The formation of honeycomb structure in polyphenylene oxide films

The ordered honeycomb polyphenylene oxide (PPO) film was prepared by casting the solution on a solid substrate in a high humid environment in this paper. It was found that PPO/CHCl₃ solution could form regular microporous film in a large range of solution concentration (2-70 g/L) and their pore size was almost equal when the concentration varied from 5 to 30 g/L. Based on these phenomena, the mechanism of the formation of PPO honeycomb film was proposed. Moreover, several solvents were chosen to investigate the influence of the compatibility between PPO and solvents, and the volatility of solvents on the pattern regularity. It was found that good compatibility between PPO and solvents, and the appropriate volatility of solvents were important for the fabrication of honeycomb structure. Finally, some other affecting factors, such as the environment temperature and the molecular weight of PPO, were also tested.