The analysis employed a polymer named poly methyl methacrylate (PMMA), which is greatly used as a substitute for glass. Generically called acrylic, and traded under trademarks like Lucite and Plexiglas, this material can be brittle and is far less resistant to scratching as compared to glass.
Former researchers added silica particles quantifying just nanometers across to PMMA, developing a polymer-particle nano-composite having much greater strength. But for the first time, this team has discovered a way to analyze the particle-polymer interactions of similar coatings at the nanoscale, which could help in finding improved coatings. Meng Qu, a postdoc in MIT’s Department of Materials Science and Engineering, along with Associate Professor of Materials Science and Engineering Krystyn Van Vliet and various researchers at DuPont Nanocomposite Technologies in Delaware executed this analysis. The work was partially financed by the DuPont-MIT Alliance.
Silica particles were employed for the coating as they are transparent, so the finished material maintains its transparency. To overcome the problem of incompatibility between silica and acrylic, the silica was treated with other “functional groups” of molecules, altering its surface chemistry so that it spreads evenly on the polymer surface. Afterwards, the researchers heated the polymer to soften it a little, and employed an atomic force microscope to observe the particles as they gradually sank into the surface, permitting the MIT team to see how fast the particles sink in and learn exactly how they interact with the polymer. The ensuing data enabled the team to work out the optimal coating materials and particle densities for toning up the polymer surface, forming possible stronger window substitutes. The work could also result in spray-on scratch-resistant coating for all things from cars to cellphones, Qu says. “Any surface that needs coating is potentially a candidate for such a treatments. We demonstrated that putting a small amount of particles on the surface increases the stiffness.”
The work could revolutionize many current uses of PMMA, such as the windows in aquarium tanks. Currently, these windows are made very thick to defy the enormous water pressure in large tanks. But if the material is tougher, the windows could be built thinner and lighter, and thus less expensive.
