Non-isocyanate polyurethanes at room temperature – a dream becoming reality

Abstract

Polyurethanes (PUs) are one of the most widely utilized classes of polymers worldwide. However, their conventional production relies on toxic and hazardous isocyanate compounds whose usage is being limited by recent regulations. This has driven the development of new chemical strategies to access non-isocyanate PUs, or NIPUs. While the traditional PU synthesis typically occurs at room temperature (r.T) due to the high reactivity of isocyanates, NIPU synthesis generally requires elevated temperatures to surpass the low reactivity of the precursors. Considering societal needs and regulatory changes, achieving NIPU synthesis at r.T could reduce the energy footprint of the process, facilitate transition to NIPUs within existing PU manufacturing facilities and in consumer-grade applications – a more seamless switch from PUs to NIPUs. Additionally, r.T reactions are desirable for minimizing side reactions and enabling a wider functional group tolerance. This review critically gathers unbridged data and recent strategies aimed at achieving NIPU synthesis at r.T. This includes advances in monomer design, catalysis, and the use of r.T-efficient hybrid chemistries. Various polymerization techniques from a wide diversity of precursors are discussed, along with the advantages and limitations of each approach.