Glycidyl Azide Polymer Crosslinked Through Triazoles by Click Chemistry: Curing, Mechanical and Thermal Properties

Abstract

Glycidyl azide polymer (GAP) was cured through “click chemistry” by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3-dipolar cycloaddition reaction to form 1,2,3-triazole network. The properties of GAP-based triazole networks are compared with the urethane cured GAP-systems. The glass transition temperature (Tg), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher Tg in comparison to the GAP-urethane system (Tg−20 °C) and the networks exhibit biphasic transitions at 61 and 88 °C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)-based theoretical calculations implied marginal preference for 1,5-addition over 1,4-addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP-triazole and the mechanism of decomposition was elucidated using pyrolysis GC-MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ ⋅ mol−1) against that of azide (317 kJ ⋅ mol−1) and better mechanical properties of the GAP-triazole renders it a better propellant binder than the GAP-urethane system.