(272c) Inkjet Printing of Charge Mosaic Membranes As a Method for Tailored Aqueous Separation
Charge mosaic membranes are capable of separating dissolved ions from neutral molecules of comparable size by facilitating the transport of charged species through oppositely charged domains. We have developed a new method for producing charge mosaic membranes in a scalable manner by ink-jet printing polymeric materials onto a structural template. Using a striped pattern, positively charged and negatively charged polyelectrolytes are alternatively printed to form the mosaic. Printing of nanomaterials allows for facile design and control over microstructure. This microstructure, in turn affects overall membrane performance. To demonstrate the versatility of this method, we printed membranes with different polyelectrolytes and printing conditions. Enrichment of small ionic salts (i.e. KCl) was first observed using this robust, reliable, and rapid method. Printing enabled us to extend this application to both acetic acid extraction and functionalization for pH-responsive salt separation. The contribution of interactions beyond electrostatics was investigated by printing with polyelectrolytes of varying solubility parameters and challenging the membrane with acetic acid at different concentrations and feed solution pH. To observe pH-responsive salt permeation, membranes were printed with a weak polyelectrolyte while the other domain was printed with a strong polyelectrolyte whose ionization does not vary with pH. The ability to easily tailor membranes for very different separations is what makes inkjet printing such a unique and attractive method for fabricating membranes.