Compositional relaxation on the approach to the glass transition in a model trehalose solution

Hannam, S, Daivis, P and Bryant, G 2019, 'Compositional relaxation on the approach to the glass transition in a model trehalose solution', Physical Review E, vol. 99, no. 3, pp. 1-12.

Document type: Journal Article
Collection: Journal Articles

Title Compositional relaxation on the approach to the glass transition in a model trehalose solution
Author(s) Hannam, S
Daivis, P
Bryant, G
Year 2019
Journal name Physical Review E
Volume number 99
Issue number 3
Start page 1
End page 12
Total pages 12
Publisher American Physical Society
Abstract Molecular dynamics simulation was used to study the temperature dependence of the mutual diffusion coefficient D-m and the intermediate scattering function of equilibrium and metastable aqueous solutions of the cryoprotectant molecule trehalose at very low (2.2 and 9 wt.%) and very high (80 and 95 wt.%) concentrations. The simulations were conducted over a range of temperatures approaching the glass transition temperature T-g for each concentration Similar to a recent observation made on a glass-forming model polydisperse colloidal suspension [Hannam et al., Phys. Rev. E 96, 022609 (2017)], we confirmed by a set of independent computations that D-m is responsible for the long-time decay of the intermediate scattering function. We observed that D-m decreased on the approach to the glass transition temperature, resulting in an extremely slow long-time decay in the intermediate scattering function that culminated in the arrest of compositional fluctuations and a plateau in the intermediate scattering function at T-g. In both cases, crystallization requires a change in the composition of the solution, which is a process controlled by D-m. This transport coefficient can either increase or decrease as solidification is approached, because it depends on a product of thermodynamic and mobility factors. Our observations show that in both cases, for the glass-forming liquids, it is observed to decrease, while for a previously studied monodisperse colloidal suspension which crystallizes easily, it increases. The similarity in the behavior of these two very different glass-forming systems (the polydisperse colloidal suspension and the sugar solution) shows the importance of the mutual diffusion coefficient to our understanding of vitrification and suggests a possible distinction between between glass-forming and crystallizing solutions.
Subject Soft Condensed Matter
Keyword(s) trehalose
glass transition
mutual diffusion
molecular dynamics
DOI - identifier 10.1103/PhysRevE.99.032602
Copyright notice © 2019 American Physical Society
ISSN 2470-0045
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