Synthesis and electropolymerization of 3,4-substituted quinoxaline functionalized pyrrole monomer and optoelectronic properties of its polymer

SyntheticMetals194(2014)19–28

ContentslistsavailableatScienceDirect

Synthetic

Metals

j ou rn a l h o m epa g e :w w w . e l s e v i e r . c o m / l o c a t e / s y n m e t

Synthesis

and

electropolymerization

of

3,4-substituted

quinoxaline

functionalized

pyrrole

monomer

and

optoelectronic

properties

of

its

polymer

Gülbin

Kurtay

a

_,

_Metin

_Ak

b,∗

_,

_Mustafa

_Güllü

a

_,

_Levent

_Toppare

c

_,

_Mine

_Sulak

_Ak

b

a_{AnkaraUniversity,FacultyofScience,ChemistryDepartment,Ankara,Turkey}

b_{PamukkaleUniversity,FacultyofArtandScience,ChemistryDepartment,Denizli,Turkey}

c_{MiddleEastTechnicalUniversity,FacultyofArtandScience,ChemistryDepartment,Ankara,Turkey}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received6January2014 Accepted8April2014 Keywords: Conductingpolymers Electrochemicalpolymerization Electrochromism Spectroelectrochemistry

a

b

s

t

r

a

c

t

We synthesized a new electroactive pyrrole functionalized monomer;

2-butyl-5,12-dihydro-2H-pyrrolo[3,4:2,3][1,4]dioxocino[6,7-b]quinoxaline(BuDQP)where␤-positionsofthepyrroleringare blocked.Withthehelpofthisstrategy,formationof␣–␤linkagesduringpolymerizationwasprevented,

resultinginamoreregiochemicallydefinedmaterial.Characterizationofnewlysynthesizedcompounds

wasperformedbyFTIR,GC–MS,1_HNMR,13_{CNMRtechniquesandelementalanalysis.Polymerizationand}

copolymerizationofBuDQPandcharacterizationoftheresultingpolymerswerealsoperformed. Spectro-electrochemicalinvestigations,switchingabilities,colorimetrystudiesandstabilityexperimentswere

performedonbothforpolymerandcopolymer.SpectroelectrochemicalanalysisofP(BuDQP)reflected

electronictransitionsat328nm(␲–␲*transition)and500nm(polaronbands)withanelectronicband gapof2.30eV,whilecopolymer(P(BuDQP-co-Py))revealedelectronictransitionsat346nm(␲–␲* tran-sition)and518nm(polaronbands)withanelectronicbandgapof2.24eV.Colorimetrystudiesrevealed

thatP(BuDQP)hasonlytwocolors(blueandyellow)whereascopolymerfilmhassixdifferentcolorsin

itsoxidizedandneutralstates.

©2014ElsevierB.V.Allrightsreserved.

1. Introduction

Electrochromismarisesfromthegenerationofdifferent elec-tronicabsorptionbandsinthevisibleregion,whichcorrespondsto thechangesbetweenatleasttworedoxstates[1].Conducting poly-mers(CPs)haveattractedconsiderableinterestaselectrochromic materials since ingenious modifications on the monomer can significantly alter the spectral properties of thepolymer. Such modifications mayalsoalter the switchingability of the mate-rial between its oxidized and neutral states over many redox cycles [2–6]. They are usually colored in their reduced states duetotheenergydifferencebetween␲-bondingorbitalsandthe ␲*-antibonding orbitals in the visible region. Whena polymer isoxidized,thelower energytransitions becomedominantand anothercolorisformed.

Polypyrrole caneasily besynthesized chemically or electro-chemically and has a wide range of optoelectronic properties

∗ Correspondingauthor.Tel.:+902582963595;fax:+902582963535.

E-mailaddresses:metinak@pau.edu.tr,metin-ak@hotmail.com(M.Ak).

available through alkyl and alkoxy substitution which gives it an extensive value as an electrochromic material. The pristine polypyrrolehowever,haslow qualityelectrochromicproperties. It switches between gray and turquoise color which makes it unusableinelectrochromicdevicessinceitswitchesbetweentwo darkcolorswithalowopticalcontrastandmoderateswitching timeinthevisibleregion[7–9].Thematerialisalsohighly sus-ceptibleto degradationupon colorswitching. Comparedto the immenseliteratureonfunctionalizedconductingpolymerssuch aspolythiophenes[10,11],thenumberoffunctionalized polypyr-role derivativesis quitelow [12–16],though numerous studies havebeenconductedonpristinepolypyrrole[17].Polypyrroleis promising forseveralapplicationssuchasbatteries, supercapa-citors,electrochemicalbiosensors,conductivetextilesandfabrics, mechanicalactuators,electromagneticinterferenceshielding, anti-staticcoating,electrochromicdevicesanddrugdeliverysystems

[18–20].Polypyrrolefilmswithbetterchemicalandphysical prop-ertiescanbeproducedbygainingbettercontrolonthestructure

[20–24].

ElectrochemicallypreparedpolypyrrolesandotherCPssuffer fromundesired␣–␤and␤–␤couplingsduringpolymerization[25].

http://dx.doi.org/10.1016/j.synthmet.2014.04.002