Regulation Mechanism of Salt Ions for Superlubricity of Hydrophilic Polymer Cross-Linked Networks on Ti6Al4V.
Poly(vinylphosphonic acid) (PVPA) cross-linked networks on Ti6Al4V show superlubricity behavior when sliding against polytetrafluoroethylene in water-based lubricants. The superlubricity can occur but only with the existence of salt ions in the polymer cross-linked networks. This is different from the phenomenon in most polymer brushes. An investigation into the mechanism revealed that cations and anions in the lubricants worked together to yield the superlubricity even under harsh conditions. It is proposed that the preferential interactions of cations with PVPA molecules rather than water molecules are the main reason for the superlubricity in water-based lubricants. The interaction of anions with water molecules regulates the properties of the tribological interfaces, which influences the magnitude of the friction coefficient. Owing to the novel cross-linked networks and the interactions between cations and polymer molecules, their superlubricity can be maintained even at a high salt ion concentration of 5 M. These excellent properties make PVPA-modified Ti6Al4V a potential candidate for application in artificial implants.
Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology , Beijing 100124, China.
Caixia
0000-0003-1312-5171
C
Zhang
State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, PR China.
Yuhong
Y
Liu
Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology , Beijing 100124, China.
Zhifeng
Z
Liu
State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, PR China.
Hongyu
H
Zhang
Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology , Beijing 100124, China.
Qiang
Q
Cheng
Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology , Beijing 100124, China.
Congbin
C
Yang