Preparation and tribological studies of stearic acid self-assembled monolayers on polymer-coated silicon surface
Preparation and tribological studies of stearic acid self-assembled monolayers on polymer-coated silicon surface
复制标题
聚合物涂覆硅表面硬脂酸自组装单层膜的制备及摩擦学研究
DOI：
10.1021/cm0345669
复制
发表时间：
2004-02-10
影响因子：
8.6
通讯作者：
Zhao, YP
中科院分区：
文献类型：
--
作者：
Ren, SL;Yang, SR;Zhao, YP
我们提出了一个很好的替代方法来改善聚合物薄膜的摩擦学性能的功能聚合物表面的化学吸附的长链单层。因此，一种新型的自组装单分子膜成功地制备在硅基板上涂有氨基基团的聚乙烯亚胺（PEI）的硬脂酸（STA）分子的化学吸附。通过接触角测量、椭偏厚度测量、傅里叶变换红外光谱分析和原子力显微镜分析，对STA-PEI膜的形成和结构进行了表征。在原子力显微镜（AFM）和单向摩擦试验机上分别研究了STA-PEI膜的微观和宏观摩擦学性能。已经发现，在N，N '-二环己基碳二亚胺（DCCD）作为脱水剂的存在下，通过PEI中的氨基与STA分子中的羧基之间的化学反应形成共价酰胺键，在PEI涂层上产生约2.1-nm厚的STA单层。通过引入STA单层，亲水性PEI聚合物表面变得疏水，水接触角为约105度。成膜的时间依赖性的研究表明，PEI的吸附是快速的，而至少需要24小时，以产生饱和STA单分子膜。而PEI涂层具有相对较高的附着力、摩擦力和较差的耐磨性，STA-PEI薄膜具有良好的附着力和高承载能力和耐磨性，这可以归因于STA-PEI薄膜的化学结构。据推测，STA-PEI膜的分子之间的氢键起到稳定膜的作用，并且可以在滑动期间断裂后恢复。因此，自组装STA-PEI薄膜在微机电系统（MEMS）的润滑方面有着广阔的应用前景。
We present a good alternative method to improve the tribological properties of polymer films by chemisorbing a long-chain monolayer on the functional polymer surface. Thus, a novel self-assembled monolayer is successfully prepared on a silicon substrate coated with amino-group-containing polyethyleneimine (PEI) by the chemical adsorption of stearic acid (STA) molecules. The formation and structure of the STA-PEI film are characterized by means of contact-angle measurement and ellipsometric thickness measurement, and of Fourier transformation infrared spectrometric and atomic force microscopic analyses. The micro- and macro-tribological properties of the STA-PEI film are investigated on an atomic force microscope (AFM) and a unidirectional tribometer, respectively. It has been found that the STA monolayer about 2.1-nm thick is produced on the PEI coating by the chemical reaction between the amino groups in the PEI and the carboxyl group in the STA molecules to form a covalent amide bond in the presence of N,N'-dicyclohexylcarbodiimide (DCCD) as a dehydrating regent. By introducing the STA monolayer, the hydrophilic PEI polymer surface becomes hydrophobic with a water contact angle to be about 105degrees. Study of the time dependence of the film formation shows that the adsorption of PEI is fast, whereas at least 24 h is needed to generate the saturated STA monolayer. Whereas the PEI coating has relatively high adhesion, friction, and poor anti-wear ability, the STA-PEI film possesses good adhesive resistance and high load-carrying capacity and anti-wear ability, which could be attributed to the chemical structure of the STA-PEI thin film. It is assumed that the hydrogen bonds between the molecules of the STA-PEI film act to stabilize the film and can be restored after breaking during sliding. Thus, the self-assembled STA-PEI thin film might find promising application in the lubrication of micro-electromechanical systems (MEMS).