College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, PR China.
College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, PR China; Department of Chemical and Petroleum Engineering, University of Calgary, Calgary T2N 1N4, Canada; Hubei Cooperative Innovation Center of Unconventional Oil and Gas, Wuhan 430100, PR China.
Colloids Surf B Biointerfaces. 2019 Sep 1;181:593-601. doi: 10.1016/j.colsurfb.2019.06.012. Epub 2019 Jun 7.
The surface properties of mono-rhamnolipid (Rha-C10-C10, R1) and di-rhamnolipid (Rha-Rha-C10-C10, R2) were investigated after separation and purification. The effects of environmental factors on equilibrium surface tension of these surfactants were studied by changing the temperature, salinity, and pH. Results show that R1 possesses a better surface activity than R2, but both are stable at low pH values and high temperature. Moreover, the diffusion and adsorption processes of R1 and R2 were studied by dynamic surface tension measurements. The initial adsorption processes of R1 and R2 were diffusion-controlled, and the effective diffusion coefficient of R1 was higher than that of R2 at the same concentration. We also monitored the dynamic interfacial tension curves of R1 and R2 with or without aging at high temperature, revealing that both feature high temperature resistance, but R1 exhibited a better interfacial activity than R2. For aggregation behavior in the bulk phase, dynamic light scattering and UV - vis spectrophotometry were used to measure and observe the aggregation of rhamnolipids R1 and R2 at different temperatures and pH values. Results show the vesicle-to-micelle transformation of R1 and R2 aggregates with decreasing pH. This result is attributed to the considerable influence of solution pH to the dissociation degree of rhamnolipids. Thus, pH values significantly influence particle size distribution.
对分离和纯化后的单鼠李糖脂（Rha-C10-C10，R1）和双鼠李糖脂（Rha-Rha-C10-C10，R2）的表面性质进行了研究。通过改变温度、盐度和 pH 值，研究了环境因素对这些表面活性剂平衡表面张力的影响。结果表明，R1 的表面活性优于 R2，但两者在低 pH 值和高温下都很稳定。此外，通过动态表面张力测量研究了 R1 和 R2 的扩散和吸附过程。R1 和 R2 的初始吸附过程是扩散控制的，在相同浓度下，R1 的有效扩散系数高于 R2。我们还监测了 R1 和 R2 在高温下有无老化的动态界面张力曲线，结果表明两者都具有耐高温性，但 R1 的界面活性优于 R2。对于在体相中的聚集行为，使用动态光散射和紫外-可见分光光度法测量和观察了不同温度和 pH 值下 R1 和 R2 鼠李糖脂的聚集。结果表明，R1 和 R2 聚集物的囊泡到胶束的转变随着 pH 值的降低而发生。这一结果归因于溶液 pH 值对鼠李糖脂离解度的巨大影响。因此，pH 值会显著影响颗粒尺寸分布。
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