CO2-sourced non-isocyanate poly(urethane)s with pH-sensitive imine linkages

Carbon dioxide is a renewable C1‐feedstock that is exploited for the production of polymers. In this work, we report on the conversion of CO2 into novel bis(oxo‐carbamate)s that are then exploited for the synthesis of degradable non‐isocyanate polyurethanes (NIPUs) bearing acid‐sensitive imine functions within the polymer backbone. Two CO2‐sourced bis(oxo‐carbamate)s were first prepared by the facile catalyst‐free and regioselective aminolysis of an α‐alkylidene cyclic carbonate (prepared by carboxylative coupling of CO2 with a propargylic alcohol) with two secondary diamines, piperazine and N,N’‐dimethyl‐1,6‐hexanediamine. A large diversity of poly(urethane‐co‐ imine)s (PUIs) with molar masses ranging from 4500 to 8500 g/mol were then prepared by polycondensation of bis(oxo‐carbamate)s with various primary diamines, and by using Ti(OEt)4 as catalyst and drying agent. Finally, the pH‐responsiveness of PUIs was demonstrated by immersing a representative polymer in aqueous solutions at different pH. This work illustrates that hydrolytically degradable NIPUs can be constructed by polycondensation of novel CO2‐sourced monomers with diamines.