Light-scattering experiments on phase-separation dynamics in binary fluid mixtures

Andrew Cumming, Pierre Wiltzius, Frank S. Bates, Jeffrey H. Rosedale

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154 Scopus citations

Abstract

We present the method and results of two phase-separation experiments performed on the binary-polymer blend polyisoprene-poly(ethylene-propylene). Elastic light scattering and optical microscopy were used to follow the phase separation after quenches into the coexistence region of the phase diagram. For off-critical quenches, we observed the formation of spherical droplets which obtained nearly monodisperse radius distributions over some fraction of the free-growth period. These results are interpreted within the framework of a heterogeneous nucleation process and diffusion-driven dynamics. For critical quenches, we observed the well-known bicontinuous infinite-cluster morphology normally associated with spinodal decomposition, but with two distinct growth modes. In the bulk, we observed L(t)t1/3, which is consistent with diffusion-driven dynamics, whereas near the sample walls we obtained a fast growth with L(t)t3/2, inconsistent with either diffusion- or interface-driven dynamics. We attribute this large exponent to wetting effects, but still lack any theoretical understanding of the phonomenon.

Original languageEnglish (US)
Pages (from-to)885-897
Number of pages13
JournalPhysical Review A
Volume45
Issue number2
DOIs
StatePublished - Jan 1 1992

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