Surface-Functionalized MoS2 Nanosheets for Enhanced Performance of SBS-Modified Asphalt Binders: Rheological Properties and Interfacial Interactions

The application of two-dimensional molybdenum disulfide (MoS2) in asphalt binder modification is limited by its inherent chemical inertness and severe agglomeration. In this study, four surface-functionalization strategies, including (3-aminopropyl)triethoxysilane (APTES) silanization, polydopamine (PDA) coating, tannic acid (TA)–APTES co-deposition, and PDA–APTES hybrid modification, were used to improve the dispersion and compatibility of MoS2 nanosheets in styrene–butadiene–styrene (SBS)-modified asphalt binders. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) results indicated that surface functionalization introduced organic functional groups, reduced nanosheet restacking, and preserved the intrinsic 2H-MoS2 crystal structure. Binder-level rheological tests and thermogravimetry–differential scanning calorimetry (TG–DSC) analysis showed that surface-functionalized MoS2 improved the high-temperature deformation resistance, creep recovery, fatigue resistance, low-temperature relaxation capacity, and thermal stability of SBS-modified asphalt. Among the investigated binders, PDA–APTES-functionalized MoS2/SBS-modified asphalt exhibited the most balanced performance. At 3.2 kPa, its recovery rate reached 79.5%, while its non-recoverable creep compliance decreased to 0.105 kPa−1. Its fatigue life at 15% strain increased by 76.8% compared with SBS-modified asphalt, and its creep stiffness at −24 °C decreased to 222 MPa. Mechanistic interpretation suggests that the PDA–APTES hybrid layer may act as an organic–inorganic interfacial transition region, improving MoS2 dispersion and compatibility with the SBS–asphalt phase and facilitating more effective integration of the nanosheets into the composite structure. These results indicate that PDA–APTES-functionalized MoS2 nanosheets are promising interfacial modifiers for improving the rheological and thermal performance of SBS-modified asphalt binders.