Among the various types of ring-opening polymerization, CROP is, arguably, the least commonly used, presumably because of the typical need for strictly anhydrous and air-free conditions. Our work demonstrates that polythioesters with dispersities below Ð = 2.0 can be derived from DOT with excellent conversions under ambient conditions. The efficiency of this synthesis is presumed to lie in the involvement of stabilised benzylic cations. Notably, this approach gave access to high molar mass DOT homopolymers that are not accessible through radical ring-opening polymerization and allowed studying depolymerization mechanisms in detail. The thiolate-initiated depolymerization was shown to involve the initial cleavage of a mid-chain thioester followed by ω-unzipping of the thiolate-terminated fragment. Thiocarboxylate α-end groups, on the other hand, were not found to play a role in the depolymerization which accounted for stability of the polymers in the presence of (non-nucleophilic) base. The thermal depolymerization was shown to originate from ω end groups and therefore depend on the end cap provided by the initiator. This depolymerization was found to be controlled, i.e. with a gradual decrease of molar mass rather than complete unzipping of some chains, while others remained intact. Overall, these insights are expected to be helpful in the design of recyclable materials with stability during use and full degradability under tailorable conditions.