Effect of Short-range Attraction on Aggregation, Gelation and Glass Transition of Colloidal Systems

Charles C. Han (Institute of Chemistry, Chinese Academy of Science)

Aggregation and gelation behaviour of mixed suspensions of polystyrene microspheres and poly(N-isopropylacrylamide) microgels have been studied. In dilute microsphere suspensions, with increasing concentration of microgel (fMG), microspheres first aggregated with each other through the bridging of the microgels, then dispersed individually when saturated adsorption was achieved, and finally depletion clusters formed at even higher concentrations of microgel. In concentrated microsphere suspensions, with increasing fMG, the mixed suspensions showed a liquid-- "bridging gel"--liquid--"depletion gel" transitions. The gelation of the microsphere can be explained by the percolation of the clusters and the elasticity of bridging gel arising from the mutual attractions between the microspheres.

This type of system can be viewed as a molecular model system with a long range repulsive interaction potential and a short range attractive potential.

Meanwhile, the short range attractive potential maybe tunable. The application through the tuning this attraction through temperature, and CO2, will be illustrated.

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