Multiarm star polymers have been synthesized by cationic ring-opening polymerization of epsilon-caprolactone from a hyperbranched poly(ethyleneimine) core and end-capped with acetic anhydride. These star polymers have been used as modifiers in diglycidylether of bisphenol A/methyl tetrahydrophthalic anhydride/benzyl dimethylamine formulations. The curing process is studied by dynamic scanning calorimetry and rheometry and the resulting thermosets are characterized by dynamic mechanical thermal analysis and thermogravimetry.; Internal stresses generated during curing are measured and interpreted in terms of the thermal mechanical properties of the cured materials. The influence of the modifier in the toughness improvement of the cured thermosets is determined by standardized impact tests and the microstructure of the material observed by scanning electron microscopy. (C) 2014 Elsevier B.V. All rights reserved.