Degradation of Chemical Threats by Brominated Polymer Networks

Poly(N-bromomaleimide) (PMAi-Br), poly(N-vinylpyrrolidone)-bromine adducts (PVPBr), and poly(ethylene-alt-N-bromomaleimide) (PEMAi-Br) and their cross-linked networks are introduced as reactive, self-decontaminating components of protective barriers. Synthetic routes toward polymaleimides include free-radical copolymerization of maleimide with divinyl cross-linkers as well as amidation of poly(ethylene-alt-maleic anhydride) with urea. The polymers are brominated by bromine in carbon tetrachloride or by copper(II) bromide in dimethylformamide, with the active bromine contents up to and above 4 mequiv/g, or >30 wt %. The brominated polymer networks exhibit considerable swelling in water and possess reversible redox peak potentials in cyclic voltammetry experiments due to the redox reactions of the bromine present in the polymer structures. In acidic aqueous media, PVPBr, PMAi-co-DVB-Br, and PEMAi-Br materials are able to degrade 100% of hydrazine, monomethylhydrazine, and 1,1-dimethylhydrazine down to concentrations below detectable levels of 0.150.25 mM. The hydrazine is converted to nitrogen gas. The insecticide malathion, tested as a simulant of a combat warfare agent VX, is efficiently and selectively oxidized to malaoxon in the presence of the brominated networks, whereas 2-(chloroethyl)ethyl sulfide (CEES), a simulant of the sulfur mustard agent, is rapidly oxidized, in both vapor and liquid states, into its less-toxic sulfone derivative, 1-chloro-2-(ethylsulfinyl)ethane (CEESO), with the only side product being 1,2-bis(ethylthio)ethane. The oxidation of CEES is proven to be selective, in that no toxic overoxidized CEES analogue, 1-chloro-2-(ethylsulfonyl)ethane, is formed. The developed brominated polymer networks are versatile materials with potential applications in coatings, filters, fabrics, and sorbents.