Spray coatable electrochromic dioxythiophene polymers with high coloration efficiencies

Article abstract of DOI:10.1021/ma049222y

Four new disubstituted propylenedioxythiophene polymers have been synthesized by Grignard metathesis on the 1-5 g scale. All polymers were found to be soluble in chloroform, methylene chloride, toluene, and tetrahydrofuran and were fully structurally characterized having GPC determined number-average molecular weights ranging from 33000 to 47000 g mol^-1. Dilute polymer solutions in toluene exhibited strong red fluorescence with moderate quantum efficiencies from 0.38 to 0.50. Homogeneous thin films were formed by electropolymerization and spray casting polymer solutions onto ITO coated glass slides at thicknesses of ca. 150 nm. The films were electroactive, switching from a dark blue-purple to a transmissive sky blue upon p-doping, often with subsecond switching times, and high electrochromic contrast luminance changes (% ΔY) of 40-70%. These studies revealed that the branched derivatives, [poly(3,3-bis(2-ethylhexyl)-3,4-dihydro-2H-thieno[3,4-o] [1,4]dioxepine)] and [poly(6,8-dibromo-3,3-bis(2-ethylhexyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1, 4]dioxepine)], gave an electrochemical response and associated color change over a much smaller voltage range in comparison to the linear chain substituted derivatives, [poly(3,3-dihexyl-3,4-dihydro-2H-thieno[3,4-o][1,4]dioxepine)] and [poly(3,3-bis(octadecyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b] [1,4]dioxepine)]. Composite coloration efficiency values were found up to 1365 cm²/C; this was considerably larger than values obtained from previously studied alkylenedioxythiophene based polymers (～375 cm²/C).

Full text of DOI:10.1021/ma049222y

Macromolecules 2004, 37, 7559-7569
7559
Spray Coatable Electrochromic Dioxythiophene Polymers with High
Coloration Efficiencies
Ben ja m in D. Reeves,† Ch r istop h e R. G. Gr en ier ,† Avn i A. Ar gu n ,† Ali Cir p a n ,†
Tr a cy D. McCa r ley,‡ a n d J oh n R. Reyn old s*,†
Department of Chemistry, Center for Macromolecular Science and Engineering: University of Florida,
Gainesville, Florida 32611-7200, and Department of Chemistry, Louisiana State University,
Baton Rouge, Louisiana 70803-1804
Received April 21, 2004; Revised Manuscript Received J uly 14, 2004
ABSTRACT: Four new disubstituted propylenedioxythiophene polymers have been synthesized by
Grignard metathesis on the 1-5 g scale. All polymers were found to be soluble in chloroform, methylene
chloride, toluene, and tetrahydrofuran and were fully structurally characterized having GPC determined
number-average molecular weights ranging from 33000 to 47000 g mol-1. Dilute polymer solutions in
toluene exhibited strong red fluorescence with moderate quantum efficiencies from 0.38 to 0.50.
Homogeneous thin films were formed by electropolymerization and spray casting polymer solutions onto
ITO coated glass slides at thicknesses of ca. 150 nm. The films were electroactive, switching from a dark
blue-purple to a transmissive sky blue upon p-doping, often with subsecond switching times, and high
electrochromic contrast luminance changes (% ∆Y) of 40-70%. These studies revealed that the branched
derivatives, [poly(3,3-bis(2-ethylhexyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)] and [poly(6,8-dibromo-
3,3-bis(2-ethylhexyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)], gave an electrochemical re-
sponse and associated color change over a much smaller voltage range in comparison to the linear chain
substituted derivatives, [poly(3,3-dihexyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)] and [poly(3,3-bis-
(octadecyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)]. Composite coloration efficiency values
were found up to 1365 cm2/C; this was considerably larger than values obtained from previously studied
alkylenedioxythiophene based polymers (∼375 cm2/C).
Sch em e 1
In tr od u ction
Great effort has been made over the last 2 decades to
study and utilize the electronic properties of thiophene-
based conducting polymers while optimizing their
processability.1-3 This has led to the use of polythio-
phenes in various applications including light emitting
devices,4 chemical sensors,5 rechargeable batteries,6
organic thin film transistors,7 and electrochromic de-
vices.8 Processability of polythiophenes has undergone
vast improvements by derivatizing the 3-position of the
ring with flexible substituents.9-11 The regioregularity
of these poly(3-alkyl thiophenes) (p3AT’s) plays an
important role in property control.12 Models of regio-
random, regioregular, and regiosymmetric polymers are
illustrated in Scheme 1. If the unsymmetrical monomer
only couples in a head-to-tail fashion, the alkyl substit-
uents do not interfere with the conjugation of the
thiophene rings via steric interactions, and the resulting
polymer is regioregular.
While numerous methods12,13 have been employed for
synthesizing regioregular p3AT’s, the latest method
developed by McCullough and co-workers, Grignard
metathesis polymerization, does not require long reac-
tion times, cryogenic temperatures, or nontrivial prepa-
ration of reagents often seen with other methods.14,15
Poly(thiophenes) show excellent potential for use in
electrochromic devices due to the drastic change in the
electromagnetic spectrum upon charge injection (doping)
with the parent polymer switching from red to blue upon
oxidation.16 Derivitizing the 3- and 4-positions of the
thiophene ring with an alkylenedioxy brigde lowers the
band gap and the oxidation potential due to the two
electron donating oxygen atoms.17,18 Poly(3,4-ethylene-
dioxythiophene) (PEDOT) is cathodically coloring, switch-
ing between a dark blue in the neutral state and a
transmissive sky blue in the oxidized state.
By taking advantage of the synthetic flexibility of the
PEDOT monomer structure, we have been successful
in synthesizing and studying the electrochromic proper-
ties of many derivatives of PEDOT.19-22 We have
developed synthetic methodologies to vary the alkylene-
* Corresponding author. E-mail: reynolds@chem.ufl.edu.
† University of Florida.
‡ Louisiana State University.
10.1021/ma049222y CCC: $27.50 © 2004 American Chemical Society
Published on Web 09/04/2004

7560 Reeves et al.
Macromolecules, Vol. 37, No. 20, 2004
Sch em e 2
Sch em e 3
Sch em e 4
dioxy ring size, and vary the size, number, and place-
ment of substituents on the ring by utilizing Williamson
etherfication,20 transetherification,21,22 and Mitsunobu
chemistry.23 A dimethyl derivative of propylenedioxy-
thiophene, PProDOT(Me)2, exhibits a contrast ratio of
78% at 585 nm and a switching time of 0.3 s, the best
values obtained from the alkylenedioxythiophene fam-
ily.21 With small substituents, electropolymerization is
used for film formation.24
In developing disubstituted poly(3,4-propylenedioxy-
thiophenes), we utilized the C2 symmetry of the propy-
lenedioxythiophene monomer to form a regiosymmetric
polymer and induce solubility in organic solvents.25
As the propylenedioxy ring functions as a spacer to
separate the alkyl chains from the polymer backbone,
there is a minimal effect on the extent of conjugation.
Grignard metathesis coupling was utilized in the syn-
thesis of a soluble and processable dibutyl derivative of
poly(3,4-propylenedioxythiophene), P P r oDOT(Bu )2
(Scheme 2).
In this work, the synthesis of four new poly(alkylene-
dioxythiophenes) by Grignard metathesis is reported.
Scheme 2 depicts the four polymer structures, 1-4. All
of these polymers, as with P P r oDOT(Bu )2, were syn-
thesized from regiosymmetric monomers to yield regio-
symmetric polymers and are soluble in organic solvents,
allowing facile characterization of the molecular weight
by GPC and primary structure by 13C and 1H NMR. This
solubility also allowed polymer solutions to be spray cast
onto working electrodes and the electrochemical and
electrochromic properties of the films to be analyzed.
The electrochemical polymerization of each monomer
was also performed and the electrochromism of spray
cast and electrochemically deposited films were com-
pared. Finally, coloration efficiency studies show these
polymers to behave as efficient, high contrast electro-
chromic materials, useful for electrochromic devices.26
thiophene with 2,2-bis(bromomethyl)-1,3-propanediol to
form P r oDOT(CH2Br )2, as shown in Scheme 3.
P r oDOT(CH2Br )2 can be used as a precursor to form
any number of structures which can be synthesized
by a Williamson etherification to afford the electro-
chemically polymerizable monomers, P r oDOT(C18)2
(5) and P r oDOT(CH 2OE t Hx)2 (6). Figure 1a shows
the 1H NMR of P r oDOT(C18)2 (5). The singlet at
6.44 ppm corresponds to the thienyl protons while
the singlets at 4 and 3.48 correspond to the meth-
ylene protons of the propylenedioxy bridge and the
methoxy ether substituent groups, respectively. The
octadecyl groups give rise to the signals at 3.36 (triplet,
O-CH 2C17H35), 0.88 (triplet, CH 3C17H35O-), and 1.5
(multiplet, O-CH2C16H32CH3) ppm.
Next, the thiophene ring was brominated at the 2-
1
and 5-positions using NBS. The H NMR of P r oDOT-
(C18) Br 2 (7) given in Figure 1b differs from P r oDOT-
(C18)22 (5) by only the absence of the thienyl proton
signal at 6.4 ppm, as expected.
As seen in Scheme 4, alkyl substituents can also be
placed on the 2-position of the propylenedioxy ring by
first synthesizing the desired diol by an alkylation of
diethyl malonate using sodium hydride and the corre-
Resu lts a n d Discu ssion
Mon om er Syn t h esis. The synthesis of alkoxy-
derivitized ProDOT monomers was accomplished by
first carrying out a transetherification of 3,4-dimethoxy-

Macromolecules, Vol. 37, No. 20, 2004
Electrochromic Dioxythiophene Polymers 7561
Sch em e 5
Ta ble 1. Molecu la r Weigh t Deter m in a tion by GP C
Mn(GPC)
Mw
Xn
PDI
1
2
3
4
38100
43000
47300
33400
65900
62600
74800
48000
117
113
107
46
1.73
1.46
1.58
1.43
hydrogens.28 The 1H NMR spectrum of the sample
(Figure 1c) gives broad signals, typical for a polymer,
and the thienyl proton end groups are undetectable as
expected for a polymer of substantial molecular weight.
Molecu la r Weigh t Ch a r a cter iza tion . Molecular
weight analyses of the purified polymers were per-
formed by GPC (see Table 1) and MALDI-TOF MS. The
GPC results gave number-average molecular weights
ranging from 33000 to 47000 g mol-1 and weight-
average molecular weights between 47000 and 75000 g
mol-1 with polydispersity ranging from 1.43 to 1.73 after
fractionation during purification. These high molecular
weights do not likely affect the optical or electronic
properties of these polymers29 but do enhance film
forming ability, leading to easier processing. The high
molecular weights obtained are as expected since the
polymer solutions spray cast to form homogeneous thin
films (discussed later in F ilm P r ep a r a tion ).
The MALDI-TOF MS analyses confirmed the pres-
ence of chains of molecular weights of up to 10000 g
mol-1 for P P r oDOT(CH2OEtHx)2 (3) and P P r oDOT-
(C18)2 (4) and up to 5000 g mol-1 for polymers P P r o-
DOT(Hx)2 (1) and P P r oDOT(EtHx)2 (2). These values
are in no way limiting or average due to the inability of
longer chains to be volatized. The MALDI spectra of
polymers P P r oDOT(Hx)2 (1), P P r oDOT(CH2OEtHx)2
(3), and P P r oDOT(C18)2 (4) exhibited intense ion
series that were separated by the expected mass of the
repeat unit of the polymer for each case. P P r oDOT-
(EtHx)2 (2) only gave a weak signal that tailed off at
m/z 5000. Further work is underway to improve the ion
signal-to-noise ratio. Figure 2 shows the spectrum of
P P r oDOT(CH2OEtHx)2 (3). The dominant peaks are
separated by 438 amu, corresponding to the mass of the
monomer repeat unit, and the residual mass corre-
sponds to two chlorine end groups [(438)n + 71 amu].
This is unexpected and differs from earlier studies of
polythiophene and poly(alkylenedioxythiophene) syn-
thesized by Grignard metathesis.25,28 The only chlorine
source available must come from the catalyst, Ni(dppp)-
Cl2. Further studies are underway to determine whether
the chlorine from the catalyst is terminating polymer-
ization.
F igu r e 1. 1H NMR of (a) P r oDOT(C18)2 (5), (b) P r oDOT-
(C18)2Br 2 (7), and (c) P P r oDOT(C18)2 (4), after end group
conversion to hydrogens by subjecting to nBuLi followed by
an aqueous work up.
sponding alkyl bromide followed by an LiAlH4 reduc-
tion.27 The diol, 9, was synthesized on a 300 g scale in
good yield.
Electrochemically polymerizable monomers, P r oDOT-
(Hx)2 (11) and P r oDOT(EtHx)2 (12), were formed by
a transetherification reaction of 3,4-dimethoxythiophene
with the corresponding diol. The chemically polymer-
izable monomers, P r oDOT(Hx)2Br 2 (13) and P r oDOT-
(E t Hx) Br 2 (14), were obtained by bromination of
P r oDO2T(Hx)2 (11) and P r oDOT(EtHx)2 (12) using
NBS followed by column chromatography. The meth-
odology used in Scheme 4 has generated the monomer,
P r oDOT(Hx)2Br 2 (13), on a 10 g scale.
P olym er Syn th esis. As seen in Scheme 5, all mono-
mers underwent Grignard metathesis polymerization.
First, a titrated methylmagnesium bromide solution was
added slowly to the monomer in dry THF and the
solution was refluxed for 1 h. Ni(dppp)Cl2 was added
immediately turning the solution from clear pink to
bright red. The mixture was heated at reflux for 20 h
followed by precipitation of the polymer into methanol.
The solid was filtered into a cellulose thimble and placed
in a Soxhlet apparatus for fractionation. Methanol was
refluxed over the thimble for 24 h to remove the mono-
mer and salts, followed by hexanes for 48 h to remove
oligomers. Finally, methylene chloride or chloroform
was refluxed over the thimble to remove the pure
polymer. After removing the solvent by rotary evapora-
tion, a dark purple solid was obtained, which was
soluble in CHCl3, CH2Cl2, THF, toluene, and benzene.
As the size of the substituent increases, the solubility
increases. Polymers 1-4 gave solubilities of 13, 36, 57,
and 124 mg/mL in toluene, respectively. The polymers
F lu or escen ce Sp ectr oscop y. Polythiophenes are
known to exhibit fluorescence in solution and in the
solid state and, thus, can be used as components in light
emitting diodes4 and chemical sensors.5 In earlier work,
a photoluminecence study of P P r oDOT(Bu )2 discov-
1
were characterized by 13C and H NMR and gave results
as expected (see Experimental Section). A 10 mg sample
n
of P P r oDOT(C18)2 (4) was reacted with BuLi followed
by an aqueous work up to convert the end groups to

7562 Reeves et al.
Macromolecules, Vol. 37, No. 20, 2004
F igu r e 3. UV-vis absorbance spectrum (left) superimposed
upon the fluorescence emission spectrum (right) of a toluene
solution of P P r oDOT(Hx)2 (1).
F igu r e 2. MALDI-TOF of P P r oDOT(CH2OEtHx)2 (3) with
HABA matrix. The dominant peaks are roughly 438 amu
apart, corresponding to the mass of the monomer repeat unit.
Ta ble 2. F lu or escen ce Sp ectr oscop y a n d Qu a n tu m
Efficien cies
a
b
λ(fluorescence)
φfl
25
PProDOT(Bu)2
617, 671
608, 664
624, 678
604, 636
602, 656
0.45
0.50
0.43
0.38
0.40
1
2
3
4
a
Peaks (nm) from the fluorescence spectra of polymer solutions
b
in toluene. Fluorescence quantum efficiency in toluene solution.
ered polymer solutions to have quantum efficiencies of
45% and emit a deep red color.25 Table 2 shows all of
the polymers have moderate quantum efficiencies in
toluene solution with emission maxima corresponding
to a deep red hue. The red fluorescence of the polymer
solutions is observable under fluorescent room lighting.
The absorbance and fluorescence spectra of P P r oDOT-
(Hx)2 (1) are shown in Figure 3. Two well-defined
vibronic bands exist in the fluorescence spectrum at 608
and 664 nm and one poorly resolved band is present at
730 nm. The spacing between each band is approxi-
mately 1370 cm,-1 most likely corresponding to the C-C
vibrational modes of the thiophene ring. A very small
Stokes shift of 675 cm-1 suggests that there is little
geometric change between the ground and excited
states. The fluorescence quantum efficiencies range from
0.38 to 0.50 with P P r oDOT(Hx)2 (1) giving the highest
value. The fluorescence spectra of drop cast and vacuum
dried films of P P r oDOT(CH2OEtHx)2 (3) and P P r o-
DOT(C18)2 (4) showed the quantum efficiency decreases
dramatically in comparison to solution, with values
ranging from 0.02 to 0.03. This is most likely due to
rapid nonradiative decay at interchain trap sites, which
was previously attributed to the low quantum efficien-
cies of P P r oDOT(Bu )2 films.25
Th er m och r om ic Stu d ies. Thermochromic studies
were performed on all polymer solutions in toluene.
Thermochromism is a useful tool to probe conforma-
tional changes in conjugated polymers, and can aid in
the development of materials suitable for sensors.30
Figure 4 shows a series of spectra of a solution of
P P r oDOT(C18)2 (4) at temperatures between -4 and
+85 °C. The spectra blue shift for all solutions from 10
to 20 nm as the temperature increases, as expected.
Although solutions of all other polymers stay the same
perceivable red color as a function of temperature,
solutions of P P r oDOT(C18)2 (4) undergo a distinct
transition, changing from red to dark purple, when
F igu r e 4. Visible spectra of a polymer solution of P P r oDOT-
(C18)2 in toluene (1.5 mg/50 mL) taken at -4, +17, +21, and
+85 °C. The photographs show the solutions at -4 (left, dark
purple) and +21 °C (right, deep red). The colors switch
reversibly when crossing +17 °C.
Ta ble 3. Electr och em ica l Da ta (V) of P P r oDOT
Der iva tives vs F c/F c+
a
b
c
Ep,m
E1/2,p
E1/2,p
PProDOT(Bu)2
1.03
1.1
1.1
-0.19
-0.12
0.05
-0.11
0.07
0.11
0.20
0.11
1
2
3
4
1.07
0.13
NAd
NAd
a
b
Monomer oxidation potential. Half-wave potential of the
electrochemically polymerized polymer. c Half-wave potential of
the spray cast polymer from toluene solution. Monomer P r o-
d
DOT(C18)2 (5) could not be electropolymerized.
cooling below 17 °C. Photographs taken at -4 and +21
°C are shown at the bottom of Figure 4.
F ilm P r ep a r a tion a n d Electr och em istr y. PPro-
DOT-R2 films were formed by one of two methods. The
first method involved the electrochemical deposition
onto a working electrode from a 0.01 M monomer/0.1
M tetrabutylammonium hexafluorophosphate (TBAPF6)
solution in propylene carbonate. Monomers P r oDOT-
(CH2OEtHx)2 (6), P r oDOT(Hx)2 (11), and P r oDOT-
(EtHx)2 (12) were electrochemically polymerized onto
a platinum button or ITO coated glass slide by poten-
stiostatic deposition using a platinum flag as a counter
electrode and a silver wire pseudo reference electrode
calibrated using a Fc/Fc+ redox couple. The oxidation
potential of the monomers are given in Table 3 and are
similar to other alkylenedioxythiophenes at approxi-
mately +1 V vs Fc/Fc+. This suggests the long and
branched alkyl chain substituents do not effect the
oxidation potential of the monomer. P r oDOT(C18)2 (5)

Macromolecules, Vol. 37, No. 20, 2004
Electrochromic Dioxythiophene Polymers 7563
Ta ble 4. P ea k s (λ, n m ) a n d Op tica l Ba n d Ga p s (E, eV) fr om th e UV-vis Sp ectr oscop y of P P r oDOT Der iva tives
a
b
c
d
e
f
λ(echem)
Eg(echem)
λ(sol)
λ(film)
λ(redox)
Eg(redox)
PProDOT(Bu)2
632, 573, 533
634, 584
623, 567, 517
609, 555, 518
NA
1.86
1.80
1.96
1.87
NA
542
544
576
575
618, 543, 521
600, 551
1.84
1.84
1.92
1.97
1.89
1
2
3
4
586, 548
595, 552
543
595, 553
611, 559
581, 543
594, 553
587, 548
590, 559
a
b
d
Electrochemically polymerized films. Optical band gap of electrodeposited films. c 1 mg/mL solution in toluene. Spray cast films
from 5 mg/mL polymer solutions in toluene. e Spray cast films from toluene solution that were switched from neutral to the oxidized state
and back to the neutral state. f Optical bangap of a previously switched spray cast film.
F igu r e 5. Photograph of spray cast films of PProDOT(CH2-
OEtHx)2 (3) (red, left) and P P r oDOT(C18)2 (4) (purple, right)
from 5 mg/mL toluene solutions using an air brush at 12 psi.
The substrates used were two sizes of ITO coated glass slides
(7 × 50 mm and 25 × 37.5 mm). Copper tape was adhered to
the top of the slides to ensure an electrical connection.
F igu r e 6. Percent relative luminance vs applied potential
(dashed line) superimposed on cyclic voltammetry (solid line,
50 mV/s) for P P r oDOT(CH2OEtHx)2 (3) (top) and P P r o-
was unable to be electrochemically polymerized/depos-
ited onto a working electrode because of the difficulty
in finding a suitable solvent that can dissolve the
monomer, but will not dissolve the resulting polymer.
P r oDOT(C18)2 (5) is not soluble in acetonitrile, pro-
pylene carbonate, or solvent systems combining these
solvents with toluene or methylene chloride. Chlori-
nated solvents, such as chloroform and methylene
chloride, which do dissolve the monomer, also dissolved
the oligomers/polymers as they formed, leading to films
of poor quality which peel from the electrode after a few
scans.
A second method of forming thin films by spray
casting polymer solution (5 mg/mL in toluene) onto
the desired substrate using an air brush (Testor Corps.)
at 12 psi has been developed. Highly homogeneous
films with thicknesses controlled from 30 to 500 nm,
and surface roughnesses of 20 nm as determined by
profilometry, were attained. A photograph of spray
cast films of P P r oDOT(CH2OE t H x)2 (3) (left) and
P P r oDOT(C18)2 (4) (right) on ITO coated glass slides
is shown in Figure 5.
All polymer films were electroactive and could be
reversibly oxidized by cyclic voltammetry (CV). Table 3
lists the half-wave potentials for all spray cast and
electropolymerized films taken from CV scans. The
spray cast films have consistently higher half-wave
potentials (∼ 60-150 mVs) than the electropolymerized
films, which may be attributed to the more thorough
incorporation of the electolyte salt. The half-wave
potentials for electrodeposited films were similar to
other alkylenedioxythiophene polymers with values
close to -0.15 V. The E1/2 increased 100-200 mV with
an increase in the bulk of the substituents, which may
indicate that they interfere in a minimal way with the
conformation of the thiophene rings.
DOT(C18)2 (4) (bottom).
observed in redox properties. The cyclic voltammo-
grams (CVs) of P P r oDOT(C18)2 (4) and P P r oDOT-
(CH2OEtHx)2 (3) are seen in Figure 6. The luminance
plot superimposed on the CVs will be discussed later in
the section “Electrochromic Properties”. P P r oDOT-
(CH2OEtHx)2 (3) has a slightly higher potential (0.0
V) at which the onset of oxidation occurs in comparison
to P P r oDOT(C18)2 (4) (-0.3 V). Since the anodic peaks
fall very close to one another, P P r oDOT(CH2OEtHx)2
(3) shows a much sharper current response, while
P P r oDOT(C18)2 (4) gives a more broad redox process.
This trend is also observed in electrochemically polym-
erized and spray cast films of polymers P P r oDOT(Hx)2
(1) and P P r oDOT(EtHx)2 (2), suggesting that the late
onset is an effect of the branching of the alkyl chain
and not the formation of the film.
Op toelectr on ic Stu d ies. Table 4 lists the major
peaks in the UV-vis spectra of polymer solutions (1 mg/
50 mL) and films as well as the optical band-gap taken
for each film. The solution spectra were found to be
slightly blue shifted from that of the films with less
resolution of the fine structure. This is expected, due to
the disorder of the polymer chains in solution, leading
to a lower effective conjugation length.
The electrochemically polymerized films all exhibit a
similar dark blue-purple color in the neutral state and
are sky-blue transmissive when a sufficient potential
is applied to fully oxidize the film. The color of the
neutral state is similar to other electrochemically po-
lymerized alkylenedioxythiophene polymers. The optical
band-gaps ranged from 1.8 to 1.9 eV for all polymers
except P P r oDOT(EtHx)2 (2), which fell at 1.96 eV. This
small increase in band-gap is due to a sharper onset on
the low energy end of the visible spectrum. The UV-
vis spectra of the polymers often gave three peaks as
In comparing polymers with branched substituents
to those with linear substituents, clear trends are

7564 Reeves et al.
Macromolecules, Vol. 37, No. 20, 2004
F igu r e 8. Three-dimensional surface of the spectroelectro-
chemistry of a previously switched spray cast film of P P r o-
DOT(Hx)2 (1) on an ITO coated glass slide. Spectra were taken
at 50 mV increments between -0.4 to 0.5 V vs Fc/Fc+.
F igu r e 7. Optoelectronic spectra of spray cast films of PPro-
DOT(CH2OEtHx)2 (3) (top) and PProDOT(C18)2 (4) (bottom)
which are neutral and unswitched (solid line), electrochemi-
cally oxidized (dotted line), and neutral after electrochemical
switching (dashed line). The insets show the color swatches
of spray cast films which are, from right to left, neutral and
unswitched, electrochemically oxidized, and neutral after
electrochemical switching.
P P r oDOT(EtHx)2 (2) is purple, a slight difference as
perceived by the human eye in comparison to that of
the electrochemically polymerized film. The lack of
doping induced chain extension and the purple color of
the as-made spray cast films of P P r oDOT(EtHx)2 (2)
and P P r oDOT(C18)2 (4) is surprising and is an indica-
tion of how a small change in the structure can lead to
different optical properties in the solid state. The
original colors were inaccessible after the first redox
process. The optical band-gaps of the spray cast films
after switching were similar to the electrodeposited
films, ranging from 1.8 to 2.0 eV.
A full spectroelectrochemical series was performed on
electrodeposited and spray cast films of all polymers in
50 mV increments as illustrated for a spray cast film of
P P r oDOT(Hx)2 (1) (see Figure 8). As the working
potential increases, the absorbance in the visible region
decreases, as transitions at ∼950 and ∼1600 nm start
to grow. At higher potentials, the π-π* transition
continues to decrease as the 950 nm peak levels out and
the 1600 nm peak continues to grow. These NIR peaks
are attributed to charge carriers that form due to
oxidation of the film. By removal of one electron, a
polaron structure is formed, giving rise to the 950 and
1600 peaks.34,35 At high potentials, a second electron will
be lost, forming a bipolaron structure which is associ-
ated with a second overlapping peak also at ∼1600 nm.
The overall effect of oxidizing the film is a bleaching of
the dark blue-purple color to a more transmissive sky
blue. The three-dimensional plot of the spray cast film
of P P r oDOT(Hx)2 (1) is representative of all alkylene-
dioxythiophene polymers.
Figure 9 compares the spectroelectrochemistry of
spray cast films of P P r oDOT(CH2OE t H x)2 (3) and
P P r oDOT(C18)2 (4) in transmittance mode in order to
probe the potential dependence of the colored to trans-
missive transition. We find that for P P r oDOT(C18)2
(4) (top), the change in transmittance in the visible re-
gion occurs gradually over a 600 mV region. The spectral
series for P P r oDOT(CH2OEtHx)2 (3) (bottom), on the
other hand, exhibit a distinctly sharper change in
transmittance as a function of voltage. More than 60%
of the total transmittance change in the visible region
occurs in a 120 mV potential range (between 0.13 and
0.25 V vs Fc/Fc+). This sharp change in the electronic
properties with small potential changes is also observed
for P P r oDOT(EtHx)2 (2), suggesting that this behavior
is associated with the branched alkyl derivatives.
listed in Table 4, but each spectrum differed in intensity
and resolution. These peaks have been attributed to
vibronic coupling,31 Davydov splitting,32 or absorption
of polymer segments with different, yet discrete, chain
lengths.11 The fine structure is much more resolved for
the polymers P P r oDOT(EtHx)2 (2) and P P r oDOT-
(CH2OEtHx)2 (3), which have branched substituents.
P P r oDOT(Hx)2 (1) and P P r oDOT(Bu )2 exhibit the
peaks, but they exist as unresolved humps and the high
energy peak exists only as a shoulder.
The as-made spray cast films, on the other hand, vary
in the UV-vis peak values as well as the perceivable
color of the films. Figure 5 shows a photograph of spray
cast films of P P r oDOT(CH2OEtHx)2 (3) (left, red color)
and P P r oDOT(C18)2 (4) (right, deep purple color) on
different sized ITO coated glass slides. Figure 7 shows
the spectra of the as-made spray cast films, electro-
chemically oxidized spray cast films, and electrochemi-
cally switched neutral films along with the correspond-
ing color swatches derived from colorimetry results for
polymers P P r oDOT(CH2OEtHx)2 (3) and P P r oDOT-
(C18)2 (4).36 Upon oxidation, the color of the films
change from the highly absorbing state to a transmis-
sive sky blue state comparable to the rest of the
dioxythiophene family as the absorption in the 400-
800 nm region is reduced in intensity. Upon reduction
of these oxidatively doped films, the color switches to
an absorptive dark blue-purple. The perceivable color
of spray cast films of P P r oDOT(C18)2 (4) show a small
change upon redox switching, while P P r oDOT-
(CH2OEtHx)2 (3) shows a more significant change from
red to dark blue-purple, corresponding to a 20 nm red
shift in the optical spectrum. This shift is attributed to
a doping induced extension of the polymer chains giving
a longer effective conjugation length, a phenomenom
observed with P P r oDOT(Bu )2.25 The quinoid geometry
of the oxidized state leads to an ordering of the chains.33
After reduction, the extension of the chains is partially
preserved, leading to a larger effective conjugation
length compared to the as-made spray cast films.
P P r oDOT(Hx)2 (1) exhibited behavior similar to that
of P P r oDOT(CH2OEtHx)2 (3), switching from red to
transparent when oxidized and then to dark blue-purple
upon electrochemical reduction. The spray cast film of

Macromolecules, Vol. 37, No. 20, 2004
Electrochromic Dioxythiophene Polymers 7565
Ta ble 5. Electr och r om ic P r op er ties of Sp r a y Ca st F ilm s
% ∆Y
% ∆T
t (s)
PProDOT(Bu)2
51
58
70
56
42
51
70
79
80
51
0.23
0.37
0.73
0.57
2.2
1
2
3
4
Ta ble 6. Electr och r om ic P r op er ties of Electr och em ica lly
Dep osited F ilm s
% ∆Y
% ∆T
t (s)
PProDOT(Bu)2
50
57
41
46
76
71
53
48
0.45
0.43
0.50
0.60
1
2
3
E lect r och r om ic P r op er t ies. Recent studies on
P P r oDOT(Bu )2 found that the electrochemically po-
lymerized films gave a higher contrast ratio than drop
cast films from toluene solution.25 The drop cast films
were inhomogeneous and tended to crack and peel upon
switching with morphologies that tend to be compact
with inconsistent thicknesses. The spray cast films used
for the current studies, on the other hand, gave highly
homogeneous films of consistent thicknesses and low
surface roughness. Table 5 lists the change in relative
luminance, singular wavelength percent transmittance
contrast ratios, and 95% switching times for the spray
cast films of 150-250 nm thickness while Table 6 lists
the values for the electrochemically polymerized films
deposited in the same thickness range. By comparing
the values obtained in Tables 5 and 6, it is readily seen
that the electrochromic properties of the spray cast films
are now comparable to the electrodeposited films, which
suggests these polymers will prove useful for large area
electrochromic devices where processing is important.26
Relative luminance studies (% ∆Y) between fully
reduced and oxidized states were performed as a func-
tion of potential on all polymers using the CIE 1931 Yxy
color space.36 The luminance is a measure of the
transmissivity of a material to visible light calibrated
to the sensitivity of the human eye, making it a valuable
technique for measuring electrochromic materials that
change from colorful absorptive states to transmissive
states. The % ∆Y values for spray cast films range from
40 to 60% while the values for electrodeposited films
range from 45 to 60%. These values compare to other
known absorptive/transmissive electrochromic polymers
such as PProDOT(Me)2 (% ∆Y ) 61%) and exceed the
unsubstituted parent, PEDOT (% ∆Y ) 33%).
F igu r e 9. Top left: Spectroelectrochemistry of a previously
switched spray cast polymer film of P P r oDOT(C18)2 (4) at
applied potentials of (a) -0.95, (b) -0.65, (c) -0.45, (d) -0.25,
(e) -0.15, (f) -0.05, (g) +0.05, (h) +0.11, (i) +0.15, (j) 0.25, (k)
+0.35, (l), +0.55, and (m) +0.75 V vs Fc/Fc.+ Top right:
Percent transmittance as a function of applied potential taken
at 559 nm from the spectroelectrohemistry of P P r oDOT(C18)2
(4). Bottom left: Spectroelectrochemistry of a previously
switched spray cast film of P P r oDOT(CH2OEtHx)2 (3) at
applied potentials of (a) -0.15, (b) +0.06, (c) +0.13, (d) +0.14,
(e) +0.15, (f) +0.16, (g) +0.25, (h) +0.45, (i) +0.65, and (j) +0.85
V vs Fc/Fc.+ Bottom right: Percent transmittance as a function
of applied potential taken at 609 nm from the spectroelectro-
chemistry of P P r oDOT(CH2OEtHx)2 (3).
F igu r e 10. Visible spectra of spray cast films of P P r oDOT-
(Hx)2 (1) (solid line) and P P r oDOT(CH2OEtHx)2 (3) (dotted
line). P P r oDOT(CH2OEtHx)2 (3) shows less tailing on the
low energy side in comparison to P P r oDOT(Hx)2 (1).
By superimposing the CV and relative luminance
results, the relationship between the electrochemical
properties and the optical properties of the film are
readily seen. Figure 6 shows the relative luminance
trace with the current response for spray cast films
of P P r oDOT(CH2OEtHx)2 (3) (top) and P P r oDOT-
(C18)2 (4) (bottom). P P r oDOT(C18)2 (4) (bottom)
shows a gradual change, beginning at -1.0 V and
continuing until saturation is reached at 0.25 V.
P P r oDOT(CH2OEtHx)2 (3), by comparison, gives a
much sharper transition for both the CV and % Y
results, undergoing zero luminance change until the
potential reaches 0.1 V, consistent with spectroelectro-
chemical studies discussed earlier. Beyond this poten-
tial, the polymer exhibits a 44% change in relative
luminance with a 100 mV potential increase. The linear
chain polymers, P P r oDOT(Hx)2 (1) and P P r oDOT-
(Bu )2, show broad curves similar to P P r oDOT(C18)2
Although the fundamental reason for this structure-
property trend is unknown at this time, it is postulated
that the branched chains interact with the thio-
phene backbone to limit the effective conjugation length.
This provides a more distinct onset for the absorption
on the low energy end due to a decrease in the popula-
tion of chains with long effective conjugation lengths.
Figure 10 compares the visible spectra of spray cast
polymer films of P P r oDOT(Hx)2 (1) and P P r oDOT-
(CH2OEtHx)2 (3). P P r oDOT(Hx)2 (1) has a lower
band-gap due to the extension of the absorption into the
low energy end while the absorbance of P P r oDOT-
(CH2OEtHx)2 (3) drops distinctly at wavelengths longer
than 600 nm. If the chains all have a smaller range of
effective conjugation lengths, this will lead to a more
distinct threshold voltage and give the film a smaller
potential window where the color transition occurs.

7566 Reeves et al.
Macromolecules, Vol. 37, No. 20, 2004
Ta ble 7. Color a tion Efficien cy Va lu es for Sp r a y Ca st a n d
Electr od ep osited F ilm s
CE(cast)a (cm2/C)
CE(echem)b (cm2/C)
PProDOT(Bu)2
1137
833
1050
1235
472
1365
1270
1204
1232
NA
1
2
3
4
a
Composite coloration efficiency taken at 95% of a full switch
b
for electrochemically deposited films of 150 nm thickness. Com-
posite coloration efficiency taken at 95% of a full switch for
previously switched spray cast films of 150 nm thickness.
F igu r e 11. Percent transmittance vs time (dashed line)
superimposed upon charge vs time (solid line) measured during
a potential switch between -0.5 and +1.2 V vs Fc/Fc+ on a
spray cast polymer film of P P r oDOT(CH2OEtHx)2 (3).
(4). P P r oDOT(EtHx)2 (2) shows a sharp transition in
the luminance as a function of potential similar to
P P r oDOT(CH2OEtHx)2 (3), demonstrating the effects
of linear vs branched derivatives on electrochromic
properties.
Switching studies of spray cast and electrodeposited
polymer films were performed by monitoring the % T
at λmax as a funtion of time during a potential step where
the polymer oxidizes and reduces. The switching times,
taken at 95% of the full switch, give subsecond times
for all films with the exception of P P r oDOT(C18)2 (4).
Earlier studies showed that increasing the number of
substituents on the alkylenedioxy ring decreased the
switching time substantially.21 Increasing steric bulk of
the substituents, on the other hand, does not signifi-
cantly decrease the switching time as polymers 1-3
gave similar values. P P r oDOT(C18)2 (4) gave a much
higher value at 2.2 s. The long alkyl chains likely
decrease ion flux, leading to longer switching times.
Color a tion Efficien cy. Composite coloration ef-
ficiency is the change in optical density as a function of
charge passed as given by eq 1
F igu r e 12. Slow coloration efficiency and percent transmit-
tance vs passed charge for a 150 nm film of P P r oDOT-
(CH2OEtHx)2 (3).
with the exception of P P r oDOT(C18)2 (4). Since the
change in optical density is similar to PProDOT(Me)2
films, the increase in composite CE values is due to a
decrease in charge needed to oxidize the films. One
possible explanation is that the conductivity of the
neutral state is higher for these polymers, leading to
less current loss, which would increase the CE.
We have also measured the coloration efficiencies of
all spray cast films by passing a low constant current
leading to bleaching of the films over a period of 20 s.
As an example, Figure 12 shows the change in the
transmittance of a film of P P r oDOT(CH2OEtHx)2 (3),
along with the variation of the coloration efficiency, as
a function of the amount of charge passed during this
slow bleaching. The overall transmitance contrast (%
∆T ) 65%) for the slow switching of this film is similar
to those observed with the large potential step switching
experiment. The η value undergoes a maximum at
∼2680 cm2/C as this is the initial coloration efficiency
and follows a form similar to that observed previously
in the literature.38 The other polymers had peak values
ranging from 650 to 2350 cm2/C. Considering the
physical significance of the peak η values, this can be
taken as the coloration efficiency for the initial change
during the electrochromic switch. A peak is observed
as the electrode charges (e.g., double layer) and the
optical response lags the current slightly when Faradaic
doping begins. Although the charging process is linear
with time (constant current), the % T curve tends to
saturate and this results in lower η values at higher
doping levels.
η ) ∆OD/Qd
(1)
where ∆OD is the change in optical density and Qd is
the charge passed in order for the change to occur.
The optical density change is determined by measur-
ing the % T at λmax before and after a full switch using
eq 2.
∆OD ) log(% T1/% T2)
(2)
Figure 11 shows the relationship between the charge
and % T as a function of time for a spray cast film of
P P r oDOT(CH2OEtHx)2 (3). The composite coloration
efficiency can be calculated at any time, but we have
chosen to report a value at 95% of the full switch in
order to allow direct comparison of different systems.37
An earlier study obtained values of 375 cm2/C for
electrodeposited films of PProDOT(Me)2 while PEDOT,
in comparison, was found to have CE values of 186 cm2/
C. Although the charge needed for the switch to occur
was similar for both polymers, PProDOT(Me)2 gave
twice the change in optical density as did PEDOT,
leading to a CE value roughly twice as large.
Con clu sion s
Table 7 lists the composite coloration efficiency values
for spray cast and electrodeposited films of all films
taken at 95% of the full switch. The CE values obtained
are two to three times larger than PProDOT(Me)2 films
Four new organic solvent soluble and spray process-
able disubstituted propylenedioxythiophene polymers
have been synthesized by Grignard metathesis polym-

Macromolecules, Vol. 37, No. 20, 2004
Electrochromic Dioxythiophene Polymers 7567
hexyl bromide, 2-ethylhexyl bromide, diethyl malonate, octa-
decanol, 2-ethylhexanol, 1.0 M MeMgBr in butyl ether, and
all other inorganic reagents and solvents were purchased from
Aldrich. Toluene was distilled over sodium before use. THF
was dispensed from a pure pack anhydrous keg and further
dried by an aluminum oxide column.
erization on the 1-5 g scale. The substituents used were
designed to increase polymer solubility, while maintain-
ing the desirable electrochromic properties of less
soluble derivatives. A technique to spray cast polymer
solutions onto ITO coated glass slides to form highly
homogeneous thin films was developed, which greatly
improved the electrochromic properties in comparison
to earlier reported drop cast films, exhibiting a dark
blue-purple color when neutral and a sky-blue trans-
missive color when oxidized. The relative luminance
change ranged from 40 to 60%, a comparable value to
the rest of the alkylenedioxythiophene family,36 and
subsecond switching times were found to be indepen-
dent of structure or film formation with the exception
of the long alkyl chain derivative, P P r oDOT(C18)2 (4).
The CE values of all polymers exceeded the largest
previously reported value for poly(alkylenedioxythio-
phenes).37 The desirable electrochromic properties, ease
in synthesis, solubility, film processability, and high
coloration efficiency values make these materials excel-
lent candidates for use in large area electrochromic
devices. A distinct structure-property relationship was
observed in this series of polymers. The polymers with
branched substituents had higher band-gaps and the
color change occurred over a smaller voltage range in
comparison to the polymers with linear substituents.
This is postulated to be due to a limited effective
conjugation length allowed in the solid state when
branched substituents are present. Further studies are
underway to understand this relationship.
Gen er a l P r oced u r e for th e Syn th esis of Alk yla ted
Dieth yl Ma lon a te. In a 5 L flame dried three-neck round-
bottom flask equipped with an argon inlet, a condenser, and
an addition funnel were combined 2 L of dry THF, 3.5 mol of
alkyl bromide (3 equiv), and 3.5 mol of NaH. The flask was
cooled to 0 °C, and 1.15 mol of freshly distilled diethyl
malonate was added dropwise through the addition funnel.
When the addition of the malonate was completed, the mixture
was refluxed overnight. The flask was then cooled at 0 °C and
the remaining sodium hydride was quenched by adding water
dropwise. The mixture was then poured into brine (2 L),
extracted two times with ether, and washed with brine. The
solvent and the alkyl bromide were removed under vacuum.
The crude oil obtained was then used in the next step without
further purification.
Gen er a l P r oced u r e for th e Syn th esis of Diols 9 a n d
10. In a 5 L flame dried three-neck round-bottom flask
equipped with an argon inlet, a condenser, and an addition
funnel were combined 2 L of dry ethyl ether and 1.7 mol of
LiAlH4 powder. The crude dialkyl malonate (1.13 mol) was
added dropwise at 0 °C. When the addition was completed,
the mixture was allowed to warm to room temperature. The
reaction mixture was stirred under argon for 20 h.
2,2-Dih exylp r op a n e-1,3-d iol (9). 1H NMR (300 MHz,
CDCl3): δ 3.59 (d, 4H, J ) 5.3 Hz), 2.39 (t, 2H, J ) 5.3 Hz),
1.40-1.10 (m, 20H), 0.90 (t, 6H, J ) 7.3 Hz). 13C NMR (75
MHz, CDCl3): δ 69.7, 41.2, 32.0, 31.1, 30,5, 29.9, 23.1, 22.9,
14.3. HRMS: calcd for C15H32O2, 245.2481; found, 245.2475.
Anal. Calcd for C15H32O2: C, 73.71; H, 14.20. Found: C, 74.12;
H, 14.18.
Exp er im en ta l Section
2,2-Bis(2-eth ylh exyl)-p r op a n e-1,3-d iol (10). 1H NMR
(300 MHz, CDCl3): δ 3.65 (s, 4H), 2.41 (s, 2H), 1.40-1.10 (m,
22H), 0.95-0.80 (m, 12H). 13C NMR (75 MHz, CDCl3): δ 70.1,
42.8, 37.1, 34.9, 33.7, 29.0, 27.9, 23.4, 14.4, 10.8. HRMS: calcd
for C19H41O2 (M + H)+, 301.3106; found, 301.3103. Anal. Calcd
for C19H40O2: C, 75.94; H, 13.42. Found: C, 75.95; H, 12.35.
Gen er a l P r oced u r e for th e Tr a n seth er ifica tion of 3,4-
Dim eth oxyth iop h en e w ith Diols. First, 21 mmol of 3,4-
dimethoxythiophene, 42 mmol of diol, 2.1 mmol of p-toluene-
sulfonic acid, and 200 mL of toluene were combined in a 500
mL flask equipped with a Soxhlet extractor with type 4A
molecular sieves in a cellulose thimble. The solution was
refluxed overnight. The reaction mixture was cooled and
washed once with water. The toluene was removed under
vacuum, and the crude product was purified by column
chromatography on silica gel with 3:2 hexanes/methylene
chloride.
In str u m en ta tion . GPC was performed on two 300 × 7.5
mm Polymer Laboratories PLGel 5 µM mixed-C columns with
Waters Associates liquid chromatography 757 UV absorbance
detector at 585 nm or a 2996 photodiode array detector.
Polymer solutions were prepared in THF and filtered through
a 50 µM filter before injection. A constant flow rate of 1 mL/
min was used. Molecular weights were obtained relative to
polystyrene standards. MALDI-TOF mass spectrometry was
performed with a Bruker ProFLEX III reflectron instrument
with delayed extraction. HABA (2-(4-hydroxyphenylazo)ben-
zoic acid) and terthiophene matrices were used. NMR spectra
were recorded on a Gemini 300 FT-NMR or a VXR 300 FT-
NMR. High-resolution mass spectrometry was carried out on
a Finnigan MAT 95Q mass spectrometer. Electrochemical
studies were carried out using an EG&G PAR model 273A
potentiostat/galvanostat in a three electrode cell configuration
consiting of a Ag° wire pseudo reference electrode calibrated
with a Fc/Fc+ couple, a glassy carbon button, platinum button,
or ITO-coated glass slide (7 × 50 × 0.6 mm, 20 Ω/cm) as the
working electrode, and a Pt flag as the counter electrode in a
0.1 M tetrabutylammonium hexafluorophospate propylene
carbonate solution. All absorption spectra from thermo-
chromism, spectroelectrochemistry, and switching studies were
carried out on a Varian Cary 500 scan UV-vis-NIR spectro-
photometer. Thermochromism was performed using a SPV
1 × 1 Varian Cary duel cell peltier accessory. Colorimetry
was carried out using a Minolta CS-100 Chroma Meter and
CIE recommended normal/normal (0/0) illuminating/viewing
geometry for transmittance measurements.36 The sample was
illuminated from behind with a D50 (5000 K) light source in
a light booth specially designed to exclude external light.
Fluorescence data was collected with a Spex F-112 photon
counting fluorimeter at room temperature. Emission quantum
yields were measured relative to Rhodamine 6G and Coumarin
6 in methanol where φf ) 1.00, and optical density of solutions
was kept below A ) 0.1. The film fluorescence was carried out
according to a known procedure.39
3,3-Bis(br om om eth yl)-3,4-dih ydr o-2H-th ien o[3,4-b][1,4]-
d ioxep in e [P r oDOT(CH2Br )2]. Yield: 5.2 g of white crystal-
1
line solid (73%). Mp: 66-68 °C. H NMR (300 MHz, CDCl3):
δ 6.49 (s, 2H), 4.10 (s, 4H), 3.61 (s, 4H). 13C NMR (75 MHz,
CDCl3): δ 148.5, 105.7, 74.1, 46.1, 34.4. HRMS calcd for
C9H10O2Br2S, 339.8768; found, 339.8820. Anal. Calcd for
C9H10O2Br2S: C, 31.60; H, 2.95; S, 9.37 Found: C, 31.83; H,
2.99; S, 9.20.
3,3-Dih e xyl-3,4-d ih yd r o-2H -t h ie n o[3,4-b][1,4]d ioxe -
1
p in e [P r oDOT(Hx)2, 11]. Yield: 10.7 g of clear oil (95%). H
NMR (300 MHz, CDCl3): δ 6.42 (s, 2H), 3.88 (s, 4H), 1.45-
1.20 (m, 20 H), 0.95-0.82 (m, 6H). 13C NMR (75 MHz,
CDCl3): δ 149.9, 104.9, 77.8, 43.9, 32.0, 32.0, 30.4, 23.0, 22.9,
14.3. HRMS: calcd for C19H32O2S, 324.2123; found, 324.2120.
Anal. Calcd for C19H32O2S: C, 70.32; H, 9.94; S, 9.88 Found:
C, 70.48; H, 10.48; S, 9.78.
3,3-Bis(2-eth ylh exyl)-3,4-d ih yd r o-2H-th ien o[3,4-b][1,4]-
d ioxep in e [P r oDOT(E t H x)2, 12] The crude oil obtained
was purified by column chromatography (3:2) hexanes/di-
chloromethane followed by another column using 3:1 hexanes/
dichloromethane to afford 6.0 g of clear oil (57%). 1H NMR
(300 MHz, CDCl3): δ 6.43 (s, 2H), 3.93 (s, 4H), 1.2-1.5 (m,
Syn th esis. 3,4-Dimethoxythiophene was synthesized using
a known procedure.40 2,2-bis(bromomethyl)-1,3-propanediol,

7568 Reeves et al.
Macromolecules, Vol. 37, No. 20, 2004
22H), 0.75-1.0 (m, 12H). 13C NMR (300 MHz, CDCl3): δ 150.0,
104.61, 78.0 (t), 45.5, 38.7, 35.0, 33.8, 29.0, 28.0, 23.3, 14.4,
10.8. HRMS: calcd for C23H40O2S, 380.2749; found, 380.2753.
Anal. Calcd for C23H40O2S: C, 72.58; H, 10.59; S, 8.42. Found:
C, 72.78; H, 10.30; S, 8.24.
Gen er a l P r oced u r e for th e Willia m son Eth er ifica tion
of P r oDOT(CH2Br )2. A 250 mL flame dried round-bottom
flask filled with 50 mL of DMF, 8.7 mmol of alcohol (3 equiv),
and 17.5 mmol of NaH (6 equiv) was heated at 110 °C
overnight. Then 2.9 mmol of P r oDOT(CH2Br )2 was added and
the reaction continued at 110 °C for another 24 h. After
completion, the flask was cooled and added to 200 mL of brine
and extracted three times with ethyl ether. The organic layer
was then washed three times with water and dried over
magnesium sulfate, and the solvent was removed by rotary
evaporation under reduced pressure. The resulting crude
product was purified by column chromatography.
3,3-Bis(oct a d ecyloxym et h yl)-3,4-d ih yd r o-2H -t h ien o-
[3,4-b][1,4]d ioxep in e [P r oDOT(C18)2, 5]. The orange solid
obtained was purified by column chromatography (3:2 hexanes,
methylene chloride) to afford 0.86 g of white solid (68%). Mp:
48-50 °C. 1H NMR (300 MHz, CDCl3): δ 6.44 (s, 2H), 4.00 (s,
4H), 3.48 (s, 4H), 3.39 (t, 4H, J ) 6.6 Hz), 1.53 (m, 4H), 1.25
(m, 64H), 0.88 (t, 6H, J ) 6.9 Hz). 13C NMR (75 MHz, CDCl3):
δ 149.9, 105.2, 73.9, 71.9, 69.7, 47.9, 32.1, 29.75, 26.3, 22.9,
14.3. HRMS: calcd for C45H84O4S, 720.6090; found, 720.6047.
Anal. Calcd for C45H84O4S: C, 74.94; H, 11.74; O, 8.87; S, 4.45.
Found: C, 74.69; H, 11.37; O, 9.19; S, 4.33.
Anal. Calcd for C19H30O2SBr2: C, 47.31; H, 6.27; S, 6.65; Br,
33.13. Found: C, 47.83; H, 6.79; S, 6.88; Br, 32.79.
6,8-Dib r om o-3,3-b is(2-e t h ylh e xyl)-3,4-d ih yd r o-2H -
th ien o[3,4-b][1,4]dioxepin e [P r oDOT(EtHx)2Br 2, 14]. Yield:
1
6.3 g of clear oil (80%). H NMR (300 MHz, CDCl3): δ 4.00 (s,
4H), 1.15-1.5 (m, 22H), 0.8-1.0 (m, 12H). 13C NMR (300 MHz,
CDCl3): δ 147.3, 90.5, 78.6, 45.8, 38.8, 35.0, 29.0, 28.0, 23.3,
14.4, 10.8. HRMS: calcd for C23H38O2SBr2, 538.0940; found,
538.0944. Anal. Calcd for C23H38O2SBr2: C, 51.31; H, 7.11; S,
5.96 Found: C, 51.28; H, 7.00; S, 6.04.
Gen er a l P r oced u r e for Gr ign a r d Meta th esis P olym -
er iza tion of P r oDOT(R)2Br 2. Into a flame dried 250 mL
round-bottom flask were added dry THF (150 mL) and 3.4
mmol of ProDOT(R)2Br2 under argon. Then methylmagnesium
bromide (3.75 mL, 3.45 mmol, 0.918 M) was slowly added by
addition funnel. The mixture was then refluxed for 1 h.
Afterward, the flask was cooled and Ni(dppp)Cl2 (18.4 mg,
0.0341 mmol) was added and the reaction was heated at reflux
overnight under argon. The solution was then cooled and the
polymer was precipitated by pouring the solution in 400 mL
of methanol. The dark purple solid was purified by Soxhlet
extraction with methanol for 24 h, hexanes for 48 h, and finally
chloroform for 24 h. The chloroform was evaporated under
reduced pressure to afford purple solid.
P oly(3,3-bis-octadecyloxym eth yl-3,4-dih ydr o-2H-th ien o-
[3,4-b][1,4]d ioxep in e [P P r oDOT(C18)2, 4]. Yield: 1.27 g of
purple solid (52%).1H NMR (300 MHz, benzene-d6): δ 4.30 (bs,
4H), 3.58 (bs, 4H), 3.35 (bs, 4H), 1.67 (bs, 4H), 1.40 (m, 64H),
0.96 (m, 6H). 13C (75 MHz, benzene-d6): δ 145.8, 115.0, 71.9,
48.3, 32.4, 30.4, 30.3, 30.2, 29.9, 26.8, 23.3, 14.5. GPC
analysis: Mn ) 33445 g mol-1; Mw ) 47958 g mol-1; PDI )
1.43.
3,3-Bis(2-eth ylh exyloxym eth yl)-3,4-d ih ydr o-2H-th ien o-
[3,4-b][1,4]dioxepin e [P r oDOT(CH2OEtHex)2, 6]. The crude
oil obtained was purified by column chromatography (CH2Cl2)
1
to afford 1.8 g of clear oil (70%). H NMR (300 MHz, CDCl3):
δ 6.42 (s,4H), 3.98 (s, 4H), 3.44 (s, 4H), 3.25 (d, 4H), 1.2-1.6
(m, 18H), 0.8-1.0 (m, 12H). 13C NMR (75 MHz, CDCl3): δ,
149.7, 104.9, 74.3, 73.8, 69.8, 47.9, 39.6, 30.7, 29.1, 24.0, 23.1,
14.1, 11.1. HRMS: calcd for C25H44O4S, 440.2960; found,
440.2964. Anal. Calcd for C25H44O4S: C, 68.14; H, 10.06; S,
7.28. Found: C, 68.17; H, 10.39; S, 7.26.
Gen er a l P r oced u r e for th e Br om in a tion of P r oDOT
Der iva tives. In a two-neck 250 mL round-bottom flask filled
with 80 mL of chloroform, 1.5 g (2.1 mmol) of ProDOT was
added and the solution was bubbled under argon for 20 min.
Then 1.12 g (6.3 mmol) N-bromosuccinimde was added, and
the solution was stirred for 20 h. After completion, the solvent
was removed by rotary evaporation under reduced pressure,
and the resulting residue was purified by column chromatog-
raphy (4:1 hexanes/methylene chloride).
P oly(6,8-Dibr om o-3,3-bis(2-eth yl-h exyloxym eth yl)-3,4-
dih ydr o-2H-th ien o[3,4-b][1,4]dioxepin e) [P P r oDOT(CH2O-
EtHx)2, 3]. Yield: 0.350 g of purple solid (93%). 1H NMR (300
MHz, benzene-d6): δ 4.25 (bs, 4H), 3.58 (bs, 4H), 3.25 (bs, 4H),
1.62-1.30 (m, 22H), 1.09-0.99 (m, 12H). 13C (75 MHz,
benzene-d6): δ 146.2, 115.3, 75.1, 74.8, 71.0, 48.7, 40.4, 31.6,
30.0, 25.0, 24.0, 14.9, 11.9. GPC analysis: Mn ) 47300 g mol-1
;
Mw ) 74850 g mol-1; PDI ) 1.58.
P oly(3,3-b is(2-et h ylh exyl)-3,4-d ih yd r o-2H -t h ien o[3,4-
b][1,4]d ioxep in e) [P P r oDOT(EtHx)2, 2]. Yield: 1.05 g of
purple solid (63%) 1H NMR (300 MHz, CDCl3): δ 4.19 (bs, 4H),
1.8-1.15 (m, 22H), 1.1-0.80 (m, 12H). 13C (75 MHz, benzene-
d6): δ 146.0, 115.1, 78.9, 46.1, 38.7, 35.8, 34.4, 29.5, 24.1, 14.9,
11.5. GPC analysis: Mn ) 42927 g mol-1; Mw ) 62602 g mol-1
PDI ) 1.46.
;
6,8-Dibr om o-3,3-bis(octa d ecyloxym eth yl)-3,4-d ih yd r o-
2H-th ien o[3,4-b][1,4]d ioxep in e [P r oDOT(C18)2Br 2, 7]. The
white solid obtained was purified by column chromatography
(4:1 hexanes, methylene chloride) and recrystallized from
CH2Cl2 to afford 1.64 g (90%) of white crystals. Mp: 65-66
°C 1H NMR (300 MHz, CDCl3): δ 4.07 (s, 4H), 3.46 (s, 4H),
3.38 (t, 4H, J ) 6.6 Hz), 1.50 (m, 4H), 1.25 (m, 64H), 0.87
(t, 6H, J ) 6.9). 13C NMR (75 MHz, benzene-d6) 148.1, 91.8,
72.1, 69.7, 48.3, 32.7, 30.6, 30.2, 26.9, 23.5, 14.7. HRMS: calcd
for C45H82O4SBr2: 876.4301 Found: 876.4305. Anal. Calcd for
P oly(3,3-Dih exyl-3,4-d ih yd r o-2H -t h ien o[3,4-b][1,4]d i-
oxep in e) [P P r oDOT(Hx)2, 1]. Yield: 5.2 g of purple solid
(62%).1H NMR (300 MHz, CDCl3): δ 3.95 (bs, 4H), 1.62-1.2
(m, 20H), 0.97-0.80 (m, 6H);13C (75 MHz, benzene-d6):
δ
146.4, 115.3, 78.0, 44.3, 32.6, 31.0, 23.5, 14.8. GPC analysis:
Mn) 38087 g mol-1; Mw ) 65893 g mol-1; PDI ) 1.73.
Ack n ow led gm en t. We gratefully acknowledge fi-
nancial support from the AFOSR (F49620-03-1-0091)
and the ARO MURI program (DAAD 19-99-1-0316). We
acknowledge Garry B. Cunningham for his technical
assistance with the solution and film fluorescence
studies.
C
45H82O4SBr2: C, 61.49; H, 9.40; O, 7.28; S, 3.65. Found: C,
61.36; H, 9.51; O, 7.45; S, 3.57.
6,8-Dibr om o-3,3-bis(2-eth ylh exyloxym eth yl)-3,4-d ih y-
dr o-2H-th ien o[3,4-b][1,4]dioxepin e [P r oDOT(CH2OEtHx)2-
1
Br 2), 8]. Yield: 5.43 g of clear oil (98%). H NMR (300 MHz,
CDCl3): δ 4.09 (s, 4H), 3.49 (s, 4H), 3.28 (d, 4H), 1.2-1.6 (m,
18H), 0.8-1.0 (m, 12H). 13C NMR (300 MHz, CDCl3): δ147.2,
91.0, 74.6, 70.0, 48.2, 39.9, 30.9, 29.4, 24.2, 23.3, 14.4, 11.4.
HRMS: calcd for C25H42O4SBr2, 596.1171; found, 596.1161.
Anal. Calcd for C25H42O4SBr2: C, 50.17; H, 7.07; S, 5.36.
Found: C, 50.43; H, 7.09; S, 5.16.
Refer en ces a n d Notes
(1) Handbook of Conducting Polymers, 2nd ed.; Skotheim, T. A.,
Elsenbaumer, R. L., Reynolds, J . R., Eds.; Marcel Dekker:
New York, 1998.
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6,8-Dibr om o-3,3-d ih exyl-3,4-d ih yd r o-2H-th ien o[3,4-b]-
[1,4]d ioxep in e [P r oDOT(Hx)2Br 2, 13]. Yield: 14.4 g of clear
oil (91%).1H NMR (300 MHz, CDCl3): δ 3.93 (s, 4H), 1.45-
(3) (a) Roncali, J . Chem. Rev. 1997, 97, 173. (b) Roncali, J . Chem.
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(4) Granstrom, M.; Harrison, M. G.; Friend, R. H. In Electro-
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1
1.15 (m, 20H), 0.90 (t, 6H, J ) 7.0 Hz); H NMR (300 MHz,
CDCl3): δ 147.4, 104.8, 90.8, 78.3, 44.2, 31.9, 30.3, 22.9, 14.3.
HRMS: calcd for C19H30O2SBr2, 480.0333; found, 480.0334.

Macromolecules, Vol. 37, No. 20, 2004
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