Deagglomeration of multi-walled carbon nanotubes via an organic modifier: structure and mechanism

Abstract

We have investigated the agglomeration behaviour of two types of multi-walled carbon nanotubes (MWNTs; N-MWNTs and D-MWNTs), which have different chemical functionalities, average diameter, varying extent of agglomeration and agglomerations. The properties were altered by varying the agglomerated structure. The strength of the MWNT agglomerates was estimated via nanoindentation. The work done to indent D-MWNT agglomerates (3910.3 × 10(-8) erg) was higher than for N-MWNTs agglomerates (2316.4 × 10(-8) erg). An organic modifier, the Li salt of 6-aminohexanoic acid (Li-AHA), was used to deagglomerate the MWNTs in an aqueous medium. The stability of the aqueous dispersion of Li-AHA-modified MWNTs was analyzed by UV-vis spectroscopy and zeta potential measurements. An increase in Li-AHA concentration increased the dispersion of MWNTs in the aqueous medium. Furthermore, the mechanism of dispersion of the two types of MWNTs in the aqueous medium in the presence of Li-AHA was determined based on the electrostatic charge repulsion between the negatively charged species. A fluorescence-activated cell sorting technique was used to assess the debundling of MWNT agglomerates in the aqueous medium. We examined the morphology-property relationship in Li-AHA-modified MWNTs.

Multiwalled carbon nanotubes-based polypropylene composites: Influence of interfacial interaction on the crystallization behavior of polypropylene

“…It is observed from the TEM micrograph that modification with Li‐AHA leads to less entangled MWCNTs of lower “agglomerates” size. Furthermore, the corresponding FEG‐SEM micrographs of Li‐AHA modified MWCNTs show the adsorption of Li‐AHA on MWCNTs surface, which is found to be consistent with the earlier reported results . The mechanism of “debundling” of MWCNTs by using a non‐covalent modifier (Li‐AHA like molecules) has been earlier proposed via electrostatic charge repulsion in the aqueous medium .…”

“…Furthermore, the corresponding FEG-SEM micrographs of Li-AHA modified MWCNTs show the adsorption of Li-AHA on MWCNTs surface, which is found to be consistent with the earlier reported results [30]. The mechanism of "debundling" of MWCNTs by using a non-covalent modifier (Li-AHA like molecules) has been earlier proposed via electrostatic charge repulsion in the aqueous medium [12,29,30]. The improvement of dispersion extent of MWCNTs was achieved earlier by using sodium salt of 6-aminohexanoic acid (Na-AHA), wherein the extent of "debundling" of MWCNTs was significantly enhanced with increased concentration of Na-AHA [35].…”

“…3b and 3c, respectively. A similar observation has been reported for PA6/MWCNTs composites with Li-AHA modified MWCNTs [30]. The higher extent of melt-interfacial reaction may be due to the presence of higher fraction of NH 2 functionality of Li-AHA, which may participate in the melt-interfacial reaction with the anhydride group associated with the PP-g-MA.…”

Morphology and Electrical Conductivity of Ternary Polymer Blends Involving Liquid Crystalline Polymer Containing Carbon Nanotubes

“…This was indicative of lesser inter‐tube interactions. A further decrease in the I D /I G values, which is indicative of the ‘de‐agglomeration’ of nanotubes has been reported in the presence of modifiers such as PyCHO, Na‐AHA and Li‐AHA …”

“…A further decrease in the I D /I G values, which is indicative of the 'de-agglomeration' of nanotubes has been reported in the presence of modifiers such as PyCHO, [14] Na-AHA [14,29] and Li-AHA. [30,31] Morphology and electrical conductivity of LCP/MWCNTs composites A preferential orientation of the polymer chains in the direction of flow has been observed in the case of the LCP/MWCNTs composites. This results in a fibrillar structure as can be seen from the SEM image ( Figure 2).…”