The synthesis and living ring opening metathesis polymerization initiated with RuCl2(=CHPh)(PCy3)(2) of three 7-oxanorbornene monomers containing two tapered 3a and respectively two conical 3b and 3c dendritic side groups is described. 3a and the corresponding polymer 4a self-assemble in a cylindrical shape, while 3b and 3c self-assemble in spherical shapes. The polymerization of 3a proceeds via a cylindrical growing chain and occurs with the same rate constant regardless of the initial monomer concentration and the initial ratio between 3a and the initiator. The polymers resulting from 3b and 3c exhibit, depending on the degree of polymerization, spherical and cylindrical shapes. The shape change of the propagating macromolecules that resulted from 3b and 3c were detected by the change in the rate constant of propagation. The implication of this kinetic method for the detection of shape change in the design of novel complex synthetic nanoscale functional macromolecules inspired from biology is discussed.