Friction Reduction of Lubricant Base Oil by Micelles and Crosslinked Micelles of Block Copolymers

Abstract

Diblock copolymers with one block soluble and the other block insoluble were dispersed in an industrial base oil (BO) to yield spherical micelles (SMs). SMs were also prepared in more manageable solvents that had similar solubility properties as the BO towards the copolymers but had lower viscosities and lower boiling points and absorbed less in the near UV region. The photocrosslinking of the cores of the latter micelles yielded crosslinked micelles or nanospheres. We have tested the lubrication properties of the micelle and nanosphere samples in BO under conditions simulating those found in automobile engines. Solutions of micelles and nanospheres with 2-cinnamoyloxyethyl acrylate units in their cores exhibited a unique friction reduction pattern and had friction coefficients that were significantly lower in the boundary lubrication regime (BLR) than in the mixed lubrication regime. Such particles reduced the friction of the BO by > 70% in the BLR and performed substantially better than the widely used industrial anti-friction agent glyceryl monooleate. The factors affecting this unique friction reduction behavior were investigated and a possible reason for it was proposed.

KEY WORDS:

• Block Copolymer
• Micelles
• Lubrication
• Friction Reduction

ACKNOWLEDGEMENTS

The NSERC CRD program of Canada and Afton Chemical, Inc., are thanked for sponsoring this research. GL thanks the Canada Research Chairs Program for a chair position in Materials Science.

Review led by Elaine Yamaguchi

Notes

^aMicelles prepared in THF/CH at v/v = 2/8. The tBA groups were partially hydrolyzed after nanosphere preparation.

^bMicelles prepared in CH at 55°C.

^cMicelles were prepared in THF/CH at v/v = 5/95. The tBA groups were hydrolyzed after nanosphere preparation.

^dMicelles were prepared in CH at 60°C. X# denotes samples with different degrees of PCEA crosslinking.

^eSamples were dissolved in THF. To the THF solutions were added EHC-45. THF was removed by rota-evaporation.