Effects of conformational entropy on antiwear performances of organic friction modifiers

Abstract

Organic friction modifiers (OFMs) are widely used in lubricants. However, the mechanism of their structure–activity relationship still needs further exploration. Herein, we found that glyceryl monoelaidate (GME) with a trans double bond, exhibits a better antifriction and antiwear performance than glyceryl monooleate (GMO), the cis isomer of GME. Glyceryl monostearate (GMS) with a saturated tail group is even better. The obvious different tribological performance of three different OFMs with slight molecular structure difference is attributed to the different entropy decreasing they form a boundary film on steel surfaces, which affected their surfacial-coverage. The disclosed conformation entropy effect on surfacial-coverage of boundary film could guide the design of more novel and effective OFMs.