A new series of poly(silylenemethylenes) of the type [Si(Me)(X)CH2](n), where X = OR (R = Et, CH2CF3, Ph, Ac), F, and R’ (R’ = n-butyl, allyl); were obtained starting from the preformed [Si(Me)(Cl)CH2](n) polymer. The OR derivatives were obtained quantitatively from the [Si(Me)(Cl)CH2](n) polymer by treatment with ROH/Et(3)N or NaOR. Reaction of the [Si(Me)(Cl)CH2](n) polymer with the allyl Grignard reagent also gave 100% substitution, but the reaction with the n-butyl Grignard reagent was found to proceed only to the extent of similar to 70%. The novel [Si(Me)(F)CH2](n) polymer was obtained by the action of BF3 . Et(2)O on the [Si(Me)(OEt)CH2](n) polymer. The atactic structures of these polymers were characterized by NMR spectroscopy,and their molecular weights and thermal properties were examined by GPC, DSC, and TGA. The [Si(Me)(OR)CH2](n) polymers were found to vary widely in terms of their hydrolytic sensitivity and glass transition temperatures.