Charge Transportation and Chirality in Liquid Crystalline Helical Network Phases of Achiral BTBT‐Derived Polycatenar Molecules

Abstract

First examples of multichain (polycatenar) compounds, based on the π‐conjugated [1]benzothieno[3,2‐b]benzothiophene unit are designed, synthesized, and their soft self‐assembly and charge carrier mobility are investigated. These compounds, terminated by the new fan‐shaped 2‐brominated 3,4,5‐trialkoxybenzoate moiety, form bicontinuous cubic liquid crystalline (LC) phases with helical network structure over extremely wide temperature ranges (>200 K), including ambient temperature. Compounds with short chains show an achiral cubic phase with the double network, which upon increasing the chain length, is at first replaced by a tetragonal 3D phase and then by a mirror symmetry is broken triple network cubic phase. In the networks, the capability of bypassing defects provides enhanced charge carrier mobility compared to imperfectly aligned columnar phases, and the charge transportation is non‐dispersive, as only rarely observed for LC materials. At the transition to a semicrystalline helical network phase, the conductivity is further enhanced by almost one order of magnitude. In addition, a mirror symmetry broken isotropic liquid phase is formed beside the 3D phases, which upon chain elongation is removed and replaced by a hexagonal columnar LC phase.

Structures, Properties, and Device Applications for [1]Benzothieno[3,2‐b]Benzothiophene Derivatives

“…Recently, 2‐brominated 3,4,5‐trialkoxybenzoyloxy moiety was introduced into BTBT derivative and it constructed the bicontinuous cubic liquid crystalline phases with helical network structures and predictable morphology. [ 26 ] The 3D conduction pathway improves the carrier transfer efficiency and allows nondispersive charge transport.…”

Mirror Symmetry Breaking and Network Formation in Achiral Polycatenars with Thioether Tail

“…Because the rods are organized almost perpendicular to the local network direction, their π-systems can overlap and these networks provide 3D conduction pathways for charge transportation (see Figure 1), which makes these Cub bi phases interesting for organic electronics applications. [7,38] In this organization of the π-conjugated rods perpendicular to the networks the rod-like units cannot align perfectly parallel, because the overcrowding of the ends by the multiple alkyl chains induces a twist (Figure 1d). Due to the network structure the twist sense is synchronized along the networks, [59] leading to a helical network with uniform chirality along the individual nets.…”

Transition from lamellar to nanostructure mesophases in azobenzene-based hockey-stick polycatenars

“…[2][3][4][5][6] Such bicontinuous network cubic (Cub bi ) phases are fascinating for various applications, including ion transportation, catalysis, drug delivery, organic electronic devices and energy conversion. 5,[7][8][9] Therefore, the design and synthesis of new functional cubic LCs are essentials for the development of current and future applications of LCs. Cub bi phases are common for non-symmetric polycatenar LCs [10][11][12][13][14][15] but rare for bent-core LCs (BCLCs).…”

“…5,[7][8][9] Therefore, the design and synthesis of new functional cubic LCs are essentials for the development of current and future applications of LCs. Cub bi phases are common for non-symmetric polycatenar LCs [10][11][12][13][14][15] but rare for bent-core LCs (BCLCs). [16][17][18][19] Polycatenars are rod-like molecules terminated with more than two flexible chains.…”

“…23 Moreover, mirror symmetry breaking was also observed in the isotropic liquid phase assigned as Iso phase in non-symmetric polycatenars. [10][11][12][13][14][15]24 Using alkyl chain engineering, we were able to report different types of functional nanostructured azobenzene-based non-symmetric polycatenars exhibiting Iso 1 [ * ] phase beside a lamellar (Smectic A = SmA) phase in tricatenar systems 25,26 or Cub bi or 3D tetragonal phases in tetracatenar molecules. 12,21,23,24,27,28 An efficient way to photocontrol the molecular structure and to improve the physical properties toward applications such as optoelectronic sensing devices 29 and organic light-driven actuators [30][31][32] is the incorporation of the azobenzene unit into the molecular structure.…”