Soft glassy materials with tunable extensibility

Extensibility is beyond the paradigm of classical soft glassy materials, and more broadly, yield-stress fluids. Recently, model yield-stress fluids with significant extensibility have been designed by adding polymeric phases to classically viscoplastic dispersions [Nelson et al., J. Rheol. 62, 357-369 (2018); Nelson et al., Curr. Opin. Solid State Mater. Sci. 23, 100758 (2019); Dekker et al., J. Non-Newtonian Fluid Mech. 310, 104938 (2022)]. However, fundamental questions remain about the design of and coupling between the shear and extensional rheology of such systems. In this work, we propose a model material, a mixture of soft glassy microgels and solutions of high molecular weight linear polymers. We establish systematic criteria for the design and thorough rheological characterization of such systems, both in shear and in extension. Using our material, we show that it is possible to dramatically change the behavior in extension with minimal change in the shear yield stress and elastic modulus, thus enabling controlled studies and engineering applications, such as direct write printing additive manufacturing, that exploit orthogonal modulation of shear and extensional material properties.