Designing Copolymer Membranes for Organic Solvent Nanofiltration and Adsorption Membrane Applications

Membranes have been used in commercial applications due to their energy efficiency, ease of operation, and modular design. The key to this success is the resiliency of membrane material, such as polymers, in aqueous environments. Organic solvent nanofiltration (OSN) is a concept where membrane technologies could be utilized to replace energy-intensive equipment, such as distillation. However, OSN has not gained as high a traction due to the lack of resiliency of commercial nanofiltration membranes in the varying organic solvents.

Copolymer materials present an interesting avenue for OSN membranes from their ability to incorporate the physical and chemical traits of the selected monomer units into the copolymer. This methodology has been used to create nanofiltration membranes through self-assembly phase induction during the casting process. In addition, copolymer materials can be reacted to incorporate functionalities that can strengthen the membrane’s resiliency and introduce electrostatic interactions that facilitate charged solute transport. Additionally, block copolymer materials can be incorporated into microfiltration membranes to adsorb target solutes from the surrounding solution that passes through the membrane itself.

This research investigates the versatility of statistical copolymer materials in varying configurations, such as flat sheet and hollow fiber. In addition, by reacting the copolymer with diamines, the membrane can be resilient to previously detrimental solvents, such as ethanol, through crosslinking. This resiliency is further evaluated by linking the effect of solvent-polymer-crosslinker interactions on the transport behavior of the membrane. Permeability and neutral solute experiments were able to identify that the solvents interact with the copolymer based on the affinity in each domain. Lastly, permanent charges were reacted to the resilient film to investigate the electrostatic interactions in organic solvents.

In addition to the OSN studies, this dissertation explores block copolymer materials for adsorption membrane applications. This study tries to integrate functional copolymer material with varying polymer matrix materials not only to investigate the effect of ferroelectric material on adsorption behavior but also to incorporate functionalities to adsorb uranyl ions from seawater.

This dissertation research has helped to better understand the copolymer interactions with the solvent environment as well as expand the understanding between the physical and chemical properties of the material used in the construction of the membrane and the membrane’s transport behavior.