π‐Conjugated Oligothiophene‐Based Polycatenar Liquid Crystals: Self‐Organization and Photoconductive, Luminescent, and Redox Properties

Abstract

A series of liquid‐crystalline (LC) π‐‐conjugated oligothiophenes bearing three or two alkoxy chains at their extremities has been designed and synthesized. These polycatenar oligothiophenes form various LC nanostructures including smectic, columnar, and micellar cubic phases. These properties depend on the number and length of the terminal alkoxy chains. The hole mobilities for the oligothiophenes have been measured. The layered smectic and columnar structures are capable of transporting holes, leading to mobilities of up to 0.01 cm2 V−1 s−1. The columnar LC assemblies have also been explored to produce linearly polarized light‐emission. Fine red polarized fluorescence is observed from a uniaxially aligned film of the oligothiophenes. The redox properties of the oligothiophenes both in solutions and in films have been examined. The oligothiophenes exhibit electrochromism upon applying an oxidative potential. The present design strategy is useful for fabricating a variety of functional electro‐active molecular assemblies.

Temperature‐Independent Hole Mobility of a Smectic Liquid‐Crystalline Semiconductor based on Band‐Like Conduction

“…[5] Efficient electronic-chargecarrier transport has been observed in columnar, [6] nematic, [7] and smectic phases, [8] and liquid-crystalline (LC) semiconductors with various molecular structures have been designed. Some LC semiconductors are also solution-processable.…”

“…(6)]: Figure 11 shows the fitting curve for the hole mobility at an electric field of 2 10 4 V cm À1 as a function of temperature in the ordered smectic phase of LC 1. The obtained data are fitted to a theoretical curve that is based on Equation (6). The best fitting reveals that m I , n, N T /N 0 , and E T are 7.25 10 1 , 1.2, 2.3 10 À5 , and 0.20 eV, respectively.…”

Solution‐Processable Septithiophene Monolayer Transistor

“…Examples of LC phases are described in the literature, wherein flexible peripheral substituents are combined with a rigid thiophene core. [11][12][13] In this work we report on the crystal structure of α,ω-substituted septithiophenes and we demonstrate that this material is an excellent candidate for the realization of monolayer OFETs. We first assessed the crystal structure of 2-octyldodecyl-disubstituted septithiophene (7T) and revealed the presence of several high temperature transitions between the crystalline and LC phases.…”

Stimuli-Responsive Photoluminescent Liquid Crystals

“…Highly functional soft materials can be prepared using the process of self-organization into such nanostructures. For example, anisotropic ionic or electrical transporting properties are observed for these materials [13][14][15][16]. Photofunctional liquid crystals have been prepared by introducing photochromic [17] and photoluminescent [11,13,16,18] moieties.…”