A series of phosphorus-containing poly(arylene ether)/poly(arylene ether ketone) copolymers were synthesized by the nucleophilic substitution through changing the molar ratio of bis(4-chlorophenyl) phenyl phosphine oxide (BFPPO) and 4

4'-difluoro diphenylmethanone (DFK).The copolymers with large side groups

twisted and noncoplanar conformation were readily soluble in a variety of organic solvents

such as DMF

DMSO and so on.The structure of the copolymers was confirmed by FTIR

31P-NMR

1H-NMR and 13C-NMR.The molecular weight and its distribution of copolymers were also investigated by GPC.Furthermore

the DSC test revealed that the glass transition temperature of the copolymers increased linearly with the BFPPO content increasing and the maximum can reach 270℃.Experimental results indicated that the polymers had good thermal stability

with the temperature at 5% weight loss of 494~498℃ and CR800 of 5.3%~11.8% at air atmosphere.Moreover

the copolymer films showed good mechanical properties with tensile strength of 74~95 MPa

tensile modulus of 2.3~2.6 GPa and elongation at break of 6.1%~9.0%.It was concluded that the polymers which kept good thermodynamic properties exhibited outstanding flame retardance due to the existence of triphenylphosphine-oxide moieties in the main chain.The UL94 of the copolymer films reached VTM-0 grade and the LOI values were up to 50% significantly.