Connection-Improved Conductive Network of Carbon Nanotubes in a Rubber Cross-Link Network.

Conductive rubber composites usually suffer a large filler content and relatively low conductivity because the uniform dispersion of conductive nanofillers in rubbers is probably inhibited by the cross-link networks. However, by establishing a double-network model of cross-link and conductive networks, we found the connection of one-dimensional nanofillers could be improved by cross-link networks, which stabilized the conductive network. The percolation value of nanofillers could reduce to 0.06 wt % in experiments, using carbon nanotubes (CNTs) with 9.5 nm diameter and 1.5 μm length as nanofillers and poly(dimethylsiloxane) as the matrix. Moreover, the conductive network owned a critical exponent of 5.63, which was higher than that of conventional conductive networks (ca. 2). This feature proved that the connection between CNTs was improved by the poly(dimethylsiloxane) cross-link network. This work subverted the fundamental conception that cross-link networks in rubbers should make fillers aggregate, and we believed it would conduce to the development of sensors and flexible devices of rubber composites.