(374b) Zwitterionic Interactions with Charge Mosaic Membranes Prepared Via Electrohydrodynamic Jet Printing

Charge mosaic membranes, which possess an array of anionic and cationic charged functionalities, can more readily transport ions compared to neutral solutes. Using inkjet printing of reactive solutions, a patterned charge mosaic membrane can be produced in a scalable manner. These membranes have an overall neutral surface charge, but within each patterned stripe exhibit a positive or negative charge, which are susceptible to fouling. Attractive dispersive, electrostatic, and hydrodynamic interactions between dissolved solutes and the membrane leads to the attachment and accumulation of material on the surface of the membrane, which reduces the throughput and performance. One of many emerging techniques for reducing fouling is the use of polyzwitterions. Zwitterions contain an equal number of anionic and cationic groups on the molecular chain, with a net neutral charge. These units form a strong hydration layer, thereby increasing the free energy of adsorption for foulants. This study evaluates novel multi-functionalized charge mosaic membranes that contain a zwitterionic anti-fouling layer.

Membranes cast from a poly(trifluoroethyl methacrylate-co-oligo-(ethylene glycol) methyl ether methacrylate-co-(3-azido-2-hydroxypropyl methacrylate) P(TFEMA-OEGMA-AHPMA) copolymer are the parent substrates utilized in this study. The azido groups lining the pore wall of the parent substrate lead to multiple functionalization avenues. A polyzwitterionic nature is attained through the controlled deposition of propiolic acid onto the membrane via electrohydrodynamic jet printing, in which an applied voltage drives fluid flow from the nozzle onto the substrate. The penetration depth of the zwitterionic anti-fouling layer, which is deposited first, is a function of the volume of reactive ink dispensed on the membrane. Reactions with 3-(dimethylamino)-1-propylamine and 1,2-propane-sultone form the zwitterionic functionality. Charge patterning was accomplished through the selective deposition of alkynyl-terminated reactants on the membrane, penetrating past the zwitterionic functionalities, creating cationic and anionic domains traversing the remaining membrane thickness. Energy dispersive x-ray spectroscopy (EDS) was used to develop elemental maps locating the presence of functional elements within the zwitterionic layer and absent from the charge-mosaic layer. Assessing the performance of these membranes was done through measuring the permeance, ionic transport, and fouling performance. Bovine serum albumin was used as the model foulant and was tested in both aqueous and salt solutions to measure permeability drop over time, along with ion permeance, to quantify the performance of these membranes.

The development of multi-functionalized membranes offers the ability to combine the attractive performance characteristics of multiple chemistries into a single membrane system. Zwitterions have been shown to possess high resistance to irreversible fouling but have shown limited ionic interactions. The incorporation of zwitterions into charge-mosaic membranes possess the ability to reduce the extent of fouling while maintaining the inherent ionic transport properties of charge mosaic membranes.