Hydro- and vinyl-bifunctionalized di- or tetrasiloxane were synthesized by degradative cleavage of functional cyclic siloxanes with methyllithium followed by quenching with a functional chlorosilane, or by ring-opening of hexamethylcyclotrisiloxane (D-3) by functional alkyllithium followed by quenching with a functional chlorosilane. These bifunctionalized siloxanes were used as monomers in polyaddition with transition metal catalysts.