ANIONIC RING-OPENING POLYMERIZATION OF CYCLOTETRASILANES

Various cyclopolysilanes are discussed as potential monomers for the ring-opening polymerization in terms of reactivity and thermodynamic feasibility. Strained and polymerizable 1,2,3,4-tetramethyl-1,2,3,4-tetraphenylcyclotetrasilanes (1) are prepared from octaphenylcyclotetrasilane by substitution of four phenyl groups with triflate groups using triflic acid, and followed by displacement of triflate groups by methyl substituents using methylmagnesium bromide. Anionic ring-opening polymerization of a mixture of stereoisomers of (1) provides poly(methylphenylsilylene) with molecular weights up to M = 100 000. Anionic polymerization of 1 was initiated by butyllithium and silylpotassium initiators with and without cryptands. Strong solvent effects on polymerization and subsequent cyclization were observed.