Morphological Control of Multifunctional Melting Gel Coatings via Electrospray Deposition*

Melting gels (MG) are hybrid organic-inorganic gels with glass transition temperatures ~28°C and consolidation temperatures ~150°C. They exhibit thermoplastic behavior below their consolidation temperature and undergo complete cross-linking to form organically modified silica networks upon consolidation. By tuning surface properties, these glass sprays can be used as protective coatings in electronics and anti-corrosion coatings in metals. Electrospray deposition was used to spray solutions of 1wt% MG in 2-butanone. The high voltage produces charged, monodisperse droplets that, due to the low solid content of solutions, deliver small amounts of MG at a continuous rate. The pH of MG synthesis, solution viscosity, and spray polarity were varied to study the effects of charge injection on the consolidation of MG into hybrid glasses. The low MG content of solutions allows for the addition of viscosity modifiers such as terpineol which alter the ability of the spray to dissipate charge. Optical images, film measurements, and FT-IR were used to evaluate the effects of these variables on both the physical morphology along with the chemical structure of the final coatings.