Wednesday February 3rd 4:00 PM (CET)
Title: Sustainable Membrane Production through Polyelectrolyte Complexation Induced Aqueous Phase Separation
Presenter: Muhammad Irshad Baig
Affiliation: Membrane Surface Science, University of Twente, The Netherlands
Nonsolvent induced phase separation (NIPS) is the most common approach to produce polymeric membranes. Unfortunately, NIPS relies heavily on aprotic organic solvents like N‐
methyl‐pyrrolidone to produce the membranes. These solvents are unsustainable, repro‐toxic for humans and have therefore been restricted within the European Union [1]. A new and sustainable method, aqueous phase separation (APS), is presented that eliminates the use of organic solvents. Polymeric membranes can be prepared entirely in water using this new APS method. A homogeneous solution of two polyelectrolytes, the strong polyanion poly(sodium 4‐styrenesulfonate) (PSS) and the weak polycation poly(allylamine hydrochloride) (PAH), is prepared at high pH, where PAH is uncharged. Immersing a film of this solution in a low pH bath charges the PAH and results in the formation of a porous, water-insoluble polyelectrolyte complex. The rate of precipitation can be controlled by a number of parameters for instance, polyelectrolyte solution concentration and pH of the bath. The pore sizes can be tuned from micrometers to just a few nanometers, and even to dense films, simply by tuning the
polyelectrolyte concentrations, molecular weights, and the salinity of the bath. This leads to excellent examples of microfiltration, ultrafiltration, and nanofiltration type membranes.
Similarly, using different types of polyelectrolytes it is possible to produce polymeric membranes in mild pH conditions. A mixture of PSS and Polyethyleneimine (PEI) can be cast at pH 4 to obtain dense nanofiltration type membranes with molecular weight cut-off ~200 g·mol–1. Polyelectrolyte complexation induced APS is indeed a viable and sustainable approach to membrane production that provides excellent control over membrane properties and even allows new types of separations.