Assessing the strengths and weaknesses of various types of pre-treatments of carbon nanotubes on the properties of polymer/carbon nanotubes composites: A critical review

The current state of research in polymer/carbon nanotubes (single wall and multiwall) composites has been reviewed in context to various types of pre-treatments presently employed. The fundamental aspects of carbon nanotubes are briefly discussed and various strategies designed to alter the dispersion stability and quality of nanotubes in the composites is highlighted. A complete survey of the published data is provided and both the opportunities and the limitations in the frame of covalent and non-covalent type of pre-treatments of carbon nanotubes are juxtaposed. In this context, diverse proposed mechanisms behind different molecular level interactions between nanotubes and the functional moieties are addressed. The effects of these pre-treatments on electrical and rheological percolation thresholds are assessed as they provide an alternative means to evaluate the state of dispersion of carbon nanotubes in the composites. In this regard, the influence of various pre-treatments on the nature of charge transfer mechanisms, system dimensions etc. deduced from different parameters of classical percolation theories are also discussed. These transport parameters offer a vital clue on the nature of the pre-treatment and the effects it has on the structure–property correlations.