Projects
Phosphonium Polymers For Anion-Exchange Membranes
Polyelectrolytes are an important class of materials that derive their unique chemical and physical properties from electrostatic interactions between ion pairs along the polymer chain. Cationic polyelectrolytes, in particular, are being extensively investigated for a variety of applications including Anion Exchange Membranes (AEMs). AEMs have shown promise as an alternative to Proton Exchange Membranes (PEMs) for fuel cell applications however, the long term stability of organic cations under alkaline conditions at higher temperatures (80° C) remains challenging. Tetrakis(dialkylamino)phosphonium, [P(NR2)4]+ cations have been shown to be highly stable in alkaline media but the number of polymeric materials bearing this cation remain limited. Our efforts have focused on synthesizing [P(NR2)4]+ based monomers and utilizing controlled/living polymerization methods, i.e. RAFT, to develop stable, well-defined polyelectrolyte architectures with tunable ion content.
Exploring Sequence in Group 16 Copolymers
Precise monomer insertion along a polymer backbone can afford biological macromolecules with a wide range of structural and functional properties. This continues to inspire researchers to synthesize macromolecules with controlled sequences as a means to manipulate structure and function. Sequence control may be especially effective in tuning the electronic structure of conjugated polymers because of the delocalized pi-electrons along the backbone. Conjugated polymers are typically synthesized in a step-growth fashion using metal catalyzed cross-coupling techniques but, chain-growth methods are possible using catalyst-transfer polycondensation (CTP). In our laboratory, we are exploring how sequence impacts the electronic properties and organization of group 16 periodic copolymers as compared to the random systems.
Suzuki Catalyst-Transfer Polycondensation using Nickel Catalysts
Controlled synthesis of conjugated polymers with functional side chains is of great importance, affording well-defined optoelectronic materials possessing enhanced stability and tunability as compared to their alkyl-substituted counterparts. However, the highly reactive monomers typically employed in catalyst-transfer polycondensation (e.g., organomagnesium or organozinc reagents) often limit the selection of solubilizing substituents tethered to the aromatic ring. We are currently exploring nickel catalysts for Suzuki polycondensation due to the lower cost as compared to palladium and the facile oxidative addition observed with a diverse range of pseudohalides or nonactivated halides. Development of this protocol should lead to enhanced substrate scope for the controlled synthesis of conjugated polymer materials with the eventual goal of electron-deficient polymers and donor-acceptor copolymers.
Synthesis of Degradable Comodity Polymer-like Materials
The rapid increase in use of commodity plastics has led to a high amount of plastic waste that is not easily broken down in the environment. Our research focuses on the incorporation of reactive functional groups to promote degradation. Functionalization of commodity plastics has also been of interest as a means of upcycling waste into specialty materials. This project is in collaboration with two other chemistry labs, a chemical engineering lab and a civil and environmental engineering group where we explore multiple strategies for addressing the excessive polymer waste.