Lubrication with oil-compatible polymer brushes

Abstract

A polymer-brush-based, surface-modification strategy for friction and wear reduction in hard contact under boundary-lubrication conditions is proposed, specifically for a non-aqueous environment. Surface-initiated Atom Transfer Radical Polymerization (SI-ATRP) was employed for the synthesis of three different oil-compatible, hydrophobic polymer brushes based on alkyl methacrylates. This study presents polymerization kinetics, chemical characterization by means of Fourier transform infrared spectroscopy (FTIR) and surface morphologies observed in atomic force microscopy (AFM). The lubrication properties of the anchored polymers were evaluated macroscopically by means of ball-on-disk methods and on the nanonewton scale by lateral force microscopy (AFM/LFM) and showed significant reduction in friction up to contact pressures as high as 460 MPa. The frictional response of surface-grafted polymers is shown to depend strongly on the compatibility of the polymer with the chosen lubricating fluid. Their good tribological performances have also been proven with watchmaking lubricants. These results do make the prevent invention a suitable candidate for a watchmaking application (such as at the balance pivot or the escapement) in order to increase the efficiency and reliability of the movements.