The present invention is directed to sulfine control agents for synthesizing polymers via controlled free radical polymerization and to the polymers resulting therefrom. Such polymers include repeat units derived from the controlled free radical polymerization, particularly reversible atom fragmentation transfer (RAFT) polymerization, of at least one vinyl-containing monomer, at least one conjugated diene monomer, or combinations thereof, in the presence of a sulfine compound having the formula: ##STR00001## wherein R.sup.1 is alkyl, cycloalkyl, substituted alkyl, heteroalkyl, heterocycloalkyl or substituted heterocycloalkyl, and wherein Y is alkyl, cycloalkyl, substituted alkyl, heteroalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkoxy, amino or thio.