From glasses that people wear to camera lenses to car windshields, transparent materials have been used in all aspects of life, and these transparent materials that are widely used in life are always facing the problem of easy fogging. For example, when we wear masks, it is easy to cause spectacles to fog when we breathe, blocking our vision.
Nowadays, there are many anti-fogging strategies for transparent materials. The most common one is to apply a hydrophilic coating treatment on the surface of the transparent lens, so that the water condensed on the transparent coating forms a water film instead of water droplets, thereby preventing fogging. effect. However, the high surface energy of the hydrophilic treated lens causes its antifouling performance to decrease. In order to ensure that the transparent material has anti-fogging and dirt resistance properties, some researchers have covered a layer of hydrophobic nanomaterials on the hydrophilic coating, and water molecules can pass through the hydrophobic nanolayer and be absorbed by the hydrophilic coating. To ensure that the surface does not fog, and the hydrophobic nano layer can play an anti-fouling effect. Although this method works well, the anti-fog function will fail when the hydrophilic coating reaches saturation.
Recently, Pohang University of Science and Technology (Pohang University of Science and Technology) Hyomin Lee team developed a new type of water-absorbing super-hydrophobic composite coating. It is composed of a hydrophilic polymer composite material substrate and a hydrophobic polymer material columnar array. The base material uses chitosan and carboxymethyl cellulose, and there is a strong electrostatic attraction between the two materials, which makes the base material tightly bound. In addition, chitosan and carboxymethyl cellulose have good hydrophilicity and can be used as water-absorbing materials for coatings.
For water-absorbing polymer substrates, the thicker the thickness, the better the anti-fog performance. However, the thicker the polymer substrate, the worse the light transmittance. Therefore, in order to balance transparency and anti-fog performance, the thickness of the polymer substrate is controlled at 1793 nm. Since the refractive index of the silica nanoparticle layer is lower than the refractive index of the polymer coating, a layer of silica nanoparticle layer is coated on the polymer substrate to effectively improve the anti-reflectivity of the polymer coating.
In addition, a template method is used to connect an array of fluorine-containing polyether materials on the surface of the polymer/nano-silica coating, so that the coating forms a hydrophobic surface. The nano-silica layer ensures that the fluorine-containing polyether nano-pillars are tightly combined with the base coating, and the distributed nano-array of fluorine-containing materials makes the composite coating more hydrophobic. In the process of condensation of water vapor on the surface of the coating, the columnar nano-array will not prevent the substrate material from absorbing water vapor. Thus, while ensuring the hydrophobic surface, the base material can smoothly absorb water vapor to ensure that there is no condensation on the coating surface. Due to the self-lubricating effect of the fluorine-containing material, the columnar array can also play a role of scratch resistance. The polymer/silica coating that is thickened with sandpaper and is not connected to the columnar fluorine-containing polyether material array has obvious scratches.
