title: Nucleophilic Polymers and Gels in Hydrolytic Degradation of Chemical Warfare Agents.
abstract: Water- and solvent-soluble polymeric materials based on polyalkylamines modified with nucleophilic groups are introduced as catalysts of chemical warfare agent (CWA) hydrolysis. A comparative study conducted at constant pH and based on the criteria of the synthetic route simplicity, aqueous solubility, and rate of hydrolysis of CWA mimic, diisopropylfluorophosphate (DFP), indicated that 4-aminopyridine-substituted polyallylamine (PAAm-APy) and polyvinylamine substituted with 4-aminopyridine (PVAm-APy) were advantageous over 4-pyridinealdoxime-modified PVAm and PAAm, poly(butadiene-co-pyrrolidinopyridine), and PAAm modified with bipyridine and its complex with Cu(II). The synthesis of PVAm-APy and PAAm-APy involved generation of a betaine derivative of acrylamide and its covalent attachment onto the polyalkylamine chain followed by basic hydrolysis. Hydrogel particles of PAAm-APy and PVAm-APy cross-linked by epichlorohydrin exhibited pH-dependent swelling and ionization patterns that affected the rate constants of DFP nucleophilic hydrolysis. Deprotonation of the aminopyridine and amine groups increased the rates of the nucleophilic hydrolysis. The second-order rate of nucleophilic hydrolysis was 5.5- to 10-fold higher with the nucleophile-modified gels compared to those obtained by cross-linking of unmodified PAAm, throughout the pH range. Testing of VX and soman (GD) was conducted in 2.5-3.7 wt % PVAm-APy suspensions or gels swollen in water or DMSO/water mixtures. The half-lives of GD in aqueous PVAm-APy were 12 and 770 min at pH 8.5 and 5, respectively. Addition of VX into 3.5-3.7 wt % suspensions of PVAm-APy in DMSO-d6 and D2O at initial VX concentration of 0.2 vol % resulted in 100% VX degradation in less than 20 min. The unmodified PVAm and PAAm were 2 orders of magnitude less active than PVAm-APy and PAAm-APy, with VX half-lives in the range of 24 h. Furthermore, the PVAm-APy and PAAm-APy gels facilitated the dehydrochlorination reaction of sulfur mustard (HD) and its analogue 2-chloroethyl ethylsulfide (CEES). The ability of the reported aminopyridine-modified polyalkylamine materials to degrade the most persistent of CWAs, coupled with aqueous solubility, and the presence of numerous amino groups that provide convenient "handles" for covalent attachment on polymeric and inorganic supports yields promise for applications such as protective fabric and textile treatment and components of decontaminating materials.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Lev
authors.initials: L
authors.lastname: Bromberg
authors.affiliation: Leidos Corp. , P.O. Box 68, Gunpowder, Maryland 21010, United States.
authors.forename: William R
authors.initials: WR
authors.lastname: Creasy
authors.affiliation: Analytical Toxicology Branch, R&T Directorate, U.S. Army Edgewood Chemical and Biological Center , Aberdeen Proving Ground, Maryland 21010, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: McGarvey
authors.affiliation: Materials Science and Engineering Branch, U.S. Army Natick Soldier Research, Development & Engineering Center , Natick, Massachusetts 01760, United States.
authors.forename: Eugene
authors.initials: E
authors.lastname: Wilusz
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: T Alan
authors.initials: TA
authors.lastname: Hatton
keywords: HD; VX; chemical warfare agents; hydrogels; nucleophilic polymers; polyallylamine; polyvinylamine; self-decontaminating fabrics