Effects of conformational entropy on antiwear performances of organic friction modifiers

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.