Sulfur-Rank-Dependent Dispersion and Precipitation Behavior of Structurally Defined Sulfur-Containing Polymers

The structural factors governing dispersion and precipitation in sulfur-containing polymer systems remain poorly understood. Sulfur-containing polymer microparticles are prepared by the dispersion copolymerization of 1,7-octadiene diepoxide (OD) with polysulfide species generated in situ from elemental sulfur and sodium sulfide. Among the examined stabilizers, only poly(vinylpyrrolidone) enables particle formation, whereas the other stabilizers result in precipitation, allowing dispersed and precipitated fractions to coexist for structural comparison. The resulting PolyOD-S_n polymers possess structurally defined backbones, enabling the average sulfur rank, n, defined as the average number of consecutive sulfur atoms in a polysulfide segment, to be estimated using ¹H NMR chemical-shift analysis combined with elemental-composition analysis. Fractionation by natural sedimentation and filtration shows that polymers with higher average sulfur ranks preferentially precipitate, whereas those with lower average sulfur ranks remain dispersed. In contrast, no clear correlation is observed between molecular weight and fractionation behavior. These findings indicate that sulfur rank, rather than overall molecular weight, provides a distinct structural basis for the dispersion/precipitation behavior of sulfur-containing polymers.