Efficient Cu(I) acetate‐catalyzed cycloaddition of multifunctional alkynes and azides: From solution to bulk polymerization

Abstract

“Click” chemistry is an effective and commonly used technique in polymer chemistry for the synthesis and modification of polymers. In this study, the bulk polymerization of multifunctional alkynes and azides was achieved by the copper(I)‐catalyzed alkyne–azide 1,3‐dipolar cycloaddition. The influence of different catalyst systems on the polymerization kinetics of the “click”reaction were evaluated by differential scanning calorimetry. Surprisingly, Cu(I) acetate showed the most efficient catalytic behavior among the applied Cu(I) salts. The polymerization kinetics in solution were investigated by 1H NMR spectroscopy and size exclusion chromatography. According to the 1H NMR investigation the copper(I)‐catalyzed cycloaddition follows a second‐order kinetics with external catalysis. Additionally, the mechanical properties of the resulting polymers were investigated by depth sensing indentation. Thereby the polymerizations of the alkyne tripropargylamine with the azides 1,3‐bis(azidomethyl)benzene and 1,4‐bis(azidomethyl)benzene resulted in mechanical hard materials. Furthermore, the combination of the alkynes tripropargylamine and di(prop‐2‐yn‐1‐yl) isophorone dicarbamate and polymerization with 1,2‐bis(2‐azidoethoxy)ethane resulted in high indentation moduli. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 239–247

Metal‐Free Cycloaddition of Internal Alkynes and Multifunctional Azides Under Solvent‐Free Conditions

“…For the CuAAC, highly effi cient catalysts are used which often leads to a release of high reaction enthalpies in a short time period. [ 11 ] By performing the click reaction without copper catalysis, the exothermicity was reduced to a value of -278 and -284 kJ mol −1 , respectively. The polyaddition reaction of oligomers 1 and 2 with the bis -alkynes 4 , 5 , and 7 results in hard polymer resins with a maximum E-modulus of 2.5 ± 0.20 GPa.…”

“…The solvents were dried and distilled according to standard procedures. 1,4-Bis (azidomethyl)benzene ( 4 ), [ 31 ] 1,2-bis (2-azidoethoxy)-ethane ( 6 ), [ 11 ] 1,3,5-tris (azido methyl) benzene ( 5 ), [ 31 ] and 1,3-bis (azidomethyl)benzene ( 7 ), [ 31 ] were synthesized and purifi ed according to previously described literature procedures.…”

“…In comparison to, the reaction heat of the Cu(I)-catalyzed click reaction of 1,2-bis (2-azidoethoxy)-ethane and di(prop-2-yn-1-yl) (2,2,4-trimethylhexane-1,6-diyl)dicarbamate with different copper(I) salts is in a range of -315 to -526 kJ mol −1 . [ 11 ] With increasing polymerization process, a postpolymerization reaction occurred at 180 °C due to sterical effects. Presumably, residual functional groups could only react at higher temperatures, due to the higher mobility at elevated temperatures.…”

“…Recently, we published the Cu(I)-catalyzed click reaction of tripropargylamine, di(prop-2-yn-1-yl)isophorone dicarbamate, 1,2-bis (2-azidoethoxy)ethane, 1,3-bis (azidomethyl)benzene, and 1,4-bis (azidomethyl)benzene under solvent-free conditions. [ 11 ] The E-moduli of the resulting polymers achieved values up to 6.25 ± 0.4 GPa due to the high network density and high monomer conversion. In comparison to these materials, the lower alkyne concentration per molecule of oligomers 1 and 2 resulted in materials with a less …”

Kinetics and mechanics of photo-polymerized triazole-containing thermosetting composites via the copper(I)-catalyzed azide-alkyne cycloaddition

“…The preeminent benefits of the photo-CuAAC polymers over conventional BisGMA-based dimethacrylate polymers lie not only in the nature of the step-growth polymerization and the associated delayed gel point conversion, which contributes to reduced shrinkage stress [29], but also on the formation of rigid triazole linkages as a product that significantly enhance the overall mechanical behavior [38–40]. Furthermore, owing to the “click” chemistry of a highly orthogonal CuAAC reaction without forming a byproduct [41,42], the kinetics and mechanics of the CuAAC resin-based crosslinked photopolymers have been explored with varying monomer structures, photoinitiators, copper salts, and/or light exposure conditions [38,39,43–45].…”