A method of manufacturing block copolymers containing a polyorganosiloxane segment, by dual polymerization involving (i) polycondensation of a silicone block followed by (ii) the free radical polymerization of a monomer that can be polymerized by free radical polymerization, such as a vinyl containing organic monomer. Initiation of free radical polymerization in step (ii) is carried out with a carbonyl functional group attached to the silicone polymer block. The carbonyl functional silicone polymer, preferably an aldehyde functional silicone polymer, is included as one component of a copper-based Redox initiating system. The method ensures no free homopolymerization, complete reactivity, and various polymer architectures are possible, including for example, polymeric structures such as AB, ABA, (AB).sub.n, brush, and radiant types. The method is fast, effective, convenient, and easier to control than typical ionic polymerization techniques. The silicone-organic block copolymers obtained by the process have utility as polymeric surfactants or as solubility modifiers.