Relating the rheological behavior of (organo)silica to its electrospinnability

In modern industry, membranes are important tools for various applications, from the separation of solvents to water purification. (Organo)silica membranes are innovative membranes and they can be produced throughout electrospinning, using different types of precursors. TEOS membranes have been widely studied during the last years, but the possibility of creating new membranes with different precursors must be investigated yet. The first step to study these different types of sol-gels and understand if they can lead to functional membranes is the deep knowledge of their rheological properties. The aim of this Master’s dissertation is to extend the knowledge about the rheological behaviour of sol-gels with blended precursors (TEOS, TEOMS, DMDES in different ratios). Various equipment were used to evaluate both the rheology and the electrospinnability of the sols considered. Two types of rheometers (rotational and extensional) were used to extract the most important rheological information, then the sols were electrospun and the quality of the membranes obtained was verify with the Scanning Electron Microscope and a high-speed camera. The most important points that were assessed with the experimental analysis is that a sol must show a mild shear thinning behavior to be electrospun, independently from the precursor(s) used, and that sols made with pure TEOMS do not lead to the formation of membranes. Moreover, it was verified that the sols with blended precursors have a lower crosslinking level than the one of pure TEOS, because they have fewer active sites. Finally, future research should confirm the results obtained analyzing different sols stopping the reaction when a predefined value of viscosity inside the electrospinnability range [100-200 cP] is reached, by using a viscosimeter, that was not available during the experimental analysis of this thesis.