Department of Chemical Engineering and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
ACS Appl Mater Interfaces. 2011 Nov;3(11):4236-41. doi: 10.1021/am200894h. Epub 2011 Nov 7.
The hydrophobic but hygroscopic nature of polydimethylsiloxane (PDMS) with quaternary ammonium cationic side chains adsorbed on a SiO(2) surface was investigated with sum frequency generation vibration spectroscopy (SFG) and attenuated total reflectance infrared spectroscopy (ATR-IR). PDMS with cationic side chains, named cationic polymer lubricant (CPL), forms a self-healing boundary lubrication film on SiO(2). It is interesting that CPL films are externally hydrophobic but internally hydrophilic. The comparison of SFG and ATR-IR data revealed that the methyl groups of the PDMS backbone are exposed at the film/air interface and the cationic side groups and counterions are embedded within the film. The hydrophobicity must originate from the surface CH(3) groups, while the ionic groups inside the film must be responsible for water uptake. The surface hydrophobicity can alleviate the capillary adhesion while the hygroscopic property enhances the mobility and self-healing capability of the CPL boundary lubrication film.
具有季铵阳离子侧链的聚二甲基硅氧烷 (PDMS) 在二氧化硅 (SiO2) 表面上的疏水性但吸湿性质用和频发生振动光谱 (SFG) 和衰减全反射红外光谱 (ATR-IR) 进行了研究。具有阳离子侧链的 PDMS，称为阳离子聚合物润滑剂 (CPL)，在 SiO2 上形成自修复边界润滑膜。有趣的是，CPL 薄膜具有外部疏水性但内部亲水性。SFG 和 ATR-IR 数据的比较表明，PDMS 主链的甲基基团暴露在薄膜/空气界面上，而阳离子侧基和抗衡离子则嵌入在薄膜内。疏水性必须源于表面 CH3 基团，而薄膜内的离子基团必须负责吸水。表面疏水性可以减轻毛细粘附，而吸湿性能增强了 CPL 边界润滑膜的流动性和自修复能力。
