SYNTHESIS AND CHARACTERIZATION OF 1,3,4-OXADIAZOLE-CONTAINING POLYETHERS FROM 2,5-BIS(4-FLUOROPHENYL)-1,3,4-OXADIAZOLE AND VARIOUS AROMATICDIOLS

Six 1,3,4-oxadiazole-containing polyethers with reduced Viscosities of 0,65-1,17 dL . g(-1) were synthesized by high-temperature solution po lycondensation of an activated difluoride, 2,5-bis(4-fluorophenyl)-1,3 ,4-oxadiazole, with aromatic diols possessing a variety of ring struct ures. The expected chemical structures were confirmed by IR and H-1 NM R spectroscopy and elemental analysis. Of all the polymers, two polyet hers were highly crystalline and soluble only in limited solvents such as o-chlorophenol and cone. sulfuric acid. The other polyethers were amorphous and dissolved readily in a variety of organic media includin g polar aprotic solvents, phenols and chlorinated hydrocarbons. Colorl ess to slightly yellow-colored, transparent and tough films could be c ast from the N-methyl-2-pyrrolidone or o-chlorophenol solutions. The m echanical properties were excellent and their tensile strength, elonga tion at break and tensile moduli were in the ranges of 53 - 80 MPa, 4 - 12% and 1,3-2,0 GPa, respectively. The amorphous polyethers had high glass transition temperatures of 195-259 degrees C. All the polyether s were highly thermally and thermooxidatively stable and exhibited no weight loss up to 400 degrees C, with 10% weight loss being recorded a t 464-514 degrees C in air.