Porous polyimide(PI) microspheres were prepared using carbon disulfide and ethyl ether as porogens.Porous PI microspheres derived from pyromellitic dianhydride(PMDA) and 4

4'-diaminodiphenyl ether(ODA) were carried out in a non-aqueous emulsion system

in which liquid paraffin was the continuous phase and N

N-dimethylformamide(DMF) was the dispersed phase.The morphologies and chemical structures of the PI porous microspheres were characterized by scanning electron microscopy

quantum chemical simulation

infrared absorption spectroscopy

mercury porosimetry and thermal gravimetric analysis.The results indicated that the morphology of microspheres is good

when carbon disulfide or methanol is used as porogen.However

if carbon disulfide is used as porogen

the number of microsphere pores is small.If methanol is used as porogen

clear pore and porous PI microspheres can be obtained.Hydrogen bonding interaction existing between polyamic acid and ethyl ether plays a critical role in the pore formation process.The pore morphology is mainly controlled through keeping the consistency of curing rate and the evaporation rate.The best porogenic conditions:the temperature of system was 20 ℃

the monomer concentration was 10%

drop speed of pyridine/acetic anhydride was 0.5 s/drop.The specific surface of the porous microspheres is increased with increasing the ratio of ethyl ether/liquid paraffin

which can reach 29.38 m2/g determined with mercury porosimetry.The average particle diameter is about 20~30 m.The resulting samples possess good thermal stability with a decomposition onset temperature of about 517 ℃.