A straightforward, isocyanate-free methodology for the synthesis of functionalized 8 polyurethanes, based on amine-thiol-ene conjugation, was elaborated. Aminolysis of a readily 9 available AB'-urethane monomer, containing both an acrylate (A) and a thiolactone unit (B'),

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Abstr act. A new approach for the metal-free functionalization of aliphatic polyurethanes has been 10 explored by the combination of polyaddition step-growth polymerization and thiol-maleimide coupling 11 reactions. A maleimide containing diol has been incorporated in different ratios into an aliphatic PU 12 backbone. The incorporated amount of a masked maleimide containing diol could be calculated from 1 H 13 NMR analysis and TGA analysis. Subsequently, the PU's were coupled with several thiols containing 14 hydroxyl, acid and chloride groups via the thiol-maleimide coupling reaction. H and 2D DOSY NMR 15techniques demonstrated that the thiols were indeed covalently bond onto the polyurethanes. Although 16 DMSO is the best solubilizing solvent for the PU's, the efficiency of the thiol-maleimide reaction is 17 lowered as a result of thiol-based impurities. Conversions higher than 90% were obtained in NMP as 18 solvent. This approach resulted in a new metal-free functionalization platform for polyurethanes, which 19could be further applied to PU-materials including elastomers and foams. 20 2 Keywor ds:Communication to the editor 2 Polyurethanes, Thiol-maleimide coupling, Metal-free functionalization 1 Polyurethanes (PU's) are a versatile class of polymers used in today's high-performance applications. 3The urethane linkage imparts most of the important physical properties, leading to the suitable use of 4 PU's in construction, automotive, flooring and sports.1 The basic feeds in the synthesis of polyurethanes 5 are diisocyanates, diols or polyols and a catalyst. Due to the wide availability of these monomers, a wide 6 range of materials can be synthesized with unique and on-demand properties.2 Recently, much attention 7 is paid to the development of functional polymers, including polyurethanes, as these materials would 8 lead to new applications that can broaden the classical market. Preferably, these functionalization 9 strategies are straightforward with high yields and with little or no by-products.3 Lately, the highly 10 efficient, regiospecific and orthogonal copper(I) catalyzed alkyne-azide cycloaddition reaction has been 11 used with great effect for this purpose. 4,5 This is the most popular reaction of the chemical concept 12'click' chemistry and has led to a significant contribution in both organic and polymer chemistry.6-9 The 13 combination of 'click' chemistry and polyurethanes has yet been explored by Fournier et al. 10,11 Recently, efforts have been made to the application of suitable metal-free click reactions, including 20 the reaction of azides with substituted cyclooctynes, A small 14 alkyne containing diol was incorporated in linear PU chains, as well as in films and foams and these 15 materials were subsequently reacted with a range of azide-containing molecules. Despite the excellent 16 yields and the universal character of this azide-alkyne cycloaddition reaction, this method has still some 17 remaining drawbacks. Firstly, the remaining copper catalyst, often difficult to remove complet...