Additive-Free MXene Liquid Crystals and Fibers

Jizhen Zhang; Simge Uzun; Shayan Seyedin; Peter A Lynch; Bilen Akuzum; Zhiyu Wang; Si Qin; Mohamed Alhabeb; Christopher E Shuck; Weiwei Lei; E Caglan Kumbur; Wenrong Yang; Xungai Wang; Genevieve Dion; Joselito M Razal; Yury Gogotsi

doi:10.1021/acscentsci.9b01217

Additive-Free MXene Liquid Crystals and Fibers

ACS Cent Sci. 2020 Feb 26;6(2):254-265. doi: 10.1021/acscentsci.9b01217. Epub 2020 Feb 6.

Authors

Jizhen Zhang¹, Simge Uzun², Shayan Seyedin^{1

2

3}, Peter A Lynch¹, Bilen Akuzum^{2

4}, Zhiyu Wang¹, Si Qin¹, Mohamed Alhabeb², Christopher E Shuck², Weiwei Lei¹, E Caglan Kumbur⁴, Wenrong Yang⁵, Xungai Wang¹, Genevieve Dion⁶, Joselito M Razal¹, Yury Gogotsi²

Affiliations

¹ Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216, Australia.
² A. J. Drexel Nanomaterials Institute, Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
³ Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, United Kingdom.
⁴ Electrochemical Energy Systems Laboratory, Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104, United States.
⁵ School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3216, Australia.
⁶ Center for Functional Fabrics, Drexel University, Philadelphia, Pennsylvania 19104, United States.

Abstract

The discovery of liquid crystalline (LC) phases in dispersions of two-dimensional (2D) materials has enabled the development of macroscopically aligned three-dimensional (3D) macrostructures. Here, we report the first experimental observation of self-assembled LC phases in aqueous Ti₃C₂T _x MXene inks without using LC additives, binders, or stabilizing agents. We show that the transition concentration from the isotropic to nematic phase is influenced by the aspect ratio of MXene flakes. The formation of the nematic LC phase makes it possible to produce fibers from MXenes using a wet-spinning method. By changing the Ti₃C₂T _x flake size in the ink formulation, coagulation bath, and spinning parameters, we control the morphology of the MXene fibers. The wet-spun Ti₃C₂T _x fibers show a high electrical conductivity of ∼7750 S cm^-1, surpassing existing nanomaterial-based fibers. A high volumetric capacitance of ∼1265 F cm^-3 makes Ti₃C₂T _x fibers promising for fiber-shaped supercapacitor devices. We also show that Ti₃C₂T _x fibers can be used as heaters. Notably, the nematic LC phase can be achieved in other MXenes (Mo₂Ti₂C₃T _x and Ti₂CT _x ) and in various organic solvents, suggesting the widespread LC behavior of MXene inks.