Hierarchical Self-Organization and Uniaxial Alignment of Well Synthesized Side-Chain Discotic Liquid Crystalline Polymers

Abstract

Liquid crystalline polymers (LCPs) combine the attributes of liquid crystals and polymers, while discotic LCPs have been less developed in sharp contrast to their calamitic counterparts mainly due to lack of suitable discotic LCP materials. Here we successfully prepared a series of welldefined triphenylene (TP) based discotic LC polyacrylates via reversible addition−fragmentation chain-transfer (RAFT) polymerization for the first time, and through a combination of multiple analysis techniques and phase transition kinetics study, a remarkable molecular weight effect or polymer effect at a critical degree of polymerization (DP) around 20 has been disclosed. Moreover, the first proposed discrete columnar stacks (DCS) based hierarchical self-organization model accounts well for the formation and transformation of ordered hexagonal columnar lattice Col ho dominated by side-chain TP stacking and oblique columnar superlattice Col ob-s induced by compaction and ordering of polymer backbones. The in-depth understanding of their superstructures and readily achieved uniaxial alignment pave the way for the rational design and preparation of such kind of solution processable cutting-edge polymeric semiconducting materials and may boost various fascinating optoelectronic applications.

Synthesis and organogelating behaviour of amino acid-functionalised triphenylenes

“…In Figure 8 three small angle peaks are observed corresponding to spacings of 2.93, 1.90 and 1.57 nm. These do not fit the pattern expected for a columnar hexagonal structure, but do fit a columnar rectangular, or columnar oblique structure such has been observed also for example in some pure thermotropic triphenylene derivatives 47 .…”

“…At high temperature (65 °C), an additional diffraction peak can be seen around q = 1.2 nm 1 that vanishes when the sample is cooled down to 25 °C. The origin of this diffraction peak remains unclear, but it might arise from a temporarily coexisting superlattice as observed by Mu et al 47 in liquid crystalline triphenylene polymers.…”

Patterning of Discotic Liquid Crystals with Tunable Molecular Orientation for Electronic Applications

“…However, the large‐area uniform molecular alignment of DLCs is the key issue for the improvement of charge transport properties, thus influencing their application in such devices. Hitherto, the self‐organized alignment of DLC molecules can be induced by different techniques, including mechanical shearing, Langmuir–Blodgett thin films, zone‐casting technique, zone melting, template growth, applying aligned polytetrafluoroethylene layers, micro‐ and nanoconfinement, magnetic and electric field alignment, and lithographically wetting technique . These methods are good examples to align DLC materials into homogeneous thin film with high quality (uniformity of macroscopic orientation of DLC molecules).…”

Charge transport in a liquid crystalline triphenylene polymer monolayer at air–solid interface

“…Ultrathin films of such functional materials on metal substrates formed by Langmuir-Blodgett (L-B) technique are ideal systems to study the nanoscale electrical properties, since L-B technique gives a good control over the thickness of the film, orientation of the molecules and surface density of the molecules 12 . Though rod-like mesogen based polymers find a variety of applications like high performance fibers, opto electronics devices, sensors and so on 13 , disc-like mesogen based polymers have not drawn much attention for their applications. This is mainly due to the fact that synthesis of discotic LCPs is relatively difficult compared to calamatic mesogens 13,14 .…”

“…Though rod-like mesogen based polymers find a variety of applications like high performance fibers, opto electronics devices, sensors and so on 13 , disc-like mesogen based polymers have not drawn much attention for their applications. This is mainly due to the fact that synthesis of discotic LCPs is relatively difficult compared to calamatic mesogens 13,14 . Here we have studied the charge transport across a monolayer of triphenylene based discotic LCP material synthesized in our laboratory.…”