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Aliphatic polyesters bearing pendant alkyne groups were successfully prepared by step‐growth polymerization of different building blocks such as adipic acid and succinic acid in combination with an acetylene‐based diol, 2‐methyl‐2‐propargyl‐1,3‐propanediol, besides 1,4‐butanediol and ethylene glycol. It was demonstrated that the alkyne groups survive the high reaction temperatures (200 °C) in the presence of a radical inhibitor. The alkyne loading has been tuned by the ratio of the different monomers used, up to 25 mol % of alkyne groups. Subsequently, the alkyne groups have been reacted with azides by the copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, a popular type of “click” chemistry. “Click” reactions have been performed quantitatively in the presence of benzyl azide and azide‐terminated poly(ethylene glycol), yielding brush copolymers in the latter case. Kinetic investigations about this click reaction have been performed by means of on‐line Fourier transform mid‐infrared spectroscopy, which was reported for the first time in the field of the click chemistry research. A whole range of functionalized polyesters, based on poly(ethylene succinate) and poly(butylene adipate), is available, the properties of which can be tailored by choosing the appropriate azide compound. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6552–6564, 2008

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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...

A straightforward strategy for the synthesis and functionalization of polyurethanes (PUs) via the use of alkyne‐functionalized polytetrahydrofuran (PTHF) diols is described. The alkyne groups have been introduced into the PTHF chains by the cationic ring‐opening copolymerization of tetrahydrofuran and glycidyl propargyl ether. These PTHF prepolymers were combined with 1,4‐butanediol and hexamethylene diisocyanate for the synthesis of linear PUs with latent functionalization sites. The polyether segments of the PUs have then been coupled with several types of functionalized azides by the copper‐catalyzed azide‐alkyne “click” chemistry, for example with phosphonium containing azides for their antibacterial properties. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011