Synthetic strategies towards ether-free polymeric hydroxide conducting membranes

The only way to combat the depletion of resources and climate crisis is to reduce
our dependence on fossil fuels. Renewable sources, such as wind and solar energy,
are increasingly used to meet our ever-growing energy demands; however, they are
intermittent. One promising solution to the power crisis in the world is fuel cells,
which, unlike the combustion engine, can operate on renewable fuels such as
hydrogen, methanol, and ethanol without emitting pollutants with high efficiency.
A conventional type of polymer electrolyte fuel cell is proton exchange fuel cells
(PEMFCs), which have already moved from laboratory to market; however, the
usage of Pt catalyst makes them costly and unstable. On the other hand, the fuel
cells operating in alkaline media, anion exchange membrane fuel cells (AEMFCs)
can use nonprecious-metal catalysts with higher redox reaction kinetics. However,
the technology of AEMFCs is currently less developed than that of PEMFCs due to
several challenges, including the need for high-performing anion exchange
membranes (AEMs) that can meet all requirements. The two main challenges
hampering the development of AEMs for fuel cells are the lower conductivity of
PEMs and the lower thermochemical stability in alkaline media. It is worth noting
that research efforts now focus on obtaining stable polymer AEMs with high
efficiency and low degradation in alkaline media.
This thesis aims to investigate different structural factors, including polymer
backbone, and the design and placement of cationic moieties on the final properties
of AEMs. Several ether-free polymers were synthesized through superacidmediated
polyhydroxyalkylation reactions and, after required functionalization,
were conducted to make fully quaternized polymers. AEMs were prepared from the
polymers and investigated in terms of water uptake, ion conductivity, thermal
properties, morphology, and alkaline stability.