Polyzwitterion based multilayers for low fouling and stimulus responsive membranes
Joris de Grooth, Wiebe M. de Vos, Kitty Nijmeijer
Membrane Science and Technology, Mesa+ Institute for Nanotechnology, University of Twente, The Netherlands
In this talk, we will demonstrate the role that polyzwitterions - polymers with both positive and negative charges on the same monomer - can play in membrane filtration. Zwitterionic moieties are known to have some specific properties, such as anti-fouling behavior and ionic strength responsiveness. We will show that also membranes, which are coated with multilayers of such polyzwitterions, are low fouling and stimulus responsive.
For the formation of these zwitterionic polymers on the membrane used the simple principle to make polyelectrolytes multilayers (PEMs)from aqueous solutions. These PEMs are prepared in a layer-by-layer fashion, in other words, we sequentially coated the membrane with a positively and a negatively charged polyelectrolyte. For these PEMs, the properties are determined by the type of polyelectrolyte and the conditions (e.g. pH, presence and type of salt) under which the layer is prepared. The suitability of this technique to improve the membrane performance with “classic” polycations and -anions will be shown. The described system becomes even more powerful when, using the same layer-by-layer approach, and incorporating zwitterionic (co-)polymers into the membrane coating. Selecting the appropriate coating conditions, allows us to get stable zwitterionic layers on the membrane. Depending on the specific layer composition, we can tailor the membrane permeation and retention behavior.
The strength of this work is that we transfer the knowledge of the layer growth obtained from spectroscopic techniques (e.g. Reflectometry) to actual membranes. We demonstrate that by carefully selecting preparation conditions for a multilayer, we can tune the system to successfully modify membranes on lab scale in terms of flux and retention, but even on a larger pilot scales (even containing >10 km of coated fibers).