Influence of the catalyst-nanotube spacing on the synthesis of polymer-functionalized multiwalled carbon nanotubes by “grafting from” approach

Polynorbornene-functionalized multiwalled carbon nanotubes (MWCNTs) were prepared by a “grafting from” approach, on varying the catalyst-MWCNT spacing to evaluate the influence of the starting catalyst-MWCNT distance on the polymerization efficiency. In particular, 2nd generation Grubbs catalysts and Hoveyda-Grubbs catalysts, both active in the ring opening metathesis polymerization of olefins, were grafted on MWCNTs at 8 to 12 atom spacing from the nanotube surface, and the activity of initiators was tested in the 2- norbornene polymerization. According to our results, initiator performances depend (i) on the length of the arm connecting the catalyst to theMWCNTs, being initiators with longer arms more efficient, and (ii) on the class of Ru catalysts, being Hoveyda-Grubbs catalysts surprisingly more active at room temperatures than 2nd generation Grubbs catalysts. High fractions (80–95 wt%) of polymer covalently bound to the nanotubes in the MWCNT-grafted polynobornene obtained composites were achieved.