Beyond microelectronics with 1,3,5,7-tetramethylcyclotetrasiloxane: A promising molecule for anti-fogging coatings

Over the past few years, a growing number of studies have focused on designing coatings for use in applications dealing with the fogging phenomenon such as endoscopes, automobile side view mirrors, and protective goggles. However, because of the long manufacturing times, the implementation on an industrial scale of most of the coating techniques used thus far is still a pending issue. Bearing this in mind, we report on the use of atmospheric pressure dielectric barrier discharges (AP-DBDs) operated in the presence of nitrous oxide (N2O) and 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), as a reliable coating strategy for the one-step fabrication of anti-fogging glass. An increase in either the [N2O]/[TMCTS] ratio or the dissipated power resulted in coatings with such hydrophilic groups on the surface as Si–OH, C–O, and OC–O; and a structure similar to that of SiO2. Because of their “water-loving” characteristics (WCA < 40°), coatings deposited under a [N2O]/[TMCTS] ratio ≥ 30 and a dissipated power ≥ 0.25 W cm−2 conferred a remarkable anti-fogging performance to glass samples when placed over water at 80 °C. After 30 s of exposure to water vapor at 50 °C (ASTM F 659-06), the coated glasses exhibited a light transmittance greater than that of the uncoated glass (90% vs. 55%). These results illustrate how by controlling the dissipated power and the [N2O]/[TMCTS] ratio in the plasma anti-fogging glass can readily be fabricated.