ABSTRACT:Anionic cyclopolymerization of bis(dimethylvinylsilyl)methane (BVSM) in hexane, which affords a polymer having six-membered rings as repeating cyclic units, is investigated. Low polymer yields in the polymerization of BVSM with n-butyllithium (n-BuLi) in the absence of N,N,N',N'-tetramethylethylenediamine (TMEDA) are attributed to cross-linking reactions and association of the propagating ends at -lO'C and elimination of lithium hydride from the propagating end at 40°C. Polymerization with n-BuLiiTMEDA is accompanied, though not frequently, by the abstraction of the methylene proton interposed by two silicon atoms, which forms an inactive anion. This abstraction is caused by the propagating end in the six-membered ring. At high monomer concentration, 0.5 moll-1 , cross-linking reaction is not negligible even in the presence of TMEDA. As initiators, n-, s-, t-BuLi are examined, and only s-BuLi/TMEDA is found to cause the proton abstraction from the methylene interposed by two silicon atoms. The effects of the initiator are explained by the nucleophilicity of BuLi and the steric hindrance in the abstraction. The effects of three amines on the polymerization arc evaluated. TMEDA is the most suitable for the cyclopolymerization of BVSM among them.