ABSTRACT
Noncovalent functionalization of materials is achieved by wrapping of polymer and adsorption of surfactants or small aromatic molecules. Polymers like poly(phenylene vinylene) and polystyrene are widely used to wrap the carbon material specially CNTs [1,2]. The stirring of carbon materials in the presence of polymer can lead to a wrapping process and hence polymers coating onto the surface materials. The physical adsorption primarily depends on the properties of surfactants, medium chemistry, or the polymer matrix. Surfactants wrapping on the surface of carbon materials can effectively decrease their surface tension, which leads to prevention of the formation of aggregates. Surfactants are mainly classi ed into three types, namely,
1. Nonionic surfactants 2. Ionic surfactants 3. Cationic surfactants
The ionic surfactant like sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) is widely used for solubilizing the CNTs in the different solvents. Both of them have the same length of the alkyl chain, but the SDBS has a phenyl ring attached between the alkyl chain and the hydrophilic group. Kang et al. [3] found that the presence of the phenyl ring makes SDBS more ef cient for solubilization of CNTs as compared to SDS because of aromatic stacking formed between the single-walled carbon nanotubes (SWCNTs) and the phenyl rings of the SDBS within the micelle. SDBS is more effective than SDS surfactant because it contains a benzyl ring in dispersing SWCNTs in water [4]. Generally, about 1% by weight SDS/SDBS is added to the distilled water to prepare the aqueous suspension, and then ultrasonication is mainly used to get the dispersion of the CNTs. These surfactants transfer the charge on the nanotubes and then dispersed them by electrostatic forces. It is found that these surfactant molecules create ordered layers on the nanotube surfaces [5]. Moreover, the diameter-dependent distribution of CNTs in the solvent of SDBS, measured by atomic force microscopy (AFM), showed that even at 20 mg/mL solution of SDBS in H2O separates, 63.5% of the SWCNT bundles exfoliate in single tubes [1,2].
