Responsive Telechelic Block Copolymers for Enhancing the Elasticity of Nanoemulsions

The rheology of emulsions dictates their performance in many scientific and industrial applications. Here, we demonstrate that high-molecular-weight telechelic triblock copolymers composed of polystyrene end blocks with a poly(ethylene oxide) midblock effectively modify the rheology of a suspension of cyclohexane nanodroplets. Because of their telechelic structure, these polymers bridge between droplets to generate elastic networks with shear moduli on the order of 1000 Pa. The network elasticity increases with polymer concentration and molecular weight as the polymers more effectively form bridges. Furthermore, we tune the nanoscale interactions that control the polymer partitioning by decreasing the temperature below the cloud point of the system. At low temperatures, the polystyrene end blocks no longer preferentially partition into the cyclohexane droplets, and the emulsions begin to exhibit terminal viscous relaxations. These results identify key properties of telechelic block copolymers that can be exploited to significantly enhance nanoemulsion elasticity to improve the processability and transport of complex fluids in applications ranging from 3D printing to functional hydrogels.