Dispersing Carbon Nanotubes in Aqueous Solutions by a Starlike Block Copolymer

Abstract

The ability of dispersing carbon nanotubes (CNTs) in aqueous solutions by a starlike amphiphilic block copolymer with PPO−PEO segments (AP432) was investigated in detail. For comparison, two commercially available linear amphiphilic block copolymers, Pluronics L64 and F127, were also selected. It was found that AP432 and F127 can get good CNT dispersions, while L64 was proved to be unable to disperse CNTs. AP432 with five branches could disperse CNTs efficiently at much lower concentrations compared with the linear F127, although it has a smaller molecular weight and shorter terminal EO groups. This indicated clearly that, once branched, copolymers would get a much better ability to disperse CNTs. Increasing concentration of AP432 or F127 would disperse more CNTs, but at high copolymer concentrations the aggregation of dispersed CNTs was observed, which may be related to the free micelles formed by AP432 or F127 around CNTs. Other influencing factors such as the mass ratio of CNTs to copolymers and sonication time and strength were also discussed. From the molecular dynamics simulation results, it can be found that copolymers with five branches can gain better steric repulsions between adjacent CNTs, which is consistent with the experimental results.