No abstract

Real-time in situ spectroelectrochemical studies have been carried out in N,NЈ-dimethyl formamide containing lithium trifluoromethane sulfonate as an electrolyte and the results are reported. The results indicate that the primary reduction product of the cyclic form of sulfur, S 8c 2Ϫ , undergoes an equilibrium reaction to its linear chain counterpart, S 8l 2Ϫ , which then dissociates into various products. These two dianions and S 3 Ϫ• were produced along with a minor product, S 4 2Ϫ , at the potential corresponding to the first electron transfer. These products were further reduced or dissociated to species including S 7 2Ϫ , S 6 2Ϫ , S 5 2Ϫ , S 4 2Ϫ , S 3 2Ϫ , S 2 2Ϫ , and S 2Ϫ at the second electron-transfer step as evidenced by the spectral shifts observed during electrolysis. The reduction reactions are generally chemically reversible, making it possible to use sulfur reduction as a cathode reaction for Li/S batteries.

and those measured on PDMS were 100.1 and 77.7. Surface energies of indium tin oxide (ITO) and Alq 3 and interfacial energy from the literature [14] which will bring revolutionary advances in the display technology, owing to attributes such as thin and flexible materials, fast switching times, and low-power consumption. However, current electrochromic technologies need to be improved in order to play moving images due to their slow color-switching rates.[1,2,5±11] Poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives are an ideal electrochromic material of conducting polymers for electronic paper due to their good color, mechanical stabilities, and facile fabrication.[5±11] Much work has been performed in order to improve contrast ratios and color switching rates by synthetic approaches.[5±11] It appears, however, that there are no examples of their use in electrochromic displays with moving-image speeds (24 frames/s; switching times of < 40 ms). This is due to the fact that the color-switching rate of PEODT is limited by the diffusion rate of counter-ions into the film during the redox process. The diffusion time, t, of ions required to reach a saturation concentration in a polymer film, that implies switching time, is proportional to the square of film thickness, x: t µ x 2 /D, where D is the diffusion coefficient of an ion in a polymer film. [12,13] Therefore, the simplest way to overcome the slow switching rates is to decrease the diffusion distance of ions, that is, to reduce film thickness. Based on the reported switching time of 2.2 s for a 300 nm thick PEDOT film, [5] we expect the switching time to be approximately 10 ms for a 20 nm thick film. However, the coloration of such a thin film is never sufficient for display applications. An array structure of PEDOT nanotubes provides an attractive solution to both of these limitations, slow switching rates and extent of coloration. Figure 1 explains that the wall thickness of PEDOT nanotubes can provide ions with short COMMUNICATIONS

Effects of counterions and growth methods on polyaniline growth have been studied using the electrochemical quartz crystal microbalance and other related techniques. The results indicate that the polymer growth rates and the morphology of polymer surfaces are very different depending on the electrolytes and growth methods used. During the first cycle of the potentiodynamic growth, the weight increase is observed with a low coulombic efficiency. However, the number of electrons required for the deposition of one aniline unit quickly approaches 2.0 beginning from the second cycle, and the current efficiency becomes higher as the number of cycles increases. As the film grows, the anion insertion and deinsertion become increasingly important. For a thick polymer film in the H 2 SO 4 solution, the doping/dedoping process is not reversible, although it is reversible in HClO 4 solutions. During the potentiostatic and galvanostatic polymerization, relatively low charge efficiencies were observed due to the degradation reactions. These results were consistent with the scanning electron microscope images.

Conducting polymer nanowires and nanorings (see Figure) can be synthesized using the strategy described here—electrochemical growth on gold electrodes modified with self‐assembled monolayers (SAMs) of well‐separated thiolated cyclodextrins in an alkanethiol “forest”. Thiolated aniline monomer is anchored to the surface within the cyclodextrin cavity and forms an initiation point for polymer wire growth.