Functionalized multilayer thin films for protection against acutely toxic agents

Abstract

The recently developed practice of spraying polyelectrolyte solutions onto a substrate in order to construct thin films via the Layer-by-Layer (LbL) technique has been further investigated and extended. In this process a fully automated system capable of depositing thin polymer films from atomized mists of solutions containing species of complementary functionality has been created. The versatility of the spray-assisted LbL (Spray-LbL) technology is demonstrated by depositing both weak and strong polyelectrolyte films, hydrogen bonded films, dendritic compounds and nanoparticles, broadening its range of future applications. This platform technology is then applied to generate three novel electrostatically assembled coatings for protection against a range of acutely toxic chemicals, including several chemical warfare agents and toxic industrial compounds. First, Spray-LbL is used to deposit colloidally stable titanium dioxide nanoparticles versus several traditional synthetic polycations. The resulting coatings are mechanically stable and offer selective protection when the wearer is exposed to UV radiation (e.g.sunlight); whereas the inherent water transmissive nature of the multilayers allows for much greater water vapor transport rates as compared to an inert rubber barrier material. Second, the physics of sprayed deposition are investigated to generate metal-ion doped polymeric coatings which are shown to be effective treatments for air filtration, functionalizing existing filters with the ability to strongly bind toxic industrial compounds such as ammonia or cyanide gases, as well as chemical warfare agent simulants such as chloroethyl ethyl sulfide.

(cont.) Finally, the Spray-LbL technique is used to asymmetrically functionalize electrospun materials with multiple coatings. By simply varying the flow rate of charged species passing through an electrospun material during Spray-LbL deposition, individual fibers within the matrix can be conformally functionalized for ultra-high surface area catalysis, or bridged to form a networked sublayer with complimentary properties. Exemplified here by the creation of selectively-reactive gas purification membranes, the myriad applications of this technology also include self-cleaning fabrics, water purification, and protein functionalization of scaffolds for tissue engineering.