CO₂‐Sourced Non‐Isocyanate Poly(Urethane)s with pH‐Sensitive Imine Linkages

Abstract

Abstract Carbon dioxide is a renewable C1‐feedstock that is exploited for the production of polymers. In this work, we report on the conversion of CO 2 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 CO 2 ‐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 CO 2 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 CO 2 ‐sourced monomers with diamines. magnified image