Synthesis and characterization of a novel nitrogen-rich PEG-based hydrogel through click chemistry

A new hydrogel entirely based on PEG was synthesized by azide-alkyne polycycloaddition reaction. For this purpose, PEG was involved in two separate two-step reactions to prepare the corresponding monomers, PEG-derived diazide and PEG-derived triyne. FT-IR spectroscopy and elemental analysis were used to confirm the hydrogel structure. ¹H-NMR and ¹³C-NMR spectroscopies were also used to verify the monomers. The micropores of the freeze-dried network were clearly recognizable in the FE-SEM micrographs. The swellability of the prepared hydrogel was studied by examining the water uptake behavior. Water uptake up to twice the weight of the dry network puts the hydrogel in a privileged position among similar networks. Although the numerous 1,2,3-triazole and 1,3,5-triazine rings in the structure somewhat overshadow the swelling ability of the hydrogel, they greatly increase the nitrogen content of the network (up to 14.5 wt.%). This gave the prepared network the capacity to be used as a propellant. The flammability behavior of the nitrogen-rich network was investigated by performing an ignition test. The ignition of the gel happened within 35 s and was accompanied by a yellow flame and sizzle, and finally an explosion.