Effect of particle/polymer number ratio on the structure and dynamics of complex between large polymer and nanoparticle
2016
Yan, Feng | Ye, Lei | Qiu, Dong
The effect of particle/polymer number ratio on the structure and dynamics of particle-polymer complexes at a fixed polymer concentration has been investigated. Mixtures of poly(ethylene oxide) (PEO, Mv=1,000,000 gmol⁻¹, Rh ∼39nm) aqueous solution and colloidal silica dispersion (Rh ∼10nm) were used as models. By adding silica particles, both zero-shear viscosity and Rh of the silica-PEO complexes increased with particle/polymer number ratio. The maximum zero-shear viscosity was reached when the PEO coils were saturated by silica particles. After that, a decrease in zero-shear viscosity and Rh was observed. SAXS results showed that PEO had a great effect on the inter-particle correlations before the PEO chains were saturated with silica particles, however, this effect diminished when even more silica particles were introduced. The reversible bridging interaction and inter-particle electrostatic repulsion were identified as the major factors accounting for the change in zero-shear viscosity and hydrodynamic size, and a tentative mechanism was proposed based on the spatial distribution of silica particles in the mixtures.
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