Length scale of dynamic heterogeneity in supercooled glycerol near Tg

This letter presents the first direct measurement of the length scale of dynamic heterogeneity in a low molecular weight glass former without the perturbing effect of probe molecules or confinement. Using a multidimensional C-13 solid-state exchange NMR experiment, 1 nm heterogeneities were found in glycerol for temperatures ranging from 199 K to 207 K (T-g = 189 K). This small size and weak temperature dependence allow some distinctions to be made among different models of the glass transition. It is shown that the dynamics are not influenced by a low concentration (0.1 wt. %) relaxation agent Cu(NO3)(2). (C) 2001 American Institute of Physics.