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Tuning the Bridging Attraction between Large Hard Particles by the Softness of Small Microgels



Junhua Luo, Guangcui Yuan, Charles C. Han


In this study, the attraction between the large hard polystyrene (PS) spheres is studied by using three types of small microgels as bridging agents. One is purely soft poly(N-isopropylacrylamide) (PNIPAM) microgel, the other two have an indeformable PS hard core surrounded by a soft PNIPAM shell but are different in core-shell ratio. The affinity in bridging the large PS spheres is provided and thus affected by the PNIPAM constituent in the microgels. The bridging effects caused by the microgels can be indirectly incorporated into their influence on the effective attraction interaction between the large hard spheres since the size of the microgel is very small in comparison to the size of the PS hard sphere. At a given volume fraction of large PS spheres, the PS spheres behave essentially has hard spheres are connected to each other through the bridging of small particles until attraction strength reaches a maximum value, after which adding more small particles slowly decrease the effective attraction strength and eventually the large particles disperse individually when saturated adsorption is achieved. The aggregation and gelation behaviors triggered by these three types of small microgels are compared and discussed. A way to tune the strength and range of the short-range attractive potential via changing the softness of bridging microgels (which can be achieved by using core-shell microgel or by changing temperature) is proposed.
Soft Matter


bridging attraction, softness, hard sphere


Luo, J. , Yuan, G. and Han, C. (2016), Tuning the Bridging Attraction between Large Hard Particles by the Softness of Small Microgels, Soft Matter, [online], (Accessed April 13, 2024)
Created August 23, 2016, Updated October 12, 2021