Noncovalent Synthesis of Organic Fibers

摘要

Organic chemists, taking a cue from the biological world, are becomingincreasingly interested in molecules that operate within organized assemblies (also called 'supramolecular systems' or 'systems'). A living cell is the most remarkable example of a chemical system. Through a poorly understood cooperation and interdependency among the cellular components, an entity is created that exceeds the sum of the parts. Groups of molecules, properly assembled, can obviously accomplish much more than an equal number of molecules functioning separately. Conventional organic chemistry and systems chemistry differ markedly in their emphasis. Whereas most organic chemists immerse themselves in the formation and destruction of covalent bonds, systems organic chemists focus on intermolecular attractions: the hydrogen bond, hydrophobic and electrostatic association, and van der Waals interactions. These attractive forces operate spontaneously, often leading to 'self-assembly' when suitably constructed molecules are simply mixed. Although collectively the non-covalent stabilization of an aggregate can be quite large, each individual associative interaction is much weaker than a covalent bond. This can be either an advantage or a disadvantage depending upon the particular goals. In any event, chemists involved with systems-research delight in the rods, worms, tubules, ribbons, and laminates that noncovalent bonding affords them. Recently, we have used noncovalent synthesis to construct organic fibers several centimeters long. The present article relates some of the details in addition to work of others in the area. Self-organized fibers have appeared on the scene only recently, and to our knowledge, they have not yet made their way into commerce.