Abstract
Liquid phase assembly is among the most industrially attractive routes for scalable carbon nanotube (CNT) processing. Chlorosulfonic acid (CSA) is known to be an ideal solvent for CNTs, spontaneously dissolving them without compromising their properties. At typical processing concentrations, CNTs form liquid crystals in CSA; however, the morphology of these phases and their concentration dependence are only qualitatively understood. Here, we use small-angle neutron scattering (SANS), combined with polarized light microscopy and cryogenic transmission electron microscopy to study solution morphology over a range of concentrations and two different CNT lengths. Our results show that at the highest concentration studied the long CNTs form a highly ordered fully nematic phase, while short CNTs remain in a biphasic regime. Upon dilution, long CNTs undergo a 2D lattice expansion, whereas short CNTs seem to have an intermediate expansion between 2D and 3D probably due to the biphasic nature of the system. The average spacing between the CNTs scaled by the CNT diameter is the same in both systems, as expected for infinitely long aligned rods.
| Original language | English |
|---|---|
| Pages (from-to) | 6892-6900 |
| Number of pages | 9 |
| Journal | Macromolecules |
| Volume | 51 |
| Issue number | 17 |
| DOIs | |
| Publication status | Published - 11 Sept 2018 |
Funding
We thank Dmitri E. Tsentalovich for providing the SWNT length. We thank Micah Green, Olga Kleinerman, and Yachin Cohen for useful discussions. Research was supported by Air Force Office of Scientific Research (AFOSR) Grants FA9550-12-1-0035 and FA9550-15-1-0370, Air Force Research Laboratories (AFRL) agreement FA8650-07-2-5061, the Robert A. Welch Foundation (C-1668), National Science Foundation (NSF) Grant CMMI-1025020, and United States−Israel Binational Science Foundation (BSF) Grants 2012223 and 2016161. Some of the measurements were conducted at the Center for Nanoscale Science and Technology, a user facility at NIST. This work benefited from the use of the SasView application, originally developed under NSF Award DMR-0520547 and currently maintained by NIST, UMD, ORNL, ISIS, ESS, and ILL. SasView also contains code developed with funding from the EU Horizon 2020 programme under the SINE2020 project Grant 654000. The cryo-TEM work was performed at the Technion Center for Electron Microscopy of Soft Materials, supported by the Technion Russell Berrie Nanotechnology Institute (RBNI). Identification of particular commercial products used in this work is intended for information purposes only and does not imply recommendation or endorsement by NIST.