Zwitterionic polymer brush grafting on anodic aluminum oxide membranes by surface-initiated atom transfer radical polymerization

Abstract

A feasible processing of zwitterionic polymer-grafted anodic aluminum oxide (AAO) membranes by surface-initiated atom transfer radical polymerization (SI-ATRP) and the geometric effect on the polymer chain growth in the confined nanopores were investigated. A zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate) (PMAPS) brush was produced on an AAO membrane via introduction of an initiator with a phosphonate group and subsequent SI-ATRP. The PMAPS-grafted AAO membranes were characterized by water droplet contact angle measurement, size exclusion chromatography (SEC), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and laser Raman micro-spectroscopy. The linear relationship between the grafting yield (Y) of the PMAPS brush and number-average molecular weight (M-n) of the unbound PMAPS indicates that there is no significant geometric effect on the chain growth under the spatial confinement inside the nanopores with diameters of similar to 200 nm. The PMAPS brushes were diminished near the center section along the nanopores because the monomer supply was retarded. The capability of the PMAPS-grafted AAO membranes for inorganic nanoparticle immobilization was also demonstrated using gold nanoparticles (AuNPs) through ion-exchange and reduction processes.