impedes their practical use to prepare homogeneous copolymers incorporating ester bonds into the backbone. Moreover, the main drawback of CKAs is also related to their sensitivity to protic sources and the competition between the two mechanisms of propagation, ie ring-opening and ring-retaining. To circumvent such drawbacks, Roth and Gutekunst 16 recently proposed thionolactones as new cyclic monomers for rROP by taking advantages of the higher reactivity of the C=S bond than the C=C bond as radical acceptor. Among a library of six thionolactones, dibenzo[c,e]-oxepane-5-thione (DOT, Figure ) was shown to copolymerize efficiently with acrylate, N,N-dimethylacrylamide and maleimide and to produce copolymers with thioester units inserted into the backbone.