Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, UK.
Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, UK; ISIS, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0RA, UK.
J Colloid Interface Sci. 2019 Jan 15;534:64-71. doi: 10.1016/j.jcis.2018.08.099. Epub 2018 Aug 31.
Optimising detergency at lower temperatures is of increasing interest due to environmental and economic factors, and requires a greater understanding of the effects of temperature on the adsorption of surfactant mixtures at interfaces. The adsorption properties of surfactant mixtures and biosurfactant/surfactant mixtures have been studied at room temperatures and at temperatures below ambient using surface tension and neutron reflectivity measurements. For the ternary surfactant mixture of octaethylene monododecyl ether, CE, sodium dodecyl 6-benzene sulfonate, LAS, and sodium dioxyethylene glycol monododecyl sulfate, SLES, the surface tension at the air-water interface increases with decreasing temperature. In contrast, there is a notable reduction in the increase in the surface tension with a decrease in temperature from 25 °C to 10 °C for the 5 component rhamnolipid/surfactant mixture of the mono-rhamnose, R1, and di-rhamnose, R2, with CE/LAS/SLES. The associated neutron reflectivity data for the ternary CE/LAS/SLES mixture and the significant observation is that the 3, 4, and 5-component mixtures containing rhamnolipids in conjunction with the other surfactants show changes in composition and adsorbed amounts of the individual components which are close to the experimental error. However the significant observation is that the neutron reflectivity data indicate that the improved surface tension tolerance at lower temperatures is associated with the dominance of the rhamnolipid adsorption in such mixtures. Hence the introduction of the rhamnolipids provides a tolerance to the adverse effects associated with reduced temperatures, and a potential for improved detergency at relatively low temperatures.
由于环境和经济因素，在较低温度下优化去污力越来越受到关注，这需要更好地了解温度对表面活性剂混合物在界面上吸附的影响。已经使用表面张力和中子反射率测量法在室温下和环境温度以下研究了表面活性剂混合物和生物表面活性剂/表面活性剂混合物的吸附特性。对于辛基聚氧乙烯十二醚、CE、十二烷基苯磺酸钠、LAS 和二氧乙烯乙二醇单十二烷基硫酸盐、SLES 的三元表面活性剂混合物，空气-水界面的表面张力随温度降低而增加。相比之下，对于单鼠李糖、R1 和二鼠李糖、R2 的 5 成分鼠李糖脂/表面活性剂混合物，从 25°C 到 10°C 时，表面张力随温度降低而显著降低，与 CE/LAS/SLES 相比。对于三元 CE/LAS/SLES 混合物的相关中子反射率数据，一个显著的观察结果是，含有鼠李糖脂的 3、4 和 5 成分混合物与其他表面活性剂一起显示出组成和单个成分吸附量的变化，这些变化接近实验误差。然而，一个显著的观察结果是，中子反射率数据表明，在较低温度下改善的表面张力耐受性与此类混合物中鼠李糖脂吸附的主导地位有关。因此，鼠李糖脂的引入为降低温度相关的不利影响提供了容忍度，并为相对较低温度下提高去污力提供了潜力。
