Novel soluble and thermally stable polyimides derived from 4-(4-diphenylphosphino)phenyl-2,6-bis(4-aminophenyl)pyridine and various aromatic dianhydrides

Abstract

4-(4-Diphenylphosphino)phenyl-2,6-bis(4-aminophenyl)pyridine, as a novel aromatic diamine, was synthesized from 4-(diphenylphosphino)benzaldehyde and 4-nitroacetophenone through two-step, Chichibabin and reduction reaction successively. A series of aromatic polyimides containing pyridine and triphenylphosphine groups were prepared from this diamine with five dianhydrides via a conventional two-step thermal imidization procedure. These resulting polyimides were amorphous and showed good solubility in common polar solvents, such as N-methyl-2-pyrrolidone and N,N-dimethylacetamide. They exhibited outstanding thermal stability with glass transition temperature of 288–380 °C, 5% weight loss temperature of 521–583, and more than 60% residue at 800 °C under nitrogen. They also showed excellent flame retardancy with limited oxygen index value of 40–45. Tough and flexible polymer films had good mechanical properties with tensile strength of 69.1–128.6 MPa, tensile modulus of 1.7–2.1 GPa, and elongation at break of 7.2–25.7%, as well as high optical transparency with the UV cutoff wavelength in the 390–410 nm range.

Graphical Abstract

Keywords:

• Aromatic polyimides
• 2,6-diphenylpyridyl units
• 4-(diphenylphosphino)phenyl pendant groups
• soluble
• heat resistant

Additional information

Funding

The financial support of this work from the National Natural Science Foundation of China (No. 51763012, 21965014), the Research Program of Jiangxi Science and Technology Department (No. 20192BBE50049), the Ground Project for Science and Technology of Jiangxi Universities (No. KJLD14022), and the Research Program of Jiangxi Province Department of Education (No. GJJ14236) is gratefully acknowledged.