Proton NMR and Piezoelectricity in Tetramethylammonium Chloride

Abstract

A proton magnetic resonance investigation has been made on tetramethylammonium chloride between 77 and 567°K. The existence of a new phase is reported, making a total of five known phases, and these are numbered from high temperature down. It is shown that methyl‐group reorientation occurs without noticeable tunneling, followed at slightly higher temperatures by pseudoisotropic reorientations of the cations. The correlation times for these motions have been measured in four phases over this temperature range, and expressed by Arrhenius‐type relations. Ionic diffusion only occurs in phase I, and then infrequently. This study shows that phase II is piezoelectric, and that in the absence of any solvent it may remain metastable at room temperature. In the presence of small quantities of solvent a transition occurs to the common stable phase III at ∼400°K.