Deuteron nuclear magnetic resonance and dielectric studies of molecular reorientation and charge transport in succinonitrile-glutaronitrile plastic crystals

Abstract

Plastic crystals are currently discussed as matrices for highly conducting materials. Among them, mixtures based on succinonitrile (SN) have received particular attention. Long ago, Austen Angell [J. Non-Cryst. Solids 131–133 (1991) 13] has shown that in mixtures with glutaronitrile (GN), the plastic phase of SN can deeply be supercooled. Here, a mixture of 60% SN – featuring deuterated methylene groups – and 40% GN is studied using 2 H nuclear magnetic resonance (NMR), thus allowing selective access to the reorientational dynamics of SN. These dynamics agree with that inferred for partially deuterated SN-GN from dielectric spectroscopy which also reveal that a significant H/D isotope effect is absent. Additionally, in the liquid and slightly below the transition to the plastically crystalline state, mixtures of 60% SN and 40% GN are studied using field-gradient NMR diffusometry as well as rotational viscometry. • Dynamics of plastic crystal from 60%-succinonitrile and 40%-glutaronitrile mixture studied over large temperature range. • Correlation times determined using deuteron NMR, dielectric spectroscopy, proton diffusometry, and viscometry. • Phase transition from liquid to plastic crystal clearly revealed by all these methods. • Time constants of protonated and deuterated mixtures agree, thus no significant H/D isotope effect. • Diffusion in the succinonitrile-glutaronitrile mixture much larger than in pure succinonitrile.