Living annulative [pi]-extension polymerization for graphene nanoribbon synthesis

• Published in: Nature (London) 2019-07, Vol.571 (7765), p.387
• Main Authors: Yano, Yuuta, Mitoma, Nobuhiko, Matsushima, Kaho, Wang, Feijiu, Matsui, Keisuke, Takakura, Akira, Miyauchi, Yuhei
• Format: Article
• Language: English
• Subjects: Graphene; Methods; Nanoparticles; Polymerization; Production processes
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-019-1331-z

The properties of graphene nanoribbons (GNRs).sup.1-5--such as conductivity or semiconductivity, charge mobility and on/off ratio--depend greatly on their width, length and edge structure. Existing bottom-up methods used to synthesize GNRs cannot achieve control over all three of these parameters simultaneously, and length control is particularly challenging because of the nature of step-growth polymerization.sup.6-18. Here we describe a living annulative [pi]-extension (APEX).sup.19 polymerization technique that enables rapid and modular synthesis of GNRs, as well as control over their width, edge structure and length. In the presence of palladium/silver salts, o-chloranil and an initiator (phenanthrene or diphenylacetylene), the benzonaphthosilole monomer polymerizes in an annulative manner to furnish fjord-type GNRs. The length of these GNRs can be controlled by simply changing the initiator-to-monomer ratio, achieving the synthesis of GNR block copolymers. This method represents a type of direct C-H arylation polymerization.sup.20 and ladder polymerization.sup.21, activating two C-H bonds of polycyclic aromatic hydrocarbons and constructing one fused aromatic ring per chain propagation step.