Controlling emulsion elasticity by bridging telechelic triblock copolymers

Suspension elasticity controls the performance of complex fluids in applications ranging from 3D printing to therapeutics to consumer products. Here, we add telechelic triblock copolymers consisting of polystyrene (PS) endblocks and a poly(ethylene oxide) (PEO) midblock to a suspension of cyclohexane droplets stabilized by non-ionic surfactants. The PS-PEO-PS chains bridge between droplets to form an elastic network. We measure the elasticity of these suspensions using standard linear oscillatory rheology and find that the telechelic polymers drastically increase the suspension elasticity relative to neutral non-associating polymers. We tune the emulsion elasticity by increasing the M_w of the endblocks to partition them more strongly within the droplets, the M_w of the midblock to increase the bridging-to-looping ratio, and by increasing the polymer concentration. Furthermore, for high M_w endblocks, we observe strong thermal dependence of the emulsion elasticity across the upper-critical solution temperature between polystyrene and cyclohexane. Whereas the emulsions undergo terminal relaxations at low temperatures, they exhibit sustained plateau moduli at elevated temperatures, indicating a fully elastic response.