• Phosphate chain length controls the stability of charged Laponite® nanoplatelet dispersions. • Short-chain phosphates enhance charge screening and promote compact platelet clustering. • Long-chain polyphosphates preferentially associate with positively charged platelet rims. • Rim-associated polyphosphates suppress dense aggregation while allowing open network formation. • Combined experiments and simulations reveal molecular design rules for stable nanoplatelet–polyphosphate formulations. The increasing demand for accessible phosphorus sources, essential for plant growth, is placing growing pressure on both industry and academia. Here, we investigate nanoplatelets as carriers for phosphate species, using Laponite® as a model system for sprayable phosphorus formulations. We examine how phosphate species chain length (1, 2, 3, 14, 60, and 130 monomers) at 1 wt% governs dispersion stability and interparticle assembly. A combination of cryogenic transmission electron microscopy (cryo-TEM), 31 P magic-angle spinning NMR, small-angle X-ray scattering (SAXS), light scattering, and coarse-grained molecular dynamics simulations reveals that electrostatic interactions between anionic phosphate species and the anisotropically charged platelet surfaces dictate structural evolution. Short-chain phosphate species (1-3 monomers) enhance charge screening, increasing compressibility and promoting clustering. In contrast, longer-chain polyphosphates ( ≥ 14 monomers) preferentially associate with the positively charged platelet rims, suppressing dense rim-face aggregation while still permitting open, weakly connected structures, thereby stabilizing the dispersions against compact flocculation. Cryo-TEM directly visualizes this transition in assembly behavior as chain length increases. These results establish a molecular-level understanding of how multivalent polyelectrolytes regulate anisotropic colloidal interactions and demonstrate that chain length provides a direct handle for tuning nanoplatelet dispersion stability. The findings offer general design principles for stable nanoplatelet-polyphosphate formulations with controllable aggregation and phosphate release characteristics.
Utzeri et al. (Fri,) studied this question.