Ifat Kaplan-Ashiri 1 Ohad Goldbart 2 Andrey Enyashin 3 Sidney R. Cohen 1 Reshef Tenne 2 H. Daniel Wagner 2
1Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
2Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
3Institute of Solid State Chemistry, Institute of Solid State Chemistry, Ekaterinburg, Russia

The use of different nanostructures as fillers in polymer composite materials attracts an ever-growing interest. While the impact of nanoparticles on composite properties is well studied, the relations between individual filler nanoparticles and the host matrix are yet to be fully understood. The elucidation of these interactions on the bulk composite properties requires the study of the wetting, adhesion to the matrix, surface energy, morphology etc. of a single nanoparticle.

It was reported that the addition of these inorganic nanoparticles leads to improved mechanical properties [1], thermal stability [2] and electrical properties [3] of the polymer composites. Although those nanoparticles alter the properties of the composite, the nature of the nanotube-matrix interactions is still vague. The goal of our study is to investigate the interactions of single WS2 nanotubes with different matrices and liquids.

In this work, a new technique to measure the interactions of individual nanotubes with different liquids and polymers is presented. This technique is based on pullouts of nanotubes from water films and other liquids using environmental scanning electron microscope (ESEM) and atomic force microscope (AFM) [4] systems. Using these techniques the effect of WS2 nanotube morphology and structure on the interaction strength between different liquids and the nanotubes are assessed. From these experiments, as well as from theoretical simulations, it follows that the morphology of the WS2 nanotube has a significant effect on the interaction of the NT and the surrounding media.

The interaction energy/cross-section area of the nanotubes falls-off dramatically with the diameter of the nanotubes (30-70 nm) and then levels-off. These differences are currently attributed to the capillary interaction of the small hollow core nanotubes and the water molecules. MD simulations show that the highly confined space results in large interaction energy between the water molecules and the inner core of the nanotubes. This interaction leads to imbibition of the water molecules into the nanotube’s hollow core. These effects and the impact of the nanotubes surface chemistry on the interaction energy are presented and discussed.

[1] Zohar, E., Baruch, S., Shneider, M., Dodiuk, H., Kenig, S., Tenne, R., Wagner, H.D., The effect of WS2 nanotubes on the properties of epoxy-based nanocomposites, J. Adhes. Sci. Technol. 25, 1603-1617 (2011).

[2] Naffakh, M., Martin, Z., Fanegas, N., Marco, C., Gomez, M., Jiménez, I., Influence of inorganic fullerene‐like WS2 nanoparticles on the thermal behavior of isotactic polypropylene, J. Polym. Sci., Part B: Polym. Phys. 45, 2309-2321 (2007).

[3] Voldman, A., Zbaida, D., Cohen, H., Leitus, G., Tenne, R., A Nanocomposite of Polyaniline/Inorganic Nanotubes, Macromol. Chem. Phys. 214, 2007-2015 (2013).

[4] Barber, A.H., Cohen, S.R., Wagner, H.D., Static and dynamic wetting measurements of single carbon nanotubes, Phys. Rev. Lett. 92, 186103 (2004).

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