Summary: 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 CH2Cl2, 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:CH2Cl2 was 90:10 and that a special structure with big pores surrounded by small pores was obtained when the volume ratio of C2HCl3:CH2Cl2 was 10:90. Based on these phenomena, possible reasons were also proposed. magnified image

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