Organic robust polyradicals are establishing their position as a new class of functional polymers, such as ferromagnetic materials, based on the spin alignment of unpaired electrons through conjugated backbones. 1 An intriguing aspect of the current research is the application of radical polymers, i.e., aliphatic polymers bearing redox-active radical pendant groups, to high capacity charge-storage materials for secondary batteries. 2 The high power characteristics of the so-called "radical battery" originate from the large heterogeneous electron-transfer rate of the redox centers and the efficient mass-transfer process within the polymer layers, allowing facile accommodation of electrolyte ions to compensate charges generated from the neutral radicals. Nernstian electrochemical behaviors have been found for a number of robust radicals, such as the 1e-oxidation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to the oxoammonium cation and the 1e-reduction of galvinoxyl radicals to the galvinolate anion. 3 Radical polymers bearing pendant TEMPO and galvinoxyl groups undergo heavy pand n-doping and are used as cathode-and anode-active materials in the radical battery, respectively, by sandwiching an electrolyte layer. We anticipated that a similar charge-storage configuration should develop for a dry system in the absence of the electrolyte layer, by sandwiching a dielectric material with the radical polymers. The expected result is an electroconductive bistability, rather than the power storage. Here we report the excellent properties of an organic "radical memory", which provided insight into the mechanism of charge storage at an electrode interface under dry conditions. The organic-based memory was first introduced for FeRAMtype devices, wherein fluorine-containing polymers were used as the dielectric material to replace silicon dioxide in combination with inorganic semiconductor-based transistors. 4 All plastic-type memory systems have attracted recent attention as a new type of low voltagedriven memory between conventional DRAM/SRAM devices and magnetic hard discs, in addition to the inherent advantages allowing for a facile wet-process fabrication. Several types of organic materials have been examined for this purpose, such as organic semiconductors, 5-7 charge-transfer complexes, 8,9 redox-active compounds, and metal nanoparticle-dispersed thin films. 10,11 However, the organic-based devices often fell into write-once-read-many type memory characteristics and suffered from a low ON-OFF ratio remaining at less than 2 orders of magnitude. We selected structuredefined radical polymers which yielded contamination-free, homogeneous, and tough organic layers for improvement of the device behaviors.The metal-insulator-metal diode-type structure of the fabricated radical memory is shown in Figure 1. The device was composed of the thin layers of poly(2,2,6,6-tetramethylpiperidine-1-oxyl methacrylate) (PTMA) as the p-type redox active material, polyvinylidene difluoride (PVDF) as the dielectric material, and poly-(4-(2...

An interpolymer complex was prepared by mixing aqueous solutions of poly(ethylene oxide) (PEO) and of a poly(carboxylic acid), i.e., poly(acrylic acid)(PAA), poly(methacrylic acid)(PMAA), or styrene‐maleic acid copolymer(PSMA). The complexation mechanism was discussed on the basis of results of such experimental methods as viscosity, potentiometric titration, and turbidimetry. The hydrogen bond is primarily involved in these complexations, but the influence of hydrophobic interaction on complexation can not be ignored. If the degree of dissociation α of carboxylic acid or the degree of polymerization Pn of PEO was perceptibly changed, a stable complex was obtained at about α 0.1 or Pn(PEO) = 40 for PMAA, 200 for PAA. This fact indicates that more than a definite number of binding sites are necessary for a stable interpolymer complex to be formed and that cooperative interaction among active sites plays an important role in complex formation.

A solid‐state thin film rechargeable battery has been prepared using a novel efficient technique of “surface complexation method” by which a thin layer of Prussian blue (PB) can be overlaid on a solid polymer electrolyte of Nafion (Nf) as matrix. An electrochemical cell made of the composite PB‐Nf film sandwiched with supporting electrodes was examined on i‐V curves in solid state and for characteristics as a rechargeable battery. The resulting PB‐Nf battery showed good durability in repetitive cycles of charging and discharging and gave the following results: open‐circuit voltage of the unit cell per 160 μm 0.68V, short‐circuit current 0.2–2 mA/cm2 depending upon the water content of the Nf matrix, and an energy density of about 50 Wh/kg.

An electrochromic (EC) cell using a viologen-based polymer as an EC material and a radical polymer bearing a redox-active 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) group per repeating unit as a counter electroactive material was fabricated. The radical polymer was spin-coated on an ITO/glass electrode as the counter electrode of the EC cell. The electrochromic material of the cell was a polyion complex consisted of poly(decyl viologen) and poly(styrene sulfonate) (PV10-PSS), which was also spin-coated on the ITO/glass. An ion-conducting polymer gel solution was sandwiched between the two electrodes. Electrochemical switching of the cell was monitored using the visible absorption of the PV10-PSS complex ( max ¼ 550 nm) that appeared in the reduced state, while the radical polymer was transparent in the visible region in both redox states. PV10-PSS and the radical polymer were concurrently reduced and oxidized, respectively, on each electrode during the charging process, which corresponded to the coloration of the cell. The decoloration of the polyion complex was effected by a discharging process under short circuit conditions. The electrochromic behavior of the cell was characterized by a remarkably low driving voltage, as a result of a small potential gap between PV10-PSS and the radical polymer. The use of the organic redox polymers, not only for the low energy-driven electrochromic switching but also for the charge-storage purposes, allowed a universal design of a battery-like display device, with possible application to a flexible and totally organic electrochromic cell.KEY WORDS: Electrochromism / Organic Redox Polymer / Radical Polymer / Battery / The electrochromism of organic and inorganic molecules have attracted much attention, with a view to apply them to windows and glasses.1 Electrochromic (EC) cells exhibit color changes, by applying specific driving voltages to cause the redox reaction of the EC materials attached to the surface of the transparent electrodes. However, there are some problems that must be overcome before consideration of practical use, such as the improvement of switching speed and cycle stability. The previously reported EC cells for display applications have mostly relied on using inorganic EC materials, such as prussian blue and WO 3 .1,2 A number of efforts to improve the stability and the life of the EC cells have been made, by incorporating redox-active materials to the counter electrode, expecting a battery-like charge-storage configuration.3 Typical examples include the use of Fe 2 (WO 4 ) 3 -containing graphite as the counter electrode for the WO 3 -based EC cells, 4 and the incorporation of anti-polarization agents such as metal oxides (i.e., MnO x , VO x , and WO x ) to prevent side reactions (e.g., hydrogen gas generation) on cathodes.Organic polymers have also been studied as EC materials which are almost free from the side reactions, by virtue of the relatively low driving voltages. 2,5,6 For example, viologenbased polymers such as poly(alkyl viologen)s have been rep...

The new iron(II), cobalt(II), and manganese(II) intercalation compounds {[M(CA)(H 2 O) 2 ]-(G)} n (M ) Fe 2+ , Co 2+ , Mn 2+ ; H 2 CA ) chloranilic acid (C 6 H 2 O 4 Cl 2 ); G ) H 2 O and phenazine (C 12 H 8 N 2 ; phz)) have been synthesized and characterized. 1b), Mn 2+ (1c)) are isomorphous to 1a. For 1a-c, crystal structures consist of uncoordinated guest water molecules and one-dimensional zigzag [M(CA)(H 2 O) 2 ] k chains. Two water molecules occupying cis positions and two chloranilate filling the remaining sites in a bis bidentate fashion create the octahedral environment around the metal ion to form a zigzag chain (type I), which extends along the diagonal between the a and c axes. The adjacent chains are interlinked by hydrogen bonds, thus forming layers, which spread out along the ac plane. Water molecules are intercalated between the 2b), Mn 2+ (2c)), which are isomorphous each other. The crystal structures of 2a-c consist of uncoordinated phenazine molecules and straight [M(CA)(H 2 O) 2 ] k chains (type II). Infinite, nearly coplanar linear chains are formed by metal ions and the bis-chelating CA 2anions, which extend along the a direction, and are linked by hydrogen bonds between the coordinated water and the oxygen atoms of the CA 2on the adjacent chains, forming a two-dimensional sheet, which spreads out along the ac plane. The intercalated phenazines are stacked along the c axis perpendicular to the [M(CA)(H 2 O) 2 ] k chain, and the planes of the phenazine molecules are tilted to the stacking direction, forming a segregated columnar structure between the {[M(CA)(H 2 O) 2 ] k } l layers. The 57 Fe Mo ¨ssbauer spectra of 1a and 2a consist of a single quadrupole doublet with IS ) 1.16 mm/s (1a), 1.16 mm/s (2a) and QS ) 2.53 mm/s (1a), 1.46 mm/s (2a) at 298 K, indicating that the oxidation state of the iron in both complexes is two. The magnetic susceptibilities were measured from 2 to 300 K and analyzed by a onedimensional Heisenberg-exchange model to yield J ) -0.74 cm -1 , g ) 2.01, F ) 1.4% (1c) and J ) -0.65 cm -1 , g ) 2.02, F ) 9.0% (2c).