Mechanochemistry of Physisorbed Molecules at Tribological Interfaces: Molecular Structure Dependence of Tribochemical Polymerization

Xin He, Seong H. Kim

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34 Scopus citations


Physisorbed molecules at a sliding solid interface could be activated by mechanical shear and react with each other to form polymeric products that are often called tribopolymers. The dependence of the tribopolymerization yield on the applied load and adsorbate molecular structure was studied to obtain mechanistic insights into mechanochemical reactions at a tribological interface of stainless steel. Three hydrocarbon precursors containing 10 carbon atoms-α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22)-were chosen for this study. α-Pinene and pinane are bicyclic compounds with different ring strains. N-Decane was chosen as a reference molecule without any internal strain. By comparing the adsorption isotherm of these molecules and the total volume of tribopolymer products, the reaction yield was found to be proportional to the number of adsorbed molecules. An Arrhenius-type analysis of the applied load dependence of the tribopolymerization yield revealed how the critical activation volume (ΔV*) varies with the structure of adsorbed molecules. The experimentally determined ΔV* values of α-pinene, pinane, and n-decane were 3, 8, and 10% of their molar volumes, respectively. The molecule with the largest ring strain (α-pinene) showed the smallest ΔV*, which implies the critical role of internal molecular strain in the mechanochemical initiation of polymerization reaction. The tribopolymer film synthesized in situ at the sliding interface exhibited an excellent boundary lubrication effect in the absence of any external supply of lubricant molecules.

Original languageEnglish (US)
Pages (from-to)2717-2724
Number of pages8
Issue number11
StatePublished - Mar 21 2017

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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