Kinetic study of copper(I)-catalyzed click chemistry step-growth polymerization
2008
Binauld, Sandra | Boisson, Fernande | Hamaide, Thierry | Pascault, Jean-Pierre | Drockenmuller, Eric | Fleury, Etienne
Oligomers and polymers containing triazole units were synthesized by the copper(I)-catalyzed 1,3-dipolar cycloaddition step-growth polymerization of four difunctional azides and alkynes. In a first part, monofunctional benzyl azide was used as a chain terminator for the polyaddition of 1,6-diazidohexane and α,ω-bis(O-propargyl)diethylene glycol, leading to polytriazole oligomers of controlled average degree of polymerization (DPn = 3-20), to perform kinetic studies on low-viscosity compounds. The monitoring of the step-growth click polymerization by ¹H NMR at 25, 45, and 60 °C allowed the determination of the activation energy of this click chemistry promoted polyaddition process, that is, Ea = 45 ± 5 kJ/mol. The influence of the catalyst content (0.1-5 mol % of Cu(PPh₃)₃Br according to azide or alkyne functionalities) was also examined for polymerization kinetics performed at 60 °C. In a second part, four high molar mass polytriazoles were synthesized from stoichiometric combinations of diazide and dialkyne monomers above with p-xylylene diazide and α,ω-bis(O-propargyl)bisphenol A. The resulting polymers were characterized by DSC, TGA, SEC, and ¹H NMR. Solubility and thermal properties of the resulting polytriazoles were discussed based on the monomers chemical structure and thermal analyses.
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