A novel ABA-triblock bottlebrush polymer (PS-PD-PS), whose terminal PS block and central PD block were densely grafted with polystyrene and poly[2-(dimethylamino) ethyl methacrylate], respectively, on polynorbornene backbones was synthesized by three mutually orthogonal types of controlled polymerization. Dynamic light-scattering analysis revealed that in polar solvents such as tetrahydrofuran/ water (99: 1, v/v), PS-PD-PS self-assembled into oligomeric-to-polymeric aggregates through solvophobic interaction of the PS block. The size of these aggregates depended on the concentration of PS-PD-PS and on the polarity of the solvent. Atomic-force microscopy (AFM), showed that single molecules of PS-PDPS adopted a dumbbell shape in which the three blocks in PS-PD-PS could be clearly distinguished. In AFM samples prepared under appropriate conditions, PS-PD-PS self-assembled into discrete oligomeric aggregates with well-defined structure, including linear and cyclic dimers, a tadpole-like trimer, and higher oligomers. The arrangement and junctions of the monomeric units could be clearly visualized at a single-molecular level.(C) 2017 Elsevier Ltd. All rights reserved.