Nanocomposites and nanomaterials

Superhydrophobic multi-walled carbon nanotubes/poly(dimethylsiloxane) nanocomposite materials: Fabrication and characterization
I.Ya. Sulym1, A. Kubiak2, Y. Sementsov1, A. Basa3,
 B. Kalska-Szostko3, F. Ciesielczyk2, T. Jesionowski2
1Chuiko Institute of Surface Chemistry, NASU, 17 General Naumov Str., 03164 Kyiv, Ukraine. E-mail: irynasulym@ukr.net.
2Faculty of Chemical Technology, Institute of Chemical Technology and Engineering Poznan University of Technology, Berdychowo 4, PL-60965 Poznan, Poland.
3Institute of Chemistry, Univesity of Białystok, K. Ciolkowskiego 1K, 15-245 Białystok, Poland.

Superhydrophobic surfaces resisting water penetration into their texture under dynamic impact conditions and offering simultaneously additional functionalities can find use in a multitude of applications. The commonly used polymer in this field is (poly)dimethylsiloxane (PDMS) which generates interest due to its low cost and properties including: thermal stability, transparency and surface activity. On the other hand carbon nanotubes are able to create a surface having both microscale and nanoscale, owing to their rigid cylindrical nanostructure.
This work concerns superhydrophobic nanocomposites based on multi-walled carbon nanotubes and linear PDMS of two molecular weights (PDMS-100 and PDMS-12500 with Mw ≈ 3410 and 39500 g/mol, respectively). The polymer fluids were physically adsorbed onto nanotubes surfaces in amounts of 5-40 wt. %. The hydrophobicity and micro-/nanostructure of the resulting nanomaterials were studied by means of contact angle measurements and microscopic investigation (TEM) with respect to the content of PDMS in MWCNTs, and polymer chain length. The pure MWCNTs gives CA = 57 ± 1° as a reference. It was found that CA sharply increases with adsorbed 5 wt. % of polymer. With further increase in PDMS content, a transition range from normal hydrophobic to superhydrophobic states was observed. A stable superhydrophobic state (152 ± 1°) was reached for MWCNTs/PDMS composites with polymer concentration of 20 – 40 wt. %. The apparent surface free energy decreases after adsorption of polymer onto nanotubes surfaces and reaches a minimum (0.91 mJ/m2) at PDMS concentration of 40 wt. %.
Acknowledgments: The authors acknowledge financial support by the Centre for East European Studies (University of Warsaw) within the framework of "NAGRODA im. I. WYHOWSKIEGO" supporting the scientific internship of Dr. I. Sulym at Poznan University of Technology and University of Bialystok as well as EU funds via project POPW.01.03.00-20-034/09-00, POPW.01.03.00-20-004/11-00.