Polymer-Encapsulated Carbon Nanotubes Prepared
through Ultrasonically Initiated In Situ Emulsion
Polymerization
Hesheng Xia, Qi Wang,* and Guihua Qiu
State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute,
Sichuan University, Chengdu 610065 China
Received March 22, 2003. Revised Manuscript Received July 25, 2003
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 spectropho-
tometry. 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 ultrasoni-
cally 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 CdO 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 carb