Sakunkaewkasem Siwakorn, Gonzalez Mario A, Marquez Maria D, Lee T Randall
Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States.
Langmuir. 2020 Sep 15;36(36):10699-10707. doi: 10.1021/acs.langmuir.0c01373. Epub 2020 Sep 1.
A series of custom-designed olefin-bridged bidentate adsorbates composed of an olefin group linking symmetrical hydrocarbon moieties of varying chain lengths was synthesized and used for the preparation of self-assembled monolayers (SAMs) on gold. The structures of the adsorbates are in the form Z-CH(CH)[CHSH] () where = 12-15 and = + 3 (, , , and ). The influence of the olefin linker on the structural and interfacial properties of the SAMs was investigated and compared to SAMs formed from analogous -alkanethiols. Characterization techniques included ellipsometry, X-ray photoelectron spectroscopy (XPS), polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS), and contact angle measurements. The SAMs exhibited ellipsometric thicknesses that were similar to their monodentate counterparts, suggesting that the new olefin-bridged adsorbates pack similarly to the monodentate analogs. Characterization by PM-IRRAS revealed that the SAMs were as conformationally ordered as those derived from the reference -alkanethiols with the exception of the adsorbate with the shortest chain length , which exhibited low coverage and a liquid-like structure. Unlike the SAMs derived from the -alkanethiols, the SAMs failed to exhibit "odd-even" effects. However, the SAMs displayed similar hexadecane contact angles as their -alkanethiol counterparts with the exception of , which exhibited markedly diminished hexadecane contact angles. The similar structural and interfacial properties of the SAMs, when compared to analogous -alkanethiol SAMs, render the molecular architecture of the olefin-bridged dithiol as a robust platform for the synthesis of adsorbates with two chemically distinct tailgroups for use in the preparation and study of phase-incompatible "conflicted" interfaces.
合成了一系列定制设计的烯烃桥连双齿吸附质，其由连接不同链长对称烃基部分的烯烃基团组成，并用于在金表面制备自组装单分子层（SAMs）。吸附质的结构为Z-CH(CH)[CHSH]（），其中 = 12 - 15且 = + 3（，，，和）。研究了烯烃连接基对SAMs结构和界面性质的影响，并与由类似的 - 烷硫醇形成的SAMs进行了比较。表征技术包括椭偏仪、X射线光电子能谱（XPS）、偏振调制红外反射吸附光谱（PM - IRRAS）和接触角测量。这些SAMs的椭偏厚度与它们的单齿对应物相似，这表明新的烯烃桥连吸附质的堆积方式与单齿类似物相似。PM - IRRAS表征显示，除了链长最短的吸附质（其覆盖率低且呈液体状结构）外，这些SAMs的构象有序性与源自参考 - 烷硫醇的SAMs相同。与源自 - 烷硫醇的SAMs不同，这些SAMs没有表现出“奇偶”效应。然而，除了表现出明显减小的十六烷接触角外，这些SAMs与它们的 - 烷硫醇对应物显示出相似的十六烷接触角。与类似的 - 烷硫醇SAMs相比，这些SAMs具有相似的结构和界面性质，这使得烯烃桥连二硫醇的分子结构成为合成具有两个化学性质不同的尾基的吸附质的强大平台，用于制备和研究相不相容的“冲突”界面。
