Molecular Interfacial Interaction Mechanism between Graphene–SBS and Bitumen Components

In recent decades, studies on graphene-modified bitumen remain limited, as the poor dispersion of graphene and its weak interfacial interaction with the bitumen matrix significantly reduce its reinforcing effectiveness. Moreover, styrene-butadiene-styrene (SBS)-modified bitumen demonstrates insufficient thermal stability. To address these issues, researchers have incorporated both graphene and SBS into bitumen. However, a comprehensive understanding of the three-phase interface interaction mechanism among graphene, SBS, and bitumen remains unclear. The objective of this research was to systematically investigate the synergistic mechanism of the three-phase molecular interface between graphene, SBS, and bitumen for the first time by applying molecular dynamics simulations. The results indicated that graphene formed stable interfacial bonds with components such as asphaltene and resin in bitumen via π-π stacking and van der Waals forces. It was shown that SBS was mechanically entangled with graphene through flexible chain segments. Together, these three components generated a three-dimensional interpenetrating network that significantly enhanced both interfacial binding energy and charge transfer efficiency. Compared to the base bitumen, SBS-, graphene-, and hybrid-modified bitumen remarkably improved the high-temperature stability, fatigue resistance, and low-temperature crack resistance. The obtained knowledge provides a theoretical base for the molecular design and interfacial improvement within high-performance pavement materials as a significant factor for extending pavement's service life.