Luminogenic materials with aggregation-induced emission (AIE) attributes have attracted much interest since the debut of the AIE concept in 2001. In this critical review, recent progress in the area of AIE research is summarized. Typical examples of AIE systems are discussed, from which their structure–property relationships are derived. Through mechanistic decipherment of the photophysical processes, structural design strategies for generating new AIE luminogens are developed. Technological, especially optoelectronic and biological, applications of the AIE systems are exemplified to illustrate how the novel AIE effect can be utilized for high-tech innovations (183 references).

Aggregation-induced emission

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials

Ionic liquid crystals.

Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.

Dendron-Mediated Self-Assembly, Disassembly, and Self-Organization of Complex Systems

Most associate liquid crystals with their everyday use in laptop computers, mobile phones, digital cameras, and other electronic devices. However, in contrast to their rodlike (calamitic) counterparts, first described in 1907 by Vorlander, disklike (discotic, columnar) liquid crystals, which were discovered in 1977 by Chandrasekhar et al., offer further applications as a result of their orientation in the columnar mesophase, making them ideal candidates for molecular wires in various optical and electronic devices such as photocopiers, laser printers, photovoltaic cells, light-emitting diodes, field-effect transistors, and holographic data storage. Beginning with an overview of the various mesophases and characterization methods, this Review will focus on the major classes of columnar mesogens rather than presenting a library of columnar liquid crystals. Emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties. Finally, some applications and perspectives in materials science and molecular electronics will be discussed.

Discotic Liquid Crystals: From Tailor-Made Synthesis to Plastic Electronics

Die meisten Menschen verbinden mit dem Begriff Flussigkristalle sofort die Displays von Laptop-Computern, Mobiltelefonen, Digitalkameras und anderen elektronischen Geraten. Im Unterschied zu ihren stabchenformigen (calamitischen) Verwandten, die erstmals 1907 von Vorlander beschrieben wurden, bieten aber die 1977 von Chandrasekhar entdeckten scheibenformigen (diskotischen) Flussigkristalle andere vielversprechende Verwendungsmoglichkeiten. Ihre einzigartige Anordnung in columnaren Mesophasen macht sie zu idealen Kandidaten fur molekulare Drahte in vielen optischen und elektronischen Geraten, beispielsweise in Photokopierern, Laserdruckern, Solarzellen, organischen Leuchtdioden und Feldeffekttransistoren oder zur holographischen Datenspeicherung. Einer Ubersicht uber die verschiedenen Mesophasentypen und Charakterisierungsmethoden columnarer Flussigkristalle folgen ausgewahlte Beispiele aus den Hauptklassen columnarer Mesogene unter besonderer Berucksichtigung effizienter Syntheseverfahren, mesomorpher Eigenschaften und der fur Anwendungen relevanten physikalischen Eigenschaften der Flussigkristalle. Abschliesend werden Anwendungsbeispiele und Perspektiven fur einen Einsatz in den Materialwissenschaften und der molekularen Elektronik vorgestellt.

Diskotische Flüssigkristalle: Von der maßgeschneiderten Synthese zur Kunststoffelektronik

Alkylation of 1-alkyl-1H-imidazoles 2a–f with citronellyl bromide 1b opens access to chiral 1H-imidazolium bromides 3a–f (Scheme 1). A similar strategy yielded the chiral pyridinium ionic liquid 6 (Scheme 2). Dialkylation of 1H-imidazole (7) gave the C2-symmetric 1,3-dicitronellyl-1H-imidazolium bromide (8) (Scheme 3). Differential scanning calorimetry and optical polarizing microscopy revealed smectic mesophases for 1-citronellyl-3-tetradecy-1H-limidazolium bromide (3e) and 1-citronellylpyridinium bromide (6) (Table). In binary mixtures with smectic and nematic liquid crystals 9 and 10, 1-citronellyl-3-methyl-1H-imidazolium bromide (3a) behaved differently. Increasing quantities of 3a cause a decrease of the smectic-phase width for the mixture 3a/9 (Fig. 3), whereas the phase width of the nematic phase for 3a/10 remained nearly constant (Fig. 4).

Martin Tosoni

Papers

Discotic Liquid Crystals: From Tailor-Made Synthesis to Plastic Electronics

Diskotische Flüssigkristalle: Von der maßgeschneiderten Synthese zur Kunststoffelektronik

Synthesis of novel chiral ionic liquids and their phase behavior in mixtures with smectic and nematic liquid crystals

Counterion Effects on the Mesomorphic Properties of Chiral Imidazolium and Pyridinium Ionic Liquids

Synthesis of Novel Chiral Ionic Liquids and Their Phase Behavior in Mixtures with Smectic and Nematic Liquid Crystals.