From the American Chemical Society, something interesting.
A new anti-frost and anti-fog coating for glass
In an advance toward glass that remains clear under the harshest of conditions, scientists are reporting development of a new water-repellant coating that resists both fogging and frosting. Their research on the coating, which could have uses ranging from automobile windshields to camera lenses, appears in the journal ACS Nano.
Michael F. Rubner, Robert E. Cohen and colleagues point out that anti-fogging coatings that absorb water have been the focus of attention lately because of their ability to reduce light scattering and the resultant distortion caused by condensation. However, under extreme fogging conditions, these surfaces may frost and become foggy. They set out to make a better coating to withstand the aggressive conditions.
Their report describes development and testing of a new coating that rapidly absorbs water molecules that cannot freeze in the coating. At the same time, the coating has a water-repelling or hydrophobic effect to larger water droplets. The hydrophobic character means that water droplets do not spread extensively on the coating but essentially remain as flattened droplets.
The authors acknowledge funding from the Samsung Scholarship and the Materials Research Science and Engineering Centers (MRSEC) Program of the National Science Foundation.
The paper (which I had to dig up since it wasn’t included in the press release, sigh….) is here:
Zwitter-Wettability and Antifogging Coatings with Frost-Resisting Capabilities
Antifogging coatings with hydrophilic or even superhydrophilic wetting behavior have received significant attention due to their ability to reduce light scattering by film-like condensation. However, under aggressive fogging conditions, these surfaces may exhibit frost formation or excess and nonuniform water condensation, which results in poor optical performance of the coating. In this paper, we show that a zwitter-wettable surface, a surface that has the ability to rapidly absorb molecular water from the environment while simultaneously appearing hydrophobic when probed with water droplets, can be prepared by using hydrogen-bonding-assisted layer-by-layer (LbL) assembly of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). An additional step of functionalizing the nano-blended PVA/PAA multilayer with poly(ethylene glycol methyl ether) (PEG) segments produced a significantly enhanced antifog and frost-resistant behavior. The addition of the PEG segments was needed to further increase the nonfreezing water capacity of the multilayer film. The desirable high-optical quality of these thin films arises from the nanoscale control of the macromolecular complexation process that is afforded by the LbL processing scheme. An experimental protocol that not only allows for the exploration of a variety of aggressive antifogging challenges but also enables quantitative analysis of the antifogging performance via real-time monitoring of transmission levels as well as image distortion is also described.
It reminds me of this that I saw at CES 2013: