Significance of interfacial interaction and agglomerates on electrical properties of polymer-carbon nanotube nanocomposites

The ability to control the dispersion state of carbon nanotubes (CNTs) in polymer matrices is closely related to the electrical tunability of polymer-CNT nanocomposites. In this study, the effect of polymer-CNT interactions at the molecular level on the extent of CNT dispersion and consequent electrical properties of the developed nanocomposites are investigated. Two polymer models with dissimilar affinities towards CNTs are studied: polyamide-6 (PA6) having high, and polystyrene (PS) having low affinity towards CNTs. Experiments demonstrate that enhanced polymer-filler interactions in PA6-CNT system lead to improved CNT dispersion at the nanoscopic level. However, PS-CNT system, having higher number density of micro-agglomerates, has approximately ten times lower percolation threshold (0.3 wt% versus 2.9wt%) and significantly enhanced electrical properties. High affinity of PA6 towards CNTs is proposed to adversely influence electrical properties via encapsulation of CNTs by PA6 through possible wrapping and interfacial crystallization of polymer chains. On the other hand, enhanced electrical properties in PS-CNT nanocomposites are attributed to higher number density of micro-agglomerates, contributing to secondary internal electric field.