Abstract
Polyurethanes (PU) constitute one of the most versatile class of polymers with respect to composition, properties and applications. However, there are a lack of synthetic strategies capable of producing PU with controlled architecture, chain end functionality, molar mass and low molar mass dispersity (Ð); these characteristics could considerably improve the use of PU in advanced applications. In this study, we report a method for synthesizing polyurethanes based on the dissociation equilibrium of hindered urea groups. Diisopropylamine reacts promptly with isocyanates, forming hindered ureas in a dynamic fashion and establishing a dissociation equilibrium shifted towards hindered urea formation. The equilibrium reduces the concentration of isocyanates susceptible to the polyaddition with diols and, therefore, the step growth polymerization follows a controlled pathway resulting in PU with Ð < 1.3 and a weight average molar mass up to 5 kDa for bulk polymerization. Moreover, urea chain end functionality is maintained after purification and telechelic PU can be obtained for further use, such as the synthesis of block copolymers capable of self-assembly.
Published Version
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