Plasma polymerization of sulfur-rich and water-stable coatings on silica particles

Abstract

The plasma polymerization of thiophene has been applied to develop sulfur-rich coatings on silica particles. A range of plasma input energies (0.06–2.4kJ⋅cm−3) and deposition times (2–30min) were applied in the plasma polymerization process. The surface chemistry of plasma polymerized thiophene (PPT)-coated particles was evaluated via X-ray photoelectron spectroscopy (XPS), while the distribution of sulfur-containing groups was studied by time of flight secondary ion mass spectroscopy (ToF-SIMS). Washburn capillary rise measurements quantified the hydrophobicity of uncoated and PPT-coated particles. The stability of PPT-coated particles in water was evaluated for immersion durations of 5min to 24h. Surface chemistry analyses showed a rapid and homogenous formation of sulfur-rich PPT layers on particles at a low plasma input energy of 0.06kJ⋅cm−3. ToF-SIMS results suggested the formation of high density thiol functionalities on surfaces. PPT coatings demonstrated high stability in water, which was attributed to their highly hydrophobic character. The deposition rate of PPT on particles and planar surfaces has also been compared in this investigation. It has been shown that the plasma polymerization of a monomer on a 2-D surface produces significantly thicker coatings in comparison to a 3-D surface. The plasma polymerization of thiophene via a rotating reactor was found to be an effective method for the fabrication of sulfur-rich coatings on particulate surfaces.