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, metal ions, 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. Using this technique, films having precise optical, electrical, biomedical, flammability, antimicrobial, and barrier properties have been demonstrated to date.
At the Polymer NanoComposites (PNC) Laboratory at Texas A&M we are producing nanocomposite films 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 “nano brick 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. In the case of cotton fabric, each 10 m fiber is individually coated to create a nano brick wall shield. 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. I’ll also describe how the LbL process can produce carbon nanotube films with low sheet resistance (< 100 /sq) and visible light transmission above 85%. 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 several times in Chemical & Engineering News as well as highlighted in Nature, ScienceNews and various other scientific news outlets.
Dr. Jaime Grunlan joined Texas A&M University as an Assistant Professor of Mechanical Engineering in July of 2004, after spending three years at the Avery Research Center in Pasadena, CA as a Senior Research Engineer. He obtained a B.S. in Chemistry, with a Polymers & Coatings emphasis, from North Dakota State University and a Ph.D. from the University of Minnesota in Materials Science and Engineering. Prof. Grunlan was promoted to Associate Professor in September 2010 and more recently appointed the Gulf Oil/Thomas A. Dietz Career Development Professor I. His current research interests lie in both the development of multifunctional thin films (< 1 m) using layer-by-layer assembly and the study of thermoelectric thick film nanocomposites (> 10 m). He won the NSF CAREER and 3M Untenured Faculty awards in 2007, the Dow 2009 Young Faculty Award, the 2010 Carl A. Dahlquist Award, and the 2012 L.E. Scriven Young Investigator Award, sponsored by the ISCST, for his work in these areas. Dr. Grunlan also holds a joint appointment in Chemical Engineering and serves on the Executive Committee for Texas A&M’s Materials Science and Engineering Program.