{
    "protocol": "The antifog coating is prepared using a bilayer configuration. The bottom layer (primer) consists of a cross-linked network of poly(acrylate) embedded with nanosized silica for mechanical strength and adhesiveness. On top of this primer, the antifog (AF) layer is formed by incorporating a modified surface-active agent, Tween 20, covalently into the polymer host. The two layers are interlinked using UV-curing of the poly(acrylate), ensuring they are mechanically inseparable and transparent. The coating can be rinsed in water without detaching from the substrate, facilitated by the hydrophobic nature of the primer.The silica sol for the bottom layer was synthesized by mixing an appropriate amount of TEOS with 2-propanol to form a homogeneous solution. HCl (aq) with a pH of 1.2 was added to induce hydrolysis-condensation of TEOS, setting the molar ratio of H2O/TEOS to four. The mixture was stirred for 3 hours at room temperature to yield a silica sol. Then, additional HCl (aq) and MSMA were slowly added, maintaining a molar ratio of H2O/MSMA equal to 3 and TEOS/MSMA to 4.5. After another reaction for 3 hours, surface-modified silica (MSiO2) was obtained. To prepare the antifog coating, 10 g of DPHA, 0.59 g of Darocure 1173, and 17.68 g of 2-propanol were added to 20 g of the MSiO2 sol, adjusting to a total solid content of 30 wt%. The mixture was spin-coated on a PMMA substrate, prebaked at 80 °C for 40 seconds, and then UV-irradiated (250 mJ/cm²) to form a cured film of approximately 1.2 μm thickness. For the AF coating, an equal number of moles of 2-HEMA and IPDI were stirred at 50 °C, with 0.1% dibutyltin dilaurate added as a catalyst. The reaction was allowed to proceed for 2 hours, after which Tween 20 was introduced and reacted for another 2 hours. The molar ratio of IPDI/Tween 20 was set to 1, with the modified Tween 20 termed T20. The AF coating sols were formed by mixing T20 with the bottom layer sol and adjusting DPHA content to maintain 30 wt% silica. The sol was spin-coated on the pre-cured bottom layer, followed by predrying at 80 °C for 40 seconds and UV-curing at 500 mJ/cm²."
}