I am interested in polymers, chemical separations, and creating more energy efficient technologies. I have experience characterizing block copolymer self-assembly through running experiments at synchrotron sources, characterizing polymers, and characterizing the performance of both gas and liquid separation membranes.
Isoporous membranes have the potential to overcome the permeability/selectivity upper bound seen for traditional, homopolymer asymmetric membranes in ultrafiltration applications due to the narrow pore size distribution that arises from the self-assembly of these block copolymers. Mechanically robust, isoporous membranes were cast using the SNIPS (self-assembly plus nonsolvent induced phase separation) process from solutions of an ABAC tetrablock polymer, polystyrene-b-poly(isoprene)-b-polystyrene-b-poly(4-vinylpyridine) (SISV). SISV was synthesized via sequential living anionic polymerization to produce the final tetrablock architecture. Casting solutions were optimized to induce self-assembly, and the mechanical properties were characterized for both dense and asymmetric SISV membranes. These membranes have a toughness an order of magnitude higher than polystyrene-b-poly(4-vinylpyridine) (SV) membranes because of the unique architecture of the tetrablock where the membrane exhibits rubber toughening due to the rubbery isoprene domains linking the two glassy polystyrene blocks. However, we note that these polymers were found to be weaker than polysulfone, a tough polymer typically used for making ultrafiltration membranes. Small angle X-ray scattering (SAXS) was used to verify polymer morphology in the casting solutions, and in situ grazing incidence SAXS experiments were conducted to track how the solution order changes during the dry step of the membrane manufacturing process. In addition, the self-assembly of this novel tetrablock polymer was explored through resonant soft x-ray scattering as well as performing spin-spin relaxation NMR experiments to determine the micelle morphology by tracking relaxation rates of different blocks in solution. The performance of these membranes was characterized through running molecular weight cut-off experiments.