Let a Hundred Polymers Bloom: Tunable Wetting of Photografted Polymer-Carbon Nitride Surfaces

Sunlight is widely used by plants to produce chemical energy fundamental for all life, a process that also serves as an inspiration for science. Recently, light-harvesting semiconductor materials, here, carbon nitrides, have been widely used in photochemistry to catalyze reactions under visible light illumination. We exploited photoactive carbon nitride thin films as a metal-free platform for one-step photografting from polymers on the surface. Here, we observe photoswitchable wetting properties of polystyrene-grafted carbon nitride, which are independent of any classical photoswitchable groups. Dense and thick polymer brush formation with a tunable thickness (up to 700 nm) was obtained, allowing for tailor surface properties. Furthermore, exploiting the reciprocal insolubility of water–dimethylacrylamide and pentane–styrene solutions, we provide a general method for the synthesis of centimeter-scale carbon nitride-based Janus asymmetric films. It is thought that the simple experimental design based on cheap and common chemicals provides a novel dimension of carbon nitride materials with advanced surface properties.