Synthesis and Characterization of N-15-Labeled Poly(sulfur nitride) in Bulk and in Superconductor Composites

N-15-labeled tetrasulfur tetranitride ((S4N4)-N-15) was synthesized by reacting S2Cl2 with (NH3)-N-15. The reaction was finalized with (NH3)-N-14. The successful labeling was confirmed by solution N-15 nuclear magnetic resonance (NMR) spectroscopy. (S4N4)-N-15 was used for the synthesis of poly(sulfur nitride) (SNx)-N-15 via the intermediate species of S2N2. It was a topochemical polymerization in the solid state. The isotope ratio in the labeled polymer was obtained by laser deposition ionization time-of-flight mass spectroscopy. Solid-state N-15 NMR spectroscopy of (SNx)-N-15 indicates that at least three different chemical environments for N-15 atoms are present in the crystals. Finally, SNx was polymerized in the presence of two other superconductors, MgB2 and yttrium barium copper oxide (YBCO), which demonstrates the capability of SNx for grain boundary engineering.