Electrochromic Polymers

Abstract

Synonyms Conjugated electrochromic polymers DefinitionPolymers changing their colors upon applied potential. ChromismChromism is defined as the reversible change of material's color resulting from a stimulus. The stimulus could be in the form of electrochemical effect (electrochromism), temperature change (thermochromism), electromagnetic radiation (photochromism), change in pH (halochromism), ion effect (ionochromism), solvent effect (solvatochromism), and mechanical effect (piezochromism). Among those, electrochromism has been the center of much interest for its highly promising applications such as smart mirrors and windows, displays, active optical filters, data storage, and camouflage material for military purposes [1]. More precisely, electrochromism is the process of reversible optical change (transmittance and/or reflectance) which is associated with the electrochemically induced oxidation-reduction of the material. Color variation generally occurs between a transparent and a colored state or between two colored states. Additionally, some exceptional electrochromic materials, which are termed as multichromic, could display several colors depending on their oxidation state. Based on their coloration process these materials are also designated as anodically coloring (coloration upon oxidation) or cathodically coloring (coloration upon reduction). Materials that possess electrochromic activity can be mainly classified as metal oxides, molecular dyes, and conducting polymers.A typical and most widely studied example of metal oxides is tungsten trioxide where electrochromic response is achieved by the reduction of W VI sites in tungsten trioxide thin film to W V. Upon this, the color of the film changes from transparent to blue. The blue color of the film can be reversibly erased by the electrochemical oxidation [2]. The generalized equation can be written as follows:

Matched‐dual‐polymer electrochromic lenses, using new cathodically coloring conducting polymers, with exceptional performance and incorporated into automated sunglasses

“…(iv) 2,2‐(bis‐4‐aminobenzyl)‐3,4‐propylenedioxythiophene (3,3‐Bis(4‐aminobenzyl)‐3,4‐dihydro‐2H‐thieno[3,4‐b][1,4]‐dioxepine; Amino‐Bz‐ProDOT). Complimentarily coloring, dual‐polymer electrochromic devices (“lenses”) made with these new monomers constituting the cathodically coloring polymer (used singly as well as in the form of copolymers), paired with several anodically coloring poly(aromatic amines), which we had reported on earlier, again used singly as well as in the form of copolymers. The cathodically and anodically coloring polymer pairs in these devices are shown to be nearly “perfectly” matched electrochemically and electrochromically, in contrast to nearly all prior art where the cathodically and anodically coloring polymers are poorly matched. The resulting electrochromic lenses display very high L/D contrast (typically up to 70/7% or 50/0.5% Transmission, integrated over the visible spectrum (“real‐life,” against air reference, not substrate reference, see below), very high cyclability (>10 K cycles) and very long (multiple‐years) shelf life.…”

“…To the best of our knowledge and based on an extensive search of the literature, the electrochromic lenses and sunglasses we report herein represent the best visible‐region electrochromic performance for dual‐polymer CP electrochromic systems to date. They also are, to our knowledge, the first practical implementation in working sunglasses, that is, they represent practical, functional, and applied polymers.…”

“…A subset of CP electrochromic systems, those based on “complimentarily coloring” or “dual‐polymer” CPs, have seen more recent development and have been extensively described . In these systems, a “cathodically coloring” CP on one electrode is paired with an “anodically coloring” CP on the other, so that they reinforce each other in lightening and darkening.…”

“…Some improvements in cyclability [i.e., number of light/dark (L/D) cycles before degradation] and switching time is also observed in these systems. In this respect however, nearly all complimentarily coloring CP electrochromics reported thus far have used CPs that are relatively poorly matched electrochemically and electrochromically. An exemplary manifestation of poor matching is that when a potential is applied, in a 2‐electrode device, at which one CP is in its fully oxidized form, its complimentary CP is not in its fully reduced form.…”

Syntheses and Optical Properties of Perfluorophenyl Containing Benzimidazole Derivatives: The Effect of Donor Units

“…Their applications like electrochromic devices, photovoltaics, sensors, organic field effect transistors and organic light emitting diodes are attractive due to these extraordinary advantages (5)(6)(7)(8)(9)(10)(11)(12). Among these advantages the most crucial one of donor -acceptor theory is tuning band gap by structural modifications (13)(14)(15).…”