Isocyanate‐ and Phosgene‐Free Routes to Polyfunctional Cyclic Carbonates and Green Polyurethanes by Fixation of Carbon Dioxide

Abstract

The catalytic chemical fixation of carbon dioxide by carbonation of oxiranes, oxetanes, and polyols represents a very versatile green chemistry route to environmentally benign di‐ and polyfunctional cyclic carbonates as intermediates for the formation of non‐isocyanate poly­urethane (NIPU). Two synthetic pathways lead to NIPU thermoplastics and thermosets: i) polycondensation of diacarbamates or acyclic dicarbonates with diols or diamines, respectively, and ii) polyaddition by ring‐opening polymerization of di‐ and polyfunctional cyclic carbonates with di‐ and polyamines. The absence of hazardous and highly moisture‐sensitive isocyanates as intermediates eliminates the need for special safety precautions, drying and handling procedures. Incorporated into polymer backbones and side chains, carbonate groups enable facile tailoring of a great variety of urethane‐functional polymers. As compared with conventional polyurethanes, ring‐opening polymerization of polyfunctional cyclic carbonates affords polyhydroxyurethanes with unconventional architectures including NIPUs containing carbohydrate segments. NIPU/epoxy hybrid coatings can be applied on wet surfaces and exhibit improved adhesion, thermal stability and wear resistance. Combining chemical with biological carbon dioxide fixation affords 100% bio‐based NIPUs derived from plant oils, terpenes, carbohydrates, and bio polyols. Biocompatible and biodegradable NIPU as well as NIPU biocomposites hold great promise for biomedical applications. image