UV and thermally stable superhydrophobic coatings from sol–gel processing

• Published in: Journal of colloid and interface science Vol. 326; no. 2; pp. 465 - 470
• Main Authors: Xiu, Yonghao, Hess, Dennis W., Wong, C.P.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15-10-2008; Elsevier
• Subjects: Accelerated UV weathering test; Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; Fluoroalkyl silane; Gels - chemistry; General and physical chemistry; Hydrocarbons, Fluorinated - chemistry; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Nanoparticles - chemistry; Organosilicon Compounds - chemistry; Silanes - chemistry; Silica; Silicon Dioxide - chemistry; Superhydrophobicity; Surface physical chemistry; Surface Properties; Temperature; Thermal stability; Thin film; Time Factors; Trimethylsilyl Compounds - chemistry; Ultraviolet Rays; UV stability; Wettability; Accelerated UV weathering test; Superhydrophobicity; UV stability; Silica; Fluoroalkyl silane; Thermal stability; Thin film; Plasma; Binary compound; Incorporation; Roughness; Etching; Contact angle; Hydrophobicity; Precursor; Sol gel process; Preparation; Weathering; Hydrophobic group; Hysteresis; Silane
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2008.06.042

A method for the preparation of inorganic superhydrophobic silica coatings using sol–gel processing with tetramethoxysilane and isobutyltrimethoxysilane as precursors is described. Incorporation of isobutyltrimethoxysilane into silica layers resulted in the existence of hydrophobic isobutyl surface groups, thereby generating surface hydrophobicity. When combined with the surface roughness that resulted from sol–gel processing, a superhydrophobic surface was achieved. This surface showed improved UV and thermal stability compared to superhydrophobic surfaces generated from polybutadiene by plasma etching. Under prolonged UV tests (ASTM D 4329), these surfaces gradually lost superhydrophobic character. However, when the as-prepared superhydrophobic surface was treated at 500 °C to remove the organic moieties and covered with a fluoroalkyl layer by a perfluorooctylsilane treatment, the surface regained superhydrophobicity. The UV and thermal stability of these surfaces was maintained upon exposure to temperatures up to 400 °C and UV testing times of 5500 h. Contact angles remained >160° with contact angle hysteresis ∼2°.
The UV stability was significantly improved after the hydrophobic surface groups (isobutyl) were replaced by fluoroalkyl groups.