Synthesis, properties and water permeability of SWNT buckypapers

The ability of macrocyclic ligands to facilitate formation of dispersions of single-walled carbon nanotubes (SWNTs) was investigated using a combination of absorption spectrophotometry and optical microscopy. Vacuum filtration of aqueous dispersions containing SWNTs and various macrocyclic ligands (derivatised porphyrin, phthalocyanine, cyclodextrin and calixarene) afforded self-supporting membranes known as buckypapers. Microanalytical data and energy dispersive X-ray spectra were obtained for these buckypapers and provided evidence for retention of the macrocyclic ligands within the structure of the membranes. The electrical conductivities of the membranes varied between 30 ± 20 and 220 ± 60 S cm ^-1, while contact angle analysis revealed they all possessed hydrophilic surfaces. The mechanical properties of buckypapers prepared using macrocyclic ligands as dispersants were shown to be comparable to that of a benchmark material prepared using the surfactant Triton X-100 (Trix). Incorporation of the macrocyclic ligands into SWNT buckypapers was found to increase their permeability up to ten-fold compared to buckypapers prepared using Trix. No correlation was observed between the water permeability of the membranes and the average size of either their surface or internal pores. However, the water permeability of the membranes was found to be inversely dependent on their surface area.