Covalent functionalization of activated MoS ₂ via using alkyl sulfide and their utilization in polymeric composites with mechanical and thermal property enhancements

Abstract Recently developed covalent functionalization of chemically exfoliated MoS ₂ (typically in alkyl lithium) allows the formation of chalcogenide‐carbon bonds by reacting with organohalides and aryl diazonium salts. We herein develop a novel method for the covalent functionalization of MoS ₂ to yield dodecylated MoS ₂ via reductive activation in a strongly reducing sodium‐naphthalene solution and using alkyl sulfide as an electrophile. Dodecylated MoS ₂ /polystyrene (PS) composites fabricated by solution casting method. Dodecyl chains are grafted successfully onto MoS ₂ nanosheets, which gives rise to the exfoliation level of few‐layer thickness and matched compatibility with the host polymeric matrix. The inclusion of dodecylated MoS ₂ at a concentration of 1.0 wt% yields a substantial improvement in both Young's modulus and tensile strength, with a 106.7% increase and a 67% enhancement, respectively, as compared to the performance of pure PS. The enhanced mechanical characteristics can be credited to the uniform dispersion of dodecylated MoS ₂ within the PS matrix and enhanced interfacial interaction between the PS material and the filler. The composites demonstrate a significant increase in their glass transition temperature ( T _g ). Notably, the dodecylated MoS ₂ /PS (1.0 wt%) composite exhibits a 59.8% elevation in storage modulus when compared to pure PS. The coke yield of dodecylated MoS ₂ /PS (1.0 wt%) reaches 2.7%, much larger than the value (only 0.2%) for pure PS. The novel functionalization might expedite the applications of molybdenum disulfide in diverse fields. Highlights A novel method for the covalent functionalization of MoS ₂ . Dodecylated MoS ₂ /PS composites were fabricated via solution casting method. Ultrathin structure of MoS ₂ nanosheets was obtained after functionalization. Composites improvement in Young's modulus and tensile strength compared to PS. The composites show significant enhancements in T _g .