Influence of molecular structure on lubrication of aqueous triblock copolymer lubricants between rutile surfaces: An MD approach

Abstract

The influence of molecular structure on adsorption and lubrication of aqueous triblock copolymer on TiO 2 surfaces has been investigated using a realistic MD model. Reference data obtained from DFT calculations have been employed to develop an interaction potential between the copolymer and TiO 2 surface. The results show that R Pluronics form an anchor–buoy–anchor structure absorbed on TiO 2 surface and L Pluronic for buoy–anchor–buoy structure. The shear of tribo-system influences slightly on the orientation of copolymers and non-slip behavior has been observed at solid-fluid interfaces due to the strong adhesion strength of copolymer on rutile surface. The shear viscosity increases with copolymer concentration and molecular chain length. L Pluronic has a lower shear stress than the R ones. • A new interacting FF between PEO, PPO and TiO 2 surface results in a better prediction of adsorption of copolymer. • The adsorption of copolymer on TiO 2 surface is physisorption with adsorption energy for PPO block larger than PEO. • The adsorption energy per PPO or PEO chain reduces with an increase of surface coverage and in the presence of water. • R Pluronics form an anchor–buoy–anchor structure on the surface while there is a buoy–anchor–buoy one for L types. • The shear affects the orientation of copolymers, and a non-slip behavior has been observed at solid-fluid interfaces. • The shear viscosity increases with the copolymer concentration and chain length. • L Pluronic has a lower shear stress than the R ones.