Brij类表面活性剂与Laponite纳米颗粒的相互作用及其稳定乳液的研究

通过表面张力、Zeta电位和流变学参数的测定, 研究了聚氧乙烯烷基醚类非离子型表面活性剂(Brij 30和Brij 35)在合成锂皂石(Laponite)纳米颗粒表面的吸附及对Laponite水分散体系中颗粒间相互作用和体系粘度的影响. 结果表明, 这类表面活性剂能显著地吸附在Laponite颗粒表面上, 且吸附量随其分子中POE链长短而不同. 这种吸附没有改变Laponite粒子的带电性质, 但一定程度地降低了Laponite颗粒Zeta电位; 吸附也会减弱颗粒间的相互作用, 降低体系的粘度. 实验以Laponite和Brij为乳化剂, 制备了O/W型乳状液. 乳液稳定性变化和乳液粒径分布结果表明, 体系中Brij的浓度较低时, 乳液的性质主要是由Laponite颗粒决定的; 而Brij浓度较高时, 则主要取决于Brij表面活性剂. 高速剪切含Brij的Laponite水分散体系, 剪切后表面张力随时间的变化表明, 剪切作用会使得吸附在Laponite颗粒表面的Brij分子不同程度地解吸下来. 这也意味着乳液制备时, 高速剪切作用也会造成Brij分子自Laponite颗粒表面的脱附, 这可能是非离子表面活性剂与阳离子表面活性剂对负电固体颗粒稳定乳液影响不同的原因.

Interactions between Brij Surfactants and Laponite Nanoparticles and Emulsions Stabilized by Their Mixtures

The adsorption of polyoxyethylene alkyl ether surfactants (Brij 30 and Brij 35) on synthetic smectite clay (Laponite) nanoparticles and the interactions between them have been investigated through surface tension, zeta potential and rheology properties measurements, showing that Brij 30 and Brij 35 are adsorbed onto Laponite surface, and the adsorption is increased with decreasing oxyethyl groups (EO). The zeta potential of the Laponite decreases slightly at the high Brij concentrations, and the rheology results indicate that the adsorption of Brij reduces the particle-particle interactions and the viscosity. Brij surfactants and Laponite nanoparticles were used to prepare emulsions containing equal volumes of oil and water. The emulsion stability and droplet size measurements indicate that the properties of the emulsions are mainly controlled by the Laponite at low Brij concentrations, whereas primarily depend on the Brij concentrations at high surfactant concentrations. To illuminate the different effects between cationics (such as CTAB) and Brij on emulsions stabilized by negatively charged solid particles, the desorptions caused by high speed shear were measured.