The Influence of Charge Injection on Melting Gels Delivered via Electrospray Deposition*

Melting gels are a class of hybrid organic-inorganic gels that are solid below their glass transition temperatures but show thermoplastic behavior when heated. While this phase change is reversible, heating the gel past its consolidation temperature produces a highly crosslinked glassy organic/inorganic material. This crosslinking is highly dependent on charge interactions, raising the question of how these materials will interact with a processing technique, like electrospray deposition (ESD), which is dependent on charge delivery. Previous results showed that both film thickness and chemistry were influenced by spray polarity and substrate temperature. Here, these explorations were furthered by controlling the rate at which charge was delivered to the substrate and by isolating the viscosity of the arriving material from temperature through the use of modifiers in the spray solution. Results were further compared to samples produced by spin coating to compare to systems without charge injection. Optical images, film thickness measurements, nanoindentation, and FTIR were used to characterize the sprayed melting gel with the goal of developing a robust processing space for producing highly cross linked, hydrophobic, dielectric coatings.