Polymethylsilsesquioxane powder prepared by morphology-controlled growth and its composite with waterborne latex for superhydrophobic coating fabrication

The incompatibility of superhydrophobic particles with waterborne latexes impedes the direct mixing of them to make mixtures for superhydrophobic coatings fabrication. Polymethylsilsesquioxane (PMSQ) prepared by methyltrialkoxysilane precursors can change from hydrophilic to hydrophobic with the increased degree of condensation. This property makes PMSQ suitable for compounding with waterborne latexes for highly hydrophobic coatings fabrication. The present work presents a method for the morphology control of PMSQ to make highly porous PMSQ particles with micro-/nano-roughness on the surface. A gel of PMSQ was first prepared in aqueous medium and broken into small pieces by a high speed homogenizer; additional acid-catalyzed hydrolyzate of methyltrimethoxysilane was added to this dispersion of broken particles. The following base-catalyzed regrowth of PMSQ on the preformed gel skeleton gave highly porous PMSQ powder suitable for compounding with waterborne latexes. The composite of PMSQ wet powder and a styrene-acrylate waterborne latex gave a superhydrophobic coating after drying in ambient condition, of which the water contact angle reaches 153.1° and sliding angle is low to 28.7°.