Starch granules are instructive scaffolds for synergistic reinforcement and dissipation in hydrogel composites

A fundamental challenge in soft material design is the competition between rigidity and dynamicity, as stiffening mechanisms typically suppress energy dissipation. Here, we demonstrate that starch granules serve as instructive scaffolds that overcome this constraint, enabling the synergistic amplification of both elastic reinforcement and dynamic dissipation in hydrogels. We show that engineering the charge and structure of the filler-matrix interface enhances this synergistic response, which we propose arises from a dual-action physical mechanism: filler-induced polymer bundling of the polymer matrix provides structural reinforcement, while transient filler-matrix hydrogen bonding facilitates dissipation. Moreover, we reveal that binary blends of disparate filler species unexpectedly suppress these emergent properties, which we argue arises from enhanced entropic mixing. Our results provide a physical framework to overcome current design limitations in soft composites and sculpt their viscoelastic response from synergistic enhancement to strategic suppression for applications ranging from high-performance soft robotics to biomimetic tissue engineering.