Time and Spatially Resolved Raman Spectroscopic Observation for Superlubricious Frictional Interfaces of Concentrated Polymer Brushes

Abstract Pursuing durable superlow friction tribological systems is essential for addressing global energy challenges and achieving carbon neutrality by 2050. Inspired by the exceptional frictional performance of human knee joints, concentrated polymer brushes (CPBs) have emerged as a promising solution for artificial tribological applications. However, a major challenge remains in the reduced durability of CPBs compared to traditional hard materials, particularly in maintaining superlow friction over extended use. This study focuses on understanding the mechanisms behind the vanishing superlow friction and wear of CPBs lubricated with ionic liquids (ILs). To investigate these phenomena, we developed a real-time and spatially resolved “in-operando Raman tribometer” for real-time monitoring of molecular dynamics at friction interfaces. Time and spatially resolved Raman measurements revealed critical insights into the polymer chain behavior, IL film drainage, and internal stress changes that influence friction and wear mechanisms. Our results suggest that the “probe vertical lift” phenomenon and distribution of the solid–liquid interface structure play key roles in the transition from superlow to high friction and accelerated wear. These findings provide a foundation for developing durable, energy-efficient tribological systems in various industrial applications.