Coating of silica particles by fluorinated diblock copolymers and use of the resultant silica for superamphiphobic surfaces

Abstract

Factors affecting the grafting of fluorinated diblock copolymers onto silica particles and the repellency of films prepared from the coated silica particles were investigated. The three copolymers used for silica coating were of the poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA) family possessing different relative block lengths. They were grafted onto silica under acidic conditions via the sol–gel chemistry of the PIPSMA block in binary solvent mixtures that solubilized the PFOEMA block but not necessarily the PIPSMA block. Depending on the solvent property, the silica type, the polymer composition, and the acid catalyst used, the coated silica could be non-dispersible or dispersible. The morphology of the coating on silica could be lumpy, smooth, or bumpy. Further, the amount of polymer grafted was also affected by these parameters. The various experimental results and observations were rationalized. In addition, the coated silica was cast to yield either smooth or rugged particulate films. The water and oil repellency or amphiphobicity of the films improved as the particle coating was changed from being smooth to bumpy, as the relative PFOEMA-to-PIPSMA block length of the coating polymer was increased, or as the roughness of the particulate film increased.