Effects of the composition and molecular weight of maleimide polymers on the dispersibility of carbon nanotubes in chloroform

We synthesized maleimide polymers (MIPs) as effective carbon nanotube (CNT) dispersants for stable CNT-dispersed solutions. The MIPs were random copolymers which consist of N-phenyl maleimide (PhMI) units that imparted strong physical adsorption to the CNT surfaces and methyl methacrylate units; we evaluated the effects of the PhMI content and molecular weight in the MIPs on the dispersibility of the CNTs in chloroform. Increasing the PhMI content in the MIPs increased the grafting amount (GA) (g m−2) of MIPs on the CNT surfaces and led to a large increase of CNT dispersion. In particular, when single-walled carbon nanotubes (SWCNTs) were used, MIPs having 100 mol% PhMI units (MIP100s) were imperative for a drastic increase in the GA value. Increasing the weight average molecular weight (Mw) of the MIPs resulted in no significant effect on CNT dispersibility; however, the particularly low Mw (⩽10,000) of the MIPs dramatically improved CNT dispersion. Therefore, MIP100s with particularly low Mw’s were extremely effective for dispersing various CNTs with different diameters. In the case of SWCNTs, much more effective exfoliation of SWCNT bundles was achieved by MIP100s with particularly low Mw’s than MIP100s with higher Mw’s.