N-14 NMR-STUDY OF ORDER FLUCTUATIONS IN ISOTROPIC PHASE OF LIQUID-CRYSTALS

Ntirogen-14 resonance lineshapes in the isotropic phase of a nematic (p-azoxyanisole) and of a smectic-A (diethylazoxybenzoate) liquid crystal have been studied using fast Fourier transform techniques. The temperature variation in linewidth is different in each sample, although both depend critically on the short range order fluctuations which exist about 10 degree to 15 degree into the isotropic phase. The experimental results for the isotropic phases of p-azoxyanisole and of diethylazoxybenzoate benzoate are explained in terms of short range order fluctuations of the nematic and of the smectic types, respectively.