<p>In conventional Pickering emulsions, particle adsorption at the oil–water interface is primarily governed by physicochemical attributes such as particle size and wettability. However, when both the oil–water interface and particles carry surface charges, electrostatic interactions may become the dominant factor governing particle adsorption. To investigate this effect, silica particles with surface potentials ranging from − 51 to + 54 mV were dispersed in an aqueous phase containing a nonionic surfactant, with amino-functionalized polydimethylsiloxane serving as the oil phase. Interfacial oscillatory rheological measurements were conducted to characterize interfacial viscoelasticity. Two charge-regulation strategies modulated particle (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation>) and oil-water interface potentials (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{o}}\)</EquationSource> </InlineEquation>): one reduced |<InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation>| via chemical modification, the other lowered pH to decrease |<InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation>| and increase |<InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{o}}\)</EquationSource> </InlineEquation>|. Emulsification experiments further evaluated long-term stability. The results demonstrate that in polar oil–water Pickering emulsions, coordinated modulation of <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{o}}\)</EquationSource> </InlineEquation> governs particle interfacial adsorption and the development of interfacial viscoelasticity, thereby determining emulsion stability. Negatively charged particles exhibited stronger adsorption and higher elasticity at positively charged interfaces, whereas like-charged combinations resulted in limited adsorption. Among negatively charged particles, those with <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation> ≈ −22 mV produced denser interfacial packing and higher elasticity than strongly anionic particles (<InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation> ≈ −51 mV). Charge-regulation experiments, including ionic-strength–dependent <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\:\zeta\:\)</EquationSource> </InlineEquation> and interfacial-rheology tests, confirm that enhanced viscoelasticity arises from optimizing the balance between interface–particle electrostatic attraction (proportional to <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{o}}\)</EquationSource> </InlineEquation>·<InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\:{\zeta\:}_{\text{p}}\)</EquationSource> </InlineEquation>) and particle–particle electrostatic repulsion (proportional to <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\:{\zeta\:}_{p}^{2}\)</EquationSource> </InlineEquation>). Emulsion stability was quantified by long-term storage and centrifugal stability tests, demonstrating an extension of stability from ≈ 55 days to > 180 days under optimized charge conditions.</p> Graphical Abstract <p></p>

Electrostatic modulation of particle adsorption and interfacial elasticity enables enhanced stability in polar-oil-based Pickering emulsions

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发表日期：

2026年5月16日

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Yuanchen Hua,
Yunfei Wang,
Junyan Shen,
Aoyun Fan,
Ye Liu,
Lei Yang

摘要

In conventional Pickering emulsions, particle adsorption at the oil–water interface is primarily governed by physicochemical attributes such as particle size and wettability. However, when both the oil–water interface and particles carry surface charges, electrostatic interactions may become the dominant factor governing particle adsorption. To investigate this effect, silica particles with surface potentials ranging from − 51 to + 54 mV were dispersed in an aqueous phase containing a nonionic surfactant, with amino-functionalized polydimethylsiloxane serving as the oil phase. Interfacial oscillatory rheological measurements were conducted to characterize interfacial viscoelasticity. Two charge-regulation strategies modulated particle ( \(\:{\zeta\:}_{\text{p}}\) ) and oil-water interface potentials ( \(\:{\zeta\:}_{\text{o}}\) ): one reduced | \(\:{\zeta\:}_{\text{p}}\) | via chemical modification, the other lowered pH to decrease | \(\:{\zeta\:}_{\text{p}}\) | and increase | \(\:{\zeta\:}_{\text{o}}\) |. Emulsification experiments further evaluated long-term stability. The results demonstrate that in polar oil–water Pickering emulsions, coordinated modulation of \(\:{\zeta\:}_{\text{p}}\) and \(\:{\zeta\:}_{\text{o}}\) governs particle interfacial adsorption and the development of interfacial viscoelasticity, thereby determining emulsion stability. Negatively charged particles exhibited stronger adsorption and higher elasticity at positively charged interfaces, whereas like-charged combinations resulted in limited adsorption. Among negatively charged particles, those with \(\:{\zeta\:}_{\text{p}}\) ≈ −22 mV produced denser interfacial packing and higher elasticity than strongly anionic particles ( \(\:{\zeta\:}_{\text{p}}\) ≈ −51 mV). Charge-regulation experiments, including ionic-strength–dependent \(\:\zeta\:\) and interfacial-rheology tests, confirm that enhanced viscoelasticity arises from optimizing the balance between interface–particle electrostatic attraction (proportional to \(\:{\zeta\:}_{\text{o}}\) · \(\:{\zeta\:}_{\text{p}}\) ) and particle–particle electrostatic repulsion (proportional to \(\:{\zeta\:}_{p}^{2}\) ). Emulsion stability was quantified by long-term storage and centrifugal stability tests, demonstrating an extension of stability from ≈ 55 days to > 180 days under optimized charge conditions.

Graphical Abstract