Preparation of open-cellular carbons from polyesterbased macroporous foams and their use in thermal energy storage

This thesis study encompasses the preparation of macroporous polymer and carbon monoliths exhibiting open-cellular structures for use in thermal energy storage. In this scope, the fundamental principle of the employed high internal phase emulsion (HIPE) templating method is based on using HIPEs as templates to create pores and control the morphological features. HIPEs are systems in which internal phase comprises at least 74.05% of the total emulsion volume. When the continuous phase or both phases contain monomer(s), the monomer-containing phase can be polymerized under suitable conditions. Subsequently, polyHIPEs are obtained by removing the internal phase. PolyHIPEs are highly cross-linked polymers exhibiting hierarchical pore morphology. PolyHIPEs can be used as templates for the preparation of porous carbons. In order to obtain a porous carbon monolith from a polyHIPE, the highly cross-linked polyHIPE monolith required to be carbonized in an inert atmosphere under controlled conditions. At this stage, preserving the monolithic structure is crucial. Since the specific surface area increases significantly with the carbonization process, the use of carbonized monoliths provides a significant advantage in applications where surface area is important. In this study, oil-in-water (oil/water) type HIPEs were prepared using a commercial unsaturated polyester resin and different crosslinking co-monomers, namely divinylbenzene (DVB) and vinylbenzyl chloride (VBC). Subsequently, polyester-based polyHIPE monoliths were synthesized by thermal curing of the HIPEs. The pore morphology of the synthesized polyHIPE monoliths was examined to determine the most suitable polyHIPE monolith matrix for thermal energy storage applications. Then, to increase the cross-link density of the selected polyHIPE monolith, hyper-crosslinking reaction was carried out via Friedel-Crafts alkylation through the aromatic rings. By hyper-crosslinking, the specific surface area of the synthesized polyHIPE monolith has been also increased significantly. Later, the synthesized polyHIPE matrix and hyper-crosslinked matrix were carbonized under inert conditions to obtain polyHIPE-derived macroporous carbons. In the final stage of the thesis study, the obtained polyHIPE monolith, hyper-crosslinked monolith, and the macroporous carbons derived from these monoliths were used to prepare composite phase change materials (PCMs) to determine their application properties. For this purpose, paraffin-based RT-18HC and fatty acid-based lauric acid (LA) were used as PCMs. Impregnation of the PCMs to macroporous matrices was achieved by using vacuum impregnation method. The chemical structure and their thermal energy storage capacities were investigated of the obtained composite PCMs. The findings revealed that polyester-based polyHIPE monoliths and hyper-crosslinked monoliths exhibited promising performance in thermal energy storage applications.