The Preparation And Modification Of Nanometer Molybdenum Disulfide And Its Application In Composite Materials

In recent years the rapid development of nanoscience has led to the polymer based composites become the prominent research interests of current research. Inclusion of nanofillers, especially for the layered nanofillers, into polymer matrices through certain physical or chemical methods has become one of the most popular ways to prepare advanced composite materials. Molybdenum disulfide （MoS₂） is a new two-dimensional （2D） layered material that has attracted considerable attention because of its unique structure and its optical and electronic properties. But the nature of MoS₂ is not compatible with the organic polymer matrix, which leads to inefficient performance improvement of polymer based composites. Besides, the individual sheet of MoS₂ tends to restack owing to the van der Waals interactions between the interlayers of nanosheets. These disadvantages limit its application. An effective way to figure out these problems is the surface modification of MoS₂ nanosheets. In addition, we also find that few reports have been focused on the polymer nanocomposites doped by functional ization of molybdenum disulfide.In this article, we adopted Morrison’s chemical Li-intercalation method, combined with hydrothermal reaction in advance to fabricate 2D MoS₂ nanosheets in a high yield. To fully harness the properties of such a new material, these chemically exfoliated MoS₂ nanosheets were modified by thiol-terminated ligands, such as 2-aminoethanethiol （HSCH₂CH₂NH₂） and mercapto acetic acid （HSCH₂CH₂COOH）. X-ray photoelectron spectroscopy （XPS） and thermogravimetric analyses （TGA） were used to verify the successful ligand conjugation. The conjugates were able to maintain the stability of MoS₂ nanosheets for more than 2 months compared to native ce-MoS₂ nanosheets, which could be seen from the digital pictures.ce-MoS₂（CH₂）₂NH₂/waterborne polyurethane （WPU） composites were prepared by solution blending method. To achieve different ce-MoS₂（CH₂）₂NH₂ concentration with respect to WPU, different amount of ce-MoS₂（CH₂）₂NH₂ dispersions were added to the WPU dispersions under stirring. The digital pictures showed that 0.05 wt% and 0.1 wt% films were dispersed uniformly with uniform color but the reunion of 0.2 wt% composite film was visible to the naked eye. The homogenous color indicated that appropriate ce-MoS₂（CH₂）₂NH₂ was not only successfully incorporated into the WPU matrix but also in a homogeneous dispersion. Scanning electron microscopy （SEM） photographs could confirm the phenomenon. The results of tensile test indicated the more addition of 2D MoS₂ nanosheets, the more excellent mechanical property was achieved, DMA picture showed that the storage modulus of composites enhanced, but glass transition temperature （Tg） had little change. TGA results suggested that incorporating ce-MoS₂（CH₂）₂NH₂ into WPU matrix delayed the thermal degradation of WPU molecular chains, to a certain extent, improved the thermal stability of the composites.ce-MoS₂（CH₂）₂NH₂/polyimide （PI） composites were fabricated by situ polymerization method. The digital pictures and SEM images confirmed the outstanding compatibility of ce-MoS₂（CH₂）₂NH₂ with PI. The use of ce-MoS₂（CH₂）₂NH₂ as filler in PI could not improve the mechanical properties of composites, which could be seen from the data of tensile test, but DMA picture indicated that low concentrations of ce-MoS₂（CH₂）₂NH₂ leaded to storage modulus of composites enhancement. Z-scan results revealed that pure PI had no contribution to the non-linear optical （NLO） response except for ce-MoS₂（CH₂）₂NH₂/PI composites and 0.05 wt% ce-concentration film had the best optical limiting performance.