Synthesis and properties of polyimides-containing benzoxazole units in the main chain

摘要

A series of polyimide (PI) films were prepared from a diamine-containing benzoxazole unit (5,4'-diamino-2-phenyl benzoxazole) and five dianhydrides via two-step polymerization process. The PI films showed outstanding mechanical properties with tensile modulus up to 7.3 GPa without preorientation process. According to the results of thermal analysis, the glass transition temperature of the films was up to 4I2°C, and the films showed good thermodimensional stability. Thermal analysis and wide-angle x-ray diffraction analysis revealed that the Pis were semicrystalline. Excellent properties of these Pis were attributed to the benzoxazole group in the main chain and accordingly to the rigid-rod structure and high level of linearity of the polymer backbones. These results correlate with each other and contribute to our overall understanding of the effects of benzoxazole moiety on the properties of the PI films.