The synthesis of polymers with well-defined composition and architecture is a key step in pursuit of materials with tailored functions and properties. Ring-opening metathesis polymerization (ROMP) has been shown to deliver highly functionalized block copolymers that serve as sensors, imaging agents, drug delivery vehicles, photonic crystals, and organic resistive memory devices. We have shown that grafting to- and from- norbornene-functionalized polymers and surfaces provides well-defined miktoarm block copolymers. Moreover, we demonstrate the influence of architecture in the nanostructure and responsiveness of these materials. Finally, we explore the use of cyclobutene esters as single-insertion monomers for preparing programmably branched polymers.