Electrochromic Conducting Polymers via Electrochemical Polymerization of Bis(2-(3,4-ethylenedioxy)thienyl) Monomers

Abstract

A series of bis(2-(3,4-ethylenedioxy)thiophene)-based monomers have been synthesized and fully characterized; specifically (E)-1,2-bis(2-(3,4-ethylenedioxy)thienyl)vinylene (BEDOT-V), 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (BEDOT-B), 4,4‘-bis(2-(3,4-ethylenedioxy)thienyl)biphenyl (BEDOT-BP), 2,5-bis(2-(3,4-ethylenedioxy)thienyl)furan (BEDOT-F), 2,5-bis(2-(3,4-ethylenedioxy)thienyl)-thiophene (BEDOT-T), and 2,2‘:5‘,2‘‘-ter(3,4-ethylenedioxy)thiophene, TER-EDOT. The X-ray crystal structures of BEDOT-V and BEDOT-B have been determined. These monomers oxidize and polymerize at low potentials relative to other reported electropolymerizable heterocycles. The electroactive polymers formed exhibit low redox switching potentials and are quite stable in the conducting state. TER-EDOT was found to have the lowest peak oxidation potential of +0.2 V vs Ag/Ag+, making it the most easily oxidized polymerizable thiophene monomer reported. The electronic bandgaps of these EDOT based polymers range from 1.4 to 2.3 eV (measured as the onset of the π−π* transition) offering a diverse range of colors which may prove useful in electrochromic devices. For example, poly(BEDOT-V) is deep purple and opaque in the reduced state and transmissive sky blue in the oxidized state, poly(BEDOT-T) is deep blue opaque in the reduced state and transmissive blue in the oxidized state, while poly(BEDOT-BP) is transmissive orange in the reduced state and opaque purple in the oxidized state. A thin film of poly(BEDOT-V) was found to switch rapidly between redox states (under 2 s) with an initial optical contrast of 43%. This polymer was found to retain 47% of its optical contrast and 48% of its original charge density after 600 double potential steps.

The electronic structure of n- and p-doped phenyl-capped 3,4-ethylenedioxythiophene trimer

“…[5][6][7][8] Until now, EDOT-based oligomers have not received as much attention, probably because they are difficult to synthesize and, in case of the longer species, sensitive to air oxidation. Recently published studies on oligomers of EDOT include bis 2-͑3,4-ethylenedioxy͒thienyl that can be electrochemically polymerized to form electrochromic conducting polymers, 9 and ␣, -bis͑mesitylthio͒͑3,4-ethylenedioxythiophene͒ for molecular scale electronics applications. 10 The phenyl-capped EDOT trimer considered in this work is quite stable in air, is solution processable and can be deposited onto suitable substrates in vacuum by sublimation at moderate temperatures.…”

A joint theoretical and experimental study on the electronic properties of phenyl-capped 3,4-ethylenedioxythiophene oligomers

“…To date, the only EDOT oligomers that have been isolated and reported in the literature are 2,2Ј:5Ј,2Љ-tris-EDOT, 7 and 2,2Ј-bis-EDOT. 8 Indeed, as compared to ␤,␤Ј-unsubstituted oligothiophenes, EDOT oligomers are more electron rich, due to the addition of electron donating ethylenedioxy groups and therefore have a lower oxidation potential.…”

Oligômeros e polímeros derivados do tiofeno: síntese e aplicações

“…82 Polímeros condutores solúveis e processáveis têm sido obtidos através da síntese de oligômeros solúveis, utilizando-se substituintes ou precursores solúveis. Como exemplo, tem-se o polímero poli(isotianafteno) (36) 89 Liu e Gregory 90 reportaram a síntese de um derivado de politiofeno com uretano substituído na posição β-do anel tiofênico (42) (Figura 16). O polímero foi obtido através da síntese química empregando-se o cloreto férrico (FeCl 3 ) como agente iniciador.…”

“…As técnicas eletroquímicas utilizadas para a realização das polimerizações são cronopotenciometria 118 e cronoamperometria 87,[119][120][121] e, a técnica mais comum, a voltametria cíclica. 7,19,95,[122][123][124][125][126][127] A polimerização através da técnica de voltametria cíclica consiste em escolher uma faixa de potencial na qual o potencial máximo de oxidação do monômero esteja incluído e o potencial varia com uma determinada velocidade de varredura. A aplicação de um potencial constante igual ou superior ao potencial de oxidação do monômero por um determinado tempo resulta na formação de filmes finos de polímeros; esta técnica é denominada cronoamperometria.…”

“…1 É digno de nota que, quando estes materiais são estimulados eletricamente, podem ter sua cor variada de forma reversível ou mesmo emitir luz visível, o que possibilita a sua aplicação em diversos dispositivos eletrocrômicos 2 ou diodos emissores de luz orgânicos (OLEDs -Organic Light Emission Diodes). Dentre outras possibilidades de aplicação, pode-se citar o desenvolvimento de condutores elétricos, células fotovoltaicas poliméricas, transistores orgânicos, 3,4 anticorrosivos, 5,6 materiais eletrocrômicos, 7 baterias recarregáveis, 8 etc.…”