Measurements of the rotational and translational motion of several probe molecules in supercooled 1,3-bis-(1-naphthyl)-5-(2-naphthyl)benzene (ααβ-TNB) are reported. Rotational correlation times from 10-10 to 103 s were measured in the temperature range from 341 to 515 K (Tg = 343.5 K). Translational diffusion coefficients ranged from 10-6 to 10-15 cm2/s over a similar temperature range. The rotational correlation times of all probes have essentially the same temperature dependence as the viscosity of TNB. In contrast, the translational diffusion of the smallest probe, tetracene, is observed to have a significantly weaker temperature dependence. At Tg, the translational diffusion coefficient of tetracene is 300 times larger than expected based on its rotational correlation time. Similar enhancements of translational diffusion near Tg have recently been observed in other glass-forming liquids. These observations suggest that dynamics in TNB and other supercooled liquids are spatially heterogeneous. The probes used in this study were tetracene, rubrene, 9,10-diphenylanthracene, and 9,10-bis(phenylethynyl)anthracene.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry