Films Containing Nanostructures and/or Reactive Scavengers

Overview

The document presents a final technical report on a research project focused on developing reactive nanoengineered coatings, aimed at significantly reducing the permeability of barrier films, such as those used in paints and packaging. Conducted by Professor Edward L. Cussler and his team at the University of Minnesota, the project was funded by the Air Force Office of Scientific Research and spanned from November 2006 to October 2007.

The research employed two primary strategies to achieve a permeability reduction of up to 10,000 times compared to existing materials. The first strategy involved the incorporation of aligned impermeable flakes into the film, which reduced both the permeability and the lag time (the time before significant penetration occurs) by approximately a factor of 50. The second strategy utilized sacrificial reagents that, while not affecting the steady-state permeability, increased the lag time by a factor of 1000 or more. This combination of strategies effectively met the project's original goals.

The report details the scientific principles behind these strategies, explaining how the addition of impermeable flakes forces solutes to navigate a tortuous path, thereby delaying their penetration. The sacrificial reagents consume diffusing solutes before they can cross the membrane, further enhancing the barrier's effectiveness. The research also highlights the importance of characterizing barrier films by their lag time and leak rate, with findings exemplified through studies on the diffusion of chlorinated hydrocarbons across polyethylene films.

Additionally, the report discusses the use of block copolymers to create self-assembled aligned flakes, allowing for the development of flexible yet low-permeability materials. The project also explored the potential of nanoparticles, such as zero valent iron, to enhance the lag time in barrier films.

Future work is suggested to extend these findings to other systems, aiming to test different polymers and solvents for ultrafiltration membranes. Although the grant has expired, the researchers express a commitment to continue their experiments and share their successes.

Overall, the document encapsulates a significant advancement in material science, with implications for environmental protection, particularly in applications like landfill barriers and water purification. The innovative approaches outlined in the report could lead to the development of more effective and sustainable barrier materials.