A straightforward synthetic approach to the preparation of disulfide linked hyperbranched polymers with peripheral pyridyl disulfide functionalities is described. The hyperbranched polymers were obtained by the condensation of novel AB2 macromonomers bearing a-dithobenzoate and co-double pyridyl disulfide end-groups. These AB2 macromonomers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene or N-(2-hydroxypropyl) methacrylamide (HPMA) using a novel RAFT agent, N, N -bis(2-(4-(2-pyridyldisulfide) ethyl butyric-1-carbonyloxo)ethyl) cyanopentanoic amide dithiobenzoate. After polymerization the a-dithobenzoate functionality was aminolyzed to yield thiol that was simultaneously subjected to an exchange reaction with pyridyl disulfide, resulting in the formation of hyperbranched structures. The primary chains of the hyperbranched polymers possessed well-defined molecular weights and low polydispersities. The linkages between primary chains consisted ofbiodegradable disulfide bonds, as confirmed by their reduction in the presence of DL-dithiothereitol (DTT), resulting in the destruction of the hyperbranched structure. The hyperbranched architectures were designed as carriers bearing excess pyridyl disulfide groups for potential reactions with any thiol-bearing biomolecule (e.g., cysteine residue in proteins, or -SH terminal nucleotides).