Electrochromic polymers films

Electrochromic polymer films have been made where the carbazole unit is not part of the main chain of the polymer, e.g., poly-iM-vinylcarbazole (29) [107—109]. When electrochemically polymerized, it has been shown that the cation radical of the carbazole unit easily dimerizes to form a 3,3 -bicarbazolyl that is more easily oxidized than the parent monomer. These films also show a colorless to green transition upon oxidation. Similarly, films of poly[3-(3-bromocarbazol-9-yl)propyl]methylsiloxane (30) have been prepared where the carbazole dimerizes creating a cross-linked film that switches between colorless and green as with the other polymers [110]. 

Electrochromic polymer films have been prepared by oxidative electropolymerization of the monomer tetrakis(2-hydroxyphenoxy)phthalocyaninato cobalt(II) (43). The technique involved voltammetric cycling at 100 mV s from —0.2 to -1-1.2 V vs SCE in dry acetonitrile, resulting in the formation of a fine green polymer. Cyclic voltammograms during pol5mier growth showed the irreversible... 

Electrochromlc performance. Primary performance metrics for electrochromic polymer films are response time and contrast. Contrast can be evaluated by many measures maximum transmittance change is often used. Contrast and response times for the PANI LBL composites surveyed herein are presented in Table 3. Response time is based on the time required for 90% of full transmittance change. In general, films of similar thickness performed... 

A better understanding of intrinsic properties of electrochromic polymer films (such as the electrical, optical and structural properties) and of the tehavior of these films at different interfaces (such as electrode surface and electrolyte solution) will permit in rovement in the design (electrode materials, conq)osition of siq>port electrolyte, contacts, etc.) and performance of ECDs. Usefol information t is needed includes ... 

This information can be obtained using various techniques. In situ UV-vis spectroscopy, electrochemistry and sur ce studies have been used to characterize electrochromic polymer films iq>on oxidation and reduction. We present here the investigation of BBB, BBL and PPTZPQ. 

Chemical oxidation of Af-methylaniline resulted in an elec-trochemically active electrochromic polymer film as reported by Comisso et al. [473]. Optical absorption bands in the UV-vis spec-... 

The apphcation of a high electric field across a thin conjugated polymer film has shown the materials to be electroluminescent (216—218). Until recentiy the development of electroluminescent displays has been confined to the use of inorganic semiconductors and a limited number of small molecule dyes as the emitter materials. Expansion to the broad array of conjugated polymers available gives advantages in control of emission frequency (color) and facihty in device fabrication as a result of the ease of processibiUty of soluble polymers (see Chromogenic materials,electrochromic). 

Polymers films formed from tr i sbipvr idineruthenium complexes and coated on electrode surfaces have been found to have interesting electrochromic and conductivity properties. 

Doped silicon, conductivity in, 23 35 Doped/undoped electrochromic organic films, 6 580-582 Dope-dyeing, 9 197 Dope-making process, in acrylic fiber solution spinning, 11 204 Dope solids, in air gap spinning, 11 209 Doping, 23 838—839 calcium, 23 842-844 conducting polymers, 7 528-529... 

As a result, an insolnble transparent blue polymer film forms on the electrode. Electrochemical oxidation of the film in acetonitrile initiates a rapid color change from bine to pale gray, while redaction to the first or second cathodic waves causes the film to become pale green or orange, respectively. These electrochromic effects are stable and reversible when air and water are excluded, even after 30,000 rednction cycles. The material has potential uses in electrochromic or electroluminescent devices. 

Steady-state photoinduced electrochromism was achieved in organic solutions [34,35], microcrystals [36,37], LB films [7,8,38,39], and polymer films [40- 48] which was due only to the photoinduced electron transfer reaction via the excited state of specific IPCT complexes [49,50], The photochemical coloring and the thermal fading due to the reverse electron transfer were highly reversible in a deaerated atmosphere in all systems [7,8,34 18], The lifetime of colored (blue)... 

The electrochromism spectrum of the visible absorption region of [Ru(bpy)3] + recorded in a PVA polymer film exhibits a second derivative pattern (Figure 9) indicative of an excitation with a substantial A/x. A symmetric excitation of all three ligands leads to no excited state dipole moment. Electrochromism spectra of mono-immine complexes were also found to be similar to the tris-immine parent complex." These results were taken as evidence for localization in the symmetric complexes. 

Figure 9 Absorption spectrum (a) and electrochromism (b) of [Ru(bpy)3] dissolved in a thin polymer film at 77 K. Absorption and electrochromism spectra are taken through semitransparent conducting electrodes. Electrochromism is usually measured with the externally applied electric field parallel to the propagation direction koflight( = 0°). Experiments can also be made with the film tilted away from the normal to the propagation direction (Drawn from data in Oh and Boxer )...

S. Kawabata, H. Yoneyama and H. Tamura, Redox behavior and electrochromic properties of polypyrrole films in aqueous solutions, Bull. Chem. Soc. Jpn., 1984, 57, 2247 P.C. Bookbinder and M.S. Wrighton, Electrochromic polymers covalently anchored to electrode surfaces. Optical and electrochemical properties of a viologen-based polymer./ Electrochem. Soc., 1983,130, 1080. 

Polymer films containing phthalocyanines have also been electrochemically investigated for their electrochromic reductions and reoxidations [12,17-18],... 

The ellipsometric technique has been used for the estimation of thickness, refractive index and optical dielectric constants of a conducting polymer film [89]. These conducting polymer films have been used for the fabrication of electrochromic and glucose biosensing... 

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