(104d) Understanding the Conformation of a Nanometer-Thick Environmentally Friendly Hydrocarbon with Short Fluorinated Side-Chains on the Solid Substrate

Understanding the conformation of a nanometer-thick environmentally friendly hydrocarbon with short fluorinated side-chains on the solid substrate

Andrew Kozbial and Lei Li

Department of Chemical and Petroleum Engineering, University of Pittsburgh, 3700 Oâ??Hara Street, Pittsburgh, PA 15261

Long-chain fluorocarbons are the state-of-the-art materials as nanometer-thick coatings in the growing nanotechnology industries. The low surface energy, resulting from the molecular nature of C-F bonds, is the key feature of the perfluoro-materials that no other materials can provide. However, the research in the past decades showed that long-chain fluorocarbons pose serious toxicological and environmental concerns because their degradation products, which has at least six fluorocarbons, are bioaccumulative, toxic and have high global warming potential. One possible solution for the dilemma is to develop hydrocarbons with short fluorocarbon side chains (HC-SFSC), which has been demonstrated to be environmentally much more friendly. Unfortunately, to date there has been few experimental study of the nanometer-thick HC-SFSC on the solid substrate. In the current study, nanometer-thick HC-SFSC has been deposited on the silica substrate by dip-coating. Contact angle testing results indicated that the as-coated HC-SFSC/silica has high surface energy and, interestingly, a simple thermal annealing reduces the surface energy to the value close to that of Teflon. X-ray photoelectron spectroscopy (XPS) results suggested that the thermodynamic equilibrium conformation of HC-SFSCs on a solid substrate is actually in favor of low surface energy and the low mobility of HC-SFSCs induced by the solid confinement traps the molecule in a non-equilibrium conformation with higher surface energy. This finding here potentially provides a viable approach to make the surface energy of HC-SFSCs as low as the conventional perfluoro-materials