Green chemical functionalization of multiwalled carbon nanotubes with poly(ε-caprolactone) in ionic liquids

摘要

Multiwalled carbon nanotubes (MWNTs) have been successfully functionalized by free radical addition of 4,4'-azobis(4-cyanopentanol) in aqueous media to generate the terminal-hydroxyl-modified MWNTs (MWNT-OH), followed by surface-initiated in situ ring-opening polymerization of e-caprolactone in l-butyl-3-methylimidazolium tetrafluoroborate (BmimBF_4) to obtain poly(e-caprolactone)-grafted MWNTs (MWNT-g-PCL). Spectroscopic methods in conjunction with electron microscopy clearly revealed that hairy PCL chains were chemically attached to the surface of MWNTs to form core-shell nanostruc-tures with the latter as core and the former as shell. With increasing polymerization time from 2 to 8 h, the amount of the grafted-PCL synthesized in BmimBF_4 varies from 30.6 to 62.7 wt%, which is clearly higher than that (41.5 wt%) obtained in 1,2-dichlorobenzene under comparable conditions (8 h). The proposed methodology here uses water and room temperature ionic liquids (RTILs) as the reaction media and promises a green chemical process for functionalizing nanotubes.