Enveloping Self-Assembly of Carbon Nanotubes at Copolymer Micelle Cores

Carbon nanotubes (CNTs) and their polymer nanocomposites are interesting materials for future applications, for example in optics or electronics. Research faces two major challenges with these outstanding nanofillers: control over dispersion and spatial arrangement within the nanocomposite, both required to achieve optimal structure and properties of CNT-based nanocomposites. We report on novel self-assembled multiwall CNT (MWCNT)/block copolymer (BCP) nanostructures realized by patterning MWCNTs with amphilphilic diblock copolymer micelles. A high molecular weight poly(styrene)-b-poly(2-vinylpyridine) BCP which forms large micelles (250 nm) was chosen to facilitate the templating by reducing the bending energy induced in the MWCNTs. We tested the hypothesis that it is possible to use an amphiphilic BCP as a dispersing agent and its spherical micelles as a template at the same time without modification of the CNTs. In thin films of the MWCNT/BCP micelles, highly separated MWCNTs were repeatedly observed which enveloped the core of the BCP micelles, i.e., the unfunctionalized MWCNTs segregated to the interface between the two BCP phases. Depending on the size of the MWCNTs, ring-like (split-ring) or network forming structures were obtained. The MWCNT templating mechanism, i.e., the segregation to the interface, is explained by the interfacial tension within the BCP interface and the chain entropy. The reported new complex nanocomposite has potential to be applied for example as cost-effective split-ring resonators for metamaterials or for conductive polymer films with an extremely low percolation threshold.