Metal-Free Functionalization of Linear Polyurethanes by Thiol-Maleimide Coupling Reactions

Abstr act.A new approach for the metal-free functionalization of aliphatic polyurethanes has been explored by the combination of polyaddition step-growth polymerization and thiol-maleimide coupling reactions.A maleimide containing diol has been incorporated in different ratios into an aliphatic PU backbone.The incorporated amount of a masked maleimide containing diol could be calculated from 1 H NMR analysis and TGA analysis.Subsequently, the PU's were coupled with several thiols containing hydroxyl, acid and chloride groups via the thiol-maleimide coupling reaction.1 H and 2D DOSY NMR techniques demonstrated that the thiols were indeed covalently bond onto the polyurethanes.Although DMSO is the best solubilizing solvent for the PU's, the efficiency of the thiol-maleimide reaction is lowered as a result of thiol-based impurities.Conversions higher than 90% were obtained in NMP as solvent.This approach resulted in a new metal-free functionalization platform for polyurethanes, which could be further applied to PU-materials including elastomers and foams.Keywor ds: Communication to the editor Polyurethanes, Thiol-maleimide coupling, Metal-free functionalization Polyurethanes (PU's) are a versatile class of polymers used in today's high-performance applications.