Electrochromic properties of conducting polyanilines

Abstract

A study has been made of the electrochromic behaviour of polyaniline films of potential use in passive display devices, and a preliminary examination of the properties of substituted polyanilines has also been carried out. Films of 'emeraldine-type' conducting polyanilines have been grown electrochemically from aqueous solutions onto glass substrates coated with gold or indium tin oxide. The authors have studied the electrochemistry of their redox reactions in acidic media to examine the kinetics and reversibility. Cyclic voltammetry was used to determine the electrode potentials for growth and redox switching and to obtain information on the electrode kinetics. The effect of electrode potential on the optical absorption spectra was observed, and was found to be consistent with polaron and bipolaron formation. The electrochromic colour contrast and switching times were measured as a function of pH; the requirements were somewhat conflicting, but a satisfactory compromise could be obtained around pH=0. By switching the electrodes over a constant potential step but from a variety of starting potentials, the influence on switching times of the initial oxidation state, and hence of the film conductivity, was investigated. Under suitable circumstances electronic conductivity, ionic transport or interfacial charge-transfer can limit the switching speed, but response times (for 50% transmission change) as short as 15 ms have been obtained without full optimisation. Of the numerous substituted polyanilines tried, only simple alkyl and alkoxy derivatives formed good polymeric films, and only the 2-ethoxy and 2-methoxy polymers gave good electrochromic behaviour. Switching times for these two were very fast, being less than 2.5 ms for both oxidising and reducing potential changes.

Studi Efek Elektrokromik Pada Film Polianilin

“…Kemudian ditemukan sifat elektrokromik pada bahan organik yaitu polianilin [7]. Polianilin memiliki sifat yang baik antara lain kontras warna yang tajam, siklus pemakaian yang awet [6], stabil [7], pada prinsipnya mudah disiapkan [8] dan mudah diperoleh di pasar lokal. Penelitian sudah dilakukan terhadap polianilin dengan 0,001M H 2 SO 4 dan 0,01M H 2 SO 4 [9], 0,1M HCl [7] dan 1,0M HCl [8,10].…”

“…Warna yang teramati secara visual dalam jangkauan tegangan antara −0.2 dan 1.0 V adalah kuning transparan, hijau muda, hijau, biru dan violet. Pada Gambar 3 dapat dilihat bahwa film polianilin menghasilkan puncak-puncak oksidasi di sekitar 0.25, 0.45 dan 0.7 V yang ditandai dengan huruf A, B dan C, sedangkan puncak reduksi berada di sekitar 0.0 , 0.35 dan 0.6 V yang ditandai dengan D, E dan F. Puncakpuncak ini disebabkan oleh peristiwa alih (transfer) muatan [8]. Pengaruh konsentrasi asam dapat diamati pada rapat arus yang berharga sampai sekitar 2.5 mA/cm 2 , lebih tinggi dari pada sekitar 0.1 mA/cm 2 yang diperoleh [9] dengan 0.001M dan 0.01M H 2 SO 4 .…”

“…Berdasarkan kurva-kurva yang diperoleh, faktor reduksi x dapat dihitung yaitu dengan mengambil asumsi bahwa ketika film mempunyai absorbansi maksimum (keadaan paling gelap), tercapai saat teroksidasi penuh atau x = 0. Pada Gambar 6 nampak bahwa puncak absorbansi diperoleh pada panjang gelombang ≈ 700 nm dengan tegangan 0.75 V. Puncak pada 700 nm diamati pula oleh peneliti lain [8], sementara dalam asam yang lebih lemah [9] tercapai puncak pada 544 nm.…”

Conjugated Polymers as Actuators for Medical Devices and Microsystems

“…This redox change results in a change of material properties such as conductivity [1], electrochromism [2], and wettability [3,4]. The ion transport during this redox switching has also been used in drug release applications [5][6][7].…”

Preparation of conductive polyaniline/chlorosulfonated polyethylene composites viain situ emulsion polymerization and study of their properties

“…Last year we reported the preparation of conductive PAn/(styrene-butadiene-styrene)triblkock copolymer (SBS) composites in one-step via in situ emulsion polymerization. 18 Foot and Simon 19 first reported that PAn can be used in electrochromic device due to the change of colors during a voltammetric cycle at pH 0 -1 media. Bernard and Hugot-LeGoff 20 showed that a weakly acidic electrolyte solution (at pH 3 but not pH 5) is best suitable for electrochromic purpose of PAn.…”