We report an efficient way, sequential double click reactions, for the preparation of brush copolymers with AB black-brush architectures containing polyoxanorbornene (poly (ONB)) backbone and poly(epsilon-caprolactone) (PCL), poly(methyl methacrylate) (PMMA) or poly(tert-butyl acrylate) (PtBA) side poly(ONB-g-PMMA)-b-poly(ONB-g-PCL) and poly(ONB-g-F tBA)-b-poly(ONB-g-PCL). The living ROMP of ONB affords the synthesis of well-defined poly(ONB-anthracene)(20)-b-Poly (ONB-azide)(5) block copolymer with anthryl and azide pendant groups. Subsequently, well-defined linear alkyne end-functionalized PCL (PCL-alkyne), maleimide end-functionalized PMMA (PMMA-MI) and Pt8A-MI were introduced onto the block copolymer via sequential azide-alkyne and Diels-Alder click reactions, thus yielding block-brush copolymers. The molecular weight of block-brush copolymers was measured via triple detection GPC (TD-GPC) introducing the experimentally calculated dn/dc values to the software. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 886-892, 2011