Synthesis and characterization of novel polyimides derived from 4,4’-bis(5-amino-2-pyridinoxy)benzophenone: effect of pyridine and ketone units in the main

A diamine monomer, 4,4'-bis(5-amino-2-pyridinoxy)benzophenone, was designed and synthesized, and used to react with commercially different kinds of aromatic dianhydrides to prepare a series of polyimides containing pyridine and ketone units via the classical two-step procedure. Glass transition temperatures (Tg) of the resultant polyimides PI-(1-5) derived from 4,4'-bis(5-amino-2-pyridinoxy) benzophenone with various dianhydrides ranged from 201 to 310 °C measured by differential scanning calorimetry. The temperatures for 5%wt loss of the resultant polyimides in nitrogen atmosphere obtained from the thermogravimetric analysis curves fell in the range of 472-501 °C. The temperatures for 10%wt loss of the resultant polyimides in nitrogen atmosphere fell in the range of 491-537 °C. Meanwhile, the char yields at 800 °C were in the range of 55.3-60.8%. Moreover, the moisture absorption of polyimide films was measured in the range of 0.37-2.09%. The thin films showed outstanding mechanical properties with tensile strengths of 103-145 MPa, an elongation at break of 12.9-15.2%, and a tensile modulus of 1.20-1.88 Gpa, respectively. The coefficients of thermal expansion of the resultant polyimides were obtained among 26-62 ppm °C-1. To sum up, this series of polyimides had a good combination of properties applied for high-performance materials and showed promising potential applications in the fields of optoelectronic devices.