Synthesis of reactive hyperbranched and star-like polyethers and their use for toughening of vinylester–urethane hybrid resins

Abstract A vinylester–urethane hybrid resin (VEUH) was toughened by adding various vinyl-functionalized branched polyethers in 10 and 20 wt%. Two sets of hyperbranched polymers (HBPs) with different branching density were compared with a set of six-arm star polymers. Besides the architecture, the polymers also varied in their characteristics (molecular mass and mass distribution, vinyl/hydroxy ratio). The morphology of the modified VEUH was studied by dynamic-mechanical thermal analysis (DMTA), transmission (TEM) and scanning electron microscopy (SEM). The toughness was characterized by the fracture energy ( G c ) determined on compact tension specimens at room temperature. It was established that the architecture and vinyl/hydroxy ratio of the HBPs are those parameters which control the morphology and thus the related linear elastic fracture mechanical response. Less compact star-like polymers with long, flexible arms and with high vinyl functionality produced the largest toughness improvement in VEUH.