Swallow‐Tailed Polycatenars: Controlling Complex Liquid Crystal Self‐Assembly and Mirror Symmetry Breaking at the Lamellae‐Network Cross‐Over

Abstract

molecules in soft self-organized supramolecular systems. [1,2] Extended π-conjugated systems are also of significant interest for application as charge carrier in organic semiconductors, [3] luminescent materials (e.g., AIEgens), [4] and for circular polarized emission in helical assemblies. [5] Therefore, tuning the organization of these π-conjugated rods in soft matter systems is fundamental and requires the understanding of their general design rules. Liquid crystals (LCs) are of great interest as stimuli-responsive and switchable optical materials in displays, photo nics [6] and in sensor applications. [7,8] Rod-like π-conjugated molecules with multiple end-chains, the so-called polycatenar molecules, have received significant interests as they provide a huge variety of different LC phases ranging from lamellar (smectic, Sm) via bicontinuous cubic (Cub bi) to columnar (Col) [9-11] and even micellar cubic phases. [3] This observation has contributed to the recognition of the importance of nano-segregation for LC phase formation and demonstrated the similarity of the fundamental self-assembly principles in lyotropic systems formed by amphiphiles, in LC phases and in the solid state morphologies of block copolymers. [12,13] Among the self-assembled structures of polycatenar molecules, the Cub bi phases [14,15] received special attention because of their potential for applications, as for example in 3D conducting [16] and photonic materials, [17] being the result of their interwoven net-* ]) as well. This work establishes rules for controlling the self-assembly of functional π-conjugated rods in soft matter and fluids.

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

“…[ 39 , 40 ] However, recently it was found that there is another type of Cub bi phase which is chiral and forms conglomerates of chiral domains with opposite handedness. [ 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ] This is due to the triple network structure of this Cub bi phase with space group I 23 (Figure 1 b), [52] previously known as Im m . [ 53 , 54 , 55 , 56 , 57 ] In this case the network chirality cannot cancel out and a conglomerate of chiral domains is observed.…”

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

“…The calculated lattice parameter a cub is 11.30 nm, which is in the expected range of this type of cubic phase. 11,14,15,27,28 The additional small reflection peaks could be also indexed to Cub bi /Ia% 3d phase (see Table S1 in the ESI †). The reconstructed electron density map based on the obtained diffraction patterns, shows the double gyroid network structure of the Ia % 3d phase (Fig.…”

“…Cub [ * ] with I23 symmetry (Cub [ * ] /I23) as would be expected upon alkyl-chain elongation. 14,15,28 However, the type of the Cub bi does not change with increasing the length of the terminal chains, indicating that the required chain volume is not achieved.…”

“…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.…”