Helicity Control of Circularly Polarized Luminescence from Aromatic Conjugated Copolymers and Their Mixture Using Reversibly Photoinvertible Chiral Liquid Crystals.

We synthesized cyclic chiral compounds [()/()-D2s] by linking a photoresponsive bisbenzothienylethene (BTE) moiety with an axially chiral binaphthyl moiety. Chiral nematic liquid crystals (N*-LCs) were prepared by adding chiral compounds as dopants to host N-LCs. These N*-LCs exhibited reversible chirality inversion upon photoisomerization between the open and closed forms of the BTE moiety.

Author Correction: Apparent Power Law Scaling of Variable Range Hopping Conduction in Carbonized Polymer Nanofibers.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Chiral Reaction Field with Thermally Invertible Helical Sense that Controls the Helicities of Conjugated Polymers.

A chiral reaction field with thermally invertible helical sense enables control of the helicity of the reaction product, which is a central challenge in asymmetric synthesis that has yet to be overcome. A novel chiral compound comprising two types of chiral moieties with opposite helicities and temperature dependences is synthesized; this compound is added as a chiral dopant to a mixture of nematic liquid crystals to prepare a chiral nematic liquid crystal (N*-LC). The N*-LC containing the chiral dopant exhibits thermally invertible helicity to yield left- and right-handed helical senses at low and high temperatures, respectively.

Low-density graphitic films prepared from iodine-doped enzymatically synthesized amylose films as carbonization precursors.

We have developed a novel approach for preparing low-density graphitic films using iodine-doped enzymatically synthesized amyloses (ESAs) with strictly controlled molecular weights as carbonization precursors. All of the iodine-doped ESA films retained their film structures and morphologies, even after the heat-treatment at 800 °C and 2600 °C. Therefore, iodine doping plays an indispensable role in retaining film structure and morphology during the carbonization of ESA polysaccharides.

Conjugated polymer-based carbonaceous films as binder-free carbon electrodes in supercapacitors.

We present a facile preparation method for carbonaceous film electrodes using poly(3,4-ethylenedioxythiophene) (PEDOT) and polyacetylene (PA) films as precursors a morphology-retaining carbonization process. Carbonization was performed on acceptor-doped conjugated polymer films in the temperature range of 600-1100 °C. The obtained carbonaceous films had similar surface morphologies to those of the original conjugated polymer films.

Probing variable range hopping lengths by magneto conductance in carbonized polymer nanofibers.

Using magneto transport, we probe hopping length scales in the variable range hopping conduction of carbonized polyacetylene and polyaniline nanofibers. In contrast to pristine polyacetylene nanofibers that show vanishing magneto conductance at large electric fields, carbonized polymer nanofibers display a negative magneto conductance that decreases in magnitude but remains finite with respect to the electric field. We show that this behavior of magneto conductance is an indicator of the electric field and temperature dependence of hopping length in the gradual transition from the thermally activated to the activation-less electric field driven variable range hopping transport.

Circularly polarized luminescence of helically assembled pyrene π-stacks on RNA and DNA duplexes.

In this report, we describe the circularly polarized luminescence (CPL) of the RNA duplexes having one to four 2'-O-pyrene modified uridines (Upy) and the DNA duplexes having two, four, and six pyrene modified non-nucleosidic linkers (Py). Both the pyrene π-stack arrays formed on the RNA and DNA double helical structures exhibited pyrene excimer fluorescence. In the pyrene-modified RNA systems, the RNA duplex having four Upys gives CPL emission with g value of <0.

Preparation of 2D Carbon Materials by Chemical Carbonization of Cellulosic Materials to Avoid Thermal Decomposition.

Cellulosic materials, including regenerated cellulose, are promising precursors for a variety of carbon materials. However, thermal decomposition, typically accompanying carbonization at high temperatures, hinders cellulosic materials from being efficiently carbonized (i.e.

Apparent Power Law Scaling of Variable Range Hopping Conduction in Carbonized Polymer Nanofibers.

We induce dramatic changes in the structure of conducting polymer nanofibers by carbonization at 800 °C and compare charge transport properties between carbonized and pristine nanofibers. Despite the profound structural differences, both types of systems display power law dependence of current with voltage and temperature, and all measurements can be scaled into a single universal curve. We analyze our experimental data in the framework of variable range hopping and argue that this mechanism can explain transport properties of pristine polymer nanofibers as well.

Helically Assembled Pyrene Arrays on an RNA Duplex That Exhibit Circularly Polarized Luminescence with Excimer Formation.

Circularly polarized luminescence (CPL) was observed in pyrene zipper arrays helically arranged on an RNA duplex. Hybridization of complementary RNA strands having multiple (two to five) 2'-O-pyrenylmethyl modified nucleosides affords an RNA duplex with normal thermal stability. The pyrene fluorophores are assembled like a zipper in a well-defined helical manner along the axis of RNA duplex, which, upon 350 nm UV illumination, resulted in CPL emission with pyrene excimer formation.

Macroscopically Aligned Graphite Films Prepared from Iodine-Doped Stretchable Polyacetylene Films Using Morphology-Retaining Carbonization.

We prepared graphite films using typical Shirakawa-type and stretchable polyacetylene (PA) films as precursors through a morphology-retaining carbonization. A macroscopically aligned PA film was prepared from the drawable PA film using a mechanical-stretching procedure. The degree of orientation of the aligned PA film was evaluated by measuring polarized infrared absorption spectra and an azimuthal-angle profile of a Laue X-ray diffraction (XRD) pattern.

Helically assembled -conjugated polymers with circularly polarized luminescence.

We review the recent progress in the field of helically assembled -conjugated polymers, focusing on aromatic conjugated polymers with interchain helical -stacking that exhibit circularly polarized luminescence (CPL). In Part 1, we discuss optically active polymers with white-colored CPL and the amplification of the circular polarization through liquid crystallinity. In Part 2, we focus on the stimuli-responsive CPL that results from changes in the conformation and aggregation state of -conjugated molecules and polymers.

Photochemically colour-tuneable white fluorescence illuminants consisting of conjugated polymer nanospheres.

π-Conjugated aromatic polymers have attracted much interest due to their semi-conducting and luminescent properties, and are therefore regarded as promising materials for next-generation optoelectronic devices. Especially, it is considered as one of the indispensable steps for advanced function to control the optoelectronic properties by external stimuli. Herein, we show photochemically fluorescent colour-tuneable systems consisting of photoresponsive conjugated polymer nanospheres.

Helical carbon and graphite films prepared from helical poly(3,4-ethylenedioxythiophene) films synthesized by electrochemical polymerization in chiral nematic liquid crystals.

Helical carbon and graphite films from helical poly(3,4-ethylenedioxythiophene) (H-PEDOT) films synthesized through electrochemical polymerization in a chiral nematic liquid-crystal (N*-LC) field are prepared. The microscope investigations showed that the H-PEDOT film synthesized in the N*-LC has large domains of one-handed spiral morphology consisting of fibril bundles. The H-PEDOT films exhibited distinct Cotton effects in circular dichroism spectra.

Electrochromism-driven linearly and circularly polarised dichroism of poly(3,4-ethylenedioxythiophene) derivatives with chirality and liquid crystallinity.

This review presents recent advances in the synthesis, electrochemical properties, and optical functions of poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives embodying chirality and liquid crystallinity. Various methods for preparing the optically active and liquid crystalline (LC) PEDOT derivatives, such as (i) the introduction of chiral substituents into polymer side chains, (ii) chemical or electrochemical polymerisation by using lipid assemblies as templates, (iii) electrochemical polymerisation in asymmetric LC reaction fields, and (iv) the addition of a chiral dopant to LC-PEDOT derivatives, are discussed. Throughout the review, linearly and/or circularly dichroic electrochromism, hierarchically controlled spiral structure, and aligned morphology are demonstrated to be promising for the development of multifunctional PEDOT derivatives.

Lyotropic chiral nematic liquid crystalline aliphatic conjugated polymers based on disubstituted polyacetylene derivatives that exhibit high dissymmetry factors in circularly polarized luminescence.

We synthesized disubstituted liquid crystalline polyacetylene (diLCPA) derivatives bearing 4-nonyloxy phenyl groups with lyotropic and thermotropic LC behavior. The poly(diphenylacetylene) main chain structure of the diLCPAs and the chirality induced with either chiral moieties or chiral dopants allow the formation of a highly ordered lyotropic N*-LC phase. Circular dichroism (CD) spectra of the diLCPAs imply that one-handed intrachain helical structures are formed in solution, while interchain helical π-stacking between the polymer main chains are formed in cast film and in the N*-LC state.

Circularly polarized blue luminescent spherulites consisting of hierarchically assembled ionic conjugated polymers with a helically π-stacked structure.

Cationic π-conjugated polymers form an interchain helically π-stacked assembly with anionic chiral compounds that is stabilized by both electrostatic and π-π interactions to hierarchically self-organize into a spherulite with a circularly polarized blue luminescence. To the best of our knowledge, this is the first example of a chiroptical spherulite that is hierarchically constructed from π-conjugated polymers.

Dynamic photoswitching of helical inversion in liquid crystals containing photoresponsive axially chiral dopants.

Chirality switching is intriguing for the dynamic control of the electronic and optical properties in nanoscale materials. The ability to photochemically switch the chirality in liquid crystals (LCs) is especially attractive given their potential applications in electro-optic displays, optical data storage, and the asymmetric synthesis of organic molecules and polymers. Here, we present a dynamic photoswitching of the helical inversion in chiral nematic LCs (N*-LCs) that contain photoresponsive axially chiral dopants.

Hierarchically controlled helical graphite films prepared from iodine-doped helical polyacetylene films using morphology-retaining carbonization.

One-handed helical graphite films with a hierarchically controlled morphology were prepared from iodine-doped helical polyacetylene (H-PA) films using the recently developed morphology-retaining carbonization method. Results from scanning electron microscopy indicate that the hierarchical helical morphology of the H-PA film remains unchanged even after carbonization at 800 °C. The weight loss of the film due to carbonization was very small; only 10-29% of the weight of the film before doping was lost.

Entanglement-free fibrils of aligned polyacetylene films that produce single nanofibers.

An aligned polyacetylene (PA) film was synthesized in a macroscopically-aligned nematic liquid crystal (N-LC) solvent using a gravity-flow method. Long and single nanofibers of less than 100 nm in radius were successfully prepared by ultrasonication of the aligned PA film immersed in ethanol. The usual PA film was synthesized in an isotropic solvent, such as toluene, only yielding short and non-dispersed fibers after the ultrasonication due to the entangled fibril morphology.

From helical polyacetylene to helical graphite: synthesis in the chiral nematic liquid crystal field and morphology-retaining carbonisation.

This tutorial review presents current progress in the synthesis of helical polyacetylene (H-PA) using a chiral nematic liquid crystal reaction field as an asymmetric polymerisation solvent. In addition, we review the morphology-retaining carbonisation for helical graphite using H-PA as a carbonisation precursor. Carbonisation of H-PA films, via iodine doping, is demonstrated to produce carbon and graphitic films bearing completely preserved morphologies and even helical nanofibril structures.

Helical polyacetylene--origins and synthesis.

We present the origins and synthesis of helical polyacetylene (H-PA) by focusing on its peculiar spiral morphology. Interfacial polymerization of acetylene was carried out in an asymmetric reaction field consisting of chiral nematic liquid crystal (N*-LC) and Ziegler-Natta catalyst. As the N*-LC is composed of nematic liquid crystal and a chiral compound such as a binaphthyl derivative with either the R- or S-configuration, the screw directions of the polyacetylene chain and fibril bundle--and even the spiral morphology--are rigorously controlled by the chirality of the selected compound.

Helical carbon and graphitic films prepared from iodine-doped helical polyacetylene film using morphology-retaining carbonization.

In this communication, we report a novel preparation of the helical carbon nanofibril-fabricated thin film from the iodine-doped filmy helical polyacetylene through a carbonization process. Carbonization of the helical polyacetylene films by way of iodine doping is found to afford carbon and graphitic films completely preserving morphologies and even helical nanofibril structures.