14N NMR Study of Order Fluctuations in the Isotropic Phase of Liquid Crystals

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