LIQUID ADHESION AND CAPILLARY ACTIONS AT THE NANOSCOPIC LEVEL: DIRECT OBSERVATIONS OF INTERACTIONS BETWEEN WATER AND SINGLE WS₂ NANOTUBES

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.

It was reported that the addition of inorganic nanoparticles leads to improved mechanical properties , thermal stability etc. of 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) systems. Using these techniques and theoretical simulations , the effect of WS₂ nanotube morphology and structure on the interaction with water were measured and assessed. From these experiments it follows that the morphology of the WS₂ nanotube has a significant effect on the interaction of the NT and the surrounding media.

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.