Supra‐Macromolecular Chemistry: Toward Design of New Organic Materials from Supramolecular Standpoints

Abstract

The quest to understand the principle of weak noncovalent interactions such as hydrogen bonding, electrostatic interaction, van der Waals force, and so on has evoked intense research in supramolecular chemistry. Molecular contrivances with noncovalent interaction sites (molecular recognition sites) have straightforwardly led to chemosensors, artificial enzymes, topological molecules, and so forth [1]. In these systems, the noncovalent interaction sites are arranged so that they can converge on the guest molecule in consideration of the additivity and the complementarity of noncovalent interactions (convergent type recognition). In contrast, divergent type molecular recognition, when properly designed, can link the corresponding molecules together, and, particularly when complementary to themselves, they selfassemble to large objects [2]. The programmed direction and the number of noncovalent interactions define not only the size and shape but also the functions of these molecular assemblies; in fact, this adaptability permits vast applications in nanotechnology and materials science. Equally attractive are supramolecular polymers which have structures analogous to those of synthetic polymers, although the repeating units are linked via divergent-type noncovalent interactions [2c].Molecular assemblies and supramolecular polymers have led to a new horizon in advanced materials. The designed unit molecules and the resultant programmed assemblies of the supramolecular systems continue to offer new and exciting alternatives to conventional covalent bond-based synthetic polymers. The attractive advantages of the supramolecular systems are as follows: (1) reversible, recyclable and/or stimuli responsiveness, (2) flexible design of functions actualized by the program of direction and/or angle of noncovalent interactions (specifically, p-p stacking is an attractive characteristic for organic electronics), and (3) accessibility of nano-sized superstructures such as spheres, tubes, fibers, helices, and so on. From these viewpoints, the definition of polymers as opposed to small molecules could be becoming less meaningful, and molecular assemblies (i.e., supramolecular polymers) nowadays have a great influence on the design of functional materials. Supramolecular Polymer Chemistry, First Edition. Edited by Akira Harada.

Hierarchical Self-Organization and Uniaxial Alignment of Well Synthesized Side-Chain Discotic Liquid Crystalline Polymers

“…In contrast with intensively studied calamitic mesogens based LCPs with extensive applications such as in high modulus fibers, optoelectronic devices, and sensors, thus far surprisingly limited progress has been made on discotic LCPs since first reported in 1983 by Ringsdorf . Although some examples of side-chain discotic LCPs have been explored adopting various discotic mesogens such as derivatives of triphenylene (TP), − hexabenzocoronene (HBC), , multialkynylbenzene, perylene, porphyrin, and phthalocyanine (Pc), whereas there is almost no systematic work pertinent to some fundamental questions of discotic LCPs such as molecular weight effect and the spacer length influence, despite such issues are closely correlated to their self-organized supramolecular structures thus crucial for organic electronic and optoelectronic applications …”