Background
Polysulfones have been increasingly studied in recent years as a class of thermoplastics with excellent strength and thermal stability used in nanofiltration, energy storage, and biochemical separation. Quaternary ammonium polymers are another class of materials that tend to have high conductivity and good ion exchange properties. Copolymers containing both materials would combine the beneficial properties to be used for a variety of applications.
Membranes containing quaternary ammonium with hydroxide counterions have been shown to have a natural affinity for carbon dioxide (CO2) due to the chemical equilibrium between carbonate, bicarbonate, and hydroxide ions. When a membrane is dry, CO2 is absorbed as hydroxide counterions are converted to bicarbonate, and as humidity increases, CO2 is released due to the high concentrations of water favoring carbonate over bicarbonate counterions. This “moisture-swing” chemical absorption and desorption offer benefits over other direct air capture (DAC) techniques because it relies on changes in relative humidity rather than the input of high levels of energy.
Invention Description
Researchers at Arizona State University and the Colorado School of Mines have developed stable, cationic multiblock polysulfones to be used in moisture-swing direct air capture applications. These copolymers were synthesized using difunctionalized ammonium oligomers reacted with quaternary ammonium monomers. Initial testing of the copolymer materials showed favorable results, with good film flexibility and strength confirmed for a range of compositions.
Potential Applications
- Direct air capture of CO2
Benefits and Advantages
- Uses moisture-swing method of DAC – relies on changes in relative humidity so does not require high energy input
- High thermal & chemical stability
- Enhanced mechanical properties – good film flexibility & strength
Related Publication: Polydiallylammonium-Polysulfone Multiblock Copolymers for Moisture-Swing Direct Air Capture of Carbon Dioxide