Wed, 20 Aug 2008 22:01:51 BST CiteULike: dchen ediger http://www.citeulike.org/user/dchen/tag/ediger CiteULike.org en-gb Copyright © 2004-2008 citeulike.org 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