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<p>We investigated structure–rheology relationships in oil-in-water Pickering emulsions stabilized by hydrophilic fumed silica (Aerosil) with a cationic co-emulsifier (didodecyldimethylammonium bromide, DDAB). A systematic composition matrix (Aerosil 2–6 wt%; DDAB 1–9&#xa0;mg per 3 mL oil) decouples particle from surfactant effects. Optical microscopy and SEM/EDS confirm silica-armored droplets; morphological stability requires sufficiently high particle loading and modest DDAB, whereas low Aerosil or very low DDAB leads to merged “lakes”. Steady flow shows strong shear-thinning and a pronounced first-interval effect: the initial high-rate sweep erases the rested structure, after which start-up curves become reproducible. Oscillatory tests establish weak-gel signatures (G’ &gt; G”, weak frequency dependence), with strain sweeps revealing a clear elastic plateau and a G” peak near yield. Increasing Aerosil elevates the modulus scale, broadens the linear-viscoelastic window, and delays softening; increasing DDAB at fixed particle fraction softens the emulsion and advances yielding. Multiple-interval thixotropic tests (miTT) quantify flow-history memory: the recovered small-amplitude moduli G’(γ̇<sub>prev</sub>) and G”(γ̇<sub>prev</sub>) decrease monotonically with prior shear rate, recover only partially between pulses, and—when normalized—show greater resilience at higher Aerosil but heightened sensitivity with surplus DDAB. These insights provide a practical formulation window for tunable, robust emulsions.</p>

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Rheology of silica nanoparticle-stabilized pickering emulsions

  • 期刊论文

  • 发表日期：

    2025年12月10日

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  • Ruihui Yun,
  • Yue Liang,
  • Jiaxin Wu,
  • Lesen Ma,
  • Florian J. Stadler

摘要

We investigated structure–rheology relationships in oil-in-water Pickering emulsions stabilized by hydrophilic fumed silica (Aerosil) with a cationic co-emulsifier (didodecyldimethylammonium bromide, DDAB). A systematic composition matrix (Aerosil 2–6 wt%; DDAB 1–9 mg per 3 mL oil) decouples particle from surfactant effects. Optical microscopy and SEM/EDS confirm silica-armored droplets; morphological stability requires sufficiently high particle loading and modest DDAB, whereas low Aerosil or very low DDAB leads to merged “lakes”. Steady flow shows strong shear-thinning and a pronounced first-interval effect: the initial high-rate sweep erases the rested structure, after which start-up curves become reproducible. Oscillatory tests establish weak-gel signatures (G’ > G”, weak frequency dependence), with strain sweeps revealing a clear elastic plateau and a G” peak near yield. Increasing Aerosil elevates the modulus scale, broadens the linear-viscoelastic window, and delays softening; increasing DDAB at fixed particle fraction softens the emulsion and advances yielding. Multiple-interval thixotropic tests (miTT) quantify flow-history memory: the recovered small-amplitude moduli G’(γ̇prev) and G”(γ̇prev) decrease monotonically with prior shear rate, recover only partially between pulses, and—when normalized—show greater resilience at higher Aerosil but heightened sensitivity with surplus DDAB. These insights provide a practical formulation window for tunable, robust emulsions.