|M.Sc Student||Shaul Gil|
|Subject||Emulsion Templating of Renewable Resource Monomers for|
Carbons with Hierarchical Porosities
|Department||Department of Materials Science and Engineering||Supervisor||PROF. Michael Silverstein|
|Full Thesis text|
Hierarchically porous polymers are used in a variety of applications such as carbon capture, gas storage, adsorbents, absorbents, tissue engineering and drug delivery. Hierarchically porous polymers are also used as precursors for porous carbons which are being developed for a range of energy storage applications including gas separation, fuel cells, hydrogen storage, and batteries. The functionality in numerous applications depends on a porous hierarchy. PolyHIPEs (PHs) are macroporous polymer monoliths that are usually synthesized within surfactant-stabilized within high internal phase emulsions (HIPEs). It should be possible to incorporate renewable resource polymers (RRPs), such as polyphenols, into these polyHIPEs to introduce microporosity and\or mesoporosity porous carbon monoliths.
The objectives of this research were to investigate and develop highly porous polymer monoliths and highly porous carbon monoliths. Three different porous polymers systems were investigated. One system was based on the hydrothermal carbonization (HTC) of a renewable resource polymer polyphenol (lignin) in the presence of borax, hydrophilic monomer (2-hydroxyethyl methacrylate, HEMA), and hydrophobic monomer (hexamethylene diisocyanate, HDI), within oil-in-water MIPEs (medium internal phase emulsions). System number two was based on renewable resource polymer polyphenol (tannic acid) in the presence of borax and hydrophobic monomer (hexamethylene diisocyanate, HDI), within oil-in-water HIPE. The last system was based on simultaneous polymerization and hypercrosslinking of divinylbenzene (DVB) with formaldehyde dimethyl acetal (FDA), and catalyst (Iron chloride, FeCl3), within oil-in-oil MIPE. The resulting porous structure, atomic compositions, , microporosities, and thermal properties were characterized. Chemical activation and pyrolysis were performed on two systems. Chemical activation involved immersing the material in as aqueous ZnCl2 solution, pyrolyzing in N2 and drying.
The lignin-based MIPE exhibited closed-cell structure with void size of 14.6 µm, open-cell structure after carbonization with pore sizes of 17.0 and 5.9 µm. The density of the HTC monolith was 0.10 g/cm3 and relatively high around 160 m2/g. The after carbonization increased to 878 m2/g, but only to 287 m2/g for chemical activation during carbonization.
The tannic acid-based HTC exhibited monoliths with structure ranging from capsule-like to open, relatively low densities (from 0.04 to 0.09 g/cm3), from 50 to 80 m2/g, and high thermal stability during carbonization at 450 ℃. The thermally polymerized monoliths from the same HIPE were unable to maintain their monolithic structure and underwent a large mass loss during carbonization.
The simultaneous polymerization and hypercrosslinking of DVB exhibit a hierarchical porosity with some mesoporosity, 300 nm macropores, and an of 377 m2/g. The sequential polymerization and hypercrosslinking of DVB exhibited a hierarchical porosity with an of 719 m2/g.