One-Step Preparation of a High-Performance Waterborne Polymer Coating via Spontaneous Uniform Distribution of Nanofillers

Large-scale fabrication of waterborne coatings with high barrier properties is essential for the future development of paper packages. This can be achieved by incorporating a high content of well-distributed inorganic fillers into polymer coatings; however, it requires complex processing and is challenging for industrial applications. Here, we report a scalable one-step fabrication method of waterborne barrier coating with 60 wt % of finntalc and mica fillers. The resultant 10 μm thick coating reduces the water vapor transmission rate (WVTR) of paper substrate by a factor of ∼37 to 8.8 g m^-2 day^-1 at 38 °C and 90% relative humidity (RH), substantially outperforming the current industrial benchmark. Advanced characterization methods including cryogenic transmission electron microscopy (cryo-TEM) and focused ion beam-scanning electron (FIB-SEM) tomography indicated spontaneous formation of a layered filler structure in the coating, where the dimethylethanolamine dispersant played a crucial role in preventing the restacking of the fillers. The method benefits the industrial fabrication of high-performance waterborne coatings.