Proceedings PaperDesign of liquid-crystalline electronic functional materials through nanosegregation
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Conventional liquid-crystalline (LC) semiconductors have been molecules consisting of a π-conjugated moiety and alkyl chains. For example, phenylterthiophene derivatives bearing alkyl chains exhibit ordered smectic phase at room temperature and are applied to field-effect transistors. In this paper, we report a molecular designs of LC electronic materials based on nanosegregation. Terthiophene derivatives bearing an imdazolium moiety exhibit supremolecular smectic phases, in which hole- and ion-conductive layers are formed separately. In the LC phase, electrochrmism is observed under the application of a DC bias without any electrolyte solutions. In simple side-chain LC polysiloxanes bearing terthiophene pendant groups, suprastructures based on nanosegregation are observed. The presence of flexible sublayers consisting of the polysiloxane backbones can relax the applied strain and decrease defect density, resulting in high hole mobility on the order of 10-2 cm2/Vs. For perylene tetracarboxylic bisimide (PTCBI) derivatives bearing oligosiloxane chains, nanosegregation between the rigid aromatic cores and flexible oligosiloxane chains promotes the formation of columnar and layer structures, in which efficient electron transport is observed. The electron mobility in the columnar phase of the PTCBI derivative bearing four trisiloxane chains exceeds 10-3 cm2/Vs at room temperature.