Conductive carbon-nanotube/polymer composites: Spectroscopic monitoring of the exfoliation process in water and the crucial role of wetting

A versatile, latex-based concept for efficiently dispersing Single Wall Carbon Nanotubes (SWNTs) in a highly viscous polystyrene matrix is described Crucial for the entire process is the ultrasound-driven exfoliation of the as produced SWNT bundles in water. The energy input must be sufficiently high to achieve the desired individualization, but at this stage sonication should be stopped to avoid damaging the SWNTs, which would reduce both electrical conductivity and strength. With UV/VIS spectroscopy the unraveling of the NT bundles can easily be monitored, a process which was simultaneously visualized with cryo-TEM and SEM images. These images were in agreement with the collected UV/VIS data. Depending on the molar mass distribution of the PS matrix, the well-dispersed SWNTs significantly raise the Tg of the PS. A low molar mass PS fraction, probably acting as a wetting agent for the SWNTs, seems to be required for an improved PS/SWNT interaction.