8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.140Wed 711:10-14:00Faceted polyhedral colloidal ‘rocks’: low-dimensionalnetworksPaddy Royall, 1 Roland Roth, 2 and Rebecca Rice 11 University of Bristol, School of Chemistry, BS8 1TS, Bristol, United Kingdom2 Universität Erlangen-Nürnberg, Erlangen, GermanyDespite the current ’explosion’ of interest in anisotropic colloids, which are predicted to exhibitnew behaviour, not least through the structures such particles form, few systems have been producedin sufficient quantity to explore the effects of particle geometry. Here we introduce a modelsystem of faceted polyhedral colloidal ‘rocks’, which we study in bulk with confocal microscopyat the single particle level. Due to their shape, the bonds between colloidal ‘rocks’ introduced vianon-absorbing polymers are rigid against rotation in profound contrast to those between sphericalparticles. In order to capture their essence theoretically we develop a simple geometric modelof colloidal ‘rocks’ as a dodecahedral cluster of 20 spheres. Both experiments and Monte-Carlosimulations show that the novel bonding leads to very low-dimensional structures with a fractaldimension 1.5. In the case of gelation, we are able to capture diffusion-limited cluster aggregationbehaviour at moderate interaction strengths. This is in stark contrast to gels of attractivespheres, whose rigidity results from locally dense regions formed during arrested spinodal phaseseparation. At higher density, size and shape polydispersity in the colloidal ‘rocks’ leads to a quasione-component glass. Our findings open up new opportunities to tackle problems such as the roleof friction in colloidal and nanoparticle assembly, processing and jamming. We hope to stimulatefurther experiments, for example direct visualisation may reveal the effect of shear on anisotropicparticles, and other hitherto unexplored phenomena including the role of surface roughness forcolloids and nanoparticles.140