Xylan Conformation and Dispersion Govern Shear-Thickening Fluid Rheology

The microscopic state of polysaccharides in solution─whether dissolved, dispersed, or aggregated─directly dictates the macroscopic properties of the bulk fluid. However, the influence of their true state in solution and nanostructures on rheology is often overlooked. Here, using non-Newtonian shear-thickening fluids (STFs, SiO₂/poly(ethylene oxide)) as a model, we systematically investigate how xylan conformation and dispersion affect STFs' rheology. Xylan nanocrystals (XNCs) and water-soluble xylan ethers with distinct dispersibility (well-dispersed vs aggregate) and solubility (room-temperature-soluble vs high-temperature-soluble) are synthesized. Among those, well-dispersed XNCs and room-temperature-soluble xylan ethers exhibit a pronounced thickening effect in STFs, reducing the critical shear rate by 2 orders of magnitude and increasing peak viscosity by 880%. This work demonstrates that polysaccharide conformation and dispersion behavior exert pronounced effects on STF rheology, providing a new avenue for leveraging polysaccharides as fluid additives.