Tethered PProDOTs: Conformationally restricted 3,4-propylenedioxythiophene based electroactive polymers

Article abstract of DOI:10.1039/b610232h

Herein we report a complete family of conformationally restricted PProDOT derivatives with varying alkylene tether lengths. It was found that variation of the tether length and structure of the electropolymerizable monomer was successful in the fine-tuning of the electrochemical and optical properties of the subsequent material. It was found that the band gap of the materials could be varied between 1.94 and 2.26 eV, with the "sweet spot" for obtaining the maximum electronic band gap existing at the n = 6 tether length, while maintaining low redox potentials. It was also found that these polymers exhibited stable electrochromic behavior with colors varying from blue-purple to orange in their neutral states and transmissive in their doped states. The Royal Society of Chemistry 2007.

Full text of DOI:10.1039/b610232h

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Tethered PProDOTs: conformationally restricted 3,4-
propylenedioxythiophene based electroactive polymers{
Ryan M. Walczak, John S. Cowart Jr. and John R. Reynolds*
Received 18th July 2006, Accepted 13th October 2006
First published as an Advance Article on the web 2nd November 2006
DOI: 10.1039/b610232h
Herein we report a complete family of conformationally restricted PProDOT derivatives with
varying alkylene tether lengths. It was found that variation of the tether length and structure of
the electropolymerizable monomer was successful in the fine-tuning of the electrochemical and
optical properties of the subsequent material. It was found that the band gap of the materials
could be varied between 1.94 and 2.26 eV, with the ‘‘sweet spot’’ for obtaining the maximum
electronic band gap existing at the n = 6 tether length, while maintaining low redox potentials. It
was also found that these polymers exhibited stable electrochromic behavior with colors varying
from blue–purple to orange in their neutral states and transmissive in their doped states.
near IR into the visible spectrum; therefore, they are referred
to as ‘‘multichromic’’ polymers.14
Introduction
Polyheterocycles have emerged at the forefront of new
materials research, in part because of their flexibility towards
synthetic modifications, and have been shown to exhibit a wide
range of useful properties that are highly dependent on the
repeat unit structure.1–7 Perhaps the most useful fundamental
property that can be controlled is the polymer band gap, Eg,
whose magnitude defines the color of an electronic device, and
determines the cutoff wavelength at which a polymer-based
solar cell can operate. The most common method for altering
the band gap of a conjugated polymer is by making changes to
the polymer repeat unit identity, for example substitution of
one heteroatom for another. Such modifications are often
accompanied by results that are difficult to predict a priori,
and there is limited ability to fine tune.
Another method for the modification of extended conjuga-
tion effects is by rotationally disrupting the degree of p-overlap
of the polymer backbone. Specifically, the extent of rotational
disruption can be controlled by restricting the rotational
freedom of polymer repeat units with a tether. These materials
can be divided into two classes: those which are polymerized
from two monomeric heterocycles linked together by the
tether (polythiophene derivatives are thus tetrafunctional),16
and those which are polymerized from macrocyclic dimers
conformationally restrained by the tether (polythiophene
derivatives are bifunctional).17–22 The difference in polymer
structure is illustrated in Fig. 1, where it can be seen that the
bifunctional macrocyclic structures form linear polymers,
whereas the tetrafunctional monomers can generate densely
cross-linked polymer networks.
Extended conjugation effects through the backbone of a
conducting polymer govern the materials properties; disrupt-
ing the degree of conjugation can have drastic effects. One
method for fine tuning the band gap by altering the conjuga-
tion that has been employed to a limited extent is introducing
conjugation breaks into the polymer backbone.8–13 For
example, our group published work in which EDOT moieties
were substituted onto the 3- and 6-positions of a carbazole
derivative, thus creating a molecule with cross-conjugation.
When copolymerized with BiEDOT, it was found that the
band gap and color states of the polymers could be finely
tuned by varying the monomer feed ratio.14,15 However, this
change in band gap was also accompanied by an increased
polymer oxidation potential with increasing band gap. These
conjugation breaks also have the effect of shortening the
conjugation length of the polaronic and bipolaronic doped
states, thus shifting the oxidized polymer absorbances from the
In previous work, we have shown that a conformationally
restricted poly(3,4-propylenedioxythiophene) (PProDOT)
derivative exhibited an elevated band gap value of 2.1 eV
The George and Josephine Butler Polymer Research Laboratory,
Department of Chemistry, Center for Macromolecular Science and
Engineering, University of Florida, Gainesville, Florida, 32611, USA
{ Electronic supplementary information (ESI) available: electropoly-
merization plots for 4 and 5, CVs for Poly4 and Poly5; competitive
NMR data for 3c–e; full experimental details. See DOI: 10.1039/
b610232h
Fig. 1 Schematic representations of the polymers derived from (top)
bifunctional macrocyclic structures and (bottom) tetrafunctional
linear structures.
254 | J. Mater. Chem., 2007, 17, 254–260
This journal is ß The Royal Society of Chemistry 2007

View Article Online
with respect to an untethered analog, which had a band gap of
1.75 eV.23 This rotational restriction imposed by the alkylene
tether prevented the polymer from adopting the preferred
planar conformation, explaining the elevated band gap, and
consequently exhibited an orange color (as opposed to the
untethered polymer, which was purple). When electro-
chemically oxidized, the polymer was found to be transmissive
over the visible region and highly absorbing in the near IR,
suggesting that the tether allows for bond rotation to a more
planar conformation in the doped state. It was also found that
the polymer synthesized from the macrocyclic derivative
exhibited superior electrochemical behavior with respect to
the polymer synthesized from the tetrafunctional linear
derivative. Here, we report on a family of conformationally
restricted PProDOT derivatives with alkylene tether lengths of
n = 4–10 and 12. It was found that variation of the tether
length and structure of the electropolymerizable monomer was
successful in the fine-tuning of the electrochemical and optical
properties of the subsequent material.
respective diols with p-toluenesulfonyl chloride in pyridine,
yielded linear monomers 2a–h, and an untethered analog,
compound 4, was synthesized by a protocol previously reported
by our group.23 Subsequent conversion to the dimerized
product was accomplished by a lithiation with n-butyllithium
followed by oxidative coupling with ferric acetylacetonate by
adapting a procedure previously reported by Zhu and Swager
in the synthesis of BiEDOT.28 For a successful macrocycliza-
tion, it was necessary to use high dilution conditions, and was
accomplished by the drop-wise addition of the dilithium salt
to the Fe(acac)3 solution. Since dilithium salts of compounds
2a–h were insoluble in THF, as well as other polar aprotic
solvents compatible with lithiation conditions, the addition of
HMPA to the solution after deprotonation was successful in
dissolving the lithium aggregates, thus producing macrocycles
3b–e in modest yields. The longer chain derivatives 2f–h, as
well as the butyl derivative 2a, did not undergo macrocycliza-
tion. It is presumed that the longer chain derivatives were too
long to affect such an entropically unfavorable reaction, and
the butyl chain was too short for the reaction to adopt proper
reaction geometry. Therefore, the intermolecular dimerization
reactions were the only isolated products. Though the yields
for the successful reactions were lower than desired for a
typical organic synthesis (presumably due to the formation
of oligomeric side-products), they were the end-product
for subsequent electrochemical polymerization; ergo a suffi-
cient quantity of material was synthesized to perform the
necessary small molecule characterization and electrochemical
experiments.
Synthesis
The main goal of this project was the modulation of polymer
properties through the use of a variable length alkylene tether,
thus conformationally restricting the polymer backbone,
affecting the degree of p-overlap, and modifying the polymer
effective conjugation length. It was hypothesized that such a
modification could directly alter the polymer band gap and
therefore change the polymer color and electrochromism.
Compound 1, ProDOT-OH (synthesized as previously
reported24,25), has proven to be a valuable synthon to new
functionalized ProDOT derivatives due to its hydroxyl func-
tionality.23,25–27 Utilizing ProDOT-OH as a common starting
material could produce a family of tethered PProDOT-based
derivatives via the linkage of two ProDOT-OH moieties
with the variable length tether. For successful application of
this design to a family of derivatives, it became desirable to
develop a general synthetic process which could be easily
utilized towards constructing the conformationally restricted
PProDOTs by changing tether length and/or composition
without significant modification to the established procedure.
As shown in Scheme 1, the reaction of ProDOT-OH with
the appropriate a,v-alkyleneditosylates, prepared from their
Electrochemical film deposition
The polymerization method of choice was electrochemical
because of the ability to directly form and characterize
polymer films. In a typical electropolymerization experiment,
a 1–10 mM solution of monomer in an electrochemically
compatible solvent with supporting electrolyte is characterized
via a linear cyclic voltammetric sweep in a three-electrode cell.
For this project, it was found that successful electropoly-
merization of all monomers occurred in 0.1 M tetrabutyl-
ammonium perchlorate (TBAP) in acetonitrile (ACN).
The first potential sweep in the cathodic-to-anodic direction
effectively characterizes the monomer oxidation process, and
upon reverse scanning from the anodic-to-cathodic direction, a
polymer reduction wave occurs upon the successful deposition
of electroactive polymer onto the electrode surface. The two
switching potentials of the linear sweep are therefore set at
points to incorporate the entire redox processes of the electro-
polymerization reaction: just positive of the monomer oxida-
tion diffusion tail, and negative of the polymer reduction
diffusion tail. The irreversible monomer oxidation process
(suggested by the absence of a reduction wave) observed is
indicative of the oxidized monomer radical cations coupling to
form a polymer.
The polymerization of the macrocyclic derivatives 3b–e can
only result in a linear polymer because each monomeric unit
contains two and only two reaction sites. However, as shown
in Fig. 2, the linear monomers 2a–h contain four reaction sites
and can produce a densely cross-linked polymer network, thus
Scheme 1 (a) TsO(CH2)nOTs, NaH, DMF (59–90%); (b) (1) 2.1 equiv.
of n-BuLi, HMPA, THF, 278 uC A RT; (2) THF, 2.5 equiv. of
Fe(acac)3 (8–30%); (c) TsO(CH2)3CH3, NaH, DMF (63%); (d) (1)
1.2 equiv. of n-BuLi, THF, 278 uC A RT; (2) Fe(acac)3 (15%).
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 254–260 | 255

View Article Online
preventing efficient ion flux and possibly shortening the
effective conjugation length of the polymer.
Polymer films were electrodeposited onto platinum button
electrodes via repeated potential scanning, as shown in Fig. 3.
To compare to the linear monomers (compounds 2c–e) with a
particular tether length to their macrocyclic derivatives with
the same tether length, Fig. 3 shows the linear monomers on
the left and the macrocycles on the right. The linear monomers
show distinctly different electropolymerization behavior than
their macrocyclic counterparts, as we communicated pre-
viously for the 2b/3b pair.23 It can be seen that all of the linear
derivatives, as expected, exhibited a peak monomer oxidation
potential of approximately 1.0 V, indicating that the alkylene
tether length has no effect on the monomer oxidation poten-
tial. As described above, it was predicted that polymerization
of 2b–e would form cross-linked networks of Poly2b–e on the
electrode surface, thus limiting the effective conjugation
length, and anodic shifts of both the polymer and monomer
Fig. 2 Competitive electrochemical polymerization pathways of the
tethered monomers.
Fig. 3 Repeated scan electrochemical polymerization at 50 mV s21 of a) 2c, b) 3c, c) 2d, d) 3d, e) 2e, f) 3e in 0.1 M TBAP–acetonitrile.
256 | J. Mater. Chem., 2007, 17, 254–260
This journal is ß The Royal Society of Chemistry 2007

View Article Online
redox processes were observed during the electropolymeriza-
tion. This phenomenon can be attributed to the competition
of in situ intramolecular macrocyclization with intermolecular
dimerization.
redox process, whereas the opposite was true of Poly4. These
lower redox potentials are indicative of their greater planarity
due to the absence of a torsional restriction, which allows for a
greater degree of p-overlap in the conjugated backbone.
After electropolymerization, all polymer films were removed
from the monomer solution, washed with and immersed into
monomer-free electrolyte solution. The polymer redox stability
was characterized by repeated scan cyclic voltammetry, as
shown in Fig. 4. It can be seen that the polymer redox
processes for all polymers were very stable. Even with the small
variation of the redox processes observed for Poly2b and
Poly2e, it was found that the entire family of linear and
macrocyclic derivatives generated polymers that did not lose
their electroactivity, even after many scans. The polymer half-
wave potential of the family of linear derivatives Poly2a–h was
dependent on the number of electrochemical sweeps employed
in the electropolymerization. For each progressive potential
sweep, the oxidation potential was observed to increase,
indicating a less electroactive polymer film.
The macrocyclic derivatives were electropolymerized in the
same manner; however, in contrast to the linear derivatives,
even after 15 repeated potential sweeps, the resulting polymer
redox peaks did not shift and remained well-defined. This
stable electrochemistry is most likely due to the fact that only
two reactive sites were present on the macrocyclic derivatives.
Therefore, the macrocyclic monomeric structure represents a
convenient means of forming the tethered polymer structure as
a linear and well-defined material without cross-linking.
An interesting phenomenon observed for the macrocyclic
derivatives 3c–e was that two distinct irreversible monomer
oxidation processes existed: one at ca. 0.6 V and one at ca.
0.7 V. However, for macrocycle 3b, which was characterized
via X-ray crystallography and found to be the pure syn-
isomer,23 only one single redox process was observed at 0.7 V.
Concurrently, it was observed that the 1H NMR spectrum
of 3b exhibited a single peak corresponding to the thienyl
aromatic proton, whereas the 1H NMR spectra of compounds
3c–e exhibited two. Furthermore, TLC and HRMS analysis of
the highly purified macrocycles 3c–e suggest a single compo-
nent. In other words, the syn- and anti-isomers, while different
in their NMR spectra, can not be distinguished by HRMS and
can not be separated by conventional chromatographic means.
We feel that we have demonstrated adequate purity for this
publication in that the products were indeed macrocyclic
derivatives. The NMR results were consistent, TLC indicated a
single spot for the purified compound in a variety of eluents,
and the HRMS method employed was a soft ionization
method: no structures which could be attributed to impurities
were observed. We speculate that the peak at 0.7 V for all
macrocycles corresponds to the syn-isomer, and the peak at
0.6 V may correspond to the anti-isomer. However, this can
not be proven until a suitable purification technique can be
utilized to separate the two isomers. The two monomer
oxidation processes were seen to increase in relative intensity
as repeated electrodepositions were performed. Experiments
were run to observe the effect of electrodeposition when the
potential was scanned out to the first peak only, and yielded
electropolymerization and polymer CVs that appeared very
similar to the full scan.
Table 1 summarizes the electrochemical results. Optical data
are also tabulated, and will be described in the next section. It
can be seen that all of the linear monomers exhibited a peak
oxidation potential at ca. 1 V, and the redox processes, as
described above, were highly dependent on the monomer
concentration and the number of potential sweeps employed in
the electropolymerization. The oxidation potential for the
macrocyclic derivatives was observed to vary as a function of
tether length, and can be roughly correlated to the band gap
measurements. Decreasing p-overlap would effect an elevated
band gap, as well as an elevated polymer E1/2
.
Optical properties
As previously mentioned, imposing a conformational restric-
tion on the polymeric backbone alters the electrochemical
behavior with respect to the untethered control system. For the
macrocyclic derivatives, the polymer redox potentials were
seen to change with varied tether length, and it was expected
that the optical properties would also change as a function of
tether length. Specifically, the twist imposed upon the polymer
backbone should alter the effective conjugation length and
thus shift the absorbance. Since the untethered PProDOT
derivatives are thought to adopt a predominantly planar
structure, and thus have maximal effective conjugation
lengths, imposing a twist on the polymeric backbone should
shorten the effective conjugation length, thus invoking a
hypsochromic shift.
Thus, because of the overlap of the two monomer oxidation
processes observed for macrocycles 3c–e, an isolated electro-
polymerization of the first monomer peak, excluding the
second, was essentially impossible. This was due to the broad
onset of monomer oxidation for the 0.7 V process overlapping
with the peak oxidation potential of the 0.6 V process.
In contrast, the electropolymerization of control polymers
Poly4 and Poly5, exhibited broad oxidation processes (see
electronic supplementary information (ESI){) and a lower
polymer oxidation potential with respect to the polymers
described above. The dimeric forms and monomeric forms
exhibited slightly different electrochemical polymerization
behavior. Both systems displayed two independent redox
processes at ca. 20.3 V and 20.1 V, but for Poly5 the
20.3 V redox process was greater in intensity than the 20.1 V
Our previous work demonstrated that Poly2b and Poly3b
exhibited elevated band gaps and different color states
compared to Poly4, Poly5, and PEDOT.23 In fact, all of the
polymers studied, whose optical data are summarized in
Table 1, exhibited band gaps and lmax values above that of
PEDOT and the control polymer, and all derivatives were
observed to be orange to red in color in their neutral states. As
seen in Table 1, a correlation between polymer band gap and
lmax exists, and the ‘‘sweet spot’’ for maximum band gap is a
six-carbon tether length. This result is not surprising given
that the five-carbon tether provides a dimer torsion angle of
30.1u.23 Presumably, the six-carbon tether would increase that
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 254–260 | 257

View Article Online
Fig. 4 Polymer CV of at 50 mV s21 of films of a) Poly2c, b) Poly3c, c) Poly2d, d) Poly3d, e) Poly2e, f) Poly3e, which were deposited as shown in
Fig. 3 in monomer-free 0.1 M TBAP–acetonitrile.
angle further, and thus decrease the extent of p-overlap.
The band gap of the dodecyl-tethered derivative Poly2h
was found to be 1.94 eV, the lowest of the family, but still
higher than the untethered control polymers. It is presumed
that tether lengths even longer than twelve carbons would
affect a further decrease in band gap. Though Poly2h was
probably a random mixture between intramolecularly macro-
cyclized repeat units and cross-linked or linear intermole-
cularly dimerized products, it is still evident that the alkylene
tether is successful in modifying the electrochromic properties
of the materials.
the spectrum was observed to change, with the depletion of
the p,p* transition. This depletion of the neutral polymer
absorbance spectrum was accompanied by emergence, blue
shift, and eventual disappearance of an intermediate absorp-
tion process at ca. 1.5 eV, attributed to the formation of
polarons; and the gradual increase in near IR absorbance,
attributed to the formation of bipolarons. As a means of fully
characterizing the neutral state of the polymer, a small amount
of hydrazine was added to the solution to effectively quench
any trapped polaronic or bipolaronic charge carriers in the
film. It can be seen that the hydrazine-reduced spectrum is only
slightly different than the 0.30 V spectrum. Therefore, it is
believed that the sharp and efficient redox chemistry observed
on the Pt button for the electrochemical measurements,
presumably due to the macrocyclic cavity allowing efficient
ion flux into and out of the polymer matrix, was also present in
the film electrodeposited onto the ITO/glass anode.
All polymers were found to exhibit stable, reversible
electrochromism. Spectroelectrochemistry was performed on
the derivatives. As a representative example, Fig. 5 illustrates
the spectroelectrochemistry of Poly3e, and it can be seen that
the neutral polymer was highly absorbing in the visible with a
p,p* onset of 2.15 eV. Upon gradual potentiostatic oxidation,
258 | J. Mater. Chem., 2007, 17, 254–260
This journal is ß The Royal Society of Chemistry 2007

View Article Online
Table 1 Summary of various electrochemical and optical data for the monomers and polymers
na
Ep,m
E1/2
DEp
Eg
lmax
b
c
d
e
f
Functionality
Compound
Linear monomers
2a
2b
2c
2d
2e
2f
4
5
6
7
8
9
10
12
1.07
1.05
1.08
1.03
1.05
1.04
1.06
1.06
0.14g
0.39g
0.42g
0.26g
0.29g
0.26g
0.36g
0.02g
0.38g
0.21g
0.07g
0.03g
0.00g
0.22g
0.17g
0.29g
2.10
2.13
2.19
2.14
2.09
2.02
2.00
1.94
480
479
477
480
483
502
508
535
2g
2h
Macrocycles
3b
3c
3d
3e
5
6
7
8
0.73
0.18
0.20
0.20
0.08
0.06
0.03
0.14
0.18
2.13
2.26
2.15
2.03
491
446
486
481
0.58, 0.74h
0.57, 0.74h
0.55, 0.68h
Untethered control
4
5
—
—
1.08
0.54
20.25, 20.10i
20.32, 20.14i
0.33, 0.43i
0.03, 0.05i
1.75
1.75
580, 627j
579, 628j
a
b
Number of carbons in the alkylene tether. Monomer peak oxidation potential (V) as a 10 mM solution in 0.1 TBAP–ACN at a scan rate of
50 mV s21
polymer peak oxidation and reduction potentials (V). Polymer band gap (eV) as measured by the onset of the p,p* transition in the neutral
.
c
d
Polymer half-wave potential (V) as measured in monomer-free electrolyte solution after electropolymerization. Separation of
e
f
g
polymer film. Absorption maximum of the neutral polymer film (nm). This value was observed to be unstable and changes as a function of
h
film thickness and number of electrochemical switches; the reported value is that of the polymer film after repeated potential sweeps. Two
i
irreversible redox processes were observed. Two independent reversible electrochemical processes were observed. Because of the presence of
j
fine structure, all lmax values in the p,p* absorption process are reported.
Fig. 5 Spectroelectrochemistry of Poly3e on ITO/glass in
a
Fig. 6 Cyclic voltammogram of Poly3e, which was electrodeposited
0.1 TBAP–ACN electrolyte solution.
onto an ITO/glass electrode, and its picture at different potentials.
Fig. 6 illustrates the actual polymer color states of Poly3e as
a function of voltage applied to the film. Digital photographs
of the film were taken at various potentials versus a silver wire
pseudoreference electrode and are placed in Fig. 6 at positions
of their approximate applied voltages. It can be seen that as the
applied potential is scanned from well negative of the polymer
oxidation wave to more positive values, the polymer’s orange
color remains unchanged. As the applied potential approaches
ca. 0.6 V, the red-orange color begins to darken, and at ca.
0.7 V, the polymer is greenish. After the polymer has reached
its peak oxidation potential and the potential resides in the
diffusion tail, the polymer is green–blue. The translucent red–
orange to transparent green–blue electrochromism was easily
achieved and found to be stable over several rapid potential
switches from the extreme de-doped to the extreme doped
states. All derivatives were transmissive blue to transmissive
gray in their oxidized states, indicating that the alkylene tether
successfully elevates the band gap of the neutral polymer
through the imposed rotational restriction without hindering
the effective conjugation of the doped state. It is evident that
this combination of unique properties that can be finely tuned
for this family of polymers constitutes a valuable addition to
the diverse PXDOT library.
Conclusions
Conformational locking of a family of tethered PProDOT
derivatives has provided a set of electrochromic polymers
with tunable and elevated band gaps with respect to their
untethered derivatives. The macrocyclic polymers produced
well-characterized repeat unit structures due to their monomer
bifunctionality. The X-ray crystal structure of the macrocycle
3b indicates a locked torsion angle, and electrochemical data
suggest that this conformational distortion reduces the extent
of p-overlap relative to the control polymers. It was found that
the six-carbon tether produces the most significant deviation in
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 254–260 | 259

View Article Online
8 K. J. Hoffmann, E. Bakken, E. J. Samuelsen and P. H. J. Carlsen,
Synth. Met., 2000, 113, 39–44.
9 K. J. Hoffmann, A. L. Graskopf, E. J. Samuelsen and
P. H. J. Carlsen, Synth. Met., 2000, 113, 89–92.
10 K. J. Hoffmann, L. Knudsen, E. J. Samuelsen and P. H. J. Carlsen,
Synth. Met., 2000, 114, 161–165.
11 K. J. Hoffmann, E. J. Samuelsen and P. H. J. Carlsen, Synth. Met.,
2000, 113, 161–166.
12 K. J. Hoffmann, E. J. Samuelsen and P. H. J. Carlsen, Synth. Met.,
2000, 114, 167–172.
13 A. Rajca, M. Miyasaka, M. Pink, H. Wang and S. Rajca, J. Am.
Chem. Soc., 2004, 126, 15211–15222.
14 C. L. Gaupp and J. R. Reynolds, Macromolecules, 2003, 36,
6305–6315.
15 D. Witker and J. R. Reynolds, Macromolecules, 2005, 38,
7636–7644.
16 I. F. Perepichka, M. Besbes, E. Levillain, M. Salle and J. Roncali,
Chem. Mater., 2002, 14, 449–457.
17 M. J. Marsella and T. M. Swager, J. Am. Chem. Soc., 1993, 115,
12214–12215.
18 T. Benincori, A. Berlin, E. Brenna, G. Pagani, F. Sannicolo,
P. Sozzani, G. Moro, D. Pitea and G. Zotti, Mol. Cryst. Liq.
Cryst., 1993, 236, 181–188.
19 M. J. Marsella, P. J. Carroll and T. M. Swager, J. Am. Chem. Soc.,
1994, 116, 9347–9348.
20 M. J. Marsella, P. J. Carroll and T. M. Swager, J. Am. Chem. Soc.,
1995, 117, 9832–9841.
its optical properties, and therefore it probably exhibits the
largest angle from planarity. These are the first known
examples of dioxythiophene-based orange or orange–red
neutral polymers that become highly transmissive when
oxidized, and have the potential to be very useful in the
construction of electrochromic devices. Their moderately high
band gaps and low oxidation potentials compare to the
poly(3,4-alkylenedioxypyrrole) family of conducting poly-
mers.7 The macrocyclic structures of the polymeric derivatives
resemble that of a crown ether and could also potentially be
used for ion sensing applications. The tethered repeat unit
structure shows enormous potential in finely tuning optical
properties by changing the composition of the tether to
incorporate other moieties such as hydrogen-bonding or
solubilizing groups, and would be the next logical step in the
further study of these derivatives.
Acknowledgements
We gratefully acknowledge the AFOSR (FA955-06-1-0192) for
the funding for this project.
21 M. J. Marsella, R. J. Newland, P. J. Carroll and T. M. Swager,
J. Am. Chem. Soc., 1995, 117, 9842–9848.
References
22 T. Benincori, E. Brenna, F. Sannicolo, L. Trimarco, G. Moro,
D. Pitea, T. Pilati, G. Zerbi and G. Zotti, J. Chem. Soc., Chem.
Commun., 1995, 881–882.
23 R. M. Walczak, J. S. Cowart, Jr., K. A. Abboud and J. R. Reynolds,
Chem. Commun., 2006, 1604–1606.
1 L. B. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik and
J. R. Reynolds, Adv. Mater., 2000, 12, 481–494.
2 D. T. McQuade, A. E. Pullen and T. M. Swager, Chem. Rev., 2000,
100, 2537–2574.
3 L. Groenendaal, G. Zotti, P.-H. Aubert, S. Waybright and
J. R. Reynolds, Adv. Mater., 2003, 15, 855–879.
4 J. Roncali, P. Blanchard and P. Frere, J. Mater. Chem., 2005, 15,
1589–1610.
5 G. Sonmez, Chem. Commun., 2005, 5251–5259.
6 I. Perepichka, D. Perepichka, H. Meng and F. Wudl, Adv. Mater.,
2005, 17, 2281–2305.
7 R. M. Walczak and J. R. Reynolds, Adv. Mater., 2006, 18,
1121–1131.
24 D. M. Welsh, A. Kumar, E. W. Meijer and J. R. Reynolds, Adv.
Mater., 1999, 11, 1379–1382.
25 S. P. Mishra, R. Sahoo, A. V. Ambade, A. Q. Contractor and
A. Kumar, J. Mater. Chem., 2004, 14, 1896–1900.
26 A. Kros, R. J. M. Nolte and N. A. J. M. Sommerdijk, J. Polym.
Sci., Part A: Polym. Chem., 2002, 40, 738–747.
27 S. P. Mishra, K. Krishnamoorthy, R. Sahoo and A. Kumar,
J. Polym. Sci., Part A: Polym. Chem., 2004, 43, 419–428.
28 S. S. Zhu and T. M. Swager, J. Am. Chem. Soc., 1997, 119,
12568–12577.
260 | J. Mater. Chem., 2007, 17, 254–260
This journal is ß The Royal Society of Chemistry 2007