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 S(N)2 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 Cu-I-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. (C) 2012 Elsevier B.V. All rights reserved.