The synthesis of polymers with well-defined composition and architecture is a key step toward materials with tailored functions and properties. We have developed a straightforward synthesis of miktoarm H-shaped pentabock copolymers by ring-opening metathesis polymerization (ROMP). A variety of norbornene monomers may be used in combination with a telechelic polymer that serves as the central block. Specifically, we have prepared norbornene end-capped poly(3-hexyl)thiophene with narrowly dispersed molecular weight using click chemistry. We have shown that grafting to and from this telechelic P3HT may be accomplished in one pot with minimal crosslinking. The properties and self-assembly of the resulting H-shaped polymer may be tuned by the choice of polynorbornene arms.