Synthesis and characterization of a polyimide containing phenolphthalein groups

A polyimide containing phthalein groups and hydroxyl side-groups was synthesized. In the synthesis, a new diamine monomer containing phenolphthalein group was prepared by nitrification of phenolphthalein and followed with further reduction. The polyimide was obtained by polycondensation of the diamine monomer with 4, 4'-hexafluoroisopropylidinedi (phtalic anhydride) (6FDA) and subsequent high temperature imidization step. The chemical structure of the monomer and polyimide was characterized by ¹H-NMR and FTIR. GPC test gives the molecular weight (M _n) and polydispersity of the polyimide of 15500 and 2. 47, respectively. The polyimide shows no obvious T in the range of 100 ∼ 350°C and a T _d of 388°C with 2. 5% mass loss by thermal analysis (DSC and TGA). The polymer has good solubility in some aprotic polar organic solvents such as DMF, DMAc, etc. but is insoluble in weak polar organic solvents such as toluene. The UV-Vis transmittance and absorbance spectra show that the polyimide possesses good optically transparency in the visible region. For its aromatic hydroxyl side-groups containing structure, the polyimide can be further used as a precursor of high performance functional materials.