparing the sample as a monodomain by cooling slowl y from the nematic phase in the magnetic field of the NMR spectrometer. The tube containing the sample is then rotated quickly through. an angle theta (+), and the subsequent field induced alignment process followed by recordi ng deuterium spectra over a period of time. The results obtained show that the magnetic field induced alignment of the directors in a smectic-A sample is qualitatively different from that of nematic samples. Results are repor ted for the pure mesogen containing deuteriums at the ct chain position, an d these are compared with data obtained on the alignment process by monitor ing the deuterium spectrum of a small amount of an added solute, p-xylene-d (10). [S1063-651X(99)06608-8].