A　promising　ionic-gemini　molecule,　4,　4＇-di　(n-tetradecyl)　diphenylmethane　disulfate　salt　(DSDM),　is　reported　for　effective　dispersion　of　multi-walled　carbon　nanotubes　(MWCNTs)　in　aqueous　medium　in　the　present　investigation.　The　dispersibility　and　stability　of　the　DSDM-modified　MWCNTs　were　characterized　by　UV-vis　spectrophotometer,　Raman　spectroscopy,　Fourier　transform　infrared　spectroscopy,　transmission　electron　microscopy　and　zeta　potential　measurements.　The　hydrophobic　interaction　between　alky　chains　and　carbon　nanotubes　as　well　as　the　pi-pi-stacking　interaction　between　benzene　rings　and　carboatomic　rings　in　MWCNTs　enables　a　successful　modification　of　DSDM　onto　the　MWCNT　surface.　The　dispersed　MWCNTs　individually　existed　in　dispersion　with　no　structural　damage,　indicating　a　much　better　performance　than　the　MWCNTs　dispersed　by　the　sodium　dodecylbenzene　sulfonate　(SDBS),　a　frequently　reported　single-chain　ionic　dispersant.　Surface　potential　measurements　showed　that　the　DSDM-modified　MWCNTs　were　negatively　charged,　giving　rise　to　electrostatic　repulsion　between　the　MWCNTs　in　aqueous　solution.　A　better　MWCNT　dispersion　effect　was　observed　with　the　increase　in　MWCNT　surface　potential,　and　the　dispersion　with　high　MWCNT　surface　potential　presents　high　dispersion　stability　with　no　agglomeration　appeared　for　more　than　5　months.　The　magnesium　(Mg)　matrix　composite　fabricated　based　on　the　DSDM-dispersed　MWCNTs　demonstrated　excellent　mechanical　properties　compared　to　pure　Mg.　Our　research　may　provide　an　alternative　way　to　improve　the　mechanical　properties　of　composites.　(C)　2017　Elsevier　Inc.　All　rights　reserved.