Synthesis and Control of Molecular Weight of Fluorinated Polyimide Based on 4, 4′-(Hexafluoroisopropylidene)diphthalic Anhydride

4,4′(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) was polymerized with 2, 2bis (3amino4hydroxyphenyl) hexafluoropropane (BAPAF). Fluorinated polyimide was obtained via a twostep polycondensaion procedure. The effect of reaction factors like raw materials′ ratio, imidization temperature, imidization time and catalyst on the molecular weight were studied. Polyimide was characterized by FTIR, GPC, XRD and solubility test. Results showed that polyimide of 6FDABAPAF obtained under imidization temperature (80 °C) had high molecular weight reaching 4.5×104, which displayed excellent thermal properties with Td higher than 490 °C and had excellent solubility in polar aprotic organic solvents such as NMP, DMF, DMAc, DMSO, THF and acetone.