Competitive Adsorption of Lubricant Base Oil and Ionic Liquid Additives at Air/Liquid and Solid/Liquid Interfaces.,Langmuir

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Competitive Adsorption of Lubricant Base Oil and Ionic Liquid Additives at Air/Liquid and Solid/Liquid Interfaces.
Langmuir ( IF 3.7 ) Pub Date : 2020-06-01 , DOI: 10.1021/acs.langmuir.0c01197
Dien Ngo ₁ , Xin He ₂ , Huimin Luo ₃ , Jun Qu ₂ , Seong H Kim ₁

Affiliation

Oil-soluble ionic liquids (ILs) have been proved as effective additives in lubricant oils through tribological experiments and post-test analytical analyses. In this study, surface structures of lubricant base oil, oil-soluble ILs, and their mixtures at the air/liquid and solid/liquid interfaces have been studied using sum frequency generation (SFG) vibrational spectroscopy. At the air/base oil and air/IL interfaces, the alkyl chains of the studied compounds were shown to be conformationally disordered and their terminal methyl groups point outward at the liquid surface. The base oil dominates the air/(base oil + IL) interface due to its higher surface excess propensity and larger bulk concentration. At the solid (silica) surface, ILs adopt a structure with their charged headgroups in contact with the silica surface, while their alkyl chains are more conformationally ordered or packed compared to the air/IL interface. At the interface between silica and (base oil + IL) mixtures, ILs also preferentially adsorb to the silica surface with their layer structures somewhat different from those of ILs alone. These results showed that ILs can adsorb onto the solid surface even before tribological contacts are made. The insights obtained from this SFG study provide a better understanding of the role of ionic liquids in lubrication.

中文翻译：

润滑油基础油和离子液体添加剂在空气/液体和固体/液体界面的竞争性吸附。

油溶性离子液体（ILs）已通过摩擦学实验和测试后的分析分析证明是润滑油中的有效添加剂。在这项研究中，已经使用总频率生成（SFG）振动光谱学研究了润滑油基础油，油溶性IL及其在空气/液体和固体/液体界面的混合物的表面结构。在空气/基础油和空气/ IL界面处，所研究化合物的烷基链显示为构象无序的，其末端甲基在液体表面朝外指向。基础油由于其较高的表面过量倾向和较大的体积浓度而在空气/（基础油+ IL）界面中占主导地位。在固体（二氧化硅）表面上，离子分子采用带电头基与二氧化硅表面接触的结构，与空气/ IL界面相比，它们的烷基链的构象更有序或排列紧密。在二氧化硅和（基础油+ IL）混合物之间的界面处，IL也会优先吸附到二氧化硅表面，其层结构与单独的IL略有不同。这些结果表明，即使在进行摩擦接触之前，离子液体也可以吸附到固体表面上。这项SFG研究获得的见解使人们对离子液体在润滑中的作用有了更好的了解。这些结果表明，即使在进行摩擦接触之前，离子液体也可以吸附到固体表面上。这项SFG研究获得的见解使人们对离子液体在润滑中的作用有了更好的了解。这些结果表明，即使在进行摩擦接触之前，离子液体也可以吸附到固体表面上。这项SFG研究获得的见解使人们对离子液体在润滑中的作用有了更好的了解。

更新日期：2020-07-07

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