Polyethersulfone- or Polyetherketone-Copolymers

The invention relates to copolyether resins having end groups -OR1 linked direct to phenyl nuclei and containing 1 to 50 mol % of repeating structural units of formula I (I) and 99 to 50 mol % of repeating structural units of formula II (II) wherein R1 is hydrogen, a phenylene radical substituted by amino groups or ethylenically unsaturated radicals or is a 2,3-epoxypropyl radical, R2 is a direct C-C bond or a group of formula -CrH2r-, -O-, -S-, -CO- or -SO2-, r is 1 to 20, R3 is hydrogen or methyl, R4, R5 and R7 are inert substituents, m, n and o are each independently 0, 1 or 2, p is 1 or 2, R6 is a radical of a bisphenol, X and Y are -SO2- or -CO-. The compounds can be used in particular in conjunction with unsaturated imides as matrix resins for the preparation of fibrous composite structures.