Physical modification of SWCNTs using an amphiphilic RAFT copolymer

Single-walled carbon nanotubes (SWCNTs) exhibit peculiar mechanical, thermal, and optical properties and are considered promising materials for a large number of applications. Regrettably, SWCNTs are insoluble in organic as well as in aqueous solvents due to strong van der Waals and ?-? intertube interactions. This makes quantitative photophysical investigations rather challenging, strongly limiting their applicative potential in optoelectronics. The establishment of dispersion protocols for SWCNTs is therefore of capital importance to enable their effective exploitation. Generally, the approaches used for the individualization of carbon nanotubes are based on chemical functionalization or physical modification. The latter approach uses non-covalent interactions between SWCNTs and suitable amphiphilic molecules that prompts debundling of the nanotubes without altering their intrinsic electronic properties. Common surfactants (e.g. SDS, SC, SDBS) are typically used for this purpose in aqueous environment. We report an effective strategy for the preparation of single-walled carbon nanotube dispersions, based on the use of an amphiphilic polymer (poly(2-hydroxy-3-morpholinopropy methacrylate)-b-polystyrene, PHMPMA-b-PSt) and compare it with a standard surfactant (SDBS) and another polymer lacking pendant phenyl groups (poly(2-hydroxy-3-morpholinopropy methacrylate)-b-poly(butyl acrylate), PHMPMA-b-PBA). The polymers used in this work are obtained by post-polymerization treatments of RAFT synthesized poly(glycidyl methacrylate)-b-polystyrene (PGMA-b-PSt) and poly(glycidyl methacrylate)-b-poly(butyl acrylate) (PGMA-b-PBA). We found that the PHMPMA-b-PSt polymer can interact non-covalently with the SWCNTs through its hydrophobic chain, whilst the hydrophilic part enables solubilization in water. The dispersion obtained and the capability of our polymer to debundle the SWCNTs is demonstrated by electronic absorption spectra, photoluminescence mapping and atomic force microscopy studies.