Effects of Solvent on HelicalWrapping of Single-walled Carbon Nanotubes by Poly(p-phenyleneethynylene-alt-m-phenyleneethynylene)

Water-soluble poly(p-phenyleneethynylene-alt-m-phenyleneethynylene)s (meta-PPEs) can wrap singlewalled carbon nanotubes (SWCNTs) helically to improve the solubility of SWCNTs and realize highly selective dispersion. In order to deeply understand the formation mechanism of such well-defined supermolecular structure, we prepared the composites of SWCNTs and the cationic water-soluble meta-PPE-N+Et2Me in DMSO/H2O mixed solvents with different ratios. The effects of polymer structure and composition of mixed solvents on the morphology and stability of the composite structure were deeply explored. Studies on the ultraviolet-visiblenear infrared absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy, Raman spectroscopy and infrared spectroscopy showed that, when the ratio of DMSO was 70%, the polymer exhibited a sudden change from random coil to helical conformation. At this time, the driving force to self-assemble into helical conformation was relatively large, so the polymer wrapped SWCNTs helically in the process of forming a helical hydrophobic cavity itself, and the hydrophobic effect and p-p interaction were further enhanced to form a stable composite. However, no obvious helical wrapping supermolecular structure was formed in the mixed solvents with other ratios. These results will provide some theoretical guidance for the controllable modification and application improvement of SWCNTs.