  Soft materials possessing tunable rheological properties are desirable in
applications ranging from 3D printing to biological scaffolds. Here, we use a
telechelic, triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene
(SEOS) to form elastic networks of polymer-linked droplets in
cyclohexane-in-water emulsions. The SEOS endblocks partition into the dispersed
cyclohexane droplets while the midblocks remain in the aqueous continuous
phase, resulting in each chain taking on either a looping or bridging
conformation. We examine the yield transition of these polymer-linked emulsions
through large amplitude oscillatory shear (LAOS) and probe the emulsion
structure through confocal microscopy, concluding that polymers that more
readily form bridges generate a strongly percolated network, whereas those that
are less prone to form bridges tend to produce networks composed of
weakly-linked clusters of droplets. When yielded, the emulsions consisting of
linked clusters break apart into individual clusters that can rearrange upon
the application of further shear. By contrast, when the systems containing a
more homogeneous bridging density are yielded, the system remains percolated
but with a reduced elasticity and bridging density. The demonstrated ability of
telechelic triblock copolymers to tune not only the linear viscoelasticity of
complex fluids but also their nonlinear yield transition enables the use of
these polymers as versatile and robust rheological modifiers. We expect our
findings to therefore aid the design of the next generation of complex fluids
and soft materials.
