A study of the microscopic interaction mechanism of styrene–butadiene-styrene modified asphalt based on density functional theory

ABSTRACT

The excellent dynamic performance of styrene–butadiene-styrene (SBS)-modified asphalt comes from the interaction of the molecules, but the interaction mechanism between the SBS polymer and asphalt molecules is not well understood. This study uses density functional theory (DFT) to explore the interaction between the SBS polymer and asphalt molecules, aiming to reveal the micromechanism of the SBS-modified asphalt mechanical response and morphology at the atomic scale. Interaction models between the SBS polymer and four component molecules (asphaltene, resin, aromatic and saturate) were constructed, and DFT simulations of these models were performed. The interaction stability was quantified by the binding energy ($E_{Binding}$), the interaction tightness and type were quantified by the charge transfer number ($Q_{transfer}$), and the microscopic mechanism of the interaction was analysed. The results show that the binding energies between the SBS polymer and asphalt molecules are all less than 0 Ha, which indicates that the SBS polymer and asphalt system can be physically mixed, and the absolute value of the binding energy does not exceed 0.4 Ha, which indicates that the interaction between the SBS polymer and asphalt is not stable. $Q_{transfer}$ are all less than 0.2 e, which indicates that the SBS polymer does not chemically react with asphalt. In addition, the interaction morphology between the SBS polymer and the asphalt molecules indicates that the SBS polymer and resin A, resin C and aromatic A have a T-type stacking interaction, while the SBS polymer and aromatic B have an F-type stacking interaction. In addition, the SBS polymer interacts tightly with the saturated molecules, but they are not stable. In general, the order of the interaction strength between the SBS polymer and the four-component molecules is aromatic > saturate > resin > asphaltene.

GRAPHICAL ABSTRACT

KEYWORDS:

• SBS-modified asphalt
• molecular interaction
• density functional theory
• microcosmic mechanism
• π-π stacking interaction

Acknowledgments

This work was financially supported by the Chinese Natural Science Foundation (51708182), cultivation programme for young backbone teachers in Henan University of Technology and the young-backbone teacher project of Henan Province in 2019 (2019GGJS087).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by National Natural Science Foundation of China [grant number 51708182]; the Young-Backbone Teacher project of Henan Province in 2019 [grant number 2019GGJS087] and Cultivation programme for Young Backbone Teachers in Henan University of Technology [in 2019].