Comparative studies on field-induced stretching behavior of single-walled and multiwalled carbon nanotube clusters

We demonstrate distinct entanglement of single-walled carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT) clusters in nematic liquid crystal medium using scanning electron microscopy technique and the entanglement influence on electric field-induced stretching phenomena of the said clusters in the same medium under optical microscopy investigation. The observed stretching threshold field for MWCNT clusters is found to be higher than the SWCNT counterpart caused by the interplay between attractive field-induced dipolar interaction of intercarbon nanotube (CNT) bundles and the distinct degree of entanglement of neighboring CNT bundles. Subsequently observed different tensile elasticity modulus results for different CNT kinds also confirm different CNT bundle entanglement and attractive dipolar interaction between adjacent CNT bundles in CNT clusters are responsible for distinct stretching threshold field behavior.

Figure 1

SEM image of dispersed SWCNTs in NLC medium.

Figure 2

Illustration of test cell driven by in-plane field.

Figure 3

SEM images of initial state of MWCNT (a), (b) and SWCNT (d), (e) cluster in NLC medium. (a), (d) and (b), (e) are SEM images with low magnification (×10 000) and high magnification (×50 000). (c) and (f) are MWCNT and SWCNT diameter distribution according to (b) and (e).

Figure 4

Optical micrographs of representative CNT cluster cases in NLC medium with initial lengths of 1.8 (a), 2.5 (b), and 4.2 μm (c) for SWCNT and 1.6 (a), 2.3 (b), and 3.8 μm (c) for MWCNT depending on electric field.

Figure 5

Length variation of SWCNT and MWCNT clusters as a function of electric field.

Figure 6

Electric field stress as a function of strain of stretched CNT clusters. The slope of the fitting curves represents the Coulomb elasticity modulus of each CNT cluster case.

Figure 7

Comparison of threshold elasticity modulus between SWCNT and MWCNT clusters with comparable lengths.