Synthesis and characterization of novel soluble pyridine-containing polyimides based on 4-phenyl-2, 6-bis[4-(4-aminophenoxy)phenyl]-pyridine and various aromatic dianhydrides

摘要

Anew kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[4-(4-aminophenoxy)phenyl]pyridine (PAPP), was successfully synthesized by a modified chichibabin reaction of benzaldehyde and a substituted acetophenone, 4-(4-nitrophenoxy)-acetophenone (NPAP), followed by a reduction of the resulting dinitro compound 4-phenyl-2,6-bis[4-(4-nitrophenoxy)phenyl]-pyridine (PNPP) with Pd/C and hydrazine monohydrate. The aromatic dian-Line was employed to synthesize a series of new pyridine-containing polyimides by polycondensation with various aromatic dianhydrides in N-methy-2-pyrrohdone (NMP) via the conventional two-step method, i.e., ring-opening polycondensation forming the poly (amic acid)s and further thermal or chemical imidization forming polyimides. The inherent viscosities of the resulting polyimides were in the range of 0.79-1.13 dL/g, and most of them were soluble in common organic solvents such as N,N-dimethylacetamide (DMAc), NMP, and tetrahydrofuran (THT), etc. Meanwhile, strong and flexible polyimide films were obtained, which had good thermal stability, with the glass transition temperatures (T-g) of 268-338 degrees C and the temperature at 5% weight loss of 521-548 degrees C in air atmosphere, as well as outstanding mechanical properties with tensile strengths of 89.2-112.1 MPa and elongations at break of 9.5-15.4%. The polyimides also were found to possess low dielectric constants ranging from 2.53 to 3.11. (c) 2007 Wiley Periodicals, Inc.