The preparation of polystyrene macromonomers containing a norbornene unit and their living ring opening metathesis polymerization (ROMP) to produce comb graft copolymers is described. The ROMP was initiated by the well defined Schrock initiators, Mo(=CHR)(=NAr)(OR’)2, where R is (CH3)3C- or C6H5C(CH3)2-, Ar is 2,6-diisopropylphenyl and R’ is (CH3)3C-. Well characterized macromonomers and comb graft copolymers with polystyryl grafts with average degrees of polymerization (DPs) of 4, 7, and 9 were successfully produced. The graft copolymers exhibit single mode molecular weight distributions and narrow polydispersities. Attempts to prepare copolymcrs with longer polystyryl grafts gave products which exhibited bimodal molecular weight distributions in which one component of the distribution had the same retention time as that of the macromonomer, this observation is rationalized in terms of steric inhibition of the ROMP of such macromonomers.