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Soft Matter and Biological Physics


Eur. Phys. J. E 6, 69-77 (2001)

Asymmetric landscapes of early spinodal decomposition

Y. Mao, T.C.B. McLeish, P.I.C. Teixeira and D.J. Read

IRC in Polymer Science and Technology, Department of Physics, University of Leeds, Leeds, LS2 9JT, UK

T.C.B.McLeish@leeds.ac.uk

(Received 28 August 2000 and Received in final form 18 July 2001)

Abstract
We address the effect of an asymmetric concentration-dependent mobility on the early stages of spinodal decomposition in polymer blends and solutions, and characterise it quantitatively. This is particularly important when one of the components has a slower dynamics than the other, e.g., because it is closer to its glass transition, or is weakly cross-linked. Composition mode coupling is proposed as the underlying physical mechanism, and then investigated by means of numerical simulations of the Cahn-Hilliard equation in one (1d) and two (2d) dimensions. In general, this coupling broadens the peak in the structure factor: in 1d an asymmetric concentration profile is obtained, with sharpened interfaces, whereas in 2d the formation is favoured of sharp peaks of the phase rich in the more mobile component. It is shown how the changing morphology of this phase-separating system can be described with the aid of Minkowski functionals.

PACS
64.75.+g - Solubility, segregation, and mixing; phase separation.
61.41.+e - Polymers, elastomers, and plastics.
47.20.Hw - Morphological instability; phase changes.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001