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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. [ABSTRACT FROM PUBLISHER]

A novel heterocyclic diamine monomer based on pyrimidine ring, 2,4-bis(4-aminophenoxy)pyrimidine, was successfully synthesized. The obtained heterocyclic diamine was fully characterized and employed to synthesize a series of polyimides (PIs) by polycondensation with commercially available aromatic dianhydrides via the conventional two-step method. The effects of the pyrimidine rings into the main chain of the PIs were evaluated through the study of their solubility, thermal, mechanical, and optical properties. The inherent viscosities of the resulting poly(amic acid)s were in the range of 0.58–1.45 dL g−1. Meanwhile, the PIs had good thermal stability with the 5% weight loss temperatures of 445–475°C under nitrogen atmosphere as well as outstanding mechanical properties with tensile strength of 93–105 MPa and elongation at break of 3.6–4.2%. The cutoff wavelength of the PI films were in the range of 348–413 nm. [ABSTRACT FROM AUTHOR]