title: Wettability interpretation of oxygen plasma modified poly(methyl methacrylate).
abstract: 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.
authors.affiliation: Nanoscale Technology and Engineering Laboratory, Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, T6G 2G8, Canada.
authors.forename: Jinan
authors.initials: J
authors.lastname: Chai
authors.forename: Fuzhi
authors.initials: F
authors.lastname: Lu
authors.forename: Baoming
authors.initials: B
authors.lastname: Li
authors.forename: Daniel Y
authors.initials: DY
authors.lastname: Kwok
mesh_terms: D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D013500:Surface Tension; D013997:Time Factors; D017155:Wettability
chemical_list: D019904:Polymethyl Methacrylate; D010100:Oxygen