Fullerenes DOI: 10.1002/ange.200900106 Self-Assembly Made Durable: Water-Repellent Materials Formed by Cross-Linking Fullerene Derivatives** Jiaobing Wang, Yanfei Shen, Stefanie Kessel, Paulo Fernandes, Kaname Yoshida, Shiki Yagai, Dirk G. Kurth, Helmuth Möhwald, and Takashi Nakanishi* The fine-tuning of the interactions between p-conjugated molecules can enable the development of supramolecular materials that have attractive properties. [1] However, the low strength and stability of these materials, which are organized by weak noncovalent interactions, impose limitations for certain applications. Most self-organized materials suffer from structural changes when exposed to organic solvents, high temperatures, or mechanical stress. Accordingly, it is crucially important to harness the sophisticated functional properties found in noncovalent assemblies while imparting them with the structural durability offered by covalent chemistry. To address this problem, covalent cross-linking of self-organized structures has been developed and has received much attention. For instance, click chemistry, [2] diene metathesis, [3] and disulfide bond formation [4] have been successfully utilized to stabilize various structures such as gel fibers, self-assembled nanotubes, and host frame- works. [5] Subtle control of the reaction conditions is required to maintain the structure and morphology and to simulta- neously achieve efficient covalent cross-linking, which are the key factors that determine the final performance of the supramolecular materials in practical applications. The fullerene C 60 possesses unique physicochemical properties, [6] and is a promising candidate for the construction of versatile supramolecular architectures. [7–10] We recently demonstrated that fullerene derivatives bearing three satu- rated aliphatic chains (such as 2) self-assemble into unique supramolecular nano- or microscopic architectures by p–p and van der Waals interactions. By tuning the boundary conditions of self-assembly, well-defined one-, two-, or three- dimensional objects with various macroscopic morphologies can be observed. [11] This strategy demonstrates the feasibility of constructing supramolecular materials through the combi- nation of appropriate molecular design and self-assembly algorithms. However, these materials are structurally fragile because of the weak intermolecular forces, which is a disadvantage in technologies that require high durability. Herein, we present a new design based on a fullerene derivative (1, Scheme 1) that contains diacetylene (DA) functional groups, which are well-known photo-cross-link- ers, [12] in long aliphatic chains. This derivative self-assembles into flakelike microparticles with a bilayer structure at the molecular level. Irradiation with ultraviolet light leads to effective cross-linking of both DA and C 60 moieties, while maintaining their nano- and macroscopic organization. This process gives rise to a material with remarkable resistivity to Scheme 1. a) Molecular structures of fullerene derivatives modified with diacetylene (1) and saturated aliphatic chains (2) employed in this study and b) a schematic representation of the photo-cross-linking process in the bilayer structural subunit of 1. [*] Dr. J. Wang, Dr. Y. Shen, Dr. S. Kessel, Dr. P. Fernandes, Prof. H. Möhwald, Dr. T. Nakanishi Department of Interfaces Max Planck Institute of Colloids and Interfaces Research Campus Golm, Potsdam 14424 (Germany) Fax: (+ 49) 331-567-9202 E-mail: nakanishi.takashi@nims.go.jp Homepage: http://www.nims.go.jp/macromol/nakanishi_eng/index.html Dr. S. Yagai, Dr. T. Nakanishi PRESTO, Japan Science and Technology Agency (JST, Japan) Prof. D. G. Kurth, Dr. T. Nakanishi Organic Nanomaterials Center National Institute for Materials Science (Japan) Dr. K. Yoshida Institute for Chemical Research, Kyoto University (Japan) Dr. S. Yagai Department of Applied Chemistry and Biotechnology Graduate School of Engineering, Chiba University (Japan) Dr. P. Fernandes Physical Chemistry II, Bayreuth University (Germany) Prof. D. G. Kurth Chemische Technologie der Materialsynthese Universität Würzburg (Germany) [**] This work was supported in part by a Grand-in-Aid from the Ministry of Education, Sciences, Sports, and Culture (Japan), and PRESTO, JST (Japan) (T.N.). We thank Dr. M. Takeuchi (NIMS) and T. Sievers (MPI) for helpful discussions. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.200900106. Zuschriften 2200  2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. 2009, 121, 2200 –2204