Sat, 26 Jul 2008 08:30:30 BST CiteULike: dchen Ediger http://www.citeulike.org/user/dchen/author/Ediger CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/1320018 <i>Annu Rev Phys Chem, Vol. 51 (2000), pp. 99-128.</i><br /><br />Although it has long been recognized that dynamics in supercooled liquids might be spatially heterogeneous, only in the past few years has clear evidence emerged to support this view. As a liquid is cooled far below its melting point, dynamics in some regions of the sample can be orders of magnitude faster than dynamics in other regions only a few nanometers away. In this review, the experimental work that characterizes this heterogeneity is described. In particular, the following questions are addressed: How large are the heterogeneities? How long do they last? How much do dynamics vary between the fastest and slowest regions? Why do these heterogeneities arise? The answers to these questions influence practical applications of glass-forming materials, including polymers, metallic glasses, and pharmaceuticals. Spatially heterogeneous dynamics in supercooled liquids. MD Ediger doi:10.1146/annurev.physchem.51.1.99 Annu Rev Phys Chem, Vol. 51 (2000), pp. 99-128. 2007-05-22T20:16:34-00:00 2000 Annu Rev Phys Chem 0066-426X 51 99 128 classic dynamics heterogeneity review supercooled http://www.citeulike.org/user/dchen/article/2453930 <i>J. Phys. Chem. B, Vol. 110, No. 1. (12 January 2006), pp. 507-511.</i><br /><br />Abstract: Self-diffusion coefficients for the low molecular weight glass former o-terphenyl have been measured near Tg by isothermally desorbing thin film bilayers of deuterio and protio o-terphenyl in a vacuum chamber. We observe translational diffusion that is about 100 times faster at Tg + 3 K than the Stokes-Einstein prediction. Predictions from random first order transition theory and a dynamic facilitation approach are in reasonable agreement with our results; in these approaches, enhanced translational diffusion is associated with spatially heterogeneous dynamics. Self-diffusion controls crystallization in o-terphenyl for most of the supercooled liquid regime, but at temperatures below Tg + 10 K, the reported crystallization rate increases suddenly while the self-diffusion coefficient does not. This work and previous work on trisnaphthylbenzene both find a self-diffusion-controlled crystal growth regime and an enhancement in self-diffusion near Tg, suggesting that these phenomena are general characteristics of fragile low molecular weight glass formers. We discuss the width of the relaxation time distributions of o-terphenyl and trisnaphthylbenzene as they relate to the observation of enhanced translational diffusion. Self-Diffusion of Supercooled <i>o</i>-Terphenyl near the Glass Transition Temperature MK Mapes SF Swallen MD Ediger doi:10.1021/jp0555955 J. Phys. Chem. B, Vol. 110, No. 1. (12 January 2006), pp. 507-511. 2008-03-01T22:46:20-00:00 2006 J. Phys. Chem. B 110 1 507 511 diffusion ediger supercooled http://www.citeulike.org/user/dchen/article/2453898 <i>J. Phys. Chem. B, Vol. 103, No. 20. (20 May 1999), pp. 4177-4184.</i><br /><br />Abstract: In supercooled o-terphenyl (OTP), subsets of probe molecules in more mobile environments can be selectively photobleached. The time required for the remaining slower-than-average probes to be redistributed into an equilibrium set of environments has been measured. At Tg + 4 K (Tg = 243 K), this exchange time is 6 times greater than the average probe rotational correlation time. These results are compared to previous optical measurements at Tg + 1 K (Cicerone, M. T.; Ediger, M. D. J. Chem. Phys. 1995, 103, 5684), which showed that the exchange time is more than 100 times the rotational correlation time, and to multidimensional NMR experiments on deuterated OTP at Tg + 10 K (Bohmer, R.; et al. Europhys. Lett. 1996, 36, 55), which showed that the exchange time is nearly equal to the correlation time. These results in aggregate suggest that a new relaxation process in equilibrium supercooled liquids emerges only at temperatures very near Tg. A model for selective photobleaching is proposed. The model reproduces the experimental data reasonably well and indicates that the photobleaching efficiency of a given probe is only weakly correlated with its rotational correlation time. How Long Do Regions of Different Dynamics Persist in Supercooled o-Terphenyl? CY Wang MD Ediger doi:10.1021/jp984149x J. Phys. Chem. B, Vol. 103, No. 20. (20 May 1999), pp. 4177-4184. 2008-03-01T22:25:47-00:00 1999 J. Phys. Chem. B 103 20 4177 4184 ediger heterogeneity systemtools http://www.citeulike.org/user/dchen/article/578879 <i>J. Phys. Chem., Vol. 100, No. 31. (1 August 1996), pp. 13200-13212.</i> Supercooled Liquids and Glasses MD Ediger CA Angell SR Nagel doi:10.1021/jp953538d J. Phys. Chem., Vol. 100, No. 31. (1 August 1996), pp. 13200-13212. 2006-04-07T00:58:56-00:00 1996 J. Phys. Chem. 100 31 13200 13212 angell ediger glass nagel review http://www.citeulike.org/user/dchen/article/2453304 <i></i> SPATIALLY HETEROGENEOUS DYNAMICS IN SUPERCOOLED LIQUIDS - Annual Review of Physical Chemistry, 51(1):99 MD Ediger 2008-03-01T18:30:34-00:00 heterogeneity review