IN-SITU, TIME-RESOLVED X-RAY-DIFFRACTION STUDY OF THE SOLID-STATE POLYMERIZATION OF DISULFUR DINITRIDE TO POLYSULFUR NITRIDE

Kinetic and mechanistic aspects of the title reaction were investigate d by time-resolved X-ray powder diffraction combined with Rietveld ref inement. The conversion of S2N2 could be followed through the whole re action with a time resolution of one diffraction pattern per minute. P olymerization of S-2 N-2 at 40 degrees C gave (SN)(x) in quantitative yield, albeit as a mixture of alpha- and beta-(SN)(x) (about 5 and 95 %, respectively). The time dependance of the formation of both (SN)(x) phases is autocatalytic. The reaction could occur as single state pol ymerization, at least up to a monomer conversion of 75 %. Refinement o f atomic coordinates for S and N up to a monomer conversion of 50 % di d not give any evidence for alterations of the molecular geometry of t he reactant, even though lattice parameters varied noticeably with pro gressing conversion.