Hairy Inorganic Nanoparticles for Oil Lubrication

High-performance, environmentally benign oil lubricants are constantly sought in industry, driven by the demands for better machine reliability, higher energy efficiency, and stricter environmental protection. This chapter shows that oil-soluble polymer brush-grafted inorganic nanoparticles (hairy NPs), synthesized by surface-initiated reversible deactivation radical polymerization, are a promising class of environmentally friendly lubricant additives for friction and wear reduction. Poly(alkyl methacrylate) brush-grafted NPs with sufficiently long alkyl pendant groups demonstrated excellent dispersibility and stability in polyalphaolefin (PAO) over a wide temperature range and significantly reduced friction and wear when used as PAO additives. A synergistic effect was observed when oil-soluble hairy silica NPs and a phosphonium–phosphate ionic liquid were combined as friction reducers at appropriate ratios for PAO, resulting in improved lubrication performances. A class of thermoresponsive polymers in PAO was discovered, making it possible to synthesize ABA triblock copolymers to gel PAO for use as injectable gel lubricants.