Layer-by-layer (LbL) assembly is wide-reaching conformal coating �platform� technology capable of imparting a multiplicity of functionalities on nearly any type of surface in a relatively environmentally friendly way. At its core, LbL is a solution deposition technique in which layers of cationic and anionic materials (e.g. colloidal or nano-particles, polymers and even biological molecules) are built up via electrostatic attractions in an alternating fashion, while controlling process variables such as pH, coating time, and concentration. Here we are producing nanocomposite multilayers having 10 � 96 wt% clay that are completely transparent and exhibit oxygen transmission rates below 0.005 cm3/m2�day (at a film thickness below 100 nm).  These same 'nanobrick wall' assemblies are very conformal and able to impart flame resistance to highly flammable foam and fabric by uniformly coating the complex three-dimensional geometries.  On foam, these coatings can simultaneously cut the heat release rate (HRR) in half, relative to uncoated foam, and eliminate melt dripping without adding halogenated flame retardants.  We've also developed intumescent recipes that do not require clay, but rather rely on the foaming action of phosphorus and nitrogen-rich molecules.  These 'intumescent' nanocoatings provide an effective, environmentally-benign alternative to the more toxic brominated compounds widely used today.  I'll also describe how these films can separate H2 from N2, with selectivity greater than 2000, which exceeds other commonly used gas separation membranes (including zeolites).  These films also have exceptional oxygen barrier that makes them interesting for food and flexible electronics packaging.  All of the materials described are water-based and processing occurs under ambient conditions in most cases. Our work in these areas has been featured numerous times in C&EN and also highlighted in Nature, ScienceNews, Smithsonian Magazine and various other scientific news outlets.

Polyelectrolyte multilayer nanocomposites for flame suppression, gas separation and so much more�

247th National Meeting (2014)

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