Cationic ring-opening polymerization of trimethylene carbonate using o-benzenedisulfonimide as a reusable catalyst under mild conditions was described. The polymerization proceeded homogeneously without decarboxylation and poly(trimethylene carbonates) (PTMCs) were synthesized with well-controlled molecular weights and narrow polydispersities (M-w/M-n = 1.12-1.18). The spectra of H-1-NMR, SEC, and MALDI-ToF MS clearly demonstrated the incorporation of the initiator residue into the polymer chains and the controlled/living nature of the polymerizations. Furthermore, the catalyst can be easily recovered, and its efficiency was fully retained. In addition, 1,3-propanediol, 1,1,1-trimethylolpropane, and pentaerythritol were successfully used as initiators to produce telechelic and star-shaped polycarbonates which were determined by intrinsic viscosity experiments. The number of arms estimated by the shrinking factors (g') were 2.0, 2.6, and 3.5, respectively, indicating the successful syntheses of the two-, three-, and four-armed PTMCs. (C) 2014 Wiley Periodicals, Inc.