One-pot synthesis of copolymers through the application of the thermally reversible furan/maleimide Diels–Alder reaction. 2. preparation of polyester–polyurethane copolymers

The furan/maleimide Diels–Alder (DA) reaction has been exploited to construct thermally reversible macromolecular structures, such as linear or cross-linked polycondensates, or to cross-link linear polymers, using the free end-type or pending furan and maleimide moieties as the diene and dienophile reagents. Here we report a different approach for the synthesis of homopolymers based on a diol, in which the DA adduct formed by the furan and the maleimide sits within the diol monomer structure. The OH end groups of the diol were used for the synthesis of a polyester and a polyurethane using conventional polycondensation methods and to study their retro DA (rDA) depolymerization through the thermal decomposition of their inner DA adducts. The relevant contribution of this study was however the possibility of synthesizing a copolymer by heating these two polymers together to induce their rDA deconstruction and then lowering the temperature in order to allow the ensuing fragments to recombine statistically by successive DA couplings, thus building the corresponding ester-urethane copolymer. ¹H NMR spectroscopy and DSC analysis were employed to confirm the success of this promising approach.