Graphitic carbon nitride colloid as one photoinitiator for two-step polymerization

Graphitic carbon nitride (g-C3N4), as a metal-free semiconductor, has been widely investigated in energy and photoelectric fields. In recent years, its excellent capacity as visible light-driven initiator for photopolymerization has also aroused increasing interests. In this work, g-C3N4 was explored to act as the sole photoinitiator in a two-step polymerization to prepare functional hybrid hydrogel. Firstly, poly(N-isopropylacrylamide) (PNIPAM) hydrogel was facilely obtained by free radical polymerization in the presence of g-C3N4 colloid and visible light. After adsorbing aniline monomer, the oxidative polymerization took place to get polyaniline (PAN) polymer in the network of g-C3N4/PNIPAM hydrogel, and the original g-C3N4 acted as the oxidative agents in the presence of oxygen. The obtained interpenetrating double network, g-C3N4/PNIPAM/PAN hydrogel, displayed an excellent photothermal effect irradiated by near-infrared (NIR) laser and good electrical conductivity. This work presents a green method to prepare functional hybrid hydrogel avoiding usage of excessive traditional molecular initiator in radical polymerization.