【Abstract】 Crystallographic equivalence of ether and ketone in all para substituted PAEKs crystallized in form Ⅰ was discussed in this paper. In a word, crystallographic equivalence between ether and ketone groups is tenable when polymer contains only phenyl rings in the repeat unit. If a polymer contains a diphenyl group in the repeat unit, two cases should be distinguished. In the case of PEDEKK and PEEKDK, crystallographic equivalence between ether and ketone linkages is untenable. However, in the case of PEDK and PEDEKDK, crystallographic equivalence between ether and ketone linkages is still tenable.更多还原