Graphene as a Target for Polymer Synthesis

Abstract

Graphene has remarkable physical properties, but existing production methods have severe deficiencies that limit its potential use in robust technologies. Opening a reliable and efficient synthetic route to graphene and its functionalized derivatives offers a path to overcome this obstacle for its practical application. Graphene can be regarded as a two-dimensional polymer (2D), and it is here argued that it, along with its derivatives, represents a realistic yet challenging target for polymer synthesis.In order to demonstrate the possibility of such syntheses, an overview is presented on the evolution of phenylene-based macromolecules. It is shown how classical linear polyphenylenes can be expanded to increasingly more sophisticated structures involving two-and three-dimensional (3D) polyphenylene architectures. A crucial aspect of the meticulous synthetic design of these molecules has been the avoidance of defects within the structures, resulting in the precise control of their physical, especially optoelectronic, properties.Linear conjugated polymers with defined optical properties have been made by controlling the degree of torsion between the benzene rings. This has included the development of efficient routes to ladder-type polymers and of step-ladder materials. Planar graphene molecules, or nanographenes, in a range of sizes and shapes have been fabricated by the controlled cyclodehydrogenation of 3D polyphenylene dendrimers. By combining knowledge gained from the synthesis of conjugated polymers, polyphenylene dendrimers, and nanographenes, it has proven feasible to make, either by solution or surface-bound methods, graphene nanoribbons with well-defined structures. These functional materials possess properties similar to graphene while displaying improved processability.Finally, we review less-sophisticated paths towards graphene materials involving processing of graphene oxide, its reduction, and its hybridization with other components. These too have a role to play in acquiring functional graphenes where K. Müllen (*) Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany e-mail: muellen@mpip-mainz.mpg.de a lesser degree of control over the properties is required. This voyage of exploration towards the precise synthesis of conjugated phenylene-based polymers has thus had the dual objectives of fundamental research and practical materials science. En route we have had to meet the sometimes conflicting gauntlets thrown down by these two aims, which has at times involved trade-offs between the theoretically desirable and the reasonably accessible.

Templated Synthesis of End-Functionalized Graphene Nanoribbons through Living Ring-Opening Alkyne Metathesis Polymerization

“…Raman spectra were obtained on a Renishaw inVia Qontor Raman microscope using a 514 nm excitation. X-ray crystallography of 1 was performed on a Rigaku XtaLab equipped with a MicroMax-007HF microfocus rotating anode source (Cu−Kα radiation), a Pilatus 200 K detector, and an Oxford Cryostream at 100 K. X-ray crystallography of 2• t BuOH was performed on a Bruker APEX II QUAZAR, using a Microfocus Sealed Source (Incoatec IμS; Mo−Kα radiation), Kappa Geometry with DX (Bruker-AXS build) goniostat, a Bruker APEX II detector, QUAZAR multilayer mirrors as the radiation monochromator, and Oxford Cryostream at 100 K. Crystallographic data were solved with SHELXT, refined with SHELXL-2014, visualized with ORTEP, and finalized with Olex (1) or WinGX (2). Compounds 3, 44 9, 45 11, 39 1,2-bis(4trifluoromethylphenyl)acetylene, 46 and authentic samples of unsubstituted cGNRs 42 were prepared according to literature procedures.…”

“…1 Bottom-up approaches instead access these narrow strips of graphene from molecular precursors, which allows organic and polymer chemistry to precisely engineer the location of every atom in each repeat unit at the sub-nanometer scale. 2 This strategy has enabled rapid advances in our understanding of the role of nanoribbon width, [3][4][5] dopant atom incorporation, [6][7][8][9] crystallographic symmetry, 10,11 and topological phenomena 12,13 in determining their electronic structure. However, the interface of two or more GNRs of dissimilar electronic band structures fused along a well-defined interface forms the basis of the most promising GNR device architectures.…”

“…Solid 1 should be stored under N 2 but can be handled in air; signs of decomposition (yellow color, reduced solubility) develop over the course of several weeks when stored at ambient conditions. pTolCMo[ONO]O t Bu(2). In a N 2 -filled glovebox a 20 mL vial was charged with pTolCMo(O t Bu) 3 •(DME) 0.5 (254 mg, 0.55 mmol) in dry toluene (4 mL) and 6,6′-(pyridine-2,6-diyl)bis(2,4-di-tertbutylphenol) (H 2 [ONO]) (244 mg, 0.5 mmol) in dry toluene (2 ) was added dropwise over 1 min.…”

Synthesis of Nitrogen‐Containing Rubicene and Tetrabenzopentacene Derivatives

“…[1][2][3][4][5][6] Thus,m uch research effort has focused on the bottom-up preparation of structurally and chemically well-defined variants (and fragments) of such materials via organic chemistry techniques. [7][8][9][10][11][12][13][14][15][16][17][18] However,asmaller number of studies have reported the solutionphase synthesis of analogous nitrogen-doped constructs. [19][20][21][22][23][24][25][26][27] Indeed, the rational incorporation of nitrogen heteroatoms, while frequently challenging,i sk nown to be valuable for tuning the properties of graphitic systems, [28][29][30][31] as demonstrated by the successful molecular engineering of various Nheteroacenes for improved transistor performance.…”

Evolution of Graphene Molecules: Structural and Functional Complexity as Driving Forces behind Nanoscience

“…In all cases, the synthesis proceeded via cyclodehydrogenation (flattening) of suitably designed polyphenylene precursors. 35,36 Indeed, the precursor of nanographene 3 (C222) is compound 3', which turned out to be nothing more than a first-generation polyphenylene dendrimer with a hexaphenylbenzene core. In every case, the synergy between synthesis and STM studies proved to be of outstanding value.…”