Controlling the polymer-nanolayer architecture on anion-exchange membrane adsorbers via surface-initiated atom transfer radical polymerization

The immobilization of a polymer-nanolayer containing ligand sites is a widely used approach to increase the binding capacity of membrane adsorbers. In this work strong anion-exchange membrane adsorbers were produced via surface-initiated atom transfer radical polymerization (SI-ATRP) using a monomer bearing a quaternary amine group (Q-type). Additionally the architecture of the polymer-nanolayer has been controlled with respect to the length and density of the grafted polymer chains and in terms of ligand density and interchain crosslinking degree. The influence of these architecture parameters on the membrane permeability and the static binding capacity towards bovine serum albumin (BSA) as a model protein has been investigated. It could be shown that these parameters have a major impact on the performance of the produced membrane adsorbers. While the chain-length and -density significantly increase the binding capacity, a decrease in permeability is observed. The interchain crosslinking degree and a reduction of the ligand density increase the permeability, but simultaneously the static binding capacity is slightly diminished. A well-chosen combination of these architecture parameters can produce membrane adsorbers with static binding capacities > 100 mg/mL membrane volume (MV) while still maintaining a specific permeability > 40 mL/(min·cm2·bar), far superior to commercially available products.