Directional Hydration Lubrication Underwater: Enabled by Tannic Acid/Polyacrylamide Submicron Particles

Abstract

Abstract. Achieving durable hydration lubrication underwater is challenging due to interference from interfacial hydration layers. This study developed tannic acid (TA)/polyacrylamide (PAAm) submicron particles, synergistically combining TA's adhesive pyrogallol groups with PAAm's hydrophilic chains to enhance aqueous lubrication. Tests demonstrated that TA/PAAm suspensions improved the wettability of ultra-high-molecular weight polyethylene (UHMWPE) surfaces by 42% compared to untreated samples. Relative to deionized water lubrication, TA/PAAm suspensions reduced the friction coefficient of UHMWPE by 29% and decreased the wear volume by 56%. The TA component immobilizes submicron particles onto surfaces via adhesion to form a protective film, while PAAm disrupts hydration layers through its hydrophilicity, thereby enhancing lubrication performance relative to deionized water. This strategy provides an environmentally friendly directional lubrication solution for marine applications such as water-lubricated bearings and subsea mechanical seals.