Synthesis and properties of novel 9,9-diphenyl xanthene-based poly(aryl ether ketone)s with methyl substituents

A new bisphenol, 9,9-bis(4-hydroxy-3-methylphenyl)xanthene, was synthesized via a one-pot, two-step synthetic procedure in good yield and used for polymerization with difluorinated aromatic ketones in tetramethylene sulfone in the presence of anhydrous potassium carbonate to form several aromatic poly(ether ketone)s (PEKs) with 9,9-diphenylxanthene moieties and methyl substituents. The newly synthesized high-molecular-weight PEKs having number-average molecular weights in the range of 20,500–25,600 g mol⁻¹ with the polydispersity index ranging from 1.9 to 2.1 were all amorphous and showed high glass transition temperatures in the range of 194–229.8°C, and the temperatures at the 5% weight loss were in the range of 420–445°C with char yields above 60% at 600°C under nitrogen atmosphere. All new PEKs are soluble in polar aprotic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, chloroform, pyridine, m-cresol, and tetrahydrofuran, and could form transparent, strong, and flexible films with tensile strengths of 66–74 MPa, Young’s moduli of 2.47–2.77 GPa, and elongations at break of 8–14%. In addition, these polymers had high transparency with an ultraviolet–visible absorption cutoff wavelength in the 352–356 nm range and low moisture absorption in the range of 0.41–0.56%.