In search of colloidal hard spheres

C. Patrick Royall, Wilson C. K. Poon, Eric R. Weeks

Research output: Contribution to journalLiterature reviewpeer-review


We recently reviewed the experimental determination of the volume fraction, phi, of hard-sphere colloids, and concluded that the absolute value of phi was unlikely to be known to better than +/- 3-6%. Here, in a second part to that review, we survey effects due to softness in the interparticle potential, which necessitates the use of an effective volume fraction. We review current experimental systems, and conclude that the one that most closely approximates hard spheres remains polymethylmethacrylate spheres sterically stabilised by polyhydroxystearic acid 'hairs'. For these particles their effective hard sphere diameter is around 1-10% larger than the core diameter, depending on the particle size. We argue that for larger colloids suitable for confocal microscopy, the effect of electrostatic charge cannot be neglected, so that mapping to hard spheres must be treated with caution.

Original languageEnglish
Pages (from-to)17-27
Number of pages11
JournalSoft Matter
Issue number1
Early online date9 Oct 2013
Publication statusPublished - 2013

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