Chai Jinan, Lu Fuzhi, Li Baoming, Kwok Daniel Y
Nanoscale Technology and Engineering Laboratory, Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, T6G 2G8, Canada.
Langmuir. 2004 Dec 7;20(25):10919-27. doi: 10.1021/la048947s.
Poly(methyl methacrylate) (PMMA) has been modified via a dc pulsed oxygen plasma for different treatment times. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), optical profilometer, zeta potential, and advancing contact angle measurements. The measured advancing contact angles of water decreased considerably as a function of discharge. Several oxygen-based functionalities (carbonyl, carboxyl, carbonate, etc.) were detected by XPS, while zeta potential measurements confirmed an increase in negative charge for the treated PMMA surface. Evaluating the correlation between the concentration of polar chemical species and zeta potential, we found that increase in surface hydrophilicity results from the coeffect due to incorporation of oxygen functional groups and creation of charge states. The electrical double layer (EDL) effect was also considered in contact angle interpretation by introducing an additional surface tension term into Young's equation. We also found that EDL contribution to the solid-liquid interfacial tension is negligible and can be safely ignored for the systems considered here.
聚甲基丙烯酸甲酯（PMMA）已通过直流脉冲氧等离子体在不同处理时间下进行了改性。通过X射线光电子能谱（XPS）、光学轮廓仪、zeta电位和前进接触角测量对改性表面进行了表征。所测得的水的前进接触角随着放电而显著降低。通过XPS检测到了几种基于氧的官能团（羰基、羧基、碳酸酯等），而zeta电位测量证实了处理后的PMMA表面负电荷增加。评估极性化学物种浓度与zeta电位之间的相关性时，我们发现表面亲水性的增加是由于氧官能团的引入和电荷态的产生所导致的协同效应。通过在杨氏方程中引入一个额外的表面张力项，在接触角解释中也考虑了电双层（EDL）效应。我们还发现，对于此处所考虑的体系，EDL对固液界面张力的贡献可以忽略不计，并且可以安全地忽略。
