Unilever Research and Development Laboratory, Port Sunlight, Bebington, Wirral, United Kingdom.
Langmuir. 2012 Oct 23;28(42):14974-82. doi: 10.1021/la303563j. Epub 2012 Oct 9.
Small-angle neutron scattering, zeta potential measurements, and dynamic light scattering have been used to investigate the adsorption of polymer-surfactant mixtures at the oil-water interface. The water-hexadecane interface investigated was in the form of small oil-in-water emulsion droplets stabilized by the anionic surfactant sodium dodecyl sulfate, SDS. The impact of the addition of two different cationic polymers, poly(ethyleneimine), PEI, and poly(dimethyldiallylammonium chloride), polydmdaac, on the SDS adsorption at the oil-water interface was studied. For both polymers, the addition of the polymer enhances the SDS adsorption at low SDS concentrations at the oil-water interface due to a strong surface polyelectrolyte-surfactant interaction and complexation, but the effects are not as pronounced as at the air-water interface. For PEI/SDS, the adsorption was largely independent of solution pH and increasing PEI concentration. In marked contrast to the adsorption at the air-water interface, only monolayer adsorption and no multilayer adsorption was observed. For the SDS-polydmdaac mixture, the enhanced SDS adsorption was in the form of a monolayer, and the adsorption increased with increasing polymer concentration. The strong SDS/polydmdaac surface interaction resulted in regions of emulsion instability. The zeta potential measurements showed that the combination of SDS and polydmdaac at the interface resulted in charge reversal at the interface. This correlates with the regions of emulsion stability at both high and low polymer concentrations, such that the instabilities arise in the regions of low or zero surface charge. The results presented and their interpretation represent a development in the understanding of polymer-surfactant adsorption at the oil-water interface.
小角中子散射、ζ 电位测量和动态光散射已被用于研究聚合物-表面活性剂混合物在油水界面的吸附。所研究的水-十六烷界面是以阴离子表面活性剂十二烷基硫酸钠（SDS）稳定的小油包水乳状液滴的形式存在。研究了两种不同的阳离子聚合物，即聚（亚乙基亚胺）（PEI）和聚（二甲基二烯丙基氯化铵）（polydmdaac）的添加对油水界面上 SDS 吸附的影响。对于这两种聚合物，由于强的表面聚电解质-表面活性剂相互作用和络合作用，聚合物的添加在低 SDS 浓度下增强了 SDS 在油水界面上的吸附，但效果不如在气-水界面上明显。对于 PEI/SDS，吸附在很大程度上与溶液 pH 值和 PEI 浓度的增加无关。与气-水界面上的吸附形成鲜明对比的是，只观察到单层吸附，没有多层吸附。对于 SDS-polydmdaac 混合物，增强的 SDS 吸附呈单层形式，吸附随聚合物浓度的增加而增加。SDS 和 polydmdaac 之间的强界面相互作用导致乳液不稳定区域。ζ 电位测量表明，界面处 SDS 和 polydmdaac 的结合导致界面处电荷反转。这与高聚物浓度和低聚物浓度下的乳液稳定性区域相关，即不稳定性出现在表面电荷低或为零的区域。所提出的结果及其解释代表了对聚合物-表面活性剂在油水界面上吸附的理解的发展。
