The use of tungsten disulfide (WS₂) nanoparticles offers the opportunity to produce novel and advanced polymer-based nanocomposite materials via melt blending. The developed materials, based on the high-performance engineering thermoplastic polyphenylene sulfide (PPS), display a unique nanostructure on variation of the nanoparticle concentration, as confirmed by time-resolved synchrotron X-ray diffraction. The cold-crystallization kinetics and morphology of PPS chains under confined conditions in the nanocomposite, as determined by differential scanning calorimetry (DSC) and atomic force microscopy (AFM), also manifest a dependence on the IF-WS₂ concentration which are unexpected for polymer nanocomposites. The addition of IF-WS₂ with concentrations greater than or equal to 0.5 wt % of IF-WS₂ remarkably improves the mechanical performance of PPS with an increase in the storage modulus of 40−75%.