Jnm ecx400

Unless otherwise stated, all starting materials were purchased from commercial sources and used without further purification. All solvents were distilled before use. Compound 1b was prepared according to the previously reported procedure (Amberchan et al., 2021 (link)). ¹H NMR spectra were recorded in CDCl₃ using the JEOL JNM-ECX400 (400 MHz) FT NMR, JEOL JNM-ECS400 (400 MHz) FT NMR, and the Bruker BioSpin Ascend 400 spectrometer (400 MHz) with Me₄Si as the internal standard. ¹³C{¹H} NMR spectra were recorded in CDCl₃ using the JEOL JNM-ECX400 (100 MHz) FT NMR, JEOL JNM-ECS400 (100 MHz) FT NMR, the Bruker BioSpin Ascend 400 spectrometer (100 MHz).

Sodium borohydride (99%), nitrobenzoylhydrazide (99.8%), alginage (98%) Na₂HPO₄ (99%), NaH₂PO₄ (99%) and dimethylsulfoxide (DMSO, 99.9%) were purchased form Adamas (Basel, Switzerland). N-hydroxysuccinimide (NHS, 99%) and N-ethyl-N’-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC, 99%) was purchased from J&K (Beijing, China). The double-distilled H₂O (ddH₂O) was purified by a Synergy (Milipore, Burlington, MA, USA). The synthesized 4,4’-azobis(benzoylhydrazide) was characterized by a JNM-ECX400S (JEOL, Tokyo, Japan). The FTIR spectra was achieved by a Nicolet iS 10 Fourier transform inferred spectrometer (ThermoFisher, Waltham, MA, USA). The mechanical properties of the gel were measured by a TA DHR rotational rheometer (TA, Newcastle, DE, USA), and 450 nm light and 365 nm light irradiation of the gel was carried by a light curing lamp equipped with 365 nm LED (20 W, 809 mW/cm²) and 450 nm LED (20 W, 809 mW/cm²) purchased from Shenzheng Bashuguang Zhaoming Co. (Shenzheng, China).

The 4,4’-azobis(benzoylhydrazide) was synthesized according to a previous report [38 (link)]. Sodium borohydride (3.405 g, 0.09 mol) was dissolved in the 25 mL of DMSO at 85 °C. Then, 4-nitrobenzoylhydrazide (2.297 g, 0.015 mol) was dissolved in 12 mL of DMSO and added dropwise into the sodium borohydride solution for over 10 min. The mixture was reacted for 1.5 h under 85 °C, and was poured into 150 mL of water, neutralized to pH 7 with diluted HCl. The precipitate was filtered and washed by methanol and dried under 80 °C for 72 h. Afterwards, the orange precipitate was recrystallized from DMSO to obtain the pure product. The product did not melt at temperatures up to 320 °C, and the yield was 60%. The synthesized 4,4’-azobis(benzoylhydrazide) was characterized by 1D ¹H Nuclear Magnetic Resonance spectroscopy carried out on a JNM-ECX400S (JEOL, Tokyo, Japan) operating at a ¹H frequency of 400 MHz (solvent: DMSO-d₆), 10.22–9.79 ppm (broad, 2H, CONH), 8.38–7.70 ppm (d, 8H, aromatic), 4.78–4.36ppm (s, 4H, NH₂), 3.3 ppm (s, water) and 2.5 ppm (s, DMSO) (Figure S1).