High-Loading MoS2 Inverse Vulcanized Glass Composites through Homogeneous Molten Sulfur as a Reactive Processing Medium

Abstract

Elemental sulfur has been used as a feedstock for polymer synthesis via the inverse vulcanization (IV) process. However, the role of molten sulfur itself as a high-temperature reactive processing medium for inorganic composite fabrication remains comparatively unexplored. Herein, we demonstrate that ultrahigh-purity sulfur (99.998%) functions simultaneously as a reactive monomer, transient dispersive medium, and processable precursor for the fabrication of highly filled inverse vulcanized glass (IVG)–molybdenum disulfide (IVG-MoS2) composites. Bulk micron-scale MoS2 particulates were incorporated at unusually high filler loadings (20–40 wt %) through iterative melt–mix–grind–remelt processing without requiring extensive nanosheet exfoliation, solvent-assisted processing, or surface functionalization. Subsequent inverse vulcanization with norbornadiene dimer (NBD2) afforded sulfur-rich glass composites exhibiting broad melt processability, centimeter-scale casting capability, and dynamic thermomechanical reprocessability arising from dense sulfur–sulfur covalent adaptability within the IVG covalent adaptable network (CAN). Mechanical characterization revealed systematic increases in flexural modulus and impact strength with increasing MoS2 incorporation, while the ability to reproducibly fabricate and notch specimens for standardized Izod impact testing highlights the unusual bulk coherence of these highly filled, sulfur-rich glass composites. Repeated hot-press reprocessing retained bulk mechanical integrity even in highly filled composites containing 20 wt % MoS2. Collectively, these findings establish homogeneous molten sulfur as an effective reactive processing medium for the fabrication of mechanically coherent, highly filled, and dynamically reprocessable sulfur-rich glass composites derived from inverse vulcanization.