a Study of the Molecular Dynamics of Cholesteric Liquid Crystals Using Pulsed Nuclear Magnetic Resonance.

Pulsed nuclear magnetic resonance techniques were employed to measure the second moment and rotating frame relaxation times of various cholesteric-nematic mixtures. The transient response of liquid crystals to the application or removal of an external field was measured. The average molecular orientation following an electric field induced cholesteric-nematic phase transition was monitored by measuring the second moment of the resonance absorption line shape. The experimental data were analyzed in terms of the Leslie-Ericksen continuum theory using an effective field approximation. The frequency and time dependences of the spin-lattice relaxation in the rotating frame were determined.