Highly Microporous Polymer Nanofilms by Interfacial Polymerization of Rigid Units for Ultrafast Organic Solvent Nanofiltration

Technology

The invention at hand is a means to produce OSN membranes of unprecedented performance using a mature method compatible with low-cost and scalable roll-to-roll fabrication. The method applied is interfacial polymerization, in which an alternating polymer of aqueous and organic soluble monomers is formed at the interface between aqueous and organic solutions thereof. The inventors have identified a suitable pair of such monomers to produce a polymer of optimal characteristics for OSN. The essential design principle is the use of monomers containing bulky structures so the resulting polymer cannot pack efficiently, leaving voids through which solvent may pass even with the dense defect-free polymer network necessary to prevent defects and engender solvent resistance. The resulting material is known as a polymer of intrinsic microporosity (PIM). This invention describes the first PIM synthesized by interfacial polymerization to which both the aqueous and organic soluble monomers contribute microporosity-inducing steric bulk, thereby achieving unprecedented solvent permeability during the filtration of molecules of modest molecular weight (~600 g/mol). 

Problem Addressed

The separation of organic solvents from solutes using currently commercialized methods is an energy intensive process. Simply filtering solutes out of organic solvents would improve energy efficiency and reduce material waste, mitigating costs and environmental impacts. This approach, known as organic solvent nanofiltration (OSN), currently has limited commercial application due to the absence of filtration membranes that combine the following necessary characteristics: 

• Permeability toward the solvent and impermeability toward small organic molecules 

• Absence of defects through which solute can pass 

• Resistance to chemical degradation by exposure to organic solvent 

Advantages

• Efficient separation small molecules from organic solvents 

• Reproducible, scalable, and low-cost roll-to-roll fabrication 

• Durable, high-quality polymer that is not susceptible to degradation from solvent exposure