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Issue 48, 2013
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Expansion of charged colloids after centrifugation: formation and crystallisation of long-range repulsive glasses

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Abstract

We studied long-range repulsive glasses formed in suspensions of sterically stabilised charged colloidal poly(methyl methacrylate) particles (σ = 2.23 μm) with low polydispersity (4%) in the low-polar solvent cyclohexyl bromide (εr = 7.92). Particle interactions were described by a long-range repulsive Yukawa potential. Glasses were obtained upon compression of the suspensions by centrifugation from a body-centred-cubic crystalline structure at low initial volume fraction (η ≈ 0.02) to a close-packed amorphous structure (η ≈ 0.64). Subsequent expansion of the sediment in gravity resulted in long-range repulsive glassy structures with volume fractions η = 0.16–0.64. The presence of small clusters (mostly dumbbells; clustered fraction fcl ≥ 0.12) formed by centrifugation prevented the glasses from crystallising for several weeks, while the sediment was still expanding. We used confocal microscopy to obtain three-dimensional datasets of the system and quantitatively analysed the structure of the glasses. The structure of the glasses was found to be remarkably similar to that of hard-sphere glasses, for which experimental data were obtained by centrifugal compression of silica spheres with a hard potential, despite the much longer-range interaction potential. After more than ten weeks the clustered fraction decreased due to spontaneous dissociation of the clusters, and finally bulk crystallisation of the glasses was observed into face-centred-cubic crystals with a volume fraction of around 0.22.

Graphical abstract: Expansion of charged colloids after centrifugation: formation and crystallisation of long-range repulsive glasses

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Publication details

The article was received on 25 Jun 2013, accepted on 03 Oct 2013 and first published on 16 Oct 2013


Article type: Paper
DOI: 10.1039/C3SM51752G
Citation: Soft Matter, 2013,9, 11618-11633
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    Expansion of charged colloids after centrifugation: formation and crystallisation of long-range repulsive glasses

    M. N. van der Linden, D. El Masri, M. Dijkstra and A. van Blaaderen, Soft Matter, 2013, 9, 11618
    DOI: 10.1039/C3SM51752G

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