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 ∼1733 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 ∼30% and the Young's modulus is improved ∼35% at only 1 wt % content of polymer-encapsulated carbon nanotubes.

Summary: Ultrasonic irradiation was employed to prepare polypyrrole (PPY)/Fe3O4 magnetic nanocomposite by chemical oxidative polymerization of pyrrole in the presence of Fe3O4 nanoparticles. This approach can solve the problem in the dispersion and stabilization of inorganic nanoparticles in polymer. The structure and properties of PPY/Fe3O4 nanocomposite were characterized by TEM, XPS, FT‐IR, TG, and XRD. PPY deposits on the surface of Fe3O4 nanoparticles while Fe3O4 nanoparticles are dispersed at the nanoscale by ultrasonic irradiation, which leads to the formation of polypyrrole‐encapsulated Fe3O4 composite particles. The doping level of PPY in PPY/Fe3O4 nanocomposite is higher than that of neat PPY. The composites possess good electrical and magnetic properties. With the increase in the Fe3O4 content, the magnetization increases and the conductivity first increases and then decreases. When the Fe3O4 content is 40 wt.‐%, the conductivity reaches a maximum value of 11.26 S · cm−1, about nine times higher than that of neat PPY, and the saturation magnetization is 23 emu · g−1. Also, the introduction of Fe3O4 nanoparticles enhances the thermal stability of PPY/Fe3O4 composite.Conductivity of PPY/Fe3O4 composite at different Fe3O4 content.magnified imageConductivity of PPY/Fe3O4 composite at different Fe3O4 content.

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.

Ultrasonic irradiation is employed to assist the chemical oxidative polymerization of aniline in the presence of Fe 3 O 4 nanoparticles in order to prepare a polyaniline (PANI)/Fe 3 O 4 magnetic nanocomposite. In the chemical oxidative polymerization of aniline in the initially neutral medium, the optimum molar ratio of the oxidant ammonium persulfate to the monomer aniline is 2 : 1. The prepared PANI is in the emeraldine form and is doped by sulfate anions.

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