Self-Assembly, Molecular Dynamics, and Kinetics of Structure Formation in Dipole-Functionalized Discotic Liquid Crystals

Abstract

The self-assembly, the molecular dynamics, and the kinetics of structure formation are studied in dipole-functionalized hexabenzocoronene (HBC) derivatives. Dipole substitution destabilizes the columnar crystalline phase except for the dimethoxy- and monoethynyl-substituted HBCs that undergo a reversible transformation to the crystalline phase. The disk dynamics are studied by dielectric spectroscopy and site-specific NMR techniques that provide both the time-scale and geometry of motion. Application of pressure results in the thermodynamic phase diagram that shows increasing stability of the crystalline phase at elevated pressures. Long-lived metastability was found during the transformation between the two phases. These results suggest new thermodynamic and kinetic pathways that favor the phase with the highest charge carrier mobility.

Conductivity of Poly(pyrrole)‐Poly(styrene sulfonate) Core–Shell Nanoparticles

“…In addition, the resemblance between some of the processes shown in Figures 3, 4 a, where the temperature dependence of the "Modulus cross" processes is shown, reveals that these processes are associated either with ionic or with electronic conductivity. [21,31,32] The origin of all processes observed herein is summarized in the last column of Table 1.…”

Polyphenylene‐Based Materials: Control of the Electronic Function by Molecular and Supramolecular Complexity

“…Soluble HBC (9a-c) can form liquid crystalline phases, in which the molecules align into ordered columns. [73][74][75] Moreover, the so-called discotic species can lie with their aromatic core on the surface in a ''faceon'' arrangement or stand with the edge of the aromatic cores in an ''edge-on'' fashion. For FETs, an ''edge-on'' organization of discotics in uniaxially oriented columns is required (Fig.…”

“…Recent investigations on a series of dipole functionalized HBCs (11a-d) showed that the presence of dipole substituents enhances intermolecular interactions, crucial for a uniform alignment of their columnar superstructures. [74,75] Furthermore, the crystalline phase was stabilized at elevated pressures (up to 600 MPa at temperature up to 450 K).…”

Fast and Slow Dynamics in a Discotic Liquid Crystal with Regions of Columnar Order and Disorder

“…In particular, NMR methods showed that the local dynamic molecular order parameter, as probed by the CÀH bond direction, is close to S CH ¼ 0:5 consistent with an axial motion of the parallel disks around the column axis [8]. Other HBC derivatives with lower symmetry exhibit a somewhat lower order (S CH ¼ 0:45-0:38), reflecting combined axial rotations and outof-plane fluctuations of the disks [9].…”