Molybdenum Sulfide Nanoparticles in Block Copolymer Micelles: Synthesis and Tribological Properties

Synthesis of polystyrene-block-polybutadiene (PS-b-PB) and polystyrene-block-polyisobutylene (PS-b-PIB) micelles filled with MoSx nanoparticles was carried out in a one-pot procedure in heptane using complexation with Mo(CO)6 followed by interaction with H2S. The structure and composition of Mo carbonyl complexes and MoSx-containing micelles were studied using FTIR, static light scattering, turbidimetry, and transmission electron microscopy. By varying the reaction atmosphere (argon or CO) during interaction with Mo(CO)6, the location of MoSx species obtained after sulfiding was tailored. Carrying out complexation with PS-b-PB in CO, which is also a reaction product, prevents complexation in the PS micelle core, thus providing location of Mo species only in the PB corona. Antifrictional tests show that this location leads to better tribological performance: lower friction coefficient or higher critical load (at which the friction coefficient is measured). When MoSx species are located in the PS core (complexation with Mo(CO)6 was carried out in argon atmosphere), low density of the micelles in the case of PS-b-PIB block copolymer with a short PS block provides much better antifrictional performance than those with the dense PS-b-PB micelles.