Conjugated thiophene-containing polymer zwitterions: Direct synthesis and thin film electronic properties

Article abstract of DOI:10.1021/ma302232q

We report a direct and facile synthesis of novel conjugated polymeric zwitterions (CPZs) as a simple route to electronically active homopolymers and copolymers containing dipole-inducing pendent zwitterions. Sulfobetaine- containing polythiophenes (PTSB-1 and PTSB-2) and alternating thiophene-benzothiadiazoles (PTBTSB-1 and PTBTSB-2) were prepared and characterized relative to alkylated polymer analogues (POT-a-T and POT-a-BT). The polar zwitterionic side chains make these polymers hydrophilic and salt-responsive, with interesting electronic properties that depend on zwitterion distance from the conjugated polymer backbone (tether length), as characterized by UV-vis absorption and ultraviolet photoelectron spectroscopy (UPS). Close proximity (CH₂ spacer) of the sulfobetaine groups to the polymer backbone results in increased ionization potential and enlarged band gaps of 2.19 and 2.04 eV for PTSB-1 and PTBTSB-1, respectively. On Au and Ag surfaces, the zwitterionic pendent groups significantly alter the work function due to the presence of an interfacial dipole, with the largest interfacial dipoles measuring -1.29 eV (PTBTSB-1/Au) and -0.69 eV (PTBTSB-1/Ag).

Full text of DOI:10.1021/ma302232q

Article
pubs.acs.org/Macromolecules
Conjugated Thiophene-Containing Polymer Zwitterions: Direct
Synthesis and Thin Film Electronic Properties
Zachariah A. Page, Volodimyr V. Duzhko, and Todd Emrick*
Polymer Science & Engineering Department, Conte Center for Polymer Research, 120 Governors Drive, University of Massachusetts,
Amherst, Massachusetts 01003, United States
*
S Supporting Information
ABSTRACT: We report a direct and facile synthesis of novel
conjugated polymeric zwitterions (CPZs) as a simple route to
electronically active homopolymers and copolymers containing dipole-
inducing pendent zwitterions. Sulfobetaine-containing polythiophenes
(
(
PTSB-1 and PTSB-2) and alternating thiophene−benzothiadiazoles
PTBTSB-1 and PTBTSB-2) were prepared and characterized relative
to alkylated polymer analogues (POT-a-T and POT-a-BT). The polar
zwitterionic side chains make these polymers hydrophilic and salt-
responsive, with interesting electronic properties that depend on
zwitterion distance from the conjugated polymer backbone (tether
length), as characterized by UV−vis absorption and ultraviolet
photoelectron spectroscopy (UPS). Close proximity (CH spacer) of
2
the sulfobetaine groups to the polymer backbone results in increased
ionization potential and enlarged band gaps of 2.19 and 2.04 eV for
PTSB-1 and PTBTSB-1, respectively. On Au and Ag surfaces, the zwitterionic pendent groups significantly alter the work
function due to the presence of an interfacial dipole, with the largest interfacial dipoles measuring −1.29 eV (PTBTSB-1/Au)
and −0.69 eV (PTBTSB-1/Ag).
1
2
INTRODUCTION
that improve polymer light-emitting diodes (PLEDs), dye-
■
1
8,19
sensitized solar cells (DSSCs),
organic thin-film transistors
light-emitting field-effect transistors (LE-
and bulk heterojunction (BHJ) solar cells.
Thin interlayers placed between organic active layers and metal
electrodes in organic electronic and optoelectronic devices offer
routes to improved device performance. In organic light-
emitting diodes (OLEDs) and field-effect transistors (OFETs),
2
0
(
OTFTs),
2
1,22
23−25
FETs),
CPE interlayers assist charge injection, generally from the
cathode to the active layer, and their aqueous solubility enables
deposition with little disruption of the underlying polymer
In PLEDs, CPE electron injection layers allow the use
of stable metal cathodes (i.e., silver and gold) and give devices
with reduced turn-on-voltage and several orders-of-magnitude
higher efficiency relative to those without an interlayer. For
OTFTs, reduced contact resistance (R ) and higher drain to
source currents (I ) were obtained with a cationic
polyfluorene layer between the source/drain electrodes and
1
,2
interlayers give higher injection current densities. In organic
photovoltaics (OPVs), a significant increase of open circuit
voltage and short circuit current is achieved, with interlayers in
1
1,16
layer.
3
4
5
conventional, inverted, and tandem device architectures.
More recently, organic and polymeric interlayer materials were
developed, since they allow synthetic tailoring of functionality
and integration into devices through simple fabrication
procedures. Interlayer materials under investigation include
2
6
c
DS
2
,6−8
self-assembled monolayers (SAMs),
neutral small mole-
20
9
10
active layers. In BHJ solar cells, a CPE layer between the
active layer and cathode enhanced the open circuit voltage
(V ) by 50% and improved short-circuit current density (J )
cules, ionic surfactants, conjugated polymers with solubiliz-
1
1
ing pendent groups, and conjugated polyelectrolytes
1
2−15
(
CPE).
Such materials are either functionalized to bind
oc
sc
2
,6
7
and fill factor (FF) to give a 2-fold increase in power
to the electrode surface, segregate on the surface, or possess
orthogonal solubility with the active layer, which enables
sequential deposition of films.
The operation of organic electronic and optoelectronic
devices relies on the electronic characteristics between the
organic active layer and the electrode. A number of inorganic
24
conversion efficiency (PCE).
1
1,12,14−16
The mechanisms invoked to explain the effect of interlayers
range from improved surface wettability and adhesion to
morphological optimization and electronic structure modifica-
11
tions. The effects from CPE interlayers are proposed to arise
interlayers (i.e., LiF, ZnO, and TiO ) have been integrated into
2
17
device architectures to improve performance. In recent years
conjugated polyelectrolytes (CPEs) have emerged as organic
interlayers. CPEs are charged hydrophilic semiconductors
Received: October 26, 2012
Revised: December 10, 2012
1
4
©
XXXX American Chemical Society
A
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
from (1) ion motion that redistributes the electric field within a
2
7
device and (2) a modification of the work function at the
2
8,29
organic/metal interface arising from dipole alignment.
An
interfacial dipole at a metal−organic interface may arise from a
30−32
compression of the metal electron density tail.
The
improvement in device performance originates from the
alteration of electronic energy level alignment at the
9
heterointerfaces. Specifically, formation of an interfacial dipole
at the interface of an organic active layer and metal electrode,
sometimes also described as electrode work function
9
,10,33,34
modification, has been discussed.
Such electronic
properties of interlayer materials are probed by ultraviolet
2
8,35
photoelectron spectroscopy (UPS).
Vacuum level align-
ment at an organic−organic interface is likely to occur for an
interfacial dipole moment induced by an organic interlayer
(
such as a CPE), resulting in a decreased injection barrier into
28,36
the active layer.
thin films on a metal substrate to determine work function
UPS probes the electronic properties of
28
37
(WF), ionization potential (I ), and vacuum energy (E ).
P vac
For example, Nguyen and co-workers used UPS to characterize
anionic and cationic CPEs on gold, finding that the presence of
an interfacial dipole leads to enhanced charge injection.
2
9,35
Figure 1. (A) Structures of novel SB-substituted polymers:
polythiophene (PTSB) and poly(thiophene−benzothiadiazole)
Conjugated polymeric zwitterions (CPZs) are neutral,
hydrophilic, electronically active polymers. They are attractive
for achieving the beneficial properties of CPEs (water
solubility; pendent dipoles) without the complications of
(
PTBTSB) CPZs and (B) alkyl-substituted analogues.
chosen for its pH insensitivity and proved effective for
solubilizing the conjugated polymers when placed on every
second aromatic unit in the backbone. For comparison, alkyl-
substituted analogues POT-a-T and POT-a-BT were also
prepared (Figure 1B).
38
counterions (e.g., long turn-on times for LEDs). However,
only a few examples of CPZs have been reported (apart from
pH-sensitive derivatives such as amino acid-substituted
3
9−41
structures
). Synthetic routes to date utilize postpolymeri-
38,42
The monomer syntheses, shown in Scheme 1, began with the
zation reactions to convert polymer precursors to CPZs.
43
ring-opening of 1,3-propane sultone with dimethylamino-
For example, Huck and co-workers synthesized an alternating
copolymer of di-n-octylfluorene and a sulfobetaine (SB)-
38
Scheme 1. (left) Synthesis of SB-Substituted Thiophene
Monomers 3 and 6; (right) Partial H NMR Spectrum in
D O Showing Thiophene Protons (α in 3 and β in 6)
2
substituted fluorene, while Huang and co-workers prepared
a
1
42
homopolymers of a SB-substituted fluorene. These CPZs
were characterized as electron-injection materials in PLEDs,
reducing response times to less than 10 μs and improving
brightness/efficiency 2-fold relative to calcium-based devi-
3
8,42
ces.
Here we describe the design and synthesis of a novel
sulfobetaine (SB)-containing CPZ polymer platform, including
thiophene- and benzothiadiazole-based structures, in which the
zwitterion is present on the monomer from the outset. As such,
the conditions described allow reliable polymerization of
zwitterionic monomers that does not hinge on postpolymeriza-
tion modification. Both homopolymers and copolymers were
prepared, having shorter (methylene) and longer (tetra-
methylene) tethers between the polymer backbone and SB
groups. These novel synthetic polymers were characterized by
solution and solid-state UV−vis absorption spectroscopy and
by UPS as thin films on gold and silver substrates. This
characterization revealed distinct electronic differences as a
function of spacer length and relative to alkyl-substituted
analogues. The electronic properties of the SB-containing CPZs
make these materials attractive for future testing in organic
electronic and optoelectronic devices.
a
Reagents and conditions: (i) Me NH, Bu NBr, CHCl :H O; (ii) 1,3-
2
4
3
2
propane sultone, CH CN; (iii) Me NH, THF; (iv) 1,3-propane
sultone, CH CN.
3
2
3
thiophene 2 (prepared from tribromide 1 and dimethylamine
under phase-transfer conditions in 82% yield). This gave
monomer 3 as a white powder (HRFAB-MS: (m/z) [M + H]+
calculated: 421.8918; found: 421.8898). A tetramethylene
spacer was introduced by reacting alkyl bromide 4 with
dimethylamine to give 5, followed by ring-opening of 1,3-
propane sultone in acetonitrile. Precipitation gave sulfobe-
taine−thiophene monomer 6 in 92% yield as a white crystalline
RESULTS AND DISCUSSION
■
The novel CPZs shown in Figure 1A are composed of SB-
substituted polythiophene (PTSB-1 and PTSB-2) and
alternating thiophene−benzothiadiazole (PTBTSB-1 and
PTBTSB-2) backbones, where 1 and 2 denote (CH ) tether
2
x
lengths of x = 1 and 4, respectively. The SB zwitterion was
B
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
+
solid (HRFAB-MS: (m/z) [M + H] calculated: 461.9408;
for NMR characterization, noting broad signals centered at ∼3
and ∼7 ppm, representing protons from the aliphatic side-
chains and aromatic backbone, respectively. Polymer molecular
weights were estimated by aqueous gel permeation chromatog-
raphy (GPC) relative to poly(ethylene oxide) (PEO) standards,
giving values ranging from 6 to 15 kDa for PTSB-1 and 7 to 10
kDa for PTBTSB-1. PTSB-2 and PTBTSB-2 were synthesized
under similar S−M conditions, with GPC estimated molecular
weights of 6−22 and 47−80 kDa, respectively, and Đ values of
1.7−2.6.
found: 461.9408).
1
H NMR spectroscopy of monomers 3 and 6 in D O reveals
2
the influence of the proximity of the zwitterions to the
thiophene ring. The 0.3 ppm downfield shift in the thiophene
proton of 3 (7.26 ppm) relative to 6 (6.96 ppm) (Scheme 1)
indicates an electron-withdrawing effect of the SB group. As
Grignard metathesis (GRIM) polymerization conditions are
unsuitable for dibromothiophene monomers 3 and 6,
alternative polymerization methodologies were examined.
Attempts to polymerize 3 by Yamamoto dehalogenative
polycondensation with dicyclooctadiene nickel(0) in DMF
afforded only oligomers. Thus, to accommodate the limited
organic solubility of these zwitterionic monomers, we examined
Suzuki−Miyaura (S−M) coupling of 3 with diboronate ester−
thiophene 7 in a biphasic solvent system (Figure 2).
The UV−vis absorption spectra of Figure 3 illustrate the
influence of the zwitterions on the polymer electronic
Figure 2. (top) Suzuki−Miyaura polycondensation of monomers 3, 6,
7, and 8. (bottom) Representative GPC traces of CPZs (left) and
corresponding number-average molecular weights (M ) and dis-
n
persities (Đ) (right).
Dichloro[bis(triphenylphosphine)]palladium(II) [Pd-
(
PPh ) Cl ] successfully produced polymers with reasonably
3 2 2
high molecular weights (ranging from 6 to 80 kDa) in ∼24 h,
while other catalysts (e.g., tetrakis(triphenylphosphino)-
palladium(0) [Pd(PPh ) ], bis(tri-o-tolylphosphine)palladium-
Figure 3. Comparison of solution (A, C) and solid-state (B, D)
absorption of CPZs and alkyl-substituted analogues. Spectra are
normalized at (longer wavelength) absorption maxima. Insets:
photograph of polymers in dilute solution (0.025 mg/mL in TFE
for CPZs and in DCB for alkylated counterparts).
3
4
(
0) [Pd(P(o-tol) ) ] and palladium(II) acetate [Pd(OAc) ])
3
2
2
were less effective. Addition of NaBr to the aqueous phase of
the S−M polycondensation was crucial for producing PTSB
and PTBTSB, giving these polymers in greater than 70%
isolated yield. The presence of salt in the reaction mixture
enhances solubility of the growing polymers and leads to
production of higher molecular weight material.
properties. PTSB-1 and PTBTSB-1, with short (methylene)
spacers are blue-shifted compared to PTSB-2 and PTBTSB-2,
with longer (tetramethylene) backbone-to-SB spacing. This is
due to an electron-withdrawing effect of the zwitterions that
PTSB-1 and PTBTSB-1 obtained by S−M polycondensation
exhibited poor solubility in water but excellent solubility in salt
water (∼10 mg/mL 0.5 M NaBr(aq)). Such a pronounced salt-
induced solubilization is known for other SB-containing
4
7,48
widens the polymer band gap.
Notably, the alkylated
versions have similar absorption spectra as the long-tethered SB
polymers. The polymer samples used to record these
absorption spectra are all at or above their effective conjugation
length, such that the shifts seen are influenced solely by the
pendent SB groups (Supporting Information Figure S2). For
the alternating polymers, a leveling in the intensity of the two
44
polymers, such as poly(sulfobetaine methacrylate); salt
interrupts dipole−dipole pairing, an “anti-polyelectrolyte”
4
5,46
effect.
The CPZs were soluble in a few organic solvents,
in particular trifluoroethanol (TFE) and hexafluoroisopropanol
HFIP) (>20 mg/mL). Deuterated trifluoroethanol was used
(
C
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 1. Summary of Electronic Energy Levels of CPZs and Alkylated Analogues and Their Interfaces with Gold and Silver
Determined by Ultraviolet Photoelectron and UV−Vis Absorption Spectroscopy
substrate
gold
polymer
Eg
Φhole
Φelectron
IP
EA
Δ
POT-a-T
PTSB-1
1.94
2.19
1.82
2.04
1.94
2.19
1.96
1.82
2.04
1.83
0.65
1.41
0.84
1.95
0.59
1.38
1.19
0.92
1.75
1.36
1.29
0.78
0.98
0.09
1.35
0.81
0.77
0.90
0.29
0.47
4.59
5.42
5.03
5.63
4.63
5.33
5.11
5.08
5.58
5.31
2.65
3.23
3.21
3.59
2.69
3.14
3.15
3.26
3.54
3.48
−1.02 ± 0.10
−0.96 ± 0.11
−0.78 ± 0.07
−1.29 ± 0.04
−0.48 ± 0.07
−0.57 ± 0.03
−0.60 ± 0.02
−0.37 ± 0.08
−0.69 ± 0.09
−0.57 ± 0.05
POT-a-BT
PTBTSB-1
POT-a-T
PTSB-1
silver
PTSB-2
POT-a-BT
PTBTSB-1
PTBTSB-2
4
9
absorptions was seen, attributed to an intermediate band, and
demonstrating color tunability based on polymer composi-
tion.
Evac = Esec − 21.2 eV
(1)
5
0,51
The lower binding energy onset corresponds to a Fermi level
EF) for metals and a HOMO energy level for semiconductors,
and their separation from the vacuum level is equal to the work
function (WF) of a metal or to the ionization potential (I ) of a
(
The band gap energies (E ) of the CPZs and their alkylated
analogues (Table 1) were determined from the long-wave-
length onset of absorption using the tangential lines indicated
g
P
semiconductor, respectively (eq 2).
in Figure 3B,D. The nearly identical E values of PTSB-2 and
g
POT-a-T (1.96 and 1.94 eV, respectively) and PTBTSB-2 and
POT-a-BT (1.83 and 1.82 eV, respectively) indicate that the
effect of the zwitterions is removed upon separation from the
backbone with a tetramethylene tether.
Ultraviolet photoelectron spectroscopy (UPS) was utilized to
characterize the intrinsic electronic characteristics in thin films
of the polymers and at the polymer−metal interface. Figure 4A
IP = hv − (E − HOMO)
(2)
sec
Combining I and E gives the electron affinity (E ) and thus
P
g
A
LUMO energy. The offset of vacuum levels at the semi-
conductor/metal interface is the interfacial dipole energy (Δ),
calculated as the difference in measured E
coated and uncoated metals (Δ = −1.29 eV as shown in Figure
A). Figure 4B shows the energy band diagram of a metal−
values of the
SEC
4
semiconductor interface and summarizes the energy character-
istics that describe the interface, as determined by UPS and
UV−vis. The energy barriers for electron and hole injection
from the metal electrode into a semiconductor LUMO and
HOMO are denoted Φ
and Φhole, respectively.
electron
Representative UPS spectra of CPZs on Au and Ag
substrates are shown in Figure 5. The intrinsic properties of
organic materials and metal substrates, I and E , respectively,
P
F
as well as the characteristics of an interfacial energy level
alignment, Δ and Φhole, were extracted from these spectra.
Additionally, using the Eg values, EA and Φ
were
electron
calculated. These are summarized in Table 1. The difference
in Eg between the CPZs and their alkyl counterparts is
attributed to the proximity of the quaternary ammonium to the
polymer backbone, withdrawing electron density and increasing
IP, i.e., lowering the HOMO level.
UV−vis absorption and UPS measurements of PTSB-2 and
PTBTSB-2 on Ag further probe the electronic properties of the
materials. CPZs with SB chains separated by one methylene
Figure 4. Schematic representation of electronic energy levels at the
polymer−metal interface characterized by UPS. (A) Overlay of UPS
spectra of PTBTSB-1 on gold (top) and bare gold (bottom). (B)
Diagram showing the effect of interfacial dipole, Δ, on vacuum and
other energy level alignment. The values of E (E and LUMO) were
group had a larger I than those separated by four methylene
P
g
A
groups, as shown in Figure 6. In addition, the band gaps of
PTSB-1 and PTBTSB-1 are larger than PTSB-2 and PTBTSB-
determined by UV−vis spectroscopy.
2
, respectively, due to their deeper HOMO levels, a finding
consistent with electron withdrawal by the SB side chains. It is
shows representative UPS spectra of PTBTSB-1 on a Au
uncertain why both E and I are significantly larger for the
A
P
21
surface (upper left pane) and of Au itself (lower left pane).
The onset at higher binding energy, a secondary electron cutoff
ESEC), corresponds to a photoexcitation of electrons (21.2 eV)
from the deep occupied electronic states to the vacuum level
Evac), where both the binding and kinetic energies of electrons
CPZs than their alkyl-substituted analogues. We speculate that
this originates from inserting the conjugated backbones into a
medium with a larger dielectric constant, i.e., a network of
dipolar side chains.
Figure 7 shows the energy band diagrams of CPZs and their
alkyl-substituted counterparts on gold and silver surfaces.
Notably, the alkyl-substituted polymers were found to have
significant interfacial dipoles: 1.02 and 0.48 eV for POT-a-T on
(
(
are zero on an absolute energy scale. The position of Evac for a
given material (relative to the instrument energy scale) is
determined from the UPS spectrum using eq 1.
D
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Figure 5. Representative UPS spectra: (A) POT-a-T and PTSB-1 on Au; (B) POT-a-BT and PTBTSB-1 on Au; (C) POT-a-T, PTSB-1, and
PTSB-2 on Ag; (D) POT-a-BT, PTBTSB-1, and PTBTSB-2 on Ag. Left and right panes of each part of the figure show the energy range near the
secondary electron cutoff and Fermi/HOMO energy level, respectively.
Figure 6. I (bottom bands), E (top bands), and E values of CPZs
P
A
g
and alkylated polymers, plotted with reference to a common vacuum
level.
Au and Ag, respectively, and 0.78 and 0.37 eV for POT-a-BT
on Au and Ag, respectively. The values for POT-a-T are similar
to those reported for P3HT, which induces larger dipoles than
52,53
other conjugated polymers.
Although UV−vis spectra in
solution and the solid state are quite similar for the alkylated
polymers POT-a-T and POT-a-BT, and the zwitterionic
PTSB-2 and PTBTSB-2, UPS characterization reveals
significant electronic differences, as PTSB-2 and PTBTSB-2
on Ag have larger interface dipoles (0.60 and 0.57 eV,
respectively), relative to 0.48 and 0.37 eV for POT-a-T and
POT-a-BT. We speculate that this increase may arise from a
preferential macroscopic alignment of dipolar side chains, with
negative charges directed toward the metal surface. The
PTBTSB-1/metal interface produced the largest interfacial
dipoles (1.29 eV on Au and 0.69 eV on Ag) a significant
increase from 0.78 and 0.37 eV, respectively, as compared to its
alkylated analogue POT-a-BT. While the macroscopic align-
ment of dipolar side chains can still contribute to the interfacial
dipole formation at the interfaces of PTBTSB-1 and PTSB-1
with Au and Ag, the interaction of the HOMO with the SB
groups must also be considered.
Figure 7. Energy band diagrams of CPZ-coated Au (A) and Ag (B).
All materials share a common Fermi level (E ). The interfacial dipole
F
(
Δ), electron (Φelectron), and hole (Φhole) injection barriers are
specified.
and the active layers are important. This interfacial dipole
introduced by CPZ interlayers is expected to reduce the
electron injection barrier between the cathode and an adjacent
2
8,36
organic active layer in a device.
For applications where a conjugated polymer serves as the
active layer at the interface with a metal cathode, smaller
electron injection barriers (Φelectron) favor efficient device
performance. Figure 7 shows all the metal−CPZ interfaces have
In summary, four novel conjugated polymers with
sulfobetaine side chains were prepared by polymerization of
the corresponding zwitterionic monomers by Suzuki−Miyaura
polycondensation. Adjusting polymerization conditions to
accommodate the zwitterions resulted in polymers with
estimated molecular weights up to 80 kDa. Structure−property
relationships with regards to ionization potential and the
proximity of the zwitterions to the polymer backbone were
identified and characterized by UV−vis absorption and UPS.
Increasing the backbone-to-zwitterion spacer length led to a
significantly reduced Φ
, relative to their alkylated
electron
analogues. Most notably was a decrease from 0.98 eV for
POT-a-BT to 0.09 eV for PTBTSB-1 on Au. This effect arises
in part from the increased dipole moments and in part from the
increased ionization potentials (except for PTSB-1 and PTSB-2
on Ag where only the latter effect applies). For interlayers, the
magnitude of injection barriers between the metal electrodes
reduction in E from 2.19 to 1.96 eV (PTSB-1 to -2) and from
g
E
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
.01 to 1.81 eV (PTBTSB-1 to -2). Utilizing UPS in
combination with UV−vis absorption revealed that the
alternating CPZs, relative to POT-a-BT, had significantly
larger Δ values (as much as 0.51 eV). These CPZs hold
potential for further examination in OTFTs, PLEDs, and solar
cells.
Article
2
stirred at room temperature for 12 h, and aqueous sodium hydroxide
10 wt %, 100 mL) was added. The product was extracted into diethyl
ether (3 × 100 mL), and the organic fractions were combined, dried
with anhydrous MgSO , and filtered; the solvent was removed under
reduced pressure to obtain an orange oil. The crude product was
purified by column chromatography on silica gel, eluting with hexanes
and then ethyl acetate:hexanes mixtures. The solvent was removed
under reduced pressure, giving a light yellow solid that was
recrystallized from hexanes to give (2,5-dibromothiophen-3-yl)-
methanol as silvery-white needles (29 g, 82%). H NMR (300 MHz,
CDCl ) δ: 7.01 (s, 1H), 4.55 (s, 2H), 1.83 (s, 1H). C NMR (101
MHz, CDCl ) δ: 59.30, 109.34, 111.55, 130.58, 141.45 ppm.
Compound 1 was then synthesized in a similar fashion to that
(
4
EXPERIMENTAL SECTION
■
1
Materials. Anhydrous magnesium sulfate (97%), phosphorus
tribromide (99%), tetra-n-butylammonium bisulfate (99%), dimethyl-
amine (40 wt % solution in water), 1,4-dibromobutane (99%),
dimethylamine (2 M solution in THF), 3-bromothiophene (97%),
aluminum oxide (activated, basic, Brockmann I), 1,3-propane sultone
1
3
3
3
5
5,56
reported in the literature for 3-bromomethylthiophene.
A dry two-
neck, 500 mL round-bottom flask equipped with a magnetic stir bar,
inlet adapter, and septum was flushed with nitrogen, and anhydrous
CH Cl (200 mL) and (2,5-dibromothiophen-3-yl)methanol (10.0 g,
(
99%), anhydrous acetonitrile (99.8%), bis(pinacolato)diboron (99%),
potassium acetate (99%), bis(triphenylphosphine)palladium(II) di-
chloride (99%), N-iodosuccinimide (95%), sodium thiosulfate (99%),
and Aliquat 336 were purchased from Sigma-Aldrich and used without
further purification. Sodium hydroxide (99%), anhydrous diethyl ether
2
2
3
6.8 mmol) were added. The mixture was cooled to 0 °C with an ice
bath, and phosphorus tribromide (3.5 mL, 37 mmol) was added slowly
by a syringe. The mixture was stirred at 0 °C for 30 min and at room
temperature for 12 h. The reaction was slowly quenched with
saturated aqueous sodium bicarbonate, and the product was extracted
into CH Cl , dried with MgSO , filtered, and concentrated to give a
yellow oil. The crude product was purified by column chromatography
(
99%), and potassium carbonate (99%) were purchased from Fisher
Scientific. Dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium-
II) dichloromethane adduct (99%) and bis(tri-o-tolylphosphine)-
(
palladium(0) (98%) were purchased from Strem Chemicals. Chloro-
2
2
4
form-d (99.8%), methylene chloride-d (99%), methanol-d (99.8%),
2
4
on silica gel, eluting with hexanes and then ethyl acetate:hexanes
10:90). Removal of the solvent under reduced pressure gave 1 as a
deuterium oxide (99.9%), and 2,2,2-trifluorethanol-d3 (99%) were
purchased from Cambridge Isotope Laboratories. Sodium bicarbonate
(
1
white solid (10.7 g, 87%). H NMR (300 MHz, CDCl ) δ: 7.00 (s,
(
99%) and 3-thiophenemethanol (98%) were purchased from Alfa
3
1
1
H), 4.36 (s, 2H). 13C NMR (101 MHz, CDCl ) δ: 25.09, 111.91,
Aesar, and silica gel (200 × 400 mesh) was purchased from Sorbent
Technologies. N-Bromosuccinimide (NBS) (99%, Acros Organics)
was recrystallized from water, and 2,5-bis-thiopheneboronic acid
pinacol ester (7) (98%, Combi-Blocks) was purified by column
chromatography on silica gel, eluting with hexanes:ethyl acetate
mixtures, followed by recrystallization from hexanes. Tetrahydrofuran
3
12.27, 131.06, 137.97 ppm.
1
-(2,5-Dibromothiophen-3-yl)-N,N-dimethylmethanamine (2).
Tetrabutylammonium bisulfate (0.3 g, 0.9 mmol), CHCl (15 mL),
3
and dimethylamine (40 wt % in water, 15 mL) were added to a one-
neck, 100 mL round-bottom flask equipped with a magnetic stir bar,
inlet adapter, and condenser. Compound 1 (3.0 g, 9.0 mmol) was
added, and the mixture was heated to reflux with vigorous stirring for 2
h. The mixture was cooled to room temperature, and the product was
(
99%, EMD) (THF) was dried over sodium/benzophenone ketyl, and
dichloromethane (99%, Fischer Scientific) was dried over calcium
hydride (under nitrogen) and distilled before use. Ethyl acetate,
hexanes, chloroform, acetone, diethyl ether, and dichloromethane were
purchased from Fisher Scientific.
extracted with CH
over MgSO , filtered, and concentrated to obtain a crude oil. The oil
was purified by column chromatography on alumina (activated basic,
Brockmann I), eluting with CH Cl :hexane mixtures. Removal of the
solvent under reduced pressure gave 2 as a colorless oil (2.2 g, 82%).
Cl . The organic fractions were combined, dried
2
2
4
1
Instrumentation. H NMR spectra were recorded at 300 MHz on
a Bruker Spectrospin and 13C NMR at 100 MHz on a Bruker
Spectrospin or 176 MHz on an Agilent Technologies Varian. UV/vis
absorbance measurements were taken on a PerkinElmer Lambda 25
UV/vis spectrometer and the fluorescence spectra on a PerkinElmer
LS 55 luminescence spectrometer. UPS measurements were
performed on the Omicron Nanotechnology Model ESCA+S,
consisting of a helium discharge lamp (He I line, 21.2 eV) as the
UV excitation source and a hemispherical SPHERA energy analyzer.
All samples were negatively biased by −3 V during the measurements.
This bias compensated for the instrument work function difference
repelling the low-kinetic-energy electrons. The energy scale of
experimental graphs was shifted by 3 eV. Polymer film thickness was
determined by the surface profiler KLA Tencor, model Alpha-Step IQ.
High-resolution mass spectral (HRMS) data were obtained on a JEOL
JMS700 MStation. Molecular weights and dispersities (Đ) were
estimated by gel permeation chromatography (GPC) in sodium nitrate
2
2
1
H NMR (300 MHz, CDCl ) δ: 6.95 (s, 1H), 3.33 (s, 2H), 2.25 (s,
3
6H). 13C NMR (101 MHz, CDCl ) δ: 45.33, 57.17, 110.09, 110.90,
3
131.60, 139.65 ppm.
3-(((2,5-Dibromothiophen-3-yl)methyl)dimethylammonio)-
propane-1-sulfonate (3). A dry one-neck, 100 mL round-bottom
flask, equipped with a magnetic stir bar, condenser, and inlet adapter
was flushed with nitrogen, and 2 (3.0 g, 10.0 mmol) and 1,3-propane
sultone (4.9 g, 40.1 mmol) were added. Anhydrous acetonitrile (60
mL) was added, and the mixture was heated to reflux for 1 h, during
which time a white precipitate formed. The mixture was cooled to
room temperature, filtered, and washed with anhydrous acetonitrile.
The product was dried under reduced pressure to afford 3 as a fluffy
1
white solid (3.9 g, 93%). H NMR (300 MHz, D
O) δ: 7.25 (s, 1H),
2
4.46 (s, 2H), 3.67−3.41 (m, 2H), 3.11 (s, 6H), 2.97 (t, J = 7.2 Hz,
1
3
(
0.1 M with 0.02 wt % of NaN ) aqueous solution, run at 30 °C
2H), 2.40−2.16 (m, 2H). C NMR (101 MHz, D
O) δ: 18.41, 47.32,
2
3
calibrated against poly(ethylene oxide) standards, operating at 1.0 mL/
min with three Waters Ultrahydrogel linear columns (each 300 × 7.8
mm).
49.78, 61.05, 62.72, 112.81, 119.19, 128.42, 132.74 ppm. HRMS-FAB
(m/z): [M + H] calculated for C10H16Br NO S : 421.8918; found:
2 3 2
+
421.8898.
Synthesis. 2,5-Dibromo-3-(bromomethyl)thiophene (1). We
note that some aromatic bromides, such as 4-bromobenzyl bromide,
are lachrymators, and we have not tested compound 1 for this
property. 2,5-Dibromothiophen-3-yl)methanol, precursor to 1, was
2,5-Dibromo-3-(4-bromobutyl)thiophene (4). 3-(4-Bromobutyl)-
thiophene was synthesized in a similar fashion to a report by
McCullough and co-workers. To a dry 250 mL, two-neck round-
bottom flask flushed with nitrogen and equipped with a magnetic stir
bar, septum, and inlet adapter was added 3-bromothiophene (6.5 g, 40
mmol) and hexanes (60 mL). The mixture was stirred and cooled to
5
7
5
4
synthesized in a similar fashion to that reported by Koide. A two-
neck, 250 mL round-bottom flask equipped with a magnetic stir bar,
inlet adapter, and septum was flushed with nitrogen, followed by
addition of 3-thiophenemethanol (15.0 g, 131 mmol) and THF (120
mL). The flask was covered with aluminum foil, and N-
bromosuccinimide (58.5 g, 328 mmol) was added over time (∼20
min) through a solid addition funnel with stirring. The reaction was
−40 °C (CH CN/dry ice bath), followed by addition of n-BuLi (2.5M,
3
16 mL, 40 mmol). Anhydrous THF (5 mL) was added dropwise,
resulting in the white precipitate (3-lithiothiophene). The mixture was
stirred at −40 °C for 15 min, and then hexanes was added (20 mL),
followed by 1,4-dibromobutane (17.3 g, 80 mmol). The mixture was
F
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
warmed to room temperature, stirred for 5 h, and quenched with
added. The cap was sealed tightly, the tube wrapped with aluminum
foil, and the mixture heated to 90 °C with vigorous stirring for 24 h.
The contents were cooled to room temperature and precipitated into
methanol:THF (2:1), centrifuged and washed with THF (4×), dried
under reduced pressure, dissolved in 1 M NaCl(aq), and transferred to
a dialysis membrane (cellulose, 1 kDa cutoff). The polymer was
dialyzed against water for 4 days, changing the water three times daily.
The contents within the dialysis bag were collected and lyophilized to
give the SB polymer as bright orange (PTSB-1), red (PTBTSB-1/
PTSB-2), or purple (PTBTSB-2) solids. Isolated yields of polymer
ranged from 70 to 90%.
water. The product was extracted with Et O (3 × 50 mL), washed with
2
water (3 × 50 mL), dried over anhydrous MgSO , filtered, and solvent
4
removed under reduced pressure to yield a crude oil that was further
purified by Kugelrohr distillation to remove excess 1,4-dibromobutane.
Column chromatography on silica gel with hexanes as the eluent gave
3
-(4-bromobutyl)thiophene as a colorless oil (3.9 g, 44%) upon
1
removal of solvent. H NMR (300 MHz, CDCl ) δ: 7.31−7.25 (m,
3
1
=
H), 7.02−6.95 (m, J = 4.2 Hz, 2H), 3.45 (t, J = 6.6 Hz, 2H), 2.70 (t, J
13
7.4 Hz, 2H), 2.01−1.87 (m, 2H), 1.87−1.76 (m, 2H). C NMR
(
176 MHz, CDCl ) δ: 29.08, 29.44, 32.36, 33.71, 120.31, 125.51,
3
1
28.17, 142.18.
Poly(thiophene-alt-thiophenemethylenesulfobetaine) (PTSB-1) was
Compound 4 was synthesized in a 250 mL, two-neck round-bottom
obtained as a bright orange solid after lyophilization (60 mg, 70%).
1
flask, equipped with a magnetic stir bar, septum, addition funnel, and
inlet adapter. The atmosphere was flushed with nitrogen, and 3-(4-
bromobutyl)thiophene (3.0 g, 13.7 mmol) was added and dissolved in
DMF (40 mL). NBS (6.1 g, 34.2 mmol) was dissolved in DMF (20
mL) and added to the addition funnel. The reaction was covered with
aluminum foil, and the contents in the addition funnel were added
dropwise, while stirring at room temperature. After complete addition
the reaction was stirred at room temperature under nitrogen for 12 h,
followed by quenching with saturated sodium carbonate (aqueous)
(GPC) M
n
= 15 500 g/mol, Đ = 2.2. H NMR (300 MHz, 2,2,2-
trifluoroethanol-d
) δ: 7.60−6.89 (br, 3H), 4.92−4.26 (br, 2H), 3.55−
3
3.29 (br, 2H), 3.27−2.71 (br, 8H), 2.52−2.02 (br, 2H).
Poly(benzothiadiazole-alt-thiophenemethylenesulfobetaine)
(PTBTSB-1) was obtained as a red solid after lyophilization (80 mg,
1
80%). (GPC) M
= 10 500 g/mol, Đ = 2.4. H NMR (300 MHz, 2,2,2-
n
trifluoroethanol-d
) δ: 8.78−8.23 (br, 1H), 8.23−7.66 (br, 2H), 5.09−
3
4.38 (br, 2H), 3.80−1.94 (br, 12H).
Poly(thiophene-alt-thiophenebutylenesulfobetaine) (PTSB-2) was
solution. The product was extracted into Et O (3 × 50 mL), and the
obtained as a red solid after lyophilization (77 mg, 80%). (GPC)
2
1
organic fractions were combined and washed with water (5 × 100
M
n
= 22 000 g/mol, Đ = 2.0. H NMR (300 MHz, 2,2,2-
mL), dried with anhydrous MgSO , filtered, and concentrated to
trifluoroethanol-d ) δ: 7.24−6.65 (br, 3H), 3.55−3.28 (br, 2H),
3
4
obtain a crude oil. The product was purified by column
3.28−3.11 (br, 2H), 3.10−2.51 (br, 10H), 2.41−2.00 (br, 2H), 1.95−
1.49 (br, 4H).
chromatography on silica gel with hexanes as the eluent. Removal of
1
Poly(benzothiadiazole-alt-thiophenebutylenesulfobetaine) (PTBTSB-
the solvent gave 4 as a colorless oil (4.18 g, 81%). H NMR (300
2
) was obtained as a dark purple solid after lyophilization (100 mg,
MHz, CD Cl ) δ: 6.87 (s, 1H), 3.47 (t, J = 6.6 Hz, 2H), 2.60 (t, J = 7.4
2
2
1
13
9
0%). (GPC) M = 47 000 g/mol, Đ = 2.2. H NMR (300 MHz, 2,2,2-
Hz, 2H), 2.00−1.84 (m, 2H), 1.83−1.67 (m, 2H). C NMR (176
MHz, CDCl ) δ: 28.17, 28.64, 32.03, 33.42, 108.55, 110.86, 130.86,
n
trifluoroethanol-d ) δ: 8.75−6.64 (br, 3H), 3.72−1.07 (br, 20H).
3
3
1
42.04.
-(2,5-Dibromothiophen-3-yl)-N,N-dimethylbutan-1-amine (5).
4
ASSOCIATED CONTENT
Supporting Information
Synthetic details, UPS sample preparation, solution and solid-
state absorption spectra, and representative band-energy
diagram of donor−acceptor polymers. This material is available
free of charge via the Internet at http://pubs.acs.org.
■
A dry 150 mL pressure flask was equipped with a magnetic stir bar
and flushed with nitrogen, and 4 (3.0 g, 8.0 mmol) and dimethylamine
*
S
(
2 M solution in THF, 80 mL, 160 mmol) were added. The mixture
was heated to 60 °C for 12 h, during which time a white salt
precipitated. The mixture was cooled to room temperature and the salt
removed by filtration and washed with Et O. The solvent was removed
2
under reduced pressure to obtain a crude oil that was purified by
column chromatography on silica gel with Hex:EtOAc (1:1) and 1%
AUTHOR INFORMATION
Corresponding Author
*E-mail tsemrick@mail.pse.umass.edu.
Notes
■
TEA as the eluent. The solvent was removed under reduced pressure
1
to give 5 as a colorless oil (1.40 g, 51%). H NMR (300 MHz, CDCl )
3
δ: 6.81 (s, 1H), 2.55 (t, J = 7.4 Hz, 2H), 2.28 (t, J = 7.4 Hz, 2H), 2.23
1
3
(
2
s, 6H), 1.63−1.48 (m, 4H). C NMR (176 MHz, CDCl ) δ: 27.36,
3
The authors declare no competing financial interest.
7.55, 29.48, 45.68, 59.61, 108.20, 110.52, 131.01, 142.72.
-((4-(2,5-Dibromothiophen-3-yl)butyl)dimethylammonio)-
3
ACKNOWLEDGMENTS
propane-1-sulfonate (6). A dry one-neck, 25 mL round-bottom flask,
equipped with a magnetic stir bar, condenser, and inlet adapter was
flushed with nitrogen, and 5 (500 mg, 1.47 mmol) and 1,3-propane
sultone (716 mg, 5.86 mmol) were added. Anhydrous acetonitrile (10
mL) was added to the mixture and heated to reflux for 2 h, during
which time a white precipitate formed. The mixture was cooled to
room temperature, filtered, and washed with anhydrous acetonitrile
followed by anhydrous diethyl ether. The product was dried under
■
Z.A.P. was supported in part by an award from the Department
of Energy (DOE) Office of Science Graduate Fellowship
Program (DOE SCGF). The DOE SCGF Program was made
possible in part by the American Recovery and Reinvestment
Act of 2009. The DOE SCGF program is administered by the
Oak Ridge Institute for Science and Education for the DOE.
ORISE is managed by Oak Ridge Associated Universities
(ORAU) under DOE Contract DE-AC05-06OR23100. Facili-
ties support is acknowledged from the NSF-MRSEC on
Polymers at UMass (DMR-0820506). The Polymer-Based
Materials for Harvesting Solar Energy (PHASE), an Energy
Frontier Research Center funded by the U.S. Department of
Energy, Office of Basic Energy Sciences, under award number
DE-SC0001087, is acknowledged for support of V.V.D., T.E.,
and facilities.
1
reduced pressure to afford 6 as a fluffy white solid (626 mg, 92%). H
NMR (700 MHz, 2,2,2-trifluoroethanol-d ) δ: 6.81 (s, 1H), 3.43−3.36
3
(
2
2
m, 2H), 3.24−3.16 (m, 2H), 2.98 (s, 6H), 2.90 (t, J = 6.8 Hz, 2H),
.65 (t, J = 7.4 Hz, 2H), 2.22−2.16 (m, 2H), 1.77 (dd, J = 10.7, 6.2 Hz,
13
H), 1.66 (p, J = 7.5 Hz, 2H). C NMR (176 MHz, 2,2,2-
trifluoroethanol-d ) δ: 20.08, 23.25, 27.27, 29.71, 48.71, 51.98, 65.13,
3
+
6
6.60, 110.12, 112.56, 132.53, 143.29. HRMS-FAB (m/z): [M + H]
calculated for C H Br NO S : 461.9408; found: 461.9408.
13
22
2
3 2
General Suzuki polycondensation for the preparation of CPZs. To a
mL pressure tube equipped with a magnetic stir bar was added
5
dichlorobis(triphenylphosphine)palladium(II) (0.005 mmol), zwitter-
ionic A2 monomer (3 or 6) (0.25 mmol), diboronate ester B2
monomer (7 or 8) (0.25 mmol), and one drop of Aliquat 336. The
atmosphere was flushed with argon and toluene (2 mL), and 2 M
K CO :2 M NaBr (1 mL) (previously degassed with argon) was
REFERENCES
■
(1) Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913−915.
(2) DiBenedetto, S. A.; Facchetti, A.; Ratner, M. A.; Marks, T. Adv.
Mater. 2009, 21, 1407−1433.
2
3
aq
G
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
(
3) Brabec, C. J.; Shaheen, S. E.; Winder, C.; Sariciftci, N. S.; Denk,
P. Appl. Phys. Lett. 2002, 80, 1288−1290.
4) Li, G.; Chu, C. W.; Shrotriya, V.; Huang, J.; Yang, Y. Appl. Phys.
Lett. 2006, 88, 253503.
5) Kim, J. Y.; Lee, K.; Coates, N. E.; Moses, D.; Nguyen, T. Q.;
Dante, M.; Heeger, A. J. Science 2007, 317, 222−225.
6) Campbell, I. H.; Kress, J. D.; Martin, R. L.; Smith, D. L.;
Barashkov, N. N.; Ferraris, J. P. Appl. Phys. Lett. 1997, 71, 3528−3530.
7) Boer, B. de; Hadipour, A.; Mandoc, M. M.; Woudenbergh, T. V.;
Blom, P. W. M. Adv. Mater. 2005, 17, 621−625.
8) Yip, H.-L.; Hau, S. K.; Baek, N. S.; Ma, H.; Jen, A. K. Adv. Mater.
008, 20, 2376−2382.
9) Wei, Q.; Nishizawa, T.; Tajima, K.; Hashimoto, K. Adv. Mater.
008, 20, 2211−2216.
10) O’Malley, K. M.; Li, C.-Z.; Yip, H.-L.; Jen, A. K.-Y. Adv. Energy
Mater. 2012, 2, 82−86.
11) Ma, H.; Yip, H.-L.; Huang, F.; Jen, A. K.-Y. Adv. Mater. 2010, 20,
371−1388.
12) Wu, H.; Huang, F.; Mo, Y.; Yang, W.; Wang, D.; Peng, J.; Cao,
Y. Adv. Mater. 2004, 16, 1826−1830.
13) Ma, W.; Iyer, P. K.; Gong, X.; Liu, B.; Moses, D.; Bazan, G. C.;
Heeger, A. J. Adv. Mater. 2005, 17 (3), 274−277.
14) Duarte, A.; Pu, K.-Y.; Liu, B.; Bazan, G. C. Chem. Mater. 2011,
3 (3), 501−515.
15) Hou, L.; Huang, F.; Peng, J.; Wu, H.; Wen, S.; Mo, Y.; Cao, Y.
Thin Solid Films 2006, 515, 2632−2634.
16) Steuerman, D. W.; Garcia, A.; Dante, M.; Yang, R.; Lo
P.; Nguyen, T.-Q. Adv. Mater. 2008, 20 (3), 528−534.
17) Dou, L.; You, J.; Yang, J.; Chen, C.-C.; He, Y.; Murase, S.;
Moriarty, T.; Emery, K.; Li, G.; Yang, Y. Nat. Photonics 2012, 6, 180−
85.
18) Liu, X.; Zhu, R.; Zhang, Y.; Liu, B.; Ramakrishna, S. Chem.
Commun. 2008, 3789−3791.
19) Mwaura, J. K.; Zhao, X.; Jiang, H.; Schanze, K. S.; Reynolds, J. R.
Chem. Mater. 2006, 18 (26), 6109−6111.
20) Seo, J. H.; Gutacker, A.; Walker, B.; Cho, S.; Garcia, A.; Yang,
R.; Nguyen, T.-Q.; Heeger, A. J.; Bazan, G. C. J. Am. Chem. Soc. 2009,
31, 18220−18221.
21) Seo, J. H.; Namdas, E. B.; Gutacker, A.; Heeger, A. J.; Bazan, G.
C. Appl. Phys. Lett. 2010, 97 (4), 043303.
22) Seo, J. H.; Namdas, E. B.; Gutacker, A.; Heeger, A. J.; Bazan, G.
C. Adv. Funct. Mater. 2011, 21, 3667−3672.
23) Seo, J. H.; Gutacker, A.; Sun, Y.; Wu, H.; Huang, F.; Cao, Y.;
Scherf, U.; Heeger, A. J.; Bazan, G. C. J. Am. Chem. Soc. 2011, 133,
416−8419.
24) Luo, J.; Wu, H.; He, C.; Li, A.; Yang, W.; Cao, Y. Appl. Phys.
Lett. 2009, 95 (4), 043301.
25) Rider, B. D. A.; Worfolk, B. J.; Harris, K. D.; Lalany, A.;
(35) Seo, J. H.; Nguyen, T.-Q. J. Am. Chem. Soc. 2008, 130, 10042−
10043.
(
(36) Hill, I. G.; Milliron, D.; Schwartz, J.; Kahn, A. Appl. Surf. Sci.
2000, 166, 354−362.
(37) Tengstedt, C.; Osikowicz, W.; Salaneck, W. R.; Parker, I. D.;
Hsu, C.-h; Parker, I. D. Appl. Phys. Lett. 2006, 88, 053502.
(38) Fang, J.; Wallikewitz, B. H.; Gao, F.; Tu, G.; Muller, C.; Pace,
G.; Friend, R. H.; Huck, W. T. S. J. Am. Chem. Soc. 2011, 133, 683−
685.
(
(
(
̈
(39) Nilsson, K. P. R.; Inganas, O. Nat. Mater. 2003, 2, 419−424.
(
2
(
2
(40) Karlsson, K. F.; Asberg, P.; Nilsson, K. P. R.; Inganas, O. Chem.
Mater. 2005, 17, 4204−4211.
(41) Andersson, M.; Ekeblad, P. O.; Hjertberg, T.; Wennerstrom, O.
Polym. Commun. 1991, 32, 546−548.
(
(42) Duan, C.; Wang, L.; Zhang, K.; Guan, X.; Huang, F. Adv. Mater.
2011, 23, 1665−1669.
(
1
(
(43) Sonnenschein, L.; Seubert, A. Tetrahedron Lett. 2011, 52, 1101−
1104.
(44) Huglin, M. B.; Radwan, M. A. Makromol. Chem. 1991, 192,
2
(
433−2445.
45) Georgiev, G. S.; Kamenska, E. B.; Vassileva, E. D.; Kamenova, I.
P.; Georgieva, V. T.; Iliev, S. B.; Ivanov, I. A. Biomacromolecules. 2006,
, 1329−1334.
46) Mary, P.; Bendejacq, D. D.; Labeau, M.; Dupuis, P. J. Phys.
Chem. B 2007, 111, 7767−7777.
47) Shi, C.; Yao, Y.; Yang, Y.; Pei, Q. J. Am. Chem. Soc. 2006, 128,
980−8986.
48) Huo, L.; Zhou, Y.; Li, Y. Macromol. Rapid Commun. 2009, 30,
(
7
(
(
2
(
(
8
(
(
̈
fvander, J.
9
(
(
25−931.
(
49) Salzner, U.; Kose, M. E. J. Phys. Chem. B 2002, 106, 9221−9226.
50) Beaujuge, P. M.; Ellinger, S.; Reynolds, J. R. Nat. Mater. 2008, 7,
1
(
7
(
2
(
95−799.
51) Beaujuge, P. M.; Amb, C. M.; Reynolds, J. R. Acc. Chem. Res.
010, 43, 1396−1407.
52) Osikowicz, W.; Jong, M. P.; Braun, S.; Tengstedt, C.; Fahlman,
M.; Salaneck, W. R. Appl. Phys. Lett. 2006, 88, 193504.
53) Lyon, J. E.; Cascio, A. J.; Beerbom, M. M.; Schlaf, R.; Zhu, Y.;
Jenekhe, S. A. Appl. Phys. Lett. 2006, 88, 222109.
54) Watanabe, Y.; Mihara, T.; Koide, N. Macromol. Chem. Phys.
998, 199, 977−983.
55) Lee, E.; Hammer, B.; Kim, J.-K.; Page, Z.; Emrick, T.; Hayward,
R. C. J. Am. Chem. Soc. 2011, 133, 10390−3.
56) Garreau, R.; Roncali, J.; Garnier, F.; Lemaire, M. J. Chim. Phys.
Phys.-Chim. Biol. 1989, 86, 93−98.
57) Stokes, K. K.; Heuze, K.; McCullough, R. D. Macromolecules
003, 36, 7114−7118.
(
(
(
1
(
(
1
(
(
(
(
(
2
8
(
(
Shahbazi, K.; Fleischauer, M. D.; Brett, M. J.; Buriak, J. M. Adv. Funct.
Mater. 2010, 20, 2404−2415.
(
26) Hoven, C. V.; Yang, R.; Garcia, A.; Crockett, V.; Heeger, A. J.;
Bazan, G. C.; Nguyen, T.-Q. Proc. Natl. Acad. Sci. U. S. A. 2008, 105
35), 12730−12735.
27) Slinker, J. D.; DeFranco, J. A.; Jaquith, M. J.; Silveira, W. R.;
Zhong, Y.-W.; Moran-Mirabal, J. M.; Craighead, H. G.; Abruna, H. D.;
Marohn, J. A.; Malliaras, G. G. Nat. Mater. 2007, 6 (11), 894−899.
28) Ishii, B. H.; Sugiyama, K.; Ito, E.; Seki, K. Adv. Mater. 1999, 11
8), 605−625.
29) Seo, J. H.; Yang, R.; Brzezinski, J. Z.; Walker, B.; Bazan, G. C.;
Nguyen, T.-Q. Adv. Mater. 2009, 21 (9), 1006−1011.
30) Crispin, X.; Geskin, V.; Crispin, A.; Cornil, J.; Lazzaroni, R.;
Salaneck, W. R.; Bredas, J.-L. J. Am. Chem. Soc. 2002, 124, 8131−8141.
(
(
̃
(
(
(
(
́
(
(
(
31) Gao, Y. Mater. Sci. Eng., R 2010, 68, 39−87.
32) Koch, N. J. Phys.: Condens. Matter 2008, 20, 184008.
33) Worfolk, B. J.; Hauger, T. C.; Harris, K. D.; Rider, D. A.;
Fordyce, J. A. M.; Beaupre, S.; Leclerc, M.; Buriak, J. M. Adv. Energy
Mater. 2012, 2, 361−368.
(
34) He, Z.; Zhong, C.; Huang, X.; Wong, W.-Y.; Wu, H.; Chen, L.;
Su, S.; Cao, Y. Adv. Mater. 2011, 23, 4636−4643.
H
dx.doi.org/10.1021/ma302232q | Macromolecules XXXX, XXX, XXX−XXX