Glass transition dynamics of hard sphere like microgel colloids with short-ranged attractions
Abstract
We have studied by dynamic light scattering the glass transition dynamics of a binary mixture of polystyrene microgel particles with a size ratio of Rsmall/Rlarge = 0.81 and a number ratio of N_{\mathrm {small}}/N_{\mathrm {large}}\approx
2.7 , where a short-ranged depletion attraction (\delta \approx 0.06 ) was induced by addition of linear polystyrene. This system shows a reentrant glass transition. We have determined the glass transition lines of this system in the experimental control parameter space given by the colloid volume fraction phiv and the polymer concentration cp by employing the power law of mode coupling theory (MCT) for the α-relaxation times. We find a reentry region which is much larger than predicted by theory and reported for another colloidal system with depletion attractions. Analysing the fluid dynamics along the transition lines with the β-scaling law of MCT we extract the cp dependence of the exponent parameter λ and the non-ergodicity parameter fqc. The results are in qualitative agreement with the prediction of MCT for increasing attraction strength. The observed 'jump' of fqc is indicative of a change of the close by glass phase from a packing-driven to a bonding-driven glass. The increase of λ to 0.91 and its subsequent decrease may indicate the neighbourhood of an A4 singularity.- Publication:
-
Journal of Physics Condensed Matter
- Pub Date:
- October 2004
- DOI:
- 10.1088/0953-8984/16/42/011
- Bibcode:
- 2004JPCM...16S4937E