Surface modification of polypropylene macroporous membrane by marrying RAFT polymerization with click chemistry

The grafting-to approach is experimentally simple and can provide better control of the grafted polymer, but it usually suffers from a lower grafting density. In the present work, a novel three-step method for polyacrylamide grafting-to the polypropylene macroporous membrane was carried out by marrying click chemistry with reversible addition-fragmentation chain transfer radical polymerization. First, the membrane was brominated via a gas phase free radical photochemical pathway, followed by SN2 nucleophilic exchange of bromine atoms in the brominated membrane with azide groups in NaN3; second, alkyne-terminated polyacrylamide with determined structure was synthesized by using reversible addition-fragmentation transfer radical polymerization method; third, alkyne-terminated polyacrylamide was coupled onto the azide-functionalized membrane surface by the CuI-catalyzed azide–alkyne cycloaddition click reaction. The permeation performances of the modified membranes were tested by the filtration of a protein dispersion. The protein filtration experiments show that, in comparison with the unmodified membrane, the modified membrane can effectively reject proteins due to the densely grafted polymer chains.