Synthesis and characterization of viologen-containing poly(vinylidene fluoride) redox-sensitive membranes

Thermally induced graft co-polymerization of 4-vinylbenzyl chloride (VBC) with ozone-preactivated poly(vinylidene fluoride) (PVDF) was carried out in N-methyl-2-pyrrolidone solution to produce VBC-gPVDF co-polymers. The resulting VBC-g-PVDF co-polymers with different VBC graft concentrations were cast into microfiltration membranes by phase inversion. Viologen moieties were introduced by the diquaternization of 4,4'-bipyridine with the VBC-g-PVDF membranes and VBC through a two-step reaction in ethanol. The viologen-containing membranes were characterized by x-ray photoelectron spectroscopy, elemental analysis, and thermogravimetric analysis. Surface morphology was studied by scanning electron microscopy. It was demonstrated that the permeability of the viologen-containing membrane can be regulated by redox reactions. This technique of fabricating viologen-containing membranes represents a relatively simple and effective approach for achieving membranes with redox-sensitive permeation properties. Copyright (C) 2004 John Wiley Sons, Ltd.