Preparation of hierarchical macroporous polymer composites with pickering emulsions and their photocatalytic applications

In recent years, highly porous polymer composites are attracting considerable interest due to their large surface area, high chemical resistance, permeability properties, and low densities. These materials have numerous applications in many fields such as catalysis, filtration, adsorption, sensors, etc. For this reason, preparation of such materials with different processes is frequently in focus of research. In this context, the subject of this thesis has been focused on the preparation of novel macroporous polymer composites for heterogeneous photocatalysis applications. With this aim, Pickering high internal phase emulsions (Pickering-HIPEs) have been used as templates to build hierarchical porous polymer networks. HIPEs are concentrated emulsions consisting of a high ratio of internal phase (or dispersed phase). In case of either one or both phases of a HIPE contain monomer(s) hierarchical macroporous polymers named "polyHIPEs" can be produced. HIPEs are usually stabilised by using relatively high amounts of emulsifiers coalescence. However, it is also possible to stabilise HIPEs with the use of nanoparticles. In this case, the resulting emulsion and the polymer are named as Pickering-HIPE and poly-Pickering-HIPE, respectively. In this thesis study, with the use of surface modified TiO2 nanoparticles macroporous polymer composites have been developed. To this end, poly-Pickering-HIPE composites have been prepared from dicyclopentadien (DCPD) based Pickering-HIPEs by using ring opening metathesis polymerization (ROMP). Afterwards, the morphological, mechanical and thermal properties of the resulting polymer composites have been investigated by varying the used nanoparticle amount. Moreover, in order to prevent oxidative degradation of the polymer chains a conventional antioxidant was introduced into the HIPE formulations and oxidative stability of the obtained poly-Pickering-HIPEs have been investigated by observing the change in mechanical properties. Photocatalytic activity of the resulting poly-Pickering-HIPE composites was determined by investigating the kinetics of the heterogeneous photocatalytic degradation reaction of 4-nitrophenol (4-NP) and a kinetic expression, which can be used in the development of large-scale photocatalytic reactor has been obtained. Keywords: emuslion templating, high internal phase emulsion (HIPE), Pickering-emulsion, poly-Pickering-HIPE, heterogenous photocatalytic degradation