Abstract: Structural studies of poly(ether ether ketone ketone) and poly(ether biphenyl ether ketone ketone) copolymers by means of SAXS and one dimensional electron density correlation function methods revealed that the structure of the aggregated state of copolymers depended closely on the biphenyl content(n_b) in the copolymers. When n_b=0.35,the invariant Q,long period L,average crystal lamellae d and electron density difference η_c-η_a(obtained by SAXS analysis) and the degree of crystallinity W_c,x gave minimum values, but the specific inner surfaces O_s possessed maximum values.

Key words: poly(ether ether ketone ketone), poly(ether biphenyl ether ketone ketone), copolymer, SAXS, structure