SYNTHESIS AND PROPERTIES OF POLYIMIDE CONTAINING ORTHO-LINKED UNITS AND PYRIDINE MOIETIES

A novel pyridine-containing aromatic diamine monomer, 4-[4-phenyl]-2, 6-his [4-(2-aminophenoxy)phenyl] pyridine (p, o-PAPP) was successfully synthesized respectively by nucleophilic substitution reaction, modified Chichibabin reaction and catalytic reduction with hydrazine monohydrate, 2-hydroxyacetophenone and benzaldehyde. The aromatic diamine was employed to prepare a series of pyridine-containing polyimides by polycondensation with various aromatic dianhydrides in N, N-dimethylformamide (DMF) via the conventional two-step method. The inherent viscosities of the resulting poly (amic acid) s (PAAs) and polyimides (PIs) were in the range of 0.59 similar to 0.73 and 0.52 similar to 0.63 dL/g, respectively. The structure and performance of polymers were characterized by FTIR, solubility testing,DSC, XRD, TGA, UV-Vis and fluorescence spectroscopy. The results showed that there were characteristic peaks of polyimide around 1780, 1720 and 1380 cm(-1) in the FTIR spectra. The obtained PIs exhibited high solubility in common organic solvents, such as m-cresol, DMF, N, N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP),tetrahydrofuran (THF) and chloroform (CHCl3). Meanwhile,flexible PI films were obtained,which had excellent thermal stability with the glass transition temperature (T-g) of 162.2 similar to 195. 2 degrees C and the temperature at 10% weight loss of 444.2 similar to 467.5 degrees C in nitrogen atmosphere. The protonated polymer showed UV-Vis absorption in the region 200 similar to 360 nm and displayed strong fluorescence intensity (460 nm) in THF solution.