Synthesis of Organosoluble Polyimides and Optical Fiber Protective Coatings on Their Basis

Homo- and copolyimides containing F, Cl, or Si atoms and COOH, OH, and cardo groups are synthesized by one-step high-temperature polycyclocondensation. It is shown that the structure of the polymer affects its solubility, thermal, mechanical, and optical properties and use as a coating. The resulting polymers with η inh = 0.3–1.3 dL/g are characterized by high heat resistance and thermal stability (240°C ≤ T g ≤ 375°C, 440°C ≤ T 10% ≤ 580°C) and also form high-strength films (55 MPa ≤ σ ≤ 140 MPa; 1.1 GPa ≤ E ≤ 2.8 GPa). The developed polyimides are promising as new highly thermostable protective coatings, in particular, of optical fibers, whose mechanical properties do not change after prolonged exposure at 300°C.