Asymmetric Electrostatic and Hydrophobic–Hydrophilic Interaction Forces between Mica Surfaces and Silicone Polymer Thin Films
| Autor: | Louis Chin Jones, Matthew A. Gebbie, Yuri Roiter, Saurabh Das, Michael V. Rapp, Yonas Gizaw, Peter H. Koenig, Stephen H. Donaldson, Jacob N. Israelachvili |
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| Rok vydání: | 2013 |
| Předmět: |
Materials science
Polymers Surface Properties Static Electricity Silicones General Physics and Astronomy Biocompatible Materials Membrane Potentials chemistry.chemical_compound symbols.namesake Silicone Polymer chemistry Nanotechnology General Materials Science Dimethylpolysiloxanes Thin film Aqueous solution Polydimethylsiloxane technology industry and agriculture General Engineering Water Surface forces apparatus Hydrogen-Ion Concentration Solutions chemistry Chemical engineering symbols Aluminum Silicates Adsorption Gold Mica Adhesive van der Waals force Hydrophobic and Hydrophilic Interactions |
| Zdroj: | Donaldson, SH; Das, S; Gebbie, MA; Rapp, M; Jones, LC; Roiter, Y; et al.(2013). Asymmetric electrostatic and hydrophobic-hydrophilic interaction forces between mica surfaces and silicone polymer thin films. ACS Nano, 7(11), 10094-10104. doi: 10.1021/nn4050112. UC Santa Barbara: Retrieved from: http://www.escholarship.org/uc/item/12h8w4qv |
| ISSN: | 1936-086X 1936-0851 |
| DOI: | 10.1021/nn4050112 |
| Popis: | We have synthesized model hydrophobic silicone thin films on gold surfaces by a two-step covalent grafting procedure. An amino-functionalized gold surface reacts with monoepoxy-terminated polydimethylsiloxane (PDMS) via a click reaction, resulting in a covalently attached nanoscale thin film of PDMS, and the click chemistry synthesis route provides great selectivity, reproducibility, and stability in the resulting model hydrophobic silicone thin films. The asymmetric interaction forces between the PDMS thin films and mica surfaces were measured with the surface forces apparatus in aqueous sodium chloride solutions. At an acidic pH of 3, attractive interactions are measured, resulting in instabilities during both approach (jump-in) and separation (jump-out from adhesive contact). Quantitative analysis of the results indicates that the Derjaguin-Landau-Verwey-Overbeek theory alone, i.e., the combination of electrostatic repulsion and van der Waals attraction, cannot fully describe the measured forces and that the additional measured adhesion is likely due to hydrophobic interactions. The surface interactions are highly pH-dependent, and a basic pH of 10 results in fully repulsive interactions at all distances, due to repulsive electrostatic and steric-hydration interactions, indicating that the PDMS is negatively charged at high pH. We describe an interaction potential with a parameter, known as the Hydra parameter, that can account for the extra attraction (low pH) due to hydrophobicity as well as the extra repulsion (high pH) due to hydrophilic (steric-hydration) interactions. The interaction potential is general and provides a quantitative measure of interfacial hydrophobicity/hydrophilicity for any set of interacting surfaces in aqueous solution. © 2013 American Chemical Society. |
| Databáze: | OpenAIRE |
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