Recent development in friction of supramolecular gel lubricant: from mechanisms to applications

Due to the unique self-assembling structure and rheological properties, supramolecular gel lubricants have become the third major type of liquid lubricating materials to supplement the lubricating oils and greases. The molecular structures of gelators applicable to oil-based, water-based and extreme conditions base oils were summarized firstly. Furthermore, this review aims at exploring the relationships between the molecular structures of gelators and the gel-forming, rheological and tribological properties of gel lubricants. Based on the wide application of gel in various lubrication fields, the synergistic lubricating effect between gel lubricants and nanomaterials, films, textured surfaces were analyzed. The design of solid-liquid composite lubrication systems based on gel lubricants and solid lubricants were attempted to be highlighted and revealed. Finally, the perspectives on the development of gel lubricants and corresponding composite lubricating materials were presented.