{
    "protocol": "The antifog coating is prepared using a bilayer configuration. The bottom layer (primer) is created by forming a cross-linked network of poly(acrylate) embedded with nanosized silica to provide mechanical strength and adhesiveness. The top layer, an antifog (AF) layer, has a surface active agent, Tween 20, that is modified and covalently incorporated into the polymer host. The two layers are interlinked by UV-cured poly(acrylate), making them mechanically inseparable while maintaining a uniform transparent appearance. The coating is designed to withstand rinsing in water and remain intact after drying, due to the hydrophobic feature of the primer, which prevents water penetration and detachment from the substrate.To synthesize hydrophilic polymers with functional groups, follow these steps: First, prepare the coating sol for the antifog (AF) layer by modifying hydrophilic agents. Stir equal moles of 2-hydroxyethyl methacrylate (2-HEMA) and isophorone diisocyanate (IPDI) in a glass reactor under temperature control. When the temperature reaches 50 °C, add dibutyltin dilaurate (0.1% of the total weight of 2-HEMA and IPDI) as the catalyst and allow the reaction to proceed for 2 hours at this temperature. Next, add the hydrophilic agent (Tween 20) and react for another 2 hours. The molar ratio of IPDI to Tween 20 should be set to 1. This produces a modified hydrophilic agent referred to as T20. Subsequently, prepare the AF coating sols by mixing T20 with the coating sol for the bottom layer, adjusting the dipentaerythritol hexaacrylate (DPHA) content to ensure 30 wt% silica in the sol. Finally, spin-coat this sol on a partly cured bottom layer, predry at 80 °C for 40 seconds, and UV-cure at 500 mJ/cm² to obtain an AF layer approximately 1 μm thick."
}