Marzena DZIDA1, S?awomir BONCEL2, Bertrand JÓ?WIAK3, Heather F. GREER4, Mateusz DULSKI5, Adrian GOLBA1, Rafa? FLAMHOLC6, Grzegorz DZIDO3, Justyna DZIADOSZ1, Anna KOLANOWSKA7, Rafa? J?DRYSIAK2, ?ukasz SCHELLER1, Krzysztof CWYNAR1, Edward ZOR?BSKI1, Carlos E.s. BERNARDES8, Maria José V. LOURENÇO8, Carlos A. NIETO DE CASTRO8
1University of Silesia in Katowice, Institute of Chemistry, Katowice, Poland
2Silesian University of Technology, Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Gliwice, Poland
3Silesian University of Technology, Department of Chemical Engineering and Process Design, Gliwice, Poland
4University of Cambridge, Department of Chemistry, Cambridge, United Kingdom
5University of Silesia in Katowice, Institute of Materials Science, Chorzów, Poland
6Anton Paar Poland, Warszawa, Poland
7Silesian University of Technology, Department of Physical Chemistry and Technology of Polymers, Gliwice, Poland
8Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
Ionanofluids (INFs) – composed of multi-walled carbon nanotubes (MWCNTs) and ionic liquids (ILs) – are systems characterized by improved thermal conductivity, non-flammability, high stability, which can lead to efficient and safe heat transfer media. We present structural and spectroscopic studies (including cryo-transmission electron microscopy and Raman spectroscopy, respectively) as well as molecular dynamics simulations correlated with excellent thermal conductivity enhancements (40%) in thermal conductivity of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide-based INFs with C-sp2 rich, long, crystalline MWCNTs . We found the subzipping of long multi-walled carbon nanotube networks in IL as a result of interactions between two neighboring nanotubes which fragmentarily coalescent by the IL nanolayers, i.e. intertube zipping together with locally unzipped individual pairs of nanotubes and/or longitudinally unzipped nanotubes.
This effect leads to formation of thermal bridges towards 3D networks in the whole INF volume. Additionally, the energy of CNTs walls–IL interaction obtained from molecular dynamics simulations indicated that the formation of CNT networks, separated by a layer of IL ions is a thermodynamically favorable process. In turn, the correlation between the integrated intensity ratios of Raman spectra suggests the formation of the new covalent bonds between the broken nanotube and, most probably, the IL cation. Thus, the molecular perfection of the MWCNT structure with its supramolecular arrangement and the MWCNT-IL interactions affect extraordinary thermal conductivity enhancement and optimal rheological characteristics.
 M. Dzida, S. Boncel, B. Jó?wiak, H.F. Greer, M. Dulski, ?. Scheller, A. Golba, R. Flamholc, G. Dzido, J. Dziadosz, A. Kolanowska, R. J?drysiak, K. Cwynar, E. Zor?bski, C.E.S. Bernardes, M.J.V. Lourenço, C.A.N.de Castro, ACS Appl. Mater. Interfaces 2022, 14, 45, 50836-50848.
This work was financially supported by the National Science Centre (Poland) Grant No. 2017/27/B/ST4/02748. C.E.S. Bernardes, M.J.V. Lourenço and C.A.N. de Castro would like to thank Fundação para a Ciência e Tecnologia, Portugal, for partial financing through projects UIDB/00100/2020 and UIDP/00100/2020 to Centro de Química Estrutural and LA/P/0056/2020 to Institute of Molecular Sciences. C.E.S. Bernardes also thanks FCT for grant 2021.03239.CEECIND.