Temperature dependence of a glass transition cooperativity

Abstract

The size of glass transition cooperativity for 11 polymers and glycerol is determined from heat capacity spectroscopy (HCS) and differential scanning calorimetry (DSC) by using a calorimetric fluctuation formula. The data cover in total the 0.25 I x I 0.95 part of the reduced temperature interval between the Vogel temperature and a cooperativity onset temperature. A steep cooperativity increase at lower temperature is observed. The data are consistent with the hypothesis that the temperature dependence can be described by the enlargement of a minimal cooperativity at the onset. Acta Polymer., 48,369-378 0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim 1997 0323-7648/97/0102-0369$10.oO+.25/0 369 S.

Characteristic Length of Dynamic Glass Transition near Tg for a Wide Assortment of Glass-Forming Substances

“…It should be mentioned again that the DSC and TMDSC experiments are independent measurements. As expected, 33 T ω > T g , δT(T ω ) > δT(T g ), and ξ R (T ω )<ξ R (T g ) in the frame of experimental uncertainty. The frequency associated with T g from DSC can approximately be calculated from 32,45 A theory for the factor 5.5 in eq 12 will be published elsewhere.…”

Length Scale of Dynamic Heterogeneities at the Glass Transition Determined by Multidimensional Nuclear Magnetic Resonance

“…(1) and (2) the present approach can be directly translated to computer simulations. The fact that our results are compatible with estimates from other experiments in glass-forming systems [14] and the results by Donth et al [13,20] show that the dynamic heterogeneities seem to be closely related to CRRs. However, a precise relation between CRRs and dynamic heterogeneities has still to be formulated.…”

A relationship between diffusivity and cooperativity of supercooled liquids in the proximity of glass transition

“…( 4) increases with the decrease of temperature. The growth behavior of the cooperativity described by this equation is consistent with the results by other studies [30,31]. However, concerning the number of correlated units involved in glassforming liquids, i.e., the number of molecules or structural units that are involved during supercooling depends on theoretical models [31,35].…”