The synthesis of hyperbranched polyglycerol dendron analogues with precisely one focal amino functionality (H2N-hbPG) and their use for the synthesis of linear-hyperbranched graft-copolymers in a grafting-to approach is reported. By use of N,N-dibenzyl tris(hydroxylmethyl) aminomethane as a novel initiator for the ring-opening multibranching polymerization of glycidol, dendron analogues with one focal amino functionality of molecular weights ranging from 500 to 15000 g mol(-1) and narrow to moderate polydispersities (M-w/M-n = 1.2-1.9) were synthesized, as confirmed by NMR and SEC. After removal of the benzyl protective groups, the accessibility and selective transformation of the focal amino group was demonstrated by NMR and MALDI-ToF MS. H2N-hbPG was then selectively grafted to a linear reactive ester polymer backbone, poly(pentafluorophenol methacrylate) (PPFPMA), to obtain linear polymers with highly branched side chains of high molecular weights (M-n > 126 kg mol(-1)) and low polydispersities (M-w/M-n = 1.1-1.3), as shown by SEC. Successful attachment of the hyperbranched polyether structure to the linear backbone was confirmed by F-19 NMR and fluorescence spectroscopy. The modular approach introduced bears some analogy to the convergent dendrimer synthesis and describes the first linear-hyperbranched graft-copolymers prepared in a grafting-to approach, resulting in hyperbranched brush-type polymers with the highest molecular weight reported to date.