Melting gel (MG) materials are hybrid polysilsesquioxanes that possess glass transition temperatures between -18.8 and 27.7<sup>o</sup>C and consolidation temperatures at ~150<sup>o</sup>C, above which they irreversibly transform into hybrid-organic inorganic silica based glasses. MGs are synthesized via a sol-gel process involving a monosubstituted alkoxide such as methyltriethoxysilane (MTES) or phenyltriethoxysilane (PhTES) along with a di-substituted alkoxide such as dimethyldiethoxysilane (DMDES) or dipheyldiethoxysilane (DPhDES). In this study two MGs with the following compositions 65%MTES-35%DMDES and 87%PhTES-13%DPhDES were employed. The main advantage of the MGs is their processing ability. MGs can be processed as a thermoplastic melt into a desired form and then converted into a permanent structure based on this property. In our study, melting gel materials are processed by electrospray deposition in order to investigate the kinetic behavior arising from different experimental conditions and how these affect the final morphologies of MG films. Due to the electrostatic breakup mechanism present in electrospray, the resulting sprays possess uniform droplets down to hundreds of nanometers. By using MG dilute loadings of 1 wt%, these microdroplets can deliver extremely small quantities of material at a continuous rate and incorporate fillers to change the properties of the spray and the functionality of the final structures. Control of spray composition, substrate temperature, flow rate, and collection distance, translates to tuning of the dynamic evolution of solvent evaporation and MG consolidation. The results reveal that these can be used to controllably tune surface structure from dense, to cellular, to superhydrophobic fractal coatings. Nanoindentation tests show that the mechanical properties of the constituent MGs are also affected by these parameters. In addition, manipulation of charge dissipation during the deposition also results in the ability to limit the extent of spray as a means to gain control over the coating thickness.

Hybrid glasses coatings obtained by electrospray deposition

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.