Poly(N-vinylguanidine): Characterization, and catalytic and bactericidal properties

Abstract

Poly(N-vinylguanidine) (PVG) is one of the simplest guanidine-bearing polyelectrolytes, but is virtually unknown in the scientific literature. An efficient synthetic route for poly(N-vinylguanidine) (PVG) is described that involves free-radical polymerization of N-vinylformamide (NVF) followed by basic hydrolysis of the PNVF and guanidinylation of the resulting polyvinylamine (PVAm). The molecular weights can be varied by altering the initial NVF/azo initiator ratio. Characterization of the PVG by 1H and 13C NMR, FTIR and FT-Raman spectroscopy methods supports the PVG structure. The PVG possesses an average pKa of 13.4 and is an active hydrolyzing species for diisopropyl fluorophosphate (DFP), an organophosphate mimic for combat nerve agents. The second-order rate constant of the DFP hydrolysis by PVG at pH 7.8 and 25°C was measured to be 3.9×10−3M−1s−1, expressed per concentration of the catalytic amino or imino moieties in each PVG monomer. The hydrolysis occurs via the general SN2 mechanism of base catalysis. The guanidinylation of PVAm affords PVG with 10- to 40-fold lower minimum inhibition concentration (MIC) when tested against four Gram-positive and four Gram-negative bacteria relative to the PVAm itself. Hence, the PVG is effective both as a hydrolyzing agent against toxic organophosphates and as a bactericide, thus exhibiting potential as a material for use in chemical and biological defense as well as a disinfectant in clinical and industrial applications.