Conducting polymers sulfonated polystyrene

Recent encouraging results have been reported by Carter et al., who have obtained room temperature lifetimes in excess of 7000 h for encapsulated ITO/PPV/Ca devices at current densities of 60 mA/cm2.37 The polymer used was the PPV copolymer shown in Fig. 5.23, where the conjugation is interrupted by nonconjugated a -acetyloxy-/ -xylylene units. The efficiency of these devices was typically 0.02 lm/W. Devices operating at 80° C had lifetimes in excess of 1100 h. Carter et al., also reported devices based on the same emissive polymer giving efficiencies between 0.5 and 2 lm/W. These devices used a layer of conducting polymer (polyethylenedioxythiophene/polystyrene sulfonate) between the ITO and the PPV, and a sputtered aluminum/lithium alloy as the cathode. The devices... 

More detailed studies were conducted by Sakurada etaL (J9). They similarly found that the catalytic efficiency increased with the increased hydrophobicity of esters or of poly(styrenesulfonic acids) 2 (e.g. ksojH/ HCl = 10 for the combination of butyl acetate and 23% sulfonated polystyrene at 40 C). These rate enhancements were attributed to the fact that ester molecules are concentrated in the neighborhood of the polymer diain by the hydrofdiobic interaction. 

The addition of templates enabled the enzymatic production of conducting polymers with well-defined structure.67 In using sulfonated polystyrene (SPS) as a template, the resulting polymer was soluble in water and the conductivity reached 5 x 10 3 S/cm without doping. Besides SPS, a strong acid surfactant (sodium dodecylbenzenesulfonic acid) or poly(vi-nylphosphonic acid) provided a suitable local template environment leading to the formation of conducting poly aniline. 

Few studies have been conducted heretofore on sulfonated ionomers in solvents which can be considered relatively polar, as defined by a high dielectric constant. A recent study (13) on acrylonitrile-methallyl sulfonate copolymers in dimethyl-formamide is a notable exception. S-PS is readily soluble in a wide variety of solvents, some of them exhibiting rather high values of dielectric constant, such as dimethylformamide (DMF) or dimethylsulfoxide (DMSO). The reduced viscosity-concentration behavior of sulfonated polystyrene is markedly different in polar solvents from that in nonpolar-solvent systems. Typically there is a marked upsweep in reduced viscosity at low polymer concentrations and clearly a manifestation of classic polyelectrolyte behavior. ( 7)... 

Aniline can also be polymerized by horseradish peroxidase and hydrogen peroxide to electrically conducting polymers.331 If run in the presence of sulfonated polystyrene, this leads to a water-soluble doped polymer in a one-pot, benign process. Horseradish peroxidase and hy-... 

Sulfonated Polystyrene (S-PS). The preparation of S-PS has been described in detail in Ref. 6. The following procedure was generally followed 104 g of PS (Styron 666 manufactured by Dow Chemical Company) were dissolved in 490 mL of 1,2-dichloroethane. The solution was heated to 50°C, and the requisite amount of acetyl sulfate was added, in this case, 30 mL of 0.996M acetyl sulfate (29.9 meq). The solution was stirred for 60 min at 50°C, and the reaction was terminated by the addition of 25 mL of methanol. Sufficient sodium hydroxide (diluted with methanol) was added to neutralize all acid present. The polymer solution was precipitated into a substantial excess of methanol with vigorous agitation, followed by filtration and washing with methanol. The product was then vacuum dried. Analyses were conducted for sulfur and sodium. The level of sulfonate incorporated was determined by sulfur analysis. 

Halik and coworkers subsequently extended this process to pattern conducting polymer electrodes, such as poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT-PSS) [11]. In this process, PEDOT-PSS is uniformly coated on a substrate that has prepattemed photoresist. The PEDOT-PSS-coated substrate is then immersed in acetone to swell the photoresist underneath the... 

Tables 6-9 give the device structures and performance metrics for monochromatic OLEDs that utilize organometallic emitters. Eigures 38-42 show the molecular structures for the various materials used in these devices. White OLEDs have also been prepared with these materials, but these will be discussed in a later section. Light-emitting electrochemical cells are treated in a separate section as well, since the finished devices have different operating characteristics than either of the other solution or vapor processed devices. Table 6 lists devices made solely with discrete molecular materials, while Table 7 gives data for devices made using polymeric materials. The only exception to the use of discrete molecular materials in Table 6 is for devices that use a conducting polymer, poly(3,4-ethylenedioxythiophene polystyrene sulfonate) (PEDOT), as a material to enhance the efficiency for hole injection into the organic layer. The mode of preparation for a given device is listed with the device parameters in the...

Other studies in 2000 by Drew et al. reported that it is very difficult to spin fibers of PANI complexed to sulfonated polystyrene (PANFSPS), even when solutions containing sodium chloride and dodecyl benzene sulfonic acid sodium salt were used to lower the surface tension and thereby enhance electrospinning [16,17]. However, PANFSPS nanofibers can be produced by adding a carrier polymer such as PEO, polyacrylonitrile, or polyurethane. Also reported was the use of electrostatically layered sulfonated polystyrene as a template for the surface polymerization of conjugated polymers in their conducting form. Enzymatic synthesis of PANI and a copolymer of pyrrole and PEDOT was done on electrospun nanofiber... 

Y. Yang, Y. Chu, F.Y. Yang, and Y.P. Zhang, Uniform hollow conductive polymer microspheres synthesized with the sulfonated polystyrene template. Mater. Chem. Phys., 92(1), 164-171 (2005). 

Since in situ PEDT polymers are quite insoluble in most commonly used solvents, in situ PEDT cannot be easily made into a processable, coatable solution. However, an industrially usefiil form of oxidized PEDT can be made by aqueous oxidative polymerization of the EDT monomer in the presence of a template polymer, usually polystyrene sulfonic acid (PSS or PSSA). PSS is a commercially available water-soluble polymer and can thus serve as a good dispersant for aqueous PEDT. Polymerization with the oxidant sodium peroxodisulfate yields a PEDT PSS-complex in its conductive, cationic form (Figure 10.5). 

Massoumi and Entezami [92] reported the controlled release of dexamethasone sodium phosphate (DMP) from a conducting polymer bilayer film consisting of a PPy inner film doped with DMP and poly(N-methylpyrrole)/polystyrene sulfonate (PNMP/PSS) or polyaniline sulfonate (SPANI) outer film. DMP was released from the inner film by an application of less than —0.6 V. In this device, the outer polymer layer functions as an ion and solvent barrier and also effectively reduces the rate of DMP release under an applied reducing electrochemical field, thereby providing an additional route to controlling release rates. 

Originally, a donor-acceptor bilayer device of two films was used as an n-p junction in solar cells. Thus, they were fabricated as sandwich structures. An example would be one where a transparent substrate is first coated with a conductor, like indium-tin oxide. A conducting polymer like, poly (ethylene dioxythiphene), doped with polystyrene-sulfonic acid, would then be applied from and aqueous solution. The indium-tin oxide acts as an electrode for hole injection or extraction. The polymer is then covered with a conductor, an aluminum foil. The doped polymer can be illustrated as follows ... 

Permanent antistats do not depend on the relative humidity and they do not lose their effectiveness in a short time. One type is exemplified by the use of polyether-polyamide block copolymers combined with an intrinsically conducting substance, and another class consists of neoalkoxytitanates or zirconates. These compounds form non-blooming, bipolar layers, producing a surface and volume electron-transfer circuit, which produces a permanent antistatic effect. They are independent of atmospheric moisture and compatible with a wide range of polymers, including polyolefins, polyesters, polystyrene and PVC. Inherently conducting polymer additives such as sulfonated polyanilines are also used. They are discussed further in Chapter 5. 

Although all solid state reference electrodes based on conducting polymers have been tested, they are still in the testing phase. The most promising systems appear to be bilayers with different ion-exchanger properties such as glassy carbon/polypyrrole in conjunction with a polypyrrole(polystyrene sulfonate) layer 64,65). 

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