(A) OPH-PEML Schematic: Cotton substrate- white, PSS- orange, PEI- blue, OPH- pink (circles); (B) Top to bottom: OPH-PEML on cotton thread, thread woven into cloth, cloth bearing adsorbed yellow p-nitrophenol MPT degradation product after use to degrade MPT pesticide in solution. (C) Yellow p-nitrophenol degradation product in MPT solution after single treatment with OPH-PEML cotton cloth from (B).
(A) OPH-PEML Schematic: Cotton substrate- white, PSS- orange, PEI- blue, OPH- pink (circles); (B) Top to bottom: OPH-PEML on cotton thread, thread woven into cloth, cloth bearing adsorbed yellow p-nitrophenol MPT degradation product after use to degrade MPT pesticide in solution. (C) Yellow p-nitrophenol degradation product in MPT solution after single treatment with OPH-PEML cotton cloth from (B).

Polyelectrolyte multilaters (PEMLs) are conformal, elctrostatically-bonded, thin films formed by alternately treating a substrate with solutions of oppositely-charged polyelectrolytes via low cost dipcoating or spray coating methods. PEMLs exhibit nanoscale thickness and structure control perpendicular to the substrate surface via choices of polyelectrolyte and deposition conditions (pH, ionic, strength, or temperature). The Naval Research laboratory is investigating hybrid PEMLs, prepared by partial substitution of polyelectrolyte layers by other charged species (e.g., enzymes or coloids), for Navy and Marine Corps applications. For example, Fig. 1A shows a schematic for a hybrid PEML in which anionic organophos-phorous hydrolase (OPH) enzyme and polystyrenesulfonate (PSS) are paired with cationic polyethylenimine (PEI) layers for degradation of and protection against organophosphorous pesticides or nerve agents. OPH PEMLs deposited on woven cotton cloth (Fig. 1B) readily degrade methylparathion (MPT) pesticide in solution (Fig. 1C), with active OPH lifetimes > 3 weeks during intermittent use (1). In contrast, OPH PEMLs deposited onto poly-β-cyclodextrin beads continuously exposed to MPT solution completely degrade MPT during > 6 months. Current efforts are focused on understanding the effects of deposition conditions and polyelectrolyte chemistry on PEML properties, such as internal structure and porosity (s), as prerequisites for improving their utility in this application as well as others, such as advanced sensors/optical materials (3) and fuel cells (4).