Effect of Functionalization of MWCNT on the Conductivity and Percolation Threshold of CNT-Polymer Composites

The chemical functionalization of CNTs is s well known approach to control and engineer the interface and has been a subject of several research groups. It has been shown that unless the interface between nanotube and polymer is carefully engineered, poor load transfer between nanotubes, when in bundles, and between nanotubes and surrounding polymer chains may result in interfacial slippage in the process of preparing CNT-Polymer composites. In the present work we have functionalized MWCNT with –OH, –COOH and –S0-O functional groups and then composites of above functionalized MWCNT were prepared with PMMA polymer. SEM imaging of functionalized MWCNT were done to see the structural changes before preparing composites. Conductivity measurements have been done on these composite specimens and results are analyzed to conclude the effect of functionalization of MWCNT. It is concluded that well dispersed CNT fillers result to lower percolation and higher conductivity is not substantiated for the COOH functionalized filler MWCNTs. The COOH-MWCNTs are best dispersed among the three functionalizations studied in this work but of lowest conductivity and largest percolation threshold. A perfect dispersion state of CNTs leads to individual CNTs separated in the matrix, and therefore, a higher percolation threshold. Higher dispersion alone does not translate to higher conductivity.