Beyond single-phase electrospinning of (organo)silica

In order to make silica nanofibers, a distinction can be made between the indirect and the direct method. In the indirect method, the silica precursor is mixed with a polymer solution that delivers the required viscosity and entanglements, electrospun and consequently heat-treated to burn out the polymer and obtain silica nanofibers. The problem with this method is that the resulting fibers are mechanically inferior and show bad coherency. The direct method on the other hand offers a solution for these problems. A silica sol is made by sol-gel synthesis, which yields the spinning solution possessing enough entanglements so that no additional polymer is needed. In this way, the heat treatment step is not necessary and the properties of the silica nanofibers are safeguarded. However, some (organo)silica precursors are very difficult to electrospin because the sol as made by sol-gel synthesis is not optimal for electrospinning. An interesting path to overcome this problem is to combine the sol of the badly electrospinnable precursor with a sol of a well electrospinnable precursor. In this way, it is still possible to obtain nanofibers (thanks to the well electrospinnable sol) with the properties of the badly electrospinnable sol. In this thesis, sol-gel synthesis is performed starting from different organosilica precursors. The sols are then combined to make multi-phase nanofibers: the sols are blended (blend electrospinning) and electrospun co-axially (core-shell electrospinning). Once the multi-phase electrospinning is optimized, the morphology and the properties of the resulting nanofibers are investigated.