ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 II. Supramolecular Membranes in Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
A. Aqueous Bilayer Membranes and Design of Bilayer-Forming Amphiphiles . . . . . . . . 482 B. Supramolecular Membranes and Related Self-Assemblies in Aqueous Media . . . . . . 484 C. Toward the Functional Supramolecular Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
1. Hydrogels Formed by Self-Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 2. Photofunctional Hydrogels via Combinatorial Approach . . . . . . . . . . . . . . . . . . . . 489
III. Amphiphilic Hydrogen-Bonded Networks in Organic Media . . . . . . . . . . . . . . . . . . . . . . . . 491 IV. Self-Assembling Nanowires of Organic/Inorganic Superstructures . . . . . . . . . . . . . . . . . . . 493
A. Quasi One-Dimensional Halogen-Bridged Mixed-Valence Complexes . . . . . . . . . . . . 493 B. Self-Assembling Inorganic Molecular Wires by Supramolecular Packaging . . . . . . . . 495 C. Supramolecular Band Gap Engineering and Solvatochromic Nanowires . . . . . . . . . . . 496 D. Self-Assembly at Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 E. Gel-Like Networks Self-Assembled from Lipophilic Complexes
and Unique Thermal Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 499 V. Amphiphilic Nanostructures Self-Assembled in Ionic Liquids . . . . . . . . . . . . . . . . . . . . . . . 499 VI. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
I. INTRODUCTION
Nanoscale materials are coming of age. Traditional chemistry has dealt with the synthesis and transformation of individual molecules in the length scale of ∼0.1-10 nm. In contrast, synthesis of nano-to mesoscopic (∼10-1000 nm) architectures is a challenging issue in molecular nanotechnology. Biological systems provide fascinating examples of such mesoscopic-scale self-assemblies. Figure 1 illustrates the hierarchy of molecular assemblies both in biological and in synthetic systems. Amino acids are polymerized to give peptides and proteins, which are spontaneously folded into
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Biological Synthetic
nano-sized structures (shown in the left column). These units may further self-assemble into ordered mesoscopic structures, as exemplified by tobacco mosaic virus, actin fibers, and microtubles [1]. These mesoscopic supramolecular assemblies are formed by ingeniously employing multiple noncovalent interactions — such as electrostatic interactions, hydrogen bonding, dipole-dipole interactions, and hydrophobic association [1,2]. In this context, weather a nanostructure is comprised of covalent bonding or noncovalent assembly is not an issue of primal importance. Moreover, formation of such supramolecular structures is directed by the aqueous environment. In other words, natural supermolecules possess amphiphilic superstructures which are most stable in water.
