Membranes Fabricated from Self-Assembled Block Copolymers

Filtration is one of the oldest separation processes known to man, with evidence of its use dating back to the ancient Egyptians. Due to the development of polymeric membranes within the last century, solutes with sizes ranging all the way from 1 nm to 1 mm can now be filtered from solution (i.e., nanofiltration to microfiltration). However, current filtration membranes are hindered by a wide pore size distribution. This wide distribution is a direct result of the nonsolvent induced phase separation (NIPS) process used to fabricate current membranes. Despite efforts to reduce the spread of this distribution by modifying the NIPS process, it remains a major hindrance to the deployment of membranes in advanced applications. Therefore, new methods and materials need to be developed in order to produce membranes with a single, well-defined pore size.

Block copolymers are an intriguing class of materials that consist of two or more chemically incompatible polymers covalently bonded together. The balance between the enthalpic desire of the constituent polymers (i.e., the blocks) to phase separate like oil and water and their entropic desire to avoid stretching results in these systems self-assembling into a variety of useful structures with characteristic dimensions on the order of 10-100 nm. One of these structures, hexagonally closed packed cylinders, provides an ideal template for producing membranes that have a high density of pores with a single, well-defined size.

We are interested in developing a facile, scalable technique to fabricate membranes from block copolymers using a combined self-assembly and non-solvent induced phase separation (SNIPS) technique. In collaboration with the POWER Lab , which is headed by Professor Bryan Boudouris, from Purdue University, our aim is to design functional copolymers in order to fabricate nanostructured, high performance membranes with chemically tailored pore walls that enhance membrane filtration and enable advanced membrane applications, such as membrane chromatography and drug delivery.