One-pot, additive-free preparation of functionalized polyurethanes via amine-thiol-ene conjugation

A straightforward, isocyanate-free method for the synthesis of functionalized polyurethanes, based on amine-thiol-ene conjugation, was elaborated. Aminolysis of a readily available AB'-urethane monomer, containing both an acrylate (A) and a thiolactone unit (B'), facilitates the preparation of various reactive thiol-acrylates. In situ polymerization via Michael addition proceeds under ambient conditions, yielding polyurethanes with a large variety of chemical functionalities. Side-chain functionality originates from the modular use of different amines, allowing for the introduction of pendent functional groups (e.g. double bond, triple bond, furfuryl, tertiary amine, morpholine) along the polyurethane backbone. Extensive model studies revealed the kinetic profile of this reaction sequence and excluded the occurrence of competing reactions, such as aza-Michael addition and disulfide formation. This mild one-pot reaction requires no additives or external trigger and the obtained polyurethanes remain soluble throughout the process, enabling post-polymerization modification in the same reaction medium.