Hyperbranched poly(aryl ether ketone)s with hydroxyl end groups (HBP-OH) and high degree of branching value (83%) were synthesized via an A(2) + B-3 approach. The polymerization conditions (e. g., polymerization temperature and time, monomer concentration, stoichiometric ratio of functional groups) were explored to avoid the gelation. Allyl-terminated hyperbranched PAEKs (HBP-AL) with low molecular weight (M-n = 3.4 x 10(3)) and narrow polydispersity (PDI = 1.65) were obtained via the etherification of HBP-OH and it has been used for the modification of bismaleimide (BMI) resins. The prepolymers showed good processibilities with a viscosity below 0.6 Pa s at 110 degrees C, though the viscosities slightly increased as the increase of HBP-AL contents. The cured BMI resins showed high glass transition temperatures (T-g > 320 degrees C) and good thermal stabilities (T-d > 400 degrees C, both in nitrogen and air). It is inspiring to note that the incorporation of HBP-AL into BMI matrix results in a significant enhancement of toughness without any noticeable loss in modulus, processibility, and T-g. (C) 2013 Society of Plastics Engineers