Tuning the Mechanics of Soft Particle-Polymer Composites Through Granule Chemistry

Engineering soft composites with programmable and tunable mechanics represents an exciting direction in materials research. Biological tissues exemplify particle-polymer systems that integrate strength with dynamic reconfigurability, offering design principles for synthetic analogs. Here, we engineer tissue-like composites by embedding chemically modified starch granules into a gelatin network to probe how particle chemistry and concentration shape emergent viscoelastic behavior. By varying granule surface chemistry (neutral, waxy, cationic, anionic) and concentration, we reveal how particle-matrix interactions govern bulk mechanical response. Increasing granule concentration enhances stiffness across all composite types, while unexpectedly amplifying energy dissipation, which is an effect consistent with transient hydrogen bonding at the interface. Moreover, combining multiple starch types produces emergent behaviors not captured by simple additive models. These results establish more precise control over viscoelasticity in particle-polymer composites, providing new design strategies for soft materials with tunable mechanical properties for industrial and biomedical applications.