A study on the interaction of single-walled carbon nanotubes (SWCNTs) and polystyrene (PS) at the interface in SWCNT–PS nanocomposites using tip-enhanced Raman spectroscopy

Abstract

Normal Raman and tip-enhanced Raman scattering (TERS) spectra were recorded for single-walled carbon nanotube (SWCNT)–polystyrene (PS) nanocomposites to investigate the distribution of SWCNTs in the nanocomposites and local interactions at an interface between SWCNTs and PS. The normal Raman spectra do not show an evident point-to-point variation. In contrast, in the TERS spectra, Raman bands of SWCNTs show obvious point-to-point shifts; the shifts depend on the points. The shift of the G′ band which has high sensitivity to the mechanical compression reflects its distribution at the surface of composites. The shift of the G band arises from two reasons: the disentanglement of SWCNTs in the SWCNT–PS system due to the penetration of PS chains into SWCNT bundles during melt mixing and the mechanical compression distribution from the PS matrix. Moreover, the relative intensity of the G′ band and the Raman band of PS at 3058 cm⁻¹ changes with the points in the TERS spectra of the nanocomposites, which further reflects the dispersion state of SWCNTs in the polymer matrix. This study demonstrates that TERS has great potential to be applied to polymer nanocomposite materials for local structure and function studies.