Solvent Isotopic Effects on a Surfactant Headgroup at the Air–Liquid Interface
Solvent Isotopic Effects on a Surfactant Headgroup at the Air–Liquid Interface
复制标题
溶剂同位素对气液界面表面活性剂头基的影响
DOI：
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发表时间：
2018
影响因子：
3.7
通讯作者：
K. Cimatu
中科院分区：
文献类型：
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作者：
U. I. Premadasa;N. Moradighadi;Kondalarao Kotturi;J. Nonkumwong;Md. Rubel Khan;M. Singer;E. Masson;K. Cimatu
在空气-水和空气-氧化氘（D2 O）界面处，使用和频产生振动光谱法评估了两侧为两个甲基、苄基头和辛基尾的季铵表面活性剂的几何形状、排列和取向。值得注意的是，对称和不对称的N-CH 3伸缩（在SSP偏振组合中分别为102979和103045 cm-1）在水中可见，但在氧化氘中可忽略不计。我们的结论是，D2 O除了触发的平均重定向的二甲基氨基单元平行于界面，并可能改变表面活性剂的整体构象。在D2 O中也观察到表面活性剂辛基链中的笨拙缺陷的数量减少。辛基链的矩形（1.0-10.8°）与气-液界面处的有序单层一致。
The geometry, arrangement, and orientation of a quaternary ammonium surfactant flanked by two methyl groups, a benzyl head, and an octyl tail were assessed at the air–water and air-deuterium oxide (D2O) interfaces using sum frequency generation vibrational spectroscopy. Remarkably, symmetric and asymmetric N–CH3 stretches (at ∼2979 and ∼3045 cm–1, respectively, in the SSP polarization combination) were visible in water but negligible in deuterium oxide. We concluded that D2O addition triggers the average reorientation of the dimethyl amino units parallel to the interface and possibly changes the overall conformation of the surfactant. A reduced number of gauche defects in the surfactant octyl chain is also observed in D2O. Tilt angles for the octyl chain (1.0–10.8°) are consistent with an ordered monolayer at the air–liquid interface.