Thermally Superstable Cellulosic-Nanorod-Reinforced Transparent Substrates Featuring Microscale Surface Patterns

The recent rapid expansion of thin-film, bendable, and wearable consumer (opto)electronics demands flexible and transparent substrates other than glass. Plastics are the traditional choice, but they require amelioration because of their thermal instability. Here, we report the successful conversion of a soft and thermally vulnerable polymer into a highly thermally stable transparent nanocomposite material. This is achieved by the meticulous choice of a polymer with a glass-transition temperature below 0 °C that gives stable mechanics above room temperature, reinforcing the polymer with a load-bearing hierarchical network of the incredibly strong and stable natural material: cellulose nanorods. Owing to the Pickering emulsification process, the nanocomposites inherit the self-assembled structural hierarchy from the cellulose nanorod-encapsulated resin droplets. The ameliorated nanocomposites have highly desirable high-temperature endurance (∼150-180 °C) in terms of the thermomechanical, thermodimensional, and thermo-optical performance. Any photonic nano- or microstructures can be directly molded on the surface of the nanocomposites in high precision for better light management in photonic and opto-electronic applications. The highlight of this work is the demonstration of a highly thermally stable microlens array on the ameliorated transparent nanocomposite.