Relationship of Extensional Viscosity and Liquid Crystalline Transition to Length Distribution in Carbon Nanotube Solutions
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2016 American Chemical Society. We demonstrate that the length of carbon nanotubes (CNTs) can be determined simply and accurately from extensional viscosity measurements of semidilute CNT solutions. The method is based on measuring the extensional viscosity of CNT solutions in chlorosulfonic acid with a customized capillary thinning rheometer and determining CNT aspect ratio from the theoretical relation between extensional viscosity and aspect ratio in semidilute solutions of rigid rods. We measure CNT diameter d by transmission electron microscopy (TEM) and arrive at CNT length L. By studying samples grown by different methods, we show that the method works well for CNT lengths ranging from 0.4 to at least 20 m, a wider range than for previous techniques. Moreover, we measure the isotropic-to-nematic transition concentration (i.e., isotropic cloud point) iso of CNT solutions and show that this transition follows Onsager-like scaling iso d/L. We characterize the length distributions of CNT samples by combining the measurements of extensional viscosity and transition concentration and show that the resulting length distributions closely match distributions obtained by cryo-TEM measurements. Interestingly, CNTs appear to have relatively low polydispersity compared to polymers and high polydispersity compared to colloidal particles.
author list (cited authors)
Tsentalovich, D. E., Ma, A., Lee, J. A., Behabtu, N., Bengio, E. A., Choi, A., ... Pasquali, M.
complete list of authors
Tsentalovich, Dmitri E||Ma, Anson WK||Lee, J Alex||Behabtu, Natnael||Bengio, E Amram||Choi, April||Hao, Junli||Luo, Yimin||Headrick, Robert J||Green, Micah J||Talmon, Yeshayahu||Pasquali, Matteo