Hydrothermal treatment: An in situ method of strengthening nanoparticle-containing layer-by-layer coatings


Zekeriyya Gemici, zgemici@mit.edu1, Hiroomi Shimomura, shimo@mit.edu2, Robert E. Cohen1, and Michael F. Rubner, rubner@mit.edu3. (1) Department of Chemical Engineering, Massachusetts Institute of Technology, 32 Vassar Street Room 13-5128, Cambridge, MA 02139, (2) Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, (3) Department of Materials Science and Engineering, MIT, 77 Massachusetts Ave, Cambridge, MA 02139
Conformal coatings can be assembled layer-by-layer (LbL), where layers of positively and negatively charged polymers, nanoparticles, or polyvalent ions can be electrostatically adsorbed on flat or textured surfaces. The LbL technique makes nanoscale control over coating morphology and chemistry possible under very simple processing conditions. Nanoparticles have been used in LbL films to achieve anti-fogging, superhydrophobic, antibacterial, anti-reflection (AR), and many other functionalities. However, lack of mechanical durability is a major barrier to commercialization. While nanoparticles can be sintered at high temperatures (>500C) to yield relatively durable coatings, the sintering process is not compatible with plastic substrates. In this work, we used hydrothermal treatments below 140C as a method of fusing silica and titania nanoparticles in situ, via a dissolution-redeposition mechanism. We demonstrate mechanical durability, mechanisms of failure, and substrate effects. Current efforts are focused on broadening choice of substrates and understanding chemical changes upon hydrothermal treatments.