Preparation and nanoscopic internal structure of single-walled carbon nanotube-ionic liquid gel

As an effort to expand their applicability of both room temperature ionic liquid (RTIL) and single-walled carbon nanotube (SWNT), we prepared a gel-like paste using imidazolium-based ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate; [Bmim] BF4) and SWNT, and investigated their internal structure and viscoelastic characteristics. The suspension containing 1 wt% of SWNT was prepared via grinding it in an agate mortar. A black paste (gel) was then obtained from its centrifugation. Rheological properties of a purified SWNT-ionic liquid ([Bmim] BF4) gel were measured using a rotational rheometer equipped with a parallel plate geometry, and then compared with those of unpurified SWNT-ionic liquid gel from both steady shear and oscillatory shear mode tests. We also examined their effects of a well-dispersed SWNT in a suspending medium on rheological properties, resulting in gel-state even at a very low filler concentration due to the nano-dimension of SWNT and its interaction with a novel ionic liquid. From this study, it is found that the characteristic rheological behaviors, such as high shear thinning, dynamic yield stress, and frequency independent dynamic behavior, not only support the gel formation due to the uniform dispersion of SWNT in the ionic liquid medium, but also explain the formation of network structure induced by a strong interaction between ionic liquid and SWNT. In addition, we also observed that such a gel structure was followed by a shear induced secondary structure in a high shear rate region.