Polyacetylene Films Research Articles

“Surface‐Filming Assembly” Strategy for Facilely Constructing and Adjusting Circularly Polarized Luminescence from Perovskite/Chiral Helical Polyacetylene Films

AbstractTunable circularly polarized luminescence (CPL) has attracted substantial research interest. Till date, the main methods for adjusting CPL is by changing the ratio of fluorescent components and/or regulating external stimuli. Although these adjustment methods have been demonstrated to be reliable, most of them show disadvantages including challenging molecular design, complicated and cumbersome material fabrication, and rigorous adjustment conditions. Herein, the “Surface‐Filming Assembly” (SFA) strategy for conveniently and efficiently modulating CPL by taking the perovskite/chiral helical polyacetylene system as a model is proposed and established. This strategy can facilely achieve multicolor CPL by simply changing the color (or number) of perovskite fluorescent layers and/or the attaching order of the perovskite layers in the assembled multilayer film. Compared with previously reported methods, the SFA strategy integrates the preparation process and adjustment in one single step, simplifying the preparation process (especially the preparation of perovskite with different ratios of halogen atoms) and making adjustment simple and efficient. The SFA strategy and different CPL generation mechanisms to achieve multicolor and white‐color emission with glum up to 10−2 are combined. Based on the CPL film and the solvent sensitivity of perovskite, a solvent‐responsive CPL‐emitting switch and further applied the CPL sample in multiple information displays and encryption are realized.

Fibril size control, tensile strength, and electrical properties of cyclic polyacetylene

We introduce a simplified synthesis of thick, flexible, cyclic polyacetylene films (c-PA) and study the relationship between stretchability and electrical conductivity of c-PA. Stretching the films 1.6 times their original length increases conductivity 5-fold.

Formación de películas de poliacetileno sobre sustrato de cobre mediante descarga luminiscente anormal

The formation of polymeric films by plasma has become an alternative for the coating of metallic materials that require varying their surface characteristics and improving their resistance to corrosion; because by this method it is possible, in principle, to polymerize any gaseous hydrocarbon. In this work, the study of the formation of acetylene polymer films on a copper substrate, previously treated in an abnormal luminescent discharge regime in argon-hydrogen atmosphere, is presented. The polymeric formation was carried out in a continuum current abnormal glow discharge in an atmosphere of 60% Ar, 35% H2 and 5% C2H2 at a pressure of 2 Torr, at a temperature of 600 °C and with deposition times between 5 and 120 s. The structural and morphological analysis of the polymeric film deposited at different temperatures was performed by Infrared Spectroscopy and Scanning Electron Microscopy. Additionally, a characterization of the materials was carried out using corrosion resistance analysis.

Graphene-Enhanced Ion Transport in Dual-Conducting Composite Films of Polyacetylene and an Imidazolium Iodide Ionic Liquid

Dual-conducting polymer films were synthesized by dispersing graphene in an aqueous solution of poly(vinyl alcohol) and 1-propyl-3-methylimidazolium iodide ([C3mim]I) ionic liquid and thermally converting the poly(vinyl alcohol) to polyene in the presence of hydroiodic acid catalyst. The electrical and mechanical properties of the resulting free-standing films of the nanocomposite, containing different concentrations of graphene, were analyzed using electrochemical impedance spectroscopy (EIS) and dynamic mechanical analysis (DMA), respectively. Nyquist plots (imaginary vs real components of the frequency-dependent impedance) showed two characteristic arcs representing the composite's electronic and ionic conduction pathways. The conductivity values corresponding to both charge transport mechanisms increased with temperature and the graphene concentration. The enhancement in electronic conductivity is expected because of graphene's high electron mobility. Interestingly, ionic conductivity also showed a significant increase with graphene concentration, approximately triple the extent of the rise in the electronic conductivity, even though the loss and storage moduli of the films increased. (Generally, a higher modulus results in lower ionic conductivities in ionic gels.) Molecular dynamics simulations of the three-component system provided some insights into this unusual behavior. Mean square displacement data showed that the diffusion of the iodide anions was relatively isotropic. The iodide diffusion coefficient was higher in a blend with 5 vol % graphene than in blends with 3 vol % graphene or no graphene. The improvement is attributed to the interfacial effects of the graphene on the free volume of the blend. Furthermore, an exclusion of the iodide ions from the vicinity of graphene was observed in the radial distribution function analysis. The increase in the effective concentration of iodide due to this exclusion and the increase in its diffusion coefficient because of the excess free volume are the primary reasons for the observed enhancement in ionic conductivity by adding graphene.

DFT simulation of conductivity of the p-type doped and charge-injected cis-polyacetylene

Semiconducting conjugated polymers (CPs) have shown great potential in organic solar cells and organic field-effect transistors (OFETs), due to their tunable electronic and optical properties. In this study, we compare computational predictions of electronic and optical properties of ensembles of cis-polyacetylene (cis-PA) multiple oligomers in two different forms (a) undoped cis-PA and (b) cis-PA doped by phosphorous fluoride () via density functional theory (DFT) with hybrid functionals. The comparison of undoped cis-PA under the constraint of injected charge carrier and cis-PA doped by shows that either doping or injection provides very similar features in electronic structure and optical properties. Doped and injected are similar to each other and different from the pristine, undoped PA. Computed results also indicate that the injection of charge carriers and adding p-type doping into the semiconducting CP model both greatly affect the conductivity. These observations provide a better understanding and practical use of the properties of polyacetylene films for flexible electronic applications.

Path to the Synthesis of Polyacetylene Films with Metallic Luster: In Response to Rasmussen’s Article

The 2000 Nobel Prize in Chemistry was awarded jointly to Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa “for the discovery and development of conductive polymers.” Unlike metals, organic polymers or plastics do not conduct electricity. The three laureates found that polyacetylene can be doped on a film, which was initially synthesized by Shirakawa following a failed experimental trial by a Korean scientist, Hyung Chick Pyun. Later, Pyun insisted that he was the discoverer of polyacetylene films with silvery sheen. This note sheds light on the true history of the synthesis of polyacetylene films.

Comments on Shirakawa’s Response

As both an active researcher in the synthesis of conjugated materials and a chemist-historian that has spent the last decade attempting to detail and clarify the history of conjugated and conducting polymers, I am overjoyed that Prof. Shirakawa has elected to provide additional personal details relating to the discovery and development of polyacetylene films. Shirakawa has provided this material in response to my most recent Substantia paper that details newly revealed accounts by Hyung Chick Pyun (1926-2018), who was a visiting Korean scientist that carried out the initial experiment that led to these films. This material is critical to advance our understanding of this important historical event.

New Insight into the “Fortuitous Error” that Led to the 2000 Nobel Prize in Chemistry

In 2000, the Nobel Prize in Chemistry was awarded to Hideki Shirakawa, Alan G. MacDiarmid, and Alan J. Heeger “for the discovery and development of electrically conductive polymers.” While this award was in reference to their collaborative efforts on conducting polyacetylene in the mid-to-late 1970s, the narrative leading up to these efforts began in 1967 with the production of polyacetylene plastic films via what has been called a "fortuitous error." At the heart of this discovery were Shirakawa and a visiting Korean scientist, Hyung Chick Pyun. The current report provides background on Pyun and, for the first time, presents his version of the events leading to the discovery of polyacetylene films in order to provide new insight into this important historical event.

Hyper-Cross-Linked Additives that Impede Aging and Enhance Permeability in Thin Polyacetylene Films for Organic Solvent Nanofiltration

Membrane materials with high permeability to solvents while rejecting dissolved contaminants are crucial to lowering the energy costs associated with liquid separations. However, the current lack of stable high-permeability materials require innovative engineering solutions to yield high-performance, thin membranes using stable polymers with low permeabilities. Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) is one of the most permeable polymers but is extremely susceptible to physical aging. Despite recent developments in anti-aging polymer membranes, this research breakthrough has yet to be demonstrated on thin PTMSP films supported on porous polymer substrates, a crucial step toward commercializing anti-aging membranes for industrial applications. Here we report the development of scalable, thin film nanocomposite membranes supported on polymer substrates that are resistant to physical aging while having high permeabilities to alcohols. The selective layer is made up of PTMSP and nanoporous polymeric additives. The nanoporous additives provide additional passageways to solvents, enhancing the high permeability of the PTMSP materials further. Through intercalation of polyacetylene chains into the sub-nm pores of organic additives, physical aging in the consequent was significantly hindered in continuous long-term operation. Remarkably we also demonstrate that the additives enhance both membrane permeability and rejection of dissolved contaminants across the membranes, as ethanol permeability at 5.5 × 10-6 L m m-2 h-1 bar-1 with 93% Rose Bengal (1017.6 g mol-1) rejection, drastically outperforming commercial and state-of-the-art membranes. These membranes can replace energy-intensive separation processes such as distillation, lowering operation costs in well-established pharmaceutical production processes.

Morphology-controlled carbonaceous and graphitic materials prepared from conjugated polymers as precursors through solid-state carbonization

This minireview highlights carbon-based materials produced from conjugated polymers as a new class of synthetic polymeric precursors through carbonization at high temperatures. Various approaches for preparing aliphatic and aromatic conjugated polymers with controlled morphologies using different polymer-processing techniques are discussed. The solid-state carbonization of highly stretched polyacetylene (PA) films, helical PAs or helical poly(3,4-ethylenedioxythiophene)s, and self-assembled poly(meta-phenylene)s was shown to produce anisotropic graphite films, helical graphites, and graphite whiskers, respectively. The conjugated-polymer-derived carbons are expected to find advanced potential applications based on their precursor-dependent morphological functions.

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. The carbonization was performed from the iodine-doped PA films as precursors at 800 °C. The carbon films were subsequently graphitized at 1400-3000 °C, yielding graphite films with almost the same surface morphology as that of the original PA films and that of the carbon films as precursors. The typical PA film graphitized at 2600 °C exhibited tensile strengths of up to 224 MPa, moduli of up to 10 GPa, and an average electrical conductivity of 2.5 × 10(2) S/cm. In contrast, the graphite film prepared from the stretched PA film presented a Laue XRD pattern in which graphitic crystal structures are aligned parallel to the direction of stretching of the PA film. The anisotropic graphite film showed an enhanced conductivity of up to 1.5 × 10(3) S/cm along the stretching direction. We demonstrated that an iodine-doped PA film is a highly efficient carbon source for producing graphite films with good mechanical and electrical properties. The total yield of a graphite film is as high as 61-74% at up to 3000 °C, which is considerably higher than that of polyacrylonitrile-based carbon fiber and polyimide-based graphite film.

Soliton electric generators based on conducting polymers

Iodide doping produces charge carriers in π-conjugated polymers. Motivated by the SSH theoretical model of solitons in one-dimensional conjugated polymers, chemical doping of polyacetylene film is experimentally carried out to generate solitons. An Arago-type wheel electric generator is assembled based on the doped polyacetylene in place of a copper or aluminium plate. This is the first report of electric generation in conducting polymers based on solitons.

Helical graphite

One-handed helical graphite films with a structure controlled by that of the original iodine-doped helical polyacetylene (H-PA) films were prepared using the recently developed morphology-retaining carbonization method. The fibrillar structure 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. Furthermore, the graphite film prepared by subsequent heating at 2600 °C retained the same structure as that of the precursor films. The screw direction, degree of twist, and vertical or horizontal alignment of the helical graphite film were well controlled by changing the sense and pitch of the helix, and the orientation of the chiral nematic liquid crystal (N*-LC) used as an asymmetric LC reaction field. The important potential of these graphite films is exemplified in their electrical properties. The horizontally aligned helical graphite film exhibits an increase in electrical conductivity compared to the nonaligned one. The aligned helical graphite film also shows an electrical anisotropy in which conductivity parallel to the helical axis of the fibril bundle is higher than that perpendicular to the axis. [TANSO 2013 (No. 258) 201–9.]

Characterizing Charge Injection, Transport, and Mobility in a Conjugated Polyelectrolyte by NIR Absorbance

We discuss the determination of concentration-dependent carrier mobility by measurement of current and charge injection in a conjugated polyelectrolyte thin film. Equilibration under bias of the mobile counterions in a cationically functionalized polyacetylene film leads to steady-state current, while total charge injection is measured through NIR absorbance spectroscopy. The charge–voltage behavior is consistent with a model of charge injection where migration of mobile ions enables injection of electronic carriers in a manner analogous to electrochemical doping, and current is limited by diffusion across the bulk. The relation between injected charge and current density is also used to obtain the functional form of the concentration dependence of mobility, and this in turn is used to model the carrier profile across the film and obtain the mobility μ = 2.8 × 10–10 + 1.6 × 10–8(c/C0)1.3 cm2/(V s) where C0 is a reference concentration of 1 C/cm3. Another method of charge quantification, integration of tra...

Vertically Aligned Carbon Film Synthesized from Magnetically Oriented Polyacetylene using Morphology Retaining Carbonization

Polyacetylene (PA) films with vertically aligned fibril morphology were synthesized in homeotropic nematic liquid crystal (N-LC) solvent by using a magnetic field of 5 Tesla as an external perturbation. Scanning electron microscope (SEM) photographs indicated that the lengths of fibrils from the substrate were 5−35 µm, depending on polymerization time. Carbonization was carried out using iodine-doped PA film and a morphology-retaining car - bonization method. From the SEM results, we confirmed that the vertical morphology of the PA remains unchanged even after carbonization at 800 o C. The weight loss of the films due to carbonization at 800 o C is about 20% of the weight of the film before iodine doping. It is ex - pected that vertically aligned carbon might be a precursor for preparing vertical graphite ma- terials, which materials could be useful for electrochemical energy storage and cell electrodes.

Electrical and optical properties of doped helical polyacetylene graphite films in terahertz frequency range

We report on electrical and optical characteristics such as power absorption, index of refraction, and conductivity of new form of the model conjugated polymer–polyacetylene (PA)–helical PA graphite films (h-PA) in the 0.1–2.5THz spectral range. The results were obtained using the transmission THz time-domain spectroscopy. The frequency dependencies of the electrical and optical characteristics can be reasonably well fitted by the Drude model, which gives a plasma frequency of about ∼124THz and a charge carrier scattering time ∼30fs, which is less by an order of magnitude than that of crystalline materials. The obtained results demonstrate that doped h-PA graphite films retain metallic behavior in the THz spectral range even at ambient conditions contrary to conventional doped PA films.

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. Furthermore, the graphite film prepared by subsequent heating at 2600 °C retained the same morphology as that of the original H-PA film and that of the helical carbon film prepared at 800 °C. The screwed direction, twisted degree, and vertical or horizontal alignment of the helical graphite film were well controlled by changing the helical sense, helical pitch, and orientation state of the chiral nematic liquid crystal (N*-LC) used as an asymmetric LC reaction field. X-ray diffraction and Raman scattering measurements showed that graphitic crystallization proceeds in the carbon film during heat treatment at 2600 °C. Transmission electron microscopy measurements indicate that ultrasonication of the helical graphite film in ethanol for several hours gives rise to a single helical graphite fibril. The profound potentiality of the present graphite films is exemplified in their electrical properties. The horizontally aligned helical graphite film exhibits an enhancement in electrical conductivity and an evolution of electrical anisotropy in which conductivity parallel to the helical axis of the fibril bundle is higher than that perpendicular to the axis.

Analyses of under Pressure Polyacetylene Conductivity

Electrical measurements under increasing hydrostatic pressure (1–4000 [bar]) have shown that electrical conductivity is closely related to the iodine doping rate (0–14%) of polyacetylene (PA) films. In pristine PA, conductivity increases with pressure while in 14% iodinedoped PA it decreases. A most important result is noticed for an intermediate doping rate (1.5%). In fact, for sweeping of the range of pressure, conductivity decreases in the beginning and then increases with pressure augmentation. This change is located at a critical pressure Pc. An empirical formula was proposed to describe this behaviour. The aim of this work is to contribute to the greater understanding of the pressure effect on the transport mechanism and/or the nature of charge carriers.

ChemInform Abstract: Adapting Semiconducting Polymer Doping Techniques to Create New Types of Click Postfunctionalization

AbstractReview: 77 refs.

Adapting semiconducting polymer doping techniques to create new types of click postfunctionalization

After the historical development from the insoluble polyacetylene film to soluble and processible aromatic polymers, donor-acceptor-type aromatic polymers have recently emerged as a new class of semiconducting polymers. The polymer energy levels and band gaps can be tuned by the appropriate selection of the donor and acceptor moieties, and some of these polymers showed good optoelectronic or photovoltaic performances. The conventional synthetic method for achieving donor-acceptor-type aromatic polymers is based on the metal-catalyzed polycondensation between donor-type monomers and acceptor-type co-monomers. In this tutorial review, a new methodology for introducing donor-acceptor chromophores into semiconducting polymers is described. The donor-acceptor structures are constructed in the main chains and side chains of semiconducting polymers using a polymer reaction based on high-yielding addition reactions between the electron-rich alkynes and strong acceptor molecules, such as tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Considering the p-type doping features of TCNE and TCNQ, the experimental procedure is the same as the conventional doping technique for semiconducting polymers. However, the resulting donor-acceptor type polymers are chemically stable due to the absence of unstable unpaired electrons (polarons). The donor-acceptor alternating polymers were achieved in one step from the precursor poly(aryleneethynylene)s and poly(arylenebutadiynylene)s. When the side chain alkynes were post-functionalized, the polymer energy levels were controlled by the species and amount of the employed acceptor molecules. These atom-economic acceptor additions satisfy most of the requirements of the "click chemistry" concept. In contrast to the conventional click chemistry reactions, the reactions between electron-rich alkynes and acceptor molecules provide a wide variety of polymers with promising optoelectronic applications.