School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.
Department of Applied Physics, School of Science, University of Granada , 18071 Granada, Spain.
Langmuir. 2017 Nov 28;33(47):13543-13553. doi: 10.1021/acs.langmuir.7b02257. Epub 2017 Nov 15.
The electrophoresis of a well-established model system of charged colloids in nonpolar solvents has been studied as a function of particle volume fraction at constant surfactant concentration. Dispersions of poly(12-hydroxystearic acid)-stabilized poly(methyl methacrylate) (PMMA) latexes in dodecane were prepared with added Aerosol OT surfactant as the charging agent. The electrophoretic mobility (μ) of the PMMA latexes is found to decrease with particle concentration. The particles are charged by a small molecule charging agent (AOT) at finite concentration, and this makes the origin of this decrease in μ unclear. There are two suggested explanations. The decrease could either be due to the reservoir of available surfactant being exhausted at high particle concentrations or the interactions between the charged particles at high particle number concentrations. Contrast-variation small-angle neutron scattering measurements of PMMA latexes and deuterated AOT-d surfactant in latex core contrast-matched solvent were used to study the former, and electrokinetic modeling was used to study the latter. As the same amount of AOT-d is found to be incorporated with the latexes at all volume fractions, the solvodynamic and electrical interactions between particles are determined to be the explanation for the decrease in mobility. These measurements show that, for small latexes, there are interactions between the charged particles at all accessible particle volume fractions and that it is necessary to account for this to accurately determine the electrokinetic ζ potential.
已经研究了在恒定表面活性剂浓度下作为粒子体积分数函数的非极性溶剂中带电胶体的成熟模型体系的电泳。通过添加作为带电剂的气溶胶 OT 表面活性剂，在十二烷中制备了聚（12-羟基硬脂酸）稳定的聚甲基丙烯酸甲酯（PMMA）乳胶分散体。PMMA 乳胶的电泳迁移率（μ）随着粒子浓度的增加而降低。由于存在有限浓度的小分子带电剂（AOT），因此这些粒子被带电，这使得μ的降低原因不清楚。有两种建议的解释。这种降低可能是由于在高粒子浓度下耗尽了可用表面活性剂的储备，或者是由于在高粒子数浓度下带电粒子之间的相互作用。对比变化小角中子散射测量了 PMMA 乳胶和乳胶核对比匹配溶剂中的氘化 AOT-d 表面活性剂，用于研究前者，而电动建模用于研究后者。由于在所有体积分数下都发现相同量的 AOT-d 与乳胶结合，因此确定了粒子之间的溶剂动力学和电相互作用是迁移率降低的原因。这些测量表明，对于小乳胶，在所有可及的粒子体积分数下都存在带电粒子之间的相互作用，并且有必要考虑到这一点以准确确定电动 ζ 电位。
