Methods for block functionalization of carbon nanotubes and applications

Abstract

This work has shown a method to produce block functionalized carbon nanotubes, BF-CNTs, with polymer covalently grafted to the sidewall with a selectivity along the length of the nanotube. This selectivity is reversible meaning either half can be polymerized. This was accomplished by doping the nanotube with nitrogen during growth. The nitrogen forms pyridine groups which then act as P-type dopants on the outer wall, weakening the bonds that CNTs form with radicals. This allowed a radical polymerization to selectively occur where the bonds were weak, allowing for a selective initiation of the polymerization reaction. These BF-CNTs were then placed at a polymer-polymer interface in which half the nanotube was selectively soluble in each phase, and the interfacial strength was tested with the asymmetric double cantilever beam test. The BF-CNTs showed interfacial toughness strengthening on par or greater than block copolymers, the currently accepted method. BF-CNTs were also created with two different metals on the different ends of the nanotube. This was done by evaporation of the selected metal on each side of a thick vertically aligned nanotube forest. The nanotubes were then tested for a variety of reactions important to upgrading of biomass derived compounds to fuel based products based on the configuration of the metals on the nanotube, either touching or separated. The active sites for three reactions were able to be identified and were either created by promotor effects or were the result of short range interactions between the two components in the bifunctional catalyst system. Hydrogen spillover across the nanotube from one metal to the other was observed in all cases, and is fast enough to not become a rate limiting step in the reactions tested.