NMR AND ELECTRON-MICROSCOPIC INVESTIGATION OF POLYMERIZED COATINGS PREPARED FROM METHACRYLATE-FUNCTIONALIZED SILICA IN AN ACRYLIC MONOMER MATRIX

Coating formulations comprised of [(methacryloxy)propyl]trimethoxysilane-functionalized colloidal silica in hexanediol diacrylate can exhibit two problems that are detrimental to their application. Higher viscosity, which hinders ease of application, has been found by transmission electron microscopy (TEM) to arise primarily from the presence of agglomerated colloidal silica. Gel formation also results in higher viscosity of the formulation. TEM and solid-state C-13 and Si-29 NMR spectroscopy showed that gelation was due to polymerization of the acrylates, with reaction at the carbon-carbon double bond of the methacrylate more prevalent than reaction of the acrylate functionality.