Soluble, transparent and heat-resistant fluorinated copoly(ether imide)s containing pyridyl and biphenyl units in the main chain

A series of new fluorinated copoly(ether imide)s containing pyridyl and biphenyl moieties were prepared by thermal imidization of poly(amic acid)s derived from 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (BATB), 4-(4-trifluoromethylphenyl)-2,6-bis(4-aminophenyl)pyridine (TFMPBPP) and 3,3’,4,4’-biphenyltetracarboxylic dianhydride with various mole ratios of BATB and TFMPBPP ranging from 80/20 to 20/80. All copoly(ether imide)s were amorphous and soluble in polar solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone at room temperature or upon heating at 70 °C, and displayed good thermal properties with gradually increasing of a glass transition temperature ranged from 282 to 347 °C as an increase of the TFMPBPP component, the temperature at 5% weight loss of 574–586 °C, and the residue of 57–62% at 750 °C in nitrogen. Tough and flexible polymer films also exhibited outstanding mechanical properties with tensile strengths of 109.1–111.9 MPa, tensile moduli of 1.3–1.5 GPa, and elongations at break of 27.9–48.7%, low dielectric constants of 2.98–3.15 (1 MHz) and water uptake 0.36–0.55%, as well as high optical transparency with the UV-vis cutoff wavelength in the 370–382 nm range and the wavelength of 80% transparency in the range 518–550 nm.