Dynamics of confined depletion mixtures of polymers and bidispersed colloids

We investigate the effect of confinement on solidification of mixtures of non-adsorbing polymers and bidispersed colloidal particles (size ratio aS/a(L) approximate to 0.49) in a low-dielectric-constant solvent. Holding the total volume fraction of particles fixed, the dynamics of the large particles become increasingly slow as either the volume fraction of small particles is increased or the confinement thickness is decreased. Confinement to ten large particle diameters induces gelation in all samples investigated, with the most arrested dynamics appearing when both the depletant concentration and volume fraction of small particles are large. The changes in dynamics are consistent with an increase in the effective interparticle attraction that is driven by changes in the electrostatic repulsion between particles as the suspension is confined, and thus are an indirect secondary effect of confinement.