Synthesis and characterization of bisphthalonitrile-terminated polyimide precursors with unique advantages in processing and adhesive properties

The realization of the synthesis of melt-processable high-performance polyimide resin is of great interest. Herein, we prepared a new class of bisphthalonitrile functional bisimides used for polyimide precursors through 4,4'-bisphenol A dianhydride (BPADA) and various dicyanoammatic monoamines, which were synthesized from aminophenols with 4-nitrophthalonitrile via a nucleophilic substitution reaction. Their structures were confirmed by FTIR, H-1 and C-13 NMR, and WXRD analyses. The obtained polyimide precursors exhibited much lower melt temperature and good solubility in diverse solvents compared to traditional ones. These cured resins based on curing accelerator 4,4'-diaminodiphenylsulfone (DDS) achieved high glass transition temperature values (T-g) between 261 and 287 degrees C and char yields above 63 wt%, depending on their backbone structures. Additionally, the lap shear strengths (LSS) were in the range of 15.4-24.4 MPa at 25 degrees C and the highest strength at 300 degrees C was observed in para-linked prepolymers derived from 4-amino-3,5-xylenol, suggesting such resin could be potentially applied as high temperature structural adhesives.

Automated summary

The synthesized polyimide precursors demonstrated lower melt temperature and good solubility, while the cured resins based on curing accelerator achieved high glass transition temperature and char yields. The para-linked prepolymers derived from 4-amino-3,5-xylenol showed the highest lap shear strength at 300 degrees C, indicating potential application as high temperature structural adhesives.