Exploring the Dynamics of Glasses Using Beta Detected NMR

We report 8Li spin lattice relaxation in two forms of the molecular glass TPD, one a normal glass and one prepared in an ultrastable configuration. The relaxation is remarkably fast, similar to 8Li relaxation in other organic materials and shows a stretched exponential behavior typical of glasses with a small stretching exponent β = 0.3. At low temperature, there is little or no difference between the two glasses, while above 250 K, the relaxation in the denser ultrastable form is faster. In addition, in this temperature range, the data shows a significant thermal hysteresis.