Carbon Nanotube – Polymer Composites

Carbon nanotubes are considered by many to be the leading new nanomaterial to have emerged in recent time.  Their high aspect ratio, coupled with excellent electronic properties and chemical robustness, makes them ideal as electron sources.  One of the major hurdles in the development of large area field emission sources is the ability to maximise the concentration of emitting carbon nanotubes.  At high nanotube concentrations, screening of the electric field by neighbouring nanotubes occurs and this gives rise to uneven emission.  This process also results in wastage of nanotubes.  One way to overcome this problem is through the use of nanotube - polymer composites whereby the nanotube concentration can be accurately controlled.  In addition, in the preparation of the composite it will be possible to adjust the chemical functionalisation of the nanotube to achieve excellent dispersion.

Two series of composite have been examined using multiwalled carbon nanotubes and a conjugated polymer PmPV and secondly, using functionalised single walled nanotubes in aqueous solutions of polyvinyl alcohol. 

In the case of PmPV – composites, we were able to observe excellent emission at low nanotube content (mass fraction) and have explained our results in terms of the electrical behaviour of the polymer acting as tunnel barrier for charge transport. We have also examined the case of single wall nanotubes using polyvinyl alcohol.  These samples exhibited excellent nanotube dispersion and the threshold field for emission was found to be optimised for mass fractions of between 1 and 10%. 

The project is a collaboration between School of Physics, Trinity College Dublin, Ireland, and the NEC.