Tailoring Triblock Copolymers for Dispersion of Individual, Pristine, Single-Walled Carbon Nanotubes in Organic Solvents

Triblock copolymers, polyethylene oxide-(hexa-p-phenylene)-polyethylene oxide, were synthesized and used for dispersing single-walled carbon nanotubes (SWNT) in organic solvents. The resulting dispersions comprise mostly of individual tubes, as indicated by transmission electron microscopy at cryogenic temperatures. The dispersions Could be dried and redispersed by the addition of a solvent, offering a useful method of application of predispersed SWNT. In situ Optical spectroscopy indicates that the block copolymers which self-assemble in the native Solution physically adsorb to the SWNT surface via the hexa-P-phenylene moiety. The noncovalent, weak adsorption competes with the polymer self-assembly, as clearly indicated by the emission spectra. The balance between self-assembly and adsorption is sensitive to the length of ethylene oxide side chains. The approach presented here may serve for optimization of the structure and composition of polymeric dispersants where one call chose between it long tall and a long adsorbing moiety, according to [lie specific needs presented by different applications of SWNT.