Soluble copoly(aryl ether ether ketone ketone)s containing xanthene and hexafluoroisopropylidene moieties

Several new copoly(aryl ether ether ketone ketone)s (PEEKKs) containing xanthene and hexafluoroisopropylidene moieties were prepared via nucleophilic substitution polycondensation of 1,4-bis(4-fluorobenzoyl)benzene with 9,9-bis(4-hydroxyphenyl)xanthene (BHPX) and 4,4′-hexafluoroisopropylidenediphenol (6F-BPA) by varying mole proportions of BHPX to 6F-BPA (5/95–75/25) in tetramethylene sulfone in the presence of anhydrous potassium carbonate. These polymers with weight-average molecular weights of 78,900–81,500 and number-average molecular weights of 38,500–40,800 were all amorphous and soluble in organic solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF), and even in THF and chloroform at room temperature. The copolymers showed glass transition temperatures (Tg's) between 180 and 216 °C, and the Tg values increased with increase in concentration of the BHPX units in the polymer. Besides, all the polymers were stable up to 470 °C with 5% weight loss temperatures ranging from 525 to 544 °C, and char yields of 58–64% at 800 °C in nitrogen. These copolymers could be cast into transparent, strong, and flexible films with tensile strengths of 52.4–75.1 MPa, elongations at break of 8–13%, and tensile moduli of 2.05–2.55 GPa. Their films had low dielectric constants of 2.58–2.84 (1 MHz) and low water absorptions in the range of 0.24–0.38%, and high transparency with an ultraviolet–visible absorption cut-off wavelengths in the 356–376 nm range.

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► Four new PEEKK copolymers containing xanthene and hexafluoroisopropylidene moieties were synthesized.
► These PEEKKs exhibited good solubilities, mechanical and thermal properties, especially higher glass transition temperatures.
► Introduction of hexafluoroisopropylidene units into the polymers afforded them low dielectric constants and high optical transparency.