Proton spin–lattice relaxation in selectively deuterated p,p′-azoxyanisoles

Abstract

Proton spin–lattice relaxation rates 1/T₁ are observed for the nematic liquid crystal PAA and its selectively deuterated species PAA‐d₆ and PAA‐d₈ in the nematic and in the isotropic states at frequencies of 15 and 55 MHz. The main relaxation process for the ring protons of PAA‐d₆ is the thermal fluctuation of the order director, and the translational diffusion of the molecules also contributes to the relaxation rate of these protons. On the other hand, the methyl protons of PAA‐d₈ relax predominantly through the translational diffusion in the nematic and isotropic phases. The thermal fluctuation of the order director makes a small contribution to the spin relaxation of the methyl protons in the nematic state and in the isotropic state near the transition point.