A series of selenium-substituted carbonates, S,Se-dibenzyl dithioselenocarbonate (DTSC), S,Se-dibenzyl thiodiselenocarbonate (TDSC), and Se,Se-dibenzyl triselenocarbonate (TSC), were synthesized and used as mediators in radical polymerization. The results indicate that these selenium-substituted carbonates can control the polymerization of styrene (St) and methyl acrylate, as evidenced by the number-average molecular weight that increased linearly with the monomer conversion, molecular weights that agreed well with the predicted values, and successful chain extensions. The treatment of the resultant polystyrene by hydrogen peroxide generated polymers with approximately half-reduced molecular weights, and the absence of carbonate groups and vinyl double bond-terminated chain ends. The polymerization with these selenium-substituted carbonates was the same polymerization mechanism as their analogue, the widely used S,S-dibenzyl trithiocarbonate. This work provided a flexible protocol to incorporate selenium into the polymer chain backbone. Specifically, the treatment of these polymers by oxidation produced clickable vinyl-terminated chain ends, which provided possibilities for further functionalization, for example, via a thiol-ene click reaction. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 26062613