Ionic conductivity of polymer electrolytes and future applications

Polymer electrolytes are solvent-free ion-conducting polymers and provide new and attractive materials in both polymer chemistry and electrochemistry. A proper understanding of ion dissociation and ion transport in such polymers is necessary for their application as solid electrolytes in electrochemical devices. Ionic conduction behaviour in polymer electrolytes is described here in relation to the characteristic properties. Of special interest is the ability of polymer electrolytes to include various kinds of electroactive molecules within them. The combination of this ability with their high ionic conductivity has enabled polymer electrolytes to be used as media for electrochemical syntheses and redox reactions.     

Recent advances in high performance donor-acceptor polymers for organic photovoltaics

Organic photovoltaic cells made with semiconducting polymers remain one of the most promising technologies for low-cost solar energy due to their compatibility with roll-to-roll printing techniques. The development of new light-absorbing polymers has driven tremendous advances in the power conversion efficiency of these devices. In particular, the use of alternating electron rich (donor) and electron poor (acceptor) segments along the polymer backbone can produce low optical bandgap materials that capture more of the solar spectrum. As a result, power conversion efficiencies over 10% are increasingly common for this technology. This review summarizes the recent advances in donor-acceptor polymer design and synthesis, highlighting the structural features that are key to providing high efficiency, scalable and stable devices.     

Synthesis and electrochemical characterization of soluble poly(p-phenylene vinylene) derivatives containing olefinic bonds at the side chain

A new kind of soluble poly(p-phenylenevinylene) (PPV) derivative containing free olefinic bonds at the side chain is prepared and studied by electrochemical measurement. The electrochemical investigations reveal that the free olefinic bonds in these polymers are electroactive; a new redox reaction occurs prior to the oxidation of PPV backbone in the cyclic voltammetry. The lower oxidation potential of the olefinic bonds hints that it is possible for these olefinic bonds to react with oxygen, which is desirable to remove the harmful oxygen in the light-emitting polymer devices. The merits and possibility of such polymers containing olefinic bonds in the fabrication of the light-emitting devices are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2535–2539, 1999     

Macromolecular anchoring layers for polymer grafting: comparative study

Comparative study of efficiency of macromolecular anchoring layers in the grafting of end-functionalized polymers to a surface was conducted. Poly(glycidyl methacrylate) (PGMA) and epoxydized polybutadienes (EPB) were utilized as the primary anchoring films. Amount of the epoxy moieties introduced to the surface was varied via thickness of the modifying polymer layer or amount of epoxy groups in the polymer backbone. Comparison between the grafting of polystyrene and poly(ethylene glycol) to the various macromolecular anchoring layers indicated that grafting ability of a layer was mostly governed by thickness of the interpenetration zone between the two polymers (anchoring and being grafted). In case of low level of the interpenetration, only functional groups at the periphery of the primary polymer layer were available for the grafting. Then, amount of grafted polymer did not increase with total number of epoxy groups in the anchoring film. However, as the thickness of the interpenetration zone increased, higher amount of the functional groups become available for the grafting.     

Sequestration of electroactive materials in a high Tg, insulating polymer matrix for optoelectronic applications. Part 2. Photovoltaic devices

The incorporation of high levels of electroactive compounds into a high T_g matrix polymer was investigated in photovoltaic (PV) devices. The combination of electron donor-electron acceptor pairs with optionally light harvesting organics (e.g. laser dyes) in the high T_g polymer matrix yielded PV performance in the range of literature data typically reported for organic based PV devices. The advantages for using a high T_g matrix include increasing the T_g of the electroactive compounds, preventing crystallization, improving the mechanical properties of the active layer(s) and the ability to employ lower cost fabrication processes. While the basic concept has been demonstrated, further optimization would be required to achieve a useful combination of photovoltaic properties. As in the companion paper on utilization of a high T_g polymer to sequester low molecular weight electroactive species for LED devices, this paper demonstrates the same concept for PV devices. The approach to solve the issues with low molecular weight electroactive species noted in the literature to date often involves covalent bonding of these compounds to polymeric backbones. This and the companion paper well-illustrates the blend approach is equally viable and offers a much simpler methodology.     

有机-无机分子印迹杂化材料的研究进展

分子印迹技术是制备选择性识别特定分子的聚合物的方法,因其制备简单、稳定性好且具有特异分子识别功能使其在色谱分离、固相萃取、化学传感和模拟酶催化等方面都有广泛的应用。有机-无机杂化分子印迹聚合物集有机和无机聚合物的优点,不仅机械强度高,而且耐溶剂性好,是分子印迹技术的一个崭新领域。在介绍有机-无机杂化分子印迹聚合物基本概况的基础上,综述了有机-无机杂化分子印迹聚合物制备的原理、方法和特点,并对未来的发展提出了展望。     

The polymer blend technique as a method for designing fine carbon materials

The polymer blend technique is proposed as a method for designing fine carbon materials. In principle a blend consisting of polymers with and without carbon residue after heating is subjected to melt-spinning, stabilization and finally carbonization. A combination of two polymers and control of the blend texture are important for using the technique successfully. In this paper, three prepared fine carbon materials are introduced, i.e. carbon fibers including thin and long pores aligned parallel to the fiber, thin carbon fibers 200-300 nm in diameter and carbon nanotubes with 10-20-nm outer diameter. In particular the carbon nanotubes are described in detail to emphasize the great potential of the polymer blend technique. Further possibilities of the technique are also discussed briefly.     

Characterization of PVC/CPE blends by thermally stimulated current

In recent years, the use of polymer blends and alloys has become increasingly important in the development of advanced engineering materials. Through the combination of existing polymers, new and improved properties such as impact strength, chemical resistance, and increased temperature use range have been achieved. An important challenge has been to develop new analytical methods capable of properly evaluating these increasingly complex polymer systems. Careful examination of the blend morphology and degree of internal stress between phases is often critical to the success of the development of new blends and alloys. Blends of grafted and crosslinked PVC and CPE were evaluated by Thermally Stimulated Current (TSC). The extent of crosslinking and degree of interpenetration between the two phases were evaluated by examination of the glass transition peaks generated during the TSC experiments. The unique sensitivity of this technique provided excellent insight, which may allow prediction of long term stability and impact strength based on the degree of internal stress that exists at the phase boundaries. This paper explores the application of TSC as a development tool in the study of impact-modified PVC.     

Vinylidene fluoride- and trifluoroethylene-containing fluorinated electroactive copolymers. How does chemistry impact properties?

Fluoropolymers are attractive niche polymers used in high added value materials for high-tech applications in aerospace, electronics, coatings, membranes, cables, and the automotive industries. Among them, VDF- and TrFE-based copolymers exhibit remarkable electroactive properties allowing their incorporation into a wide range of devices such as printed memories, sensors, actuators, artificial muscles, and energy storage devices. In a first section, a detailed overview of semi-crystalline poly(VDF-co-TrFE) copolymers and of their ferroelectric (FE) properties from the point of view of polymer chemists is supplied. In addition to the polymer microstructure that may sometimes be controlled or influenced by the synthesis strategies, physical properties such as the phase transitions, and electroactivity are also affected by processing, such as annealing for example, and film thickness for example. Building on the conclusions and understanding obtained from the first section, the effect of the introduction of a termonomer (leading to poly(VDF-ter-TrFE-ter-M) terpolymers) is detailed in a second section of this review. Modifying the terpolymer chain microstructure has a major impact on the crystalline phase of the terpolymers that may result in a relaxor-ferroelectric behavior (RFE). The distribution of the termonomer along the polymer chain, the capacity of the termonomer units to enter the crystal lattice, as well as its dipole moment govern in large part the terpolymer electroactive properties. Poly(VDF-ter-TrFE-ter-CFE) and poly(VDF-ter-TrFE-ter-CTFE) terpolymers appeared to be the best candidates for RFE properties and were thus the most studied. In two following sections, the block or graft architectures of VDF- and TrFE- based copolymers, and the various crosslinking strategies used so far for such copolymers are described. Chemical modification is indeed a very powerful tool to tune electroactive properties of copolymers or to impart additional properties. Finally, in the last section, a few examples of emerging applications for these fluorinated electroactive polymers (EAPs) are briefly discussed. This review aims to provide a comprehensive report on the use of polymer chemistry as a tool to produce better electroactive fluorinated polymers, and highlights possible opportunities and perspectives for future progress in this field. Research in this interdisciplinary field requires different kinds of expertise, ranging from organic and polymer chemistries, polymer films engineering, physics of semi-crystalline polymers and electroactivity, to the design and fabrication of electronic devices.     

Dye-sensitized solar cells employing polymers

Dye-sensitized solar cells (DSSCs) are of interest due to their potential use as inexpensive and environmentally friendly photovoltaic (PV) devices with acceptable power conversion efficiency (PCE). Platinum (Pt) metal is, traditionally, the preferred material for the counter electrode (CE) component of DSSCs, however, further development of iodide/triiodide (I⁻/I₃⁻) based liquid-electrolyte DSSCs using Pt remains challenging due to the high cost of this scarce metal and its susceptibility to corrosion. Additional concerns include solvent leakage and low chemical stability resulting from volatile liquid electrolyte used in DSSCs. In order to counteract this issue, polymer electrolytes or hole-transporters with higher mobilities are employed as a replacement for liquid electrolytes. In this regard, polymers can serve as efficient CE materials by replacing the platinized electrode in liquid-electrolyte DSSCs, while also substituting for the liquid electrolytes as polymer electrolytes or hole-transporters in solid-state or quasi solid-state DSSCs. Considering the fragility and shape restrictions of glass substrates, polymer substrates may also be used to replace rigid glass substrates, providing more flexible DSSCs. Herein, applications of the polymers as cell components (CEs, polymer electrolytes or hole-transporter, and plastic substrates) in DSSCs are discussed, with special focus on the role that polymers play in DSSCs and widely accepted reports of PV performance. The current understanding of the factors and strategies involved in improving the performance of polymers in DSSCs are reviewed and analyzed. In addition, the benefits, challenges and potential utility of polymers for use in DSSCs are assessed.     

有机硅材料技术发展动向

当前,世界有机硅技术的发展方向是高性能、多功能和复合化,即通过改变交联方式,配合技术的进步和添加新的添加剂,通过共聚共混等改性技术实现有机聚合物与有机硅材料复合。对有机硅材料(包括医用有机硅材料)技术发展动向进行论述与展望。     

智能高分子材料

介绍了几种新型的智能高分子材料,指出合成新的聚合物、制造构造规则的高分子凝胶及增加材料的表面积与体积比是加快智能高分子材料响应速率的方法,同时指出仿生化和模糊化是智能高分子材料的发展方向。     

Ionic electroactive polymer actuators based on nano‐carbon electrodes

This review paper focuses on the recent studies of electroactive polymer actuators that have a triple‐layered configuration composed of an ionic‐gel electrolyte layer sandwiched by nano‐carbon dispersed ionic‐liquid gel electrode layers (bucky‐gel actuator) for the purpose of development of practical devices. The review covers recent studies of the developments of the materials of the bucky‐gel actuators and their electromechanical modeling. In the final section, the application to an ultra‐thin and ultra‐light Braille display based on the bucky‐gel actuator is described. © 2013 Society of Chemical Industry     

Sequestration of electroactive materials in a high Tg, insulating polymer matrix for optoelectronic applications. Part 1. Light emitting diode devices

The use of a high T_g, insulating polymer to sequester low molecular weight electroactive materials at high addition levels for utility in LED devices has been demonstrated. The threshold for effective light emission appears to be in the range of 15 wt% electroactive compounds in agreement with the percolation theory of deGennes. The high T_g polymer allows for suppression or elimination of the undesired crystallization of the electroactive species and yields a significant increase in the T_g of the light emitting layer (also required). Additionally this approach offers the potential for easier (and lower cost) fabrication routes not generally employed for low molecular weight electroactive materials (e.g. spin coating, ink jet printing, roll-to-roll printing). The improved mechanical properties of the light emitting layer with high molecular weight polymer addition should allow for improved performance/durability in flexible displays. The simple blend approach should be an attractive alternative to other more common methods reported in the literature employing covalent bonding of electroactive species to polymeric backbones to achieve the same results. This approach also allows for multiple addition of dopants (e.g. laser dyes), hole transport materials and electron transport materials in a single light emitting layer. While these results demonstrate the concept, optimization was not conducted and significant improvements would be expected with proper adjustment of the many variables possible with this approach.     

Recent advances in conjugated polymers for light emitting devices

A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.     

All‐polymer electromechanical systems consisting of electrostrictive poly(vinylidene fluoride‐trifluoroethylene) and conductive polyaniline

The low elastic modulus and the ability to withstand high strain without failure make the conducting polymer attractive for a wide range of acoustic applications based on high‐strain electroactive polymers. In this article, we examine the electric and electromechanical performance of all‐polymer electromechanical systems, fabricated by painting conductive polyaniline (PANI) doped with camphor sulfonic acid (HCSA) on both sides of electrostrictive Poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) copolymer films, and compare them with those from the same copolymers with gold electrodes. The all‐polymer composite films are flexible, with strong coherent interfaces between the electrostrictive polymer layer and the conductive polymer layer. The electric performance such as dielectric properties and polarization hysteresis loops from P(VDF‐TrFE)/PANI film is nearly identical to those of P(VDF‐TrFE)/gold films in a wide temperature (from −50 to 120°C), and frequency range (from 1 Hz to 1 MHz). The all‐polymer systems also show a similar or even larger electric field induced strain response than that of films with electrodes under identical measurement conditions. The results demonstrate that the polyaniline/HCSA is good candidate material as the electrodes for electroactive polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 945–951, 2000     

Rigid and microporous polymers for gas separation membranes

Microporous polymers are a class of microporous materials with high free volume elements and large surface areas. Microporous polymers have received much attention for various applications in gas separation, gas storage, and for clean energy resources due to their easy processability for mass production, as well as microporosity for high performance. This review describes recent research trends of microporous polymers in various energy related applications, especially for gas separations and gas storages. The new classes of microporous polymers, so-called thermally rearranged (TR) polymers and polymers of intrinsic microporosity (PIMs), have been developed by enhancing polymer rigidity to improve microporosity with sufficient free volume sizes. Their rigidity improves separation performance and efficiency with extraordinary gas permeability. Moreover, their solubility in organic solvents allows them to have potential use in large-scale industrial applications.     

BSE-IA reveals retardation mechanisms of polymer powders on cement hydration

The retardation effects of two polymer powders, styrene butadiene rubber and ethylene-vinyl acetate, on cement hydration and the mechanisms in terms of hydration degree and microstructure characteristics were investigated by the combination of backscattered electron image analysis, scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction. Results show that the cement hydration can be significantly retarded by both polymers with the reductions in cement hydration degrees and hydration products thickness. Polymers retard cement hydration by agglomerating the polymer particles on the surfaces of cement grains, forming films in different thickness and bonding the calcium ions in the pore solutions. Consequentially, the formation of C-S-H and CH is depressed and the Ca/Si ratios in the hydration product layer are raised. The retardation is enhanced with the increase in polymer content. This work helps understand the retardation effect of polymers on cement hydration in depth, which enables rational development of polymer-modified cement-based materials for further applications.     

Polymer Inclusion Compounds: Model Systems for Ordered Bulk Polymer Phases and Starting Materials for Fabricating Polymer–Polymer Molecular Composites

Several small molecules can be cocrystallized with polymers to form inclusion compounds (ICs). Urea, perhydrotriphenylene and the cyclodextrins are examples, and serve to form the host crystalline lattice containing the guest polymer chains in their ICs. The guest polymer chains are confined to narrow, cylindrical channels created by the host, small-molecule lattice, where the polymers are highly extended as a consequence of being squeezed, and are separated from neighbouring polymer chains by the IC channel walls composed exclusively of the small-molecule lattice. The net result is a unique solid-state environment for polymers residing in IC channels, which can be utilized as model systems for ordered, bulk polymer phases. Comparison of the behaviour of polymer chains isolated and extended in IC crystals with the behaviour observed for ordered, bulk phases of polymers is beginning to permit an assessment of contributions made by the inherent, single chain and the cooperative, interchain interactions to the properties of ordered, bulk polymers. It is also possible to release and coalesce polymers from their IC crystals in a manner which leads to their consolidation with a chain-extended morphology. Embedding polymer IC crystals into a carrier polymer, followed by in situ release and coalescence of the included polymers from their IC crystals, offers a means to obtain polymer–polymer composites with unique morphologies. Several such polymer IC-generated composites are described and it is suggested that their unique morphologies might translate into useful, tailorable properties, as well as providing a means for addressing several questions that are fundamental to the behaviour of both phase-separated and homogeneous polymer solids. © 1997 SCI     

Electrochromic Solid-State Devices Using Organic-Metallic Hybrid Polymers

Organic-metallic hybrid polymers are formed by the complexation of metal ions with organic modules bearing two coordination sites. The hybrid polymers consisting of bis-terpyridines and metal ions such as Fe(II) or Ru(II) have a specific color based on the metal-to-ligand charge transfer (MLCT) absorption. Cyclic voltammograms of the polymers exhibit a reversible redox wave according to the redox reaction of the metal ions. Interestingly, a polymer film cast on an indium tin oxide (ITO) electrode exhibits excellent electrochromic properties; the color of the film disappears when a higher potential as compares to the redox potential of the metal ions is applied to the polymer film. In addition, multicolor electrochromic changes appear on introducing two types of metal ions to the polymer. Electrochromic solid-state devices are successfully fabricated by using these polymers. This paper is dedicated to Professor Takakazu Yamamoto in honor of his pioneering research efforts and accomplishments in the fields of organometallics and π-conjugated polymers.