| Several membrane-based technologies are emerging as potential bridges to sustainability at the water -- energy nexus. However, production of high-performance membranes to enable the beneficial implementation of these technologies still faces a variety of challenges. Suitable membranes must simultaneously achieve perm-selectivity, material stability, mechanical integrity, and fouling resistance while remaining manufacturable and relatively cheap. The methods of membrane fabrication that have facilitated the commercial success of pressure-driven membrane processes have been established for several decades. To meet the demanding requirements of novel membrane technologies like forward osmosis and pressure-retarded osmosis, novel fabrication approaches must be developed to extend control of membrane structure and material properties beyond the constraints of traditional techniques, to the nanoscale.;This dissertation explores the use of one such novel technique, electrospinning, for its potential in fabricating specialized membranes to fit the needs of forward and pressure-retarded osmosis. Electrospinning uses electric fields to form nanofibers from viscous solutions of a wide variety of materials, achieving fiber diameters orders of magnitude smaller than those possible with traditional mechanical methods. The mats of layered nanofibers produced have great potential for membrane applications, far exceeding the porosity and thinness that can be obtained through phase separation approaches.;Herein, electrospinning is evaluated for enhancing mechanical integrity in support layers for forward and pressure-retarded osmosis membranes. The unique structure produced increases resistance to shear stress without compromising membrane transport performance. The potential to electrospin nanofiber structures from block copolymers to obtain fibers having independently tailored surface and bulk properties is also demonstrated. In this case, a mat was produced that had water-insoluble fibers with highly hydrophilic surfaces, representing progress in design of anti-fouling membranes. Finally, a nanoscale investigation of salt-rejecting polyamide layers reveals new insights into their structure. These insights were enabled by the use of a nanofiber mat as a support layer substrate for polyamide layer formation, and they have implications for transport and fouling in both emerging and established membrane technologies.;Taken together, these findings suggest that the nanoscale control of structure and material properties afforded by electrospinning may hold the key to reaching a new level of membrane design customization and performance. Such advancements beyond the limitations of current membrane fabrication practices are critical for implementing emerging membrane technologies and realizing their potential gains in energy and water efficiency, protection of the environment, and waste re-utilization. |
