Abstract: A linear conjugated diene of 4 to 8 carbon atoms or a mixture of such conjugated dienes or a mixture of such a conjugated diene and a vinyl aromatic monomer is polymerized in a monomer-starved process to yield homopolymers of copolymers of low molecular weight containing as low as 35 and up to 90 or 95% or more of microcyclic structures, if properly catalyzed and depending upon the temperature and other conditions of the reaction. These microcylic structures are defined as microcyclic rings of molecules containing 6 to 18 or more alkylene units. These cyclic structures are produced by the monomer-starved process which causes the bond between the carbon and the metal to bite back on itself.