Mechanochemical Association Reaction of Interfacial Molecules Driven by Shear
journal contributionposted on 29.04.2018, 00:00 authored by Arash Khajeh, Xin He, Jejoon Yeon, Seong H. Kim, Ashlie Martini
Shear-driven chemical reaction mechanisms are poorly understood because the relevant reactions are often hidden between two solid surfaces moving in relative motion. Here, this phenomenon is explored by characterizing shear-induced polymerization reactions that occur during vapor phase lubrication of α-pinene between sliding hydroxylated and dehydroxylated silica surfaces, complemented by reactive molecular dynamics simulations. The results suggest that oxidative chemisorption of the α-pinene molecules at reactive surface sites, which transfers oxygen atoms from the surface to the adsorbate molecule, is the critical activation step. Such activation takes place more readily on the dehydroxylated surface. During this activation, the most strained part of the α-pinene molecules undergoes a partial distortion from its equilibrium geometry, which appears to be related to the critical activation volume for mechanical activation. Once α-pinene molecules are activated, association reactions occur between the newly attached oxygen and one of the carbon atoms in another molecule, forming ether bonds. These findings have general implications for mechanochemistry because they reveal that shear-driven reactions may occur through reaction pathways very different from their thermally induced counterparts and specifically the critical role of molecular distortion in such reactions.
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shear-driven reactionstransfers oxygen atomsα- pineneshear-induced polymerization reactionsvapor phase lubricationreaction pathwaysassociation reactionsShear Shear-driven chemical reaction mechanismsdehydroxylated surfaceoxidative chemisorptionactivation volumeSuch activationreactive surface sitesequilibrium geometryactivation stepα- pinene moleculesInterfacial Moleculescarbon atomsether bondsadsorbate moleculeMechanochemical Association Reactiondynamics simulationsdehydroxylated silica surfaces