A new anionic ring-opening polymerization (ROP) was used to synthesize polydithiocarbonates from cyclic dithiocarbonates. The polymerization was optimized in the presence of dibenzo-18-C-6 and NaH/EtOH, and carried out at 50 degrees C to suppress any retropolymerization. Six- and seven-membered cyclic dithiocarbonates underwent ROP to afford the corresponding polymers. Thermal depolymerization of the prepared polymers generated a dimer, which was found to be a back-biting mechanism according to H-1 nuclear magnetic resonance (NMR) spectroscopy. The characteristic structure of the linear polymer was defined by H-1 NMR and C-13 NMR spectroscopy, and compared with the monomer. The ROP at 80 degrees C exhibited the formation of a polymer contaminated by a dimer. Thermal analysis of the polymers by differential scanning calorimetry and thermogravimetric analysis revealed a melting process at 85-110 degrees C and thermal instability accompanying a 5% weight loss at 150-230 degrees C. (C) 2016 Elsevier B.V. All rights reserved.