Chemical protection fabrics via surface oximation of electrospun polyacrylonitrile fiber mats

Polyacrylonitrile (PAN) submicron fiber mats were modified to become reactive components of self-detoxifying chemical protection fabrics. Oximation of the mats with excess hydroxylamine resulted in functionalization of the fibers to form polyacrylamidoxime (PAAO). The fiber morphology remains intact after oximation, with fiber diameters ranging from 250 to 500 nm. Nucleophilic amidoxime groups enable the fiber mats to react with organophosphate pesticides or chemical warfare agents (CWA), as demonstrated using diisopropyl fluorophosphate (DFP) as a CWA simulant. The DFP decomposition kinetics were investigated using P-31 MAS NMR, which afforded measurement of the observed pseudo-first order reaction rate constant, k(obs). The values of k(obs) with PAAO-functionalized fibers exceed those of the parent PAN fibers by as much as 80-fold at a water content of 130% by weight. The observed reaction rates depend on the amount of the reactive fiber mats, yielding an apparent second-order rate constant, k(2) = 1.0 x 10(-6) s(-1) mg(-1). The hydrolytic degradation of DFP occurs only in the presence of free water, which serves as a medium to promote the nucleophilic action of the amidoxime groups in the fibers by facilitating proton transfer and stabilizing the transition state.