Mo(VI) dithiocarbamate with no pre-existing Mo-S-Mo core as an active lubricant additive

MoDTC molecular additives reduce friction in boundary lubricated steel-steel contacts through formation of MoS2 sheets. The chemical pathway from MoDTC to MoS2 is investigated for optimizing MoS2 formation. Our experiments show that a MoDTC molecule containing sulfur only in its thiocarbamate ligands forms MoS2 sheets during friction, demonstrating that the presence of peripheral thiocarbamate ligands can be sufficient to provide the required sulfur source. This molecule is not only competitive with MoDTC containing sulfur in the core of the molecule but also more efficient at high contact pressures. Mechanistic investigations on the chemical transformation of MoDTC to MoS2 reveal that thermal activation alone is not sufficient thus suggesting that pressure and/or shear are necessary for MoS2 generation in this system.

Automated summary

MoDTC molecular additives reduce friction in boundary lubricated steel-steel contacts by forming MoS2 sheets. The presence of peripheral thiocarbamate ligands is sufficient to provide the required sulfur source. Pressure and/or shear are necessary for MoS2 generation in this system as thermal activation alone is not sufficient.