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Hybrid-Supported Bilayers Formed with Mixed-Charge Surfactants on C18-Functionalized Silica Surfaces.
Langmuir ( IF 3.9 ) Pub Date : 2020-06-05 , DOI: 10.1021/acs.langmuir.0c01210
Maryam Zare 1 , Jay P Kitt 1 , Joel M Harris 1
Affiliation  

Mixtures of cationic–anionic surfactants have been shown to spontaneously form ordered monolayers at hydrophobic–hydrophilic boundaries, including air–water and oil–water interfaces. In this work, confocal Raman microscopy is used to investigate the structure of hybrid-supported surfactant bilayers (HSSBs) formed by deposition of a distal leaflet of mixed cationic–anionic surfactants onto a proximal leaflet of n-alkane (C18) chains on the interior surfaces of chromatographic silica particles. The surface coverage of the two surfactants in a hybrid bilayer was determined from carbon analysis and the relative Raman scattering of their respective head-groups. Within the measurement uncertainty, the stoichiometric ratio of the two surfactants is one-to-one, equivalent to mixed-charge-surfactant monolayers at air–water and oil–water interfaces and consistent with the role of the head-group electrostatic interactions in their formation. When self-assembled on the hydrophobic surface, pairs of oppositely charged n-alkyl chain surfactants resemble a phospholipid (phosphatidylcholine) molecule, with its zwitterionic head-group and two hydrophobic acyl chain tails. Indeed, the structure of these hybrid-supported surfactant bilayers on C18-modified silica surfaces is similar to that of hybrid-supported lipid bilayers (HSLBs) on the same supports, but with denser and more-ordered n-alkyl chains. Hybrid-supported surfactant bilayers exhibit a melting phase transition (gel to liquid-crystalline phase) with structural and energetic characteristics similar to those of hybrid-supported bilayers prepared from a zwitterionic phospholipid of the same alkyl chain length. These mixed-charge surfactants on n-alkane-modified silica are stable in water over time (months), results that suggest the potential use of these hybrid bilayers for generating supported lipid-bilayer-like surfaces or for separation applications.

中文翻译:

在C18功能化的二氧化硅表面上由混合电荷表面活性剂形成的杂化支撑双层。

阳离子-阴离子表面活性剂的混合物已显示在疏水-亲水边界(包括空气-水和油-水界面)处自发形成有序单层。在这项工作中,使用共聚焦拉曼显微镜研究了混合支撑的表面活性剂双层(HSSB)的结构,该结构是将远端混合的阳离子-阴离子表面活性剂小叶沉积到构烷烃的近端小叶上形成的(C 18)硅胶色谱内表面上的链。混合双层中两种表面活性剂的表面覆盖率是通过碳分析和其各自首基的相对拉曼散射确定的。在测量不确定性范围内,两种表面活性剂的化学计量比为一对一,相当于空气-水和油-水界面处的混合电荷表面活性剂单层,并且与头基静电相互作用在它们中的作用一致编队。当在疏水性表面上自组装时,成对的带相反电荷的烷基链表面活性剂类似于具有两性离子头基和两个疏水性酰基链尾的磷脂(磷脂酰胆碱)分子。确实,这些杂化支撑的表面活性剂双层在C上的结构18-改性的二氧化硅表面类似于在相同载体上的杂化支撑的脂质双层(HSLB)的表面,但是具有更致密和更有序的烷基链。杂化支撑的表面活性剂双层表现出熔融相转变(凝胶至液晶相),其结构和能量特征类似于由相同烷基链长的两性离子磷脂制备的杂化支撑的双层。这些在构烷烃改性的二氧化硅上的混合电荷表面活性剂在水中随时间(数月)稳定,结果表明这些杂化双层可以潜在地用于产生支持的脂质双层表面或用于分离应用。
更新日期:2020-07-07
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