Mechanistic insights into molecular buffering at self-assembled interfaces for gas drag reduction

Controlling energy dissipation at gas-solid interfaces is crucial for efficient gas transport, yet the mechanism of drag-reducing agents (DRAs) in natural gas pipelines remains debated due to a lack of direct microscopic evidence: does it work primarily by surface smoothing or by forming an elastic interface? Herein, we combine molecular dynamics simulations, density functional theory, and pipeline loop experiments to unveil, at the molecular level, how a self-assembled DRA-film acts as a molecular buffer to reduce energy loss. We show that an ordered monolayer, formed at a critical density of 0.867 N/nm2, reduces drag via two mechanisms: a structural deflection effect that increases the methane deflection angle from 60° to 110°, promoting forward transport; an energy buffering effect where flexible alkyl chains absorb kinetic energy via conformational changes, reducing energy loss per collision by 42%-54% moving beyond the traditional surface smoothing paradigm. Macroscopically, loop experiments confirm a drag reduction rate of 4.3%-6.6% during the stable film stage. This work establishes a fundamental structure of property relationship from molecular-scale interfacial design to macroscopic flow performance, providing a mechanistic foundation for developing next-generation energy-saving pipeline technologies and principles for managing interfacial energy dissipation.