The synthesis of the urazole gel is shown in Scheme 1. In the first step, a multifunctional isocyanate, namely (1) poly(hexamethylene diisocyanate), was reacted with the equimolar ethyl carbazate to form an isocyanate semicarbazidecontaining prepolymer intermediate (2). In the same reaction flask, polymerization of this intermediate was initiated via the addition of a small amount of water. The polymerization of poly(urea) was also accompanied with gelation. This process is highly sensitive to moisture and heat. High temperatures or open air conditions results in bubbles in the gel (Electronic Supporting Information: ESI Figure ). However, bubble free gels can be obtained by carrying the gelation reaction at ambient temperatures and inert conditions.(ESI Figure ) The semicarbazide-containing gel (3) was cyclized into a urazole-potassium gel (4) under strong basic conditions at high temperature. Urazole cyclization is efficient and fast when Ethanol/K2CO3 is used. However, ethanol-water switch may damage hydrogels. Therefore, at the gel washing step, solvent exchange should be done carefully and slowly to prevent stress on the gels. Although aqueous K2CO3 cyclization is very slow and less efficient, the gels can be washed easily with water. Urazole potassium gel can be acidified to obtain a urazole gel in a free acid form (5). Interestingly, a urazole-potassium gel (4) can hold a large amount of water owing to its urazole-potassium salt groups. The gels synthesized were characterized by FT-IR and Raman spectroscopy. 1 H-nuclear magnetic resonance (NMR) analysis of urazole cyclization was done using a model compound, as the gels are crosslinked and not soluble. To obtain a soluble model compound, all isocyanates group of poly(hexamethylene diisocyanate) was reacted with ethyl carbazate to form poly(hexamethylene semicarbazide) (ESI, Scheme S1). The model compound is soluble in DMSO, and 1 H-NMR spectrum analysis showed that semicarbazide and urazole formation was successful (Fig. ). FT-IR spectrum of semicarbizde gel (3) and urazole gel (4) reveals that new carbonyl mode at 1767 cm -1 is appeared after urazole formation when gel is in free acid form (Fig. ). Additionally, carbonyl mode of semicarbazide at 1724 cm -1 is disappeared. These FT-IR findings are also in agreement with our previously synthesized urazole compounds in which their structures were also confirmed with 1 H-NMR. Urazole potassium salt has a unique mode at 1597cm -1 and carbonyl mode at 1767 cm -1 is also not present when analysis was done under dry and neat conditions. Urazole formation was determined qualitatively and quantitively by oxidizing them into triazolinediones (TAD). TAD formation can be monitored by naked eye owing to distinct red/pink color of TAD groups. The oxidation can be with strong oxidants such HNO3 or dibromohyndation in dichloromethane. In some cases, semicarbazide derivatives may form diethylazodicarboxylate (DEAD)-like structures upon oxidation, which have a similar color (orange to red) to TADs and similar reactivity to TADs. When we treated the semicarbazide gels (3) with strong oxidizers, including HNO3 and 1,3-Dibromo-5,5dimethylhydantoin, at least for 1 hour, we observed no color change in the material. This indicated that the red color of the gel was due to the urazole group instead of a possible DEAD like by-product.