Probing the Polymer/Solid Interface and Interphase in Mesostructured 2D-Carbon Nanotube/Polymer Composites: A Combined Study of Experiment and Theory.
Final Report Abstract
One of our central goals in this collaborative project, was to employ a concerted experimental and theoretical approach to understand the interaction of single phase polymers with 3d spatially arranged carbon nanotubes (CNTs) architectures as model systems. The interaction of the CNT material with single phase polymers, such as deuterated polystyrene and PMMA was studied with microscopic and especially diffraction methods (SAXS) in order to gain a deeper understanding of the crucial factors determining the interface and interphase formation in such CNT/polymer hybrids. For the synthesis and alignment of the CNTs, a template-based approach was used. After successful results using this synthetic approach to obtain parallel and aligned CNT/Polymer composites we have focussed in the last part of the funding period towards a catalytically driven CVD technique, which allows to obtain arranged and ordered freestanding CNT arrays without the use of a template. This was a newly introduced process in the project which could result in highly arranged CNTs with narrower diameters and intersticial space between individual CNTs, and importantly an even higher vertical alignment of individual CNTs over larger spatial areas as the one with the so far emplyoyed template technique. It therefore was a meaningful extension of the materials basis in this project. Even so these experiments were proposed originally for a second funding period we were already able in a joint experimental efforts with the Stühn group to obtain important preliminary results providing a fruitful basis for further studies. The application of SAXS to the strictly oriented arrays of CNTs has been shown to be extremely fruitful. A quantitative analysis of the scattering pattern turned out to be possible and it provided detailed information on the distribution of polymer inside the CNTs as well as in the interstices. The method has been extended to the above mentioned free standing CNT arrays. Moreover the imbibition of polymer into the system could be studied with time resolved experiments and provided insight into the flow mechanism. The structure of the interface between polymer and CNT has been characterized. However, the measurement of the single-chain structure factor of chains inside the nanotubes with SANS has not yet been successful. For the theoretical modeling, we used two types of models, one being based on calculating the density of molecules, the other one being based on Monte-Carlo computer simulations. The combined effect of the attractive interaction with the nanotube walls, the entropy decrease due to the impenetrability of the walls and the hexagonal arrangement of the nanotubes with varying gap size in between them leads to a wide array of possible density profiles and polymer configurations as a function of the model parameters. In both models, the effect of the wall can be felt throughout the entire melt at intermediate temperatures. For lower temperatures, polymer chains can become absorbed at the nanotube surface. The knowledge and understanding gained by these theoretical investigations can be a guide for future experiments.
Publications
- "Polymer confinement effects in aligned carbon nanotubes arrays." Physical Chemistry Chemical Physics, 12(17):4407-4417, 2010
Pitamber Mahanandia, Jörg J. Schneider, Marina Khaneft, Bernd Stühn, Tiago P. Peixoto, and Barbara Drossel
(See online at https://doi.org/10.1039/B922906J) - “Density profile and polymer configurations for a polymer melt in a regular array of nanotubes.” New Journal of Physics, 13: 073030, 2011
Tiago Peixoto, Barbara Drossel
(See online at https://doi.org/10.1088/1367-2630/13/7/073030) - "Imbibition of polystyrene melts in aligned carbon nanotube arrays." Journal of Applied Physics, 113(7):074305, 2013
Marina Khaneft, Bernd Stühn, Jörg Engstler, Hermann Tempel, Jörg J. Schneider, Tobias Pirzer, and Thorsten Hugel
(See online at https://doi.org/10.1063/1.4793087)
