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

Convoluted micellar morphological transitions driven by tailorable mesogenic ordering effect from discotic mesogen-containing block copolymer

Solution-state self-assemblies of block copolymers to form nanostructures are tremendously attractive for their tailorable morphologies and functionalities. While incorporating moieties with strong ordering effects may introduce highly orientational control over the molecular packing and dictate assembly behaviors, subtle and delicate driving forces can yield slower kinetics to reveal manifold metastable morphologies. Herein, we report the unusually convoluted self-assembly behaviors of a liquid crystalline block copolymer bearing triphenylene discotic mesogens. They undergo unusual multiple morphological transitions spontaneously, driven by their intrinsic subtle liquid crystalline ordering effect. Meanwhile, liquid crystalline orderedness can also be built very quickly by doping the mesogens with small-molecule dopants, and the morphological transitions are dramatically accelerated and various exotic micelles are produced. Surprisingly, with high doping levels, the self-assembly mechanism of this block copolymer is completely changed from intramolecular chain shuffling and rearrangement to nucleation-growth mode, based on which self-seeding experiments can be conducted to produce highly uniform fibrils.

Enhanced Conductivity and Thermochromic Luminescence in Hydrogen Bond-Stabilized Columnar Liquid Crystals

Developing discotic columnar liquid crystals (LCs) with both high electrical conductivity and strong luminescence remains a challenge because the intracolumnar interdisc π-π stacking usually in ordered discotic columnar LCs is essential to generate charge transport pathways but normally detrimental to light emissions. We here present tricyanotristyrylbenzene-based quasi-discotic LCs upon bearing three wedge-shaped alkyl tails for addressing this issue. The resulted columnar materials displayed both high electrical conductivity and strong luminescence, especially for the ones stabilized by multivalent hydrogen-bonding interactions. Besides, an interesting thermochromic luminescence tuning behavior in a smooth manner was observed over a wide wavelength range for the hydrogen bond-stabilized columnar LCs. This study will lead to the future design and application of new multifunctional optoelectronic materials by integrating excellent conductivity and luminescence tuning behaviors.

Effect of grafting density on the self-assembly of side-chain discotic liquid crystalline polymers with triphenylene discogens

The self-assembly of triphenylene (TP)-based side-chain discotic liquid crystalline polymers (SDLCPs) with different grafting densities was investigated by using the dissipative particle dynamics (DPD) method. We explored the coupling effect between the main chain and the side-chain TP discogens with various length alkyl tails, and how the rigidity of the main chain, grafting density and spacer lengths affect the self-assembled morphologies of SDLCPs. By changing the above factors, we have obtained nine phases. It is deduced that a moderate grafting density, a polymer backbone with sufficient length and alkyl tails with medium length ensure SDLCPs form ordered columnar mesophases. It is worth noting that double columnar phases (Colne-Col and Colh-Col) were obtained with high grafting densities and sufficiently long backbones. All these results provide an effective basis and helpful guidance for the in-depth research of such kinds of fascinating organic semiconducting materials, SDLCPs, from the perspective of grafting density.

Can one determine the density of an individual synthetic macromolecule?

Dendronized polymers (DPs) are large and compact main-chain linear polymers with a cylindrical shape and cross-sectional diameters of up to ∼15 nm. They are therefore considered molecular objects, and it was of interest whether given their experimentally accessible, well-defined dimensions, the density of individual DPs could be determined. We present measurements on individual, deposited DP chains, providing molecular dimensions from scanning and transmission electron microscopy and mass-per-length values from quantitative scanning transmission electron microscopy. These results are compared with density values obtained from small-angle X-ray scattering on annealed bulk specimen and with classical envelope density measurements, obtained using hydrostatic weighing or a density gradient column. The samples investigated comprise a series of DPs with side groups of dendritic generations g = 1-8. The key findings are a very large spread of the density values over all samples and methods, and a consistent increase of densities with g over all methods. While this work highlights the advantages and limitations of the applied methods, it does not provide a conclusive answer to the question of which method(s) to use for the determination of densities of individual molecular objects. We are nevertheless confident that these first attempts to answer this challenging question will stimulate more research into this important aspect of polymer and soft matter science.

Enhanced fluorescence quantum yield of syndiotactic side-chain TPE polymers via Rh-catalyzed carbene polymerization: influence of the substitution density and spacer length

The fluorescence quantum yields of the TPE-based C1 polymers also increase with the shortened spacer lengths and further improve by about 20% as compared with the corresponding C2 polyacrylate counterparts.

Hierarchically ordered nanostructures of a supramolecular rod-coil block copolymer with a hydrogen-bonded discotic mesogen

Supramolecular liquid crystalline block copolymers prepared via hydrogen bonding exhibit hierarchical structures that can be tuned by varying the molar ratio of the discotic hydrogen-bonding acceptor to the block copolymer donor.

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

The large-area formation of functional micropatterns with liquid crystals is of great significance for diversified applications in interdisciplinary fields. Meanwhile, the control of molecular alignment in the patterns is fundamental and prerequisite for the adequate exploitation of their photoelectric properties. However, it would be extremely complicated and challenging for discotic liquid crystals (DLCs) to achieve the goal, because they are insensitive to external fields and surface chemistry. Herein, a simple method of patterning and aligning DLCs on flat substrates is disclosed through precise control of the formation and dewetting of the capillary liquid bridges, within which the DLC molecules are confined. Large-area uniform alignment occurs spontaneously due to directional shearing force when the solvent is slowly evaporated and programmable patterns could be directly generated on desired substrates. Moreover, the in-plane column direction of DLCs is tunable by slightly tailoring their chemical structures which changes their self-assembly behaviors in liquid bridges. The patterned DLCs show molecular orientation-dependent charge transport properties and are promising for templating self-assembly of other materials. The study provides a facile method for manipulation of the macroscopic patterns and microscopic molecular orientation which opens up new opportunities for electronic applications of DLCs.

Highly efficient luminescent side-chain polymers with short-spacer attached tetraphenylethylene AIEgens via RAFT polymerization capable of naked eye explosive detection

The fluorescence quantum yield of side-chain AIE polymers was remarkably promoted just by shortening the linking spacer.

Synthesis and organogelating behaviour of amino acid-functionalised triphenylenes

Four novel amino acid-functionalised triphenylenes have been prepared with glycine, l-alanine, l-phenylalanine and l-tryptophan ethyl ester side-chains. The glycine derivative is a good gelator of chloroform, the alanine derivative gels ethanol and toluene, and the phenylalanine derivative gels benzene and toluene. The tryptophan derivative does not gel any of the solvents tested, most probably due to its more bulky structure, but forms microspheres by evaporation-induced self-assembly. The self-assembly properties of the π-gelators have been investigated using infrared, UV-absorption and fluorescence spectroscopy, concentration- and temperature-dependent NMR, and X-ray scattering experiments on dried xerogel as well as the wet organogel. The latter experiments suggest the glycine gel in chloroform includes columnar aggregates, with an overall disordered columnar oblique mesophase. These compounds are of interest because of the well-known hole-transporting properties of triphenylene liquid crystals: 1-D columnar assemblies of these compounds may find applications in organic electronic devices.

Discotic columnar liquid-crystalline polymer semiconducting materials with high charge-carrier mobility via rational macromolecular engineering

Well-prepared side-chain discotic liquid crystal polymers with shorter spacers in ordered columnar phases are fascinating and promising cost-effective, solution-processable organic semiconducting materials for various potential optoelectronic device applications.

Self-assembled helical columnar superstructures with selective homochirality

Helical columnar polymeric complexes with selective homochirality have been achieved from side-chain discotic liquid crystalline polymers doped with chiral acceptors.

Synthetic approaches towards structurally-defined electrochemically and (photo)redox-active polymer architectures

This review details synthetic strategies leading to structurally-defined electrochemically and (photo)redox-active polymer architectures,e.g.block, graft and end functionalized (co)polymers.

Facile preparation of a novel nickel-containing metallopolymer via RAFT polymerization

While the metallocene polymers were comprehensively studied, other metallopolymers are rarely explored. The major challenge is the lack of a synthetic platform for the preparation of metal coordinated derivatives, monomers, and polymers. Therefore, the development of a facile synthesis of new metal coordinated monomers and polymers is critically needed. A novel successfully synthesized methacrylate-containing nickel complex is reported in this communication. Controlled RAFT polymerizations are further carried out to prepare a series of side-chain nickel containing polymers with different molecular weight and narrow Polydispersity Index (PDI). This new metallopolymer performs specific electrochemical and excellent thermal properties. This study provides a novel and convenient strategy to prepare metallopolymer with controllable molecular weight, which has potential applications in assembled, catalytic and magnetic materials.

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

We have prepared a monolayer of a novel liquid crystalline polymer derived from 2,6-dihydroxy-3,7,10,11-tetraalkoxy-triphenylene (PHAT) at an air-water interface and transferred it onto freshly cleaved mica as well as gold coated mica substrates by the Langmuir-Blodgett (L-B) technique. The atomic force microscope (AFM) images of these L-B films show a uniform coverage with a thickness of 1.5 nm. Electrical conductivity measurements were carried out on the PHAT monolayer deposited on the gold coated mica substrate using a current sensing AFM (CSAFM). The gold substrate-PHAT monolayer-cantilever tip of CSAFM forms a metal-insulator-metal (M-I-M) junction. The CSAFM yields a non-linear current-voltage (I-V) curve for the M-I-M junction. The analysis of the I-V characteristics of the M-I-M junction indicated that the charge transport in the liquid crystalline polymer monolayer is by the direct tunneling mechanism. The barrier height for the PHAT monolayer was estimated to be 1.22 ± 0.02 eV.

Competition and compromise between discotic and calamitic mesogens in triphenylene and azobenzene based shape-amphiphilic liquid crystals

Nirvana Phoenix: a shot showing the transformation from dendritic to focal conic fan-shaped POM texture of different type of lamello-columnar mesophases of a typical disc-rod hybrid dimer TP6–AZO6 reminiscent of the sacred scene of nirvana phoenix.

Systematic studies on structure–properties relationship of main chain discotic liquid crystalline polyethers: effects of the spacer lengths and substitution positions

The perfect spacer length and substitution positions were foundviasystematical study on triphenylene-based discotic liquid crystalline polyethers.

Synthesis and self-organization of azobenzene containing hemiphasmidic side-chain liquid-crystalline polymers with different spacer lengths

Hemiphasmidic side-chain liquid-crystal polymers form different columnar phases depending on the spacer lengthnand temperatureT.

Cyclic polymers with pendant triphenylene discogens: convenient synthesis and topological effect on thermotropic liquid crystal behavior and fluorescence enhancement

Cyclic topological constraint suppresses columnar ordering while showing remarkably enhanced fluorescence as a supplement of aggregation-induced emission (AIE).