Polysiloxane Surfactants for the Dispersion of Carbon Nanotubes in Nonpolar Organic Solvents

Abstract

We develop two new amphiphilic molecules that are shown to act as efficient surfactants for carbon nanotubes in non-polar organic solvents. The active conjugated groups, which are highly attracted to graphene nanotube surface, are based on pyrene and porphyrin. We show that relatively short (C18) carbon tails are insufficient to provide stabilization. As our ultimate aim is to disperse and stabilize nanotubes in siloxane matrix (polymer and crosslinked elastomer), both surfactant molecules were made with long siloxane tails to facilitate solubility and steric stabilization. We show that pyrene-siloxane surfactant is very effective in dispersing multi-wall nanotubes, while the porphyrin-siloxane is making single-wall nanotubes soluble, both in petroleum ether and in siloxane matrix. * Electronic address: emt1000@cam.ac.uk

Dispersion of Carbon Nanotubes: Mixing, Sonication, Stabilization, and Composite Properties

“…Lastly, the molecular structure associated with the π−π stacking complex can vary considerably depending on the location of the rigid π-bondings. They can be in a block [54][55][56][57], or in the backbone [58]. The resultant supramolecular structure is usually formed to maximize the π-stacking interaction, inducing alignment of the π bonding with respect to the CNT chirality.…”

“…Especially, surfactants designed for non-polar organic solvent are rare, and a pyrene-siloxane based surfactant is only recently developed [57]. Table 1.…”

“…For the conductive composites, the MWu-PSi(6) composite also has the conductivity lower than the MWm-PSi(4) sample. The effect of surfactants assisting exfoliation, was also studied on an example of purpose-developed pyrene-siloxane (PSi) [57]. Although one might assume that a surfactant coating would prevent good electric contact between tubes, PSi has induced an electrical percolation in the 2 wt% MWNT-PDMS composite which is otherwise insulating in the pure form (compare MWm-PSi(2) and MWm(2)(24hr)).…”

Fast and reversible microscale formation of columns in carbon nanotube suspensions

“…An extensive discussion of surfactant optimisation and the details of synthesis of the pyrene-siloxane molecule PySi70 are described in an earlier paper. 25 The multi-wall CNTs were dispersed in petroleum ether (boiling point 40-60 C) in the presence of PySi70 (PySi70 : CNT ¼ 60 : 1 by weight). A vial of the dispersion was left idle for 2 days, after which the upper 90% that contained creamed impurities was carefully removed.…”

Improving mechanical, thermal, and electrical properties of polyimide by incorporating vinyltriethoxysilane functionalized graphene oxide

“…It is well known that organo‐functionalized silanes have been widely used as coupling agents to improve the total adhesive strength of organic and inorganic substrates . One of the most known bifunctional silanes is vinyltriethoxysilane (VTES), which has hydrolysable methoxy groups as well as one vinyl group attached to silicon, this imparts additional chain flexibility and improves the adhesive properties against substrates such as glass and carbon nanotubes . Yuen et al reported the poly(vinyltriethoxysilane) modified multi‐walled carbon nanotube (PVTES‐MWCNT)/PI nanocomposites .…”