Glass transition dynamics of hard sphere like microgel colloids with shortranged 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 R_{small}/R_{large} = 0.81 and a number ratio of N_{\mathrm {small}}/N_{\mathrm {large}}\approx
2.7 , where a shortranged 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 c_{p} by employing the power law of mode coupling theory (MCT) for the αrelaxation 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 βscaling law of MCT we extract the c_{p} dependence of the exponent parameter λ and the nonergodicity parameter f_{q}^{c}. The results are in qualitative agreement with the prediction of MCT for increasing attraction strength. The observed 'jump' of f_{q}^{c} is indicative of a change of the close by glass phase from a packingdriven to a bondingdriven glass. The increase of λ to 0.91 and its subsequent decrease may indicate the neighbourhood of an A_{4} singularity.
 Publication:

Journal of Physics Condensed Matter
 Pub Date:
 October 2004
 DOI:
 10.1088/09538984/16/42/011
 Bibcode:
 2004JPCM...16S4937E