用纳米SiO2颗粒与微量氨基酸型两性表面活性剂十二烷基氨基丙酸钠作复合乳化剂，以正癸烷为油相，制备了pH响应性O／W型Pickering乳状液．室温下该乳状液在pH≤4．0时稳定，在pH≥6．0时不稳定，因此，可以通过改变水相的pH值使乳状液在稳定和破乳之间多次循环．在酸性水介质中，氨基酸型两性表面活性剂分子呈阳离子状态，可通过静电作用吸附到带负电荷的SiO2颗粒表面，产生原位疏水化作用，使其转变为表面活性颗粒；而在中性和碱性水介质中，氨基酸型两性表面活性剂呈两性或阴离子状态，不能产生原位疏水化作用，因而导致乳状液破乳．相关作用机理通过吸附量、Zeta电位及接触角等实验数据得以论证．该刺激-响应性Pickering乳状液在乳液聚合、油品输送以及燃料生产等领域具有重要的应用价值．%pH-responsive Pickering oil-in-water emulsion with n-decane as oil phase was prepared using negatively charged silica nanoparticles in combination with trace amount of amphoteric surfactant, N-dodecyl-β-aminopropionate(DAP), as stabilizer. The emulsion is stable at pH≤4. 0 but unstable at pH≥6. 0 at am-bient temperature, and therefore can be cycled between stable and unstable for many times. In acidic aqueous media the amphoteric surfactant molecules of amino acid type are turned to cationic form and can then adsorb at negatively charged silica nanoparticle surface with head-on configuration via electrostatic interaction, ren-dering particles surface activity by in situ hydrophobization. However in neutral and alkali aqueous media the amphoteric surfactant molecules are turned back to amphoteric or anionic forms which mostly desorb from parti-cles surface, triggering de-hydrophobization of the particles and coalescence of the oil droplets in emulsion. The relative mechanisms are revealed by measurements of adsorption, Zeta potential, as well as contact angles.
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