Length and Time Scales of Structural Heterogeneities in Deeply Supercooled Propylene Carbonate

Abstract

Deactivation of excited phenanthrene by molecular oxygen is utilized to probe the structural heterogeneity of supercooled propylene carbonate. The diffusion rate of oxygen molecules in different regions varies over two orders of magnitude. The size of the regions of different oxygen mobility was determined to be 1.5 nm. Values from 0.2 to 30 s have been obtained for the lifetime of these regions over a temperature range from T(g)-1 to T(g)+4 K (T(g)=158 K). The heterogeneity lifetime is in close agreement with the α-relaxation time determined by dielectric spectroscopy. The obtained results argue in favor of the statement that the heterogeneous cooperative dynamics of host molecules (so-called dynamical heterogeneity) is of structural origin.

Individual gold nanorods report on dynamical heterogeneity in supercooled glycerol

“…These distances are more than 30 times larger than earlier estimates of the length scales for dynamical heterogeneity in supercooled liquids, some nanometers. 9,16,50 Our results thus show for the rst time that dynamical heterogeneity not only persists at the scale of a large dye molecule (one nanometer), but is still not averaged out over distances of several tens of nm. Presumably, the length scales of heterogeneity may extend even further, as there was no fundamental reason for the choice of this particular size of nanorods.…”

“…[1][2][3][4] Heterogeneity is believed to be a key element for a deeper mechanistic understanding of the glass transition of supercooled liquids. Although rst observed in various bulk experiments, [5][6][7][8][9][10][11][12] heterogeneity in supercooled liquids remains difficult to observe and characterize at the ensemble level. In particular, the spatial and temporal scales associated to heterogeneity in supercooled liquids are still under debate.…”

Phenol, the simplest aromatic monohydroxy alcohol, displays a faint Debye-like process when mixed with a nonassociating liquid

“…56 Furthermore, PC was studied by numerous other techniques as well. [57][58][59][60] PhOH, a very weak acid, and PC, a very weak base, 61 are not expected to react with each other. 62 A potential drawback of choosing PC as a mixing partner may be its large dipole moment of about 5 D, [63][64][65] while for PhOH some solution studies indicate an ''infinite dilution'' value of ''only'' 1.5 D. The sizeable dependence of PhOH's dipole moment on concentration and solvent could be taken as a hint for self-association effects.…”