Enhanced shear thickening of polystyrene-poly(acrylamide) and polystyrene-poly(HEMA) particles

Shear thickening (ST) refers to the drastic increment of viscosity that occurs when a high shear force is applied to certain concentrated colloidal suspensions. The hydrocluster mechanism for ST indicates that inter-particle interaction is important for ST behavior. Therefore, we prepared polystyrene particles with polyacrylamide particles (PS-PAAm particles) to control inter-particle interactions. Colloidal suspensions of polystyrene-poly(2-hydroxyethyl methacrylate) (PS-PHEMA) particles in ethylene glycol were prepared and shown to exhibit strong ST behavior. The effect of PS-PAAm particles on the ST behavior of a PS-PHEMA particle colloidal suspension was investigated; ST behavior of shear thickening fluids (STFs) was controlled by doping different amounts of PS-PAAm particles. We suggested inter-particle interaction was enhanced by abundant hydrogen-bonding donor groups in PS-PAAm particles. Based on this study, the applicability of STF can be increased through the STF fabrication exhibiting desired ST behavior. Also, this study will help to understand fundamental ST mechanism.

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