Polymer-grafted multi-walled carbon nanotubes through surface-initiated ring-opening polymerization and click reaction

Multi-walled carbon nanotubes (MWNTs) are modified to possess the hydroxyl groups and are used as coinitiators to polymerize poly(ε-caprolactone) (PCL) or poly(α-chloro-ε-caprolactone) (PαClCL) by surface-initiated ring-opening polymerization. Pendent chlorides were converted into azides by the reaction with sodium azides. Finally, various types of terminal alkynes were reacted with pendent azides by copper-catalyzed Huisgen's 1,3-dipolar cycloaddition (click reaction). Chemical structure of resulting product and the quantities of grafted polymer were determined by Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) images clearly indicate that the nanotubes were coated with a polymer layer. The MWNT-g-PCLs and MWNT-g-(PαN3CL-g-alkyne)s are well dispersed in the organic solvent. The dispersability of MWNTs with grafted organic moieties is easier in CHCl3 than in THF. The average thickness of the enwrapped polymer layer is approximately 8-10 nm for MWNT-g-PCL and 3 nm for MWNT-g-(PαN3CL-g-PBA).