Polymer-encapsulated carbon nanotubes prepared through ultrasonically initiated in situ emulsion polymerization

In this study, a novel ultrasonically initiated in situ emulsion polymerization approach was used to modify multi-walled carbon nanotubes (MWCNTs). The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. Ultrasonically initiated emulsion polymerization of monomer n-butyl acrylate (BA) and methyl methacrylate (MMA) are reported. By employing the multiple effects of ultrasound, i.e., dispersion, pulverizing, activation, and initiation, the aggregation and entanglement of carbon nanotubes in aqueous solution can be broken down, while in situ polymerization of monomer BA or MMA on the surface of MWCNTs proceeds without any added chemical initiator; consequently, the MWCNTs are coated by the formed polymer. Transmission electron microscopy confirms that after surface modification through ultrasonically initiated in-situ polymerization, the size of MWCNTs increased; even after 72 h of Soxhlet extraction with boiling acetone there are still unextracted polymers in the modified MWCNTs, indicating strong interaction between the polymer and carbon nanotubes. The results of thermogravimetric analysis show that there are high encapsulation rates for PBA. The characteristic peak of C=O in carbonyl groups at similar to1733 cm(-1) still appears in the Fourier transform infrared spectrum of the extracted polymer-encapsulated MWCNTs. X-ray photoelectron spectroscopy further confirms the presence of polymer-encapsulated MWCNTs and strong interaction between polymer and MWCNTs. Therefore, ultrasonically initiated in situ emulsion polymerization provides a novel surface modification method for carbon nanotubes. The polymer-encapsulated carbon nanotubes can be well dispersed in Nylon 6 matrix. The interface adhesion between polymer-encapsulated carbon nanotubes and Nylon 6 is improved. The yield strength is improved similar to30% and the Young's modulus is improved similar to35% at only 1 wt % content of polymer-encapsulated carbon nanotubes.