Impact of surfactants on SWCNT dispersion in N-methylmorpholine N-Oxide for cellulose dissolution

A well dispersed slurry of single-walled carbon nanotube (SWCNT) and 60 % hydrated N-methylmorpholine N-oxide (NMMO) solution was prepared by probe sonicator. The proper dispersion of carbon nanotube (CNT) has been verified by optical microscope by varying the sonication time. Further, the slurry was concentrated to 76% (for cellulose dissolution) and during this process some agglomeration of CNTs has been observed. The dispersion of CNT aggregation was checked by addition of surfactants like sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) (with 2% (w/w) with respect to CNT) to the surface of CNT. SDBS is giving better dispersion as compared to SDS when the slurry is heated to obtain 76% NMMO as checked by optical microscope and UV-Vis spectrophotometer to get quantitative amount of dispersed CNT. 88% dispersion has been obtained in case of SDBS-assisted CNT after heating followed by centrifugation of the concentrated solution. Similarly, 78% dispersion has been observed in case of SDS-assisted CNT and 46% dispersion in case of CNT without any surfactant. The stronger dispersion ability of SDBS could improve its use for SWCNT separation in NMMO solution which can be used further for cellulose dissolution to prepare lyocell fiber.