Wang Yuchun, Du Xuezhong, Guo Lin, Liu Huijin
Key Laboratory of Mesoscopic Chemistry, Nanjing University, Nanjing 210093, People's Republic of China.
J Chem Phys. 2006 Apr 7;124(13):134706. doi: 10.1063/1.2185629.
The monolayers of stearic acid at the air-water interface on pure water and ion-containing subphases have been studied using infrared reflection-absorption spectroscopy. In the presence of Co(2+), Zn(2+), and Pb(2+), ordered hydrocarbon chains and hexagonal subcell structure remain almost unchanged in comparison with those for the monolayer on pure water at the surface pressure of 20 m/Nm. In the cases of Co(2+) and Zn(2+), the H-bonded monodentate and unsymmetric bidentate chelating structure within the headgroups were formed, and in the case of Pb(2+), three types of structures, bidentate chelating, unsymmetric chelating, and bidentate bridging coordinations, were formed. The hydrocarbon chains in the monolayers are uniaxially oriented at a tilt angle of approximately 0 degrees with respect to the surface normal in contrast to a tilt angle of approximately 20 degrees on pure water surface at 20 m/Nm by the computer simulation of theoretical calculation to experimental data. In the presence of Ag(+), multilayers were developed with the highly ordered hydrocarbon chains in a triclinic subcell structure and a bidentate bridging structure within the headgroups. The multilayers were composed of three monolayers and the hydrocarbon chains in each monolayer were oriented at an angle of approximately 30 degrees away from the surface normal with their C-C-C planes almost perpendicular to the water surface.
利用红外反射吸收光谱法研究了硬脂酸在纯水和含离子亚相的空气-水界面上的单分子层。在Co(2+)、Zn(2+)和Pb(2+)存在的情况下，与表面压力为20 m/Nm时纯水表面的单分子层相比，有序的烃链和六边形亚晶胞结构几乎保持不变。在Co(2+)和Zn(2+)的情况下，在头基内形成了氢键单齿和不对称双齿螯合结构，而在Pb(2+)的情况下，形成了三种结构，即双齿螯合、不对称螯合和双齿桥连配位。通过理论计算与实验数据的计算机模拟对比可知，与表面压力为20 m/Nm时纯水表面约20度的倾斜角相比，单分子层中的烃链相对于表面法线以约0度的倾斜角单轴取向。在Ag(+)存在的情况下，形成了多层结构，其中烃链高度有序，呈三斜亚晶胞结构，头基内存在双齿桥连结构。多层由三个单分子层组成，每个单分子层中的烃链与表面法线成约30度角取向，其C-C-C平面几乎垂直于水面。
