Influence of solvents on the formation of honeycomb films by water droplets templating

Several solvents were utilized to investigate their influence on the formation of honeycomb patterns. The polymers PPO, PLGA and PLLGA were dissolved in different solvents or mixed solvents to form porous membranes. It was found that a good compatibility between the polymers and their solvents, and an appropriate volatility of the solvent were beneficial for the formation of regular structures. Moreover, C₂HCl₃ and CH ₂Cl₂, neither of whose PPO solutions could form regular structures at 30°C, were mixed at different volume ratios to dissolve PPO and fabricate porous structures. The result showed that a regular pattern was achieved when the volume ratio of C₂HCl₃:CH ₂Cl₂ was 90:10 and that a special structure with big pores surrounded by small pores was obtained when the volume ratio of C ₂HCl₃:CH₂Cl₂ was 10:90. Based on these phenomena, possible reasons were also proposed.