Synthesis and characterization of a low-bandgap poly(arylene ethynylene) having donor-acceptor type chromophores in the side chain

Article abstract of DOI:10.1021/ma302576p

A low-bandgap poly(arylene ethynylene) (PAE) having donor-acceptor type chromophores in the side chain was synthesized. A π-conjugated PAE precursor having electron-rich dioctylanilino-substituted alkynes in the side chain was polymerized through Sonogashira cross-coupling reaction between functional monomers M-I with terminal acetylenes and M-II with diiodide, using tetrakis(tripheneylphosphine)palladium and copper iodide catalysts in a mixed solvent of triethylamine and tetrahydrofuran (THF) at 50°C. The electronically rich N,N-dioctylamino groups in M-I activated the alkynes in the side chains of M-I, thus making the selective reaction of sidechain alkynes with TCNE possible in the post-functionalization step. The selective reaction of TCNE (tetracyanoethylene) with activated dioctylanilino substituted alkynes in the side chains of precursor polymer afforded the target poly(arylene ethynylene). This unique polymer shows enhanced thermal stability and exhibits strong intramolecular charge-transfer interactions, resulting in a very low bandgap of poly(arylene ethynylene).

Full text of DOI:10.1021/ma302576p

Note
pubs.acs.org/Macromolecules
Synthesis and Characterization of a Low-Bandgap Poly(arylene
ethynylene) Having Donor−Acceptor Type Chromophores in the
Side Chain
Wenyi Huang* and Hongyan Chen
Department of Polymer Engineering, The University of Akron, Akron, Ohio 44325-0301, United States
S
* Supporting Information
derivatives would always form strong complexes with these
metal-ion catalyst and reduce their catalytic performance.14
This synthetic obstacle can be circumvented by postfunction-
alization with TCNE after polymerization, which requires that
the reaction must be extremely reactive and highly selective.
This can be realized by the “click” type reaction of
tetracyanoethylene (TCNE) with electron-rich alkyne to afford
1,1,4,4-tetracyanobuta-1,3-diene (TCBD) derivatives in a
quantitative yield.15,16 The underlying mechanism lies in the
fact that the electron accepting TCNE would undergo thermal
[2 + 2] cycloaddition with electron-rich alkynes followed by
spontaneous electrocyclic ring-opening of the initially formed
cyclobutenes under mild conditions without the necessity of
any catalyst.17 This cycloaddition/retroelectrocyclization reac-
tion has been borne out to be very fruitful in the synthesis of
donor−acceptor type organic molecules or dendrimers having
interesting electrical, electrochemical, or nonlinear optical
properties.17−20 Very recently, this synthetic protocol has
been generalized into macromolecular systems using aromatic
polyamines bearing electron-rich alkyne side chains21 and PAEs
containing ferrocene in the main chain as precursors.22 In the
latter case, only partial adduction of TCNE occurred due to the
low electron donating property of ferrocene as well as the high
steric hindrance in the main chain.
Herein, we report an effective approach, for the first time, to
synthesizing a low-bandgap PAE having donor−acceptor type
chromophores in the side chain. Specifically, a PAE precursor
with electron-rich alkynes in the side chain was accomplished
through judicious molecular design to endow the polymer with
reasonably high molecular weight. The extremely selective
reaction of TCNE with dialkylanilino-activated alkynes in the
side chains of the polymer afforded donor−acceptor type
chromophores while maintaining the important features of
alternating aromatic ring and ethynylene bonds in the main
chain of the polymer, which have never been accomplished
before.21,22 Such a unique polymer exhibited interesting
intramolecular charge-transfer interactions, leading to a lower
bandgap, potent redox activity, and improved thermal stability.
INTRODUCTION
■
As one of the most important π-conjugated polymers,
poly(arylene ethynylene)s (PAEs) have unique features of
aromatic rings and ethynylene units alternating in the
macromolecular chains, giving rise to distinct electronic and
optical properties as well as outstanding mechanical properties
with enhanced thermal stability and photostability.1,2 Such
features originate, at least in part, from the cylindrical symmetry
of ethynyl bonds, which stabilizes the conjugation of adjacent
aromatic rings irrespective of the orientation of aromatic
planes.1 However, PAEs usually exhibit large bandgaps greater
than 2.0 eV due to their inherent chemical structures. This
restricts their potential applications in many important areas
such as solar cells, light-emitting diodes, field-effect transistors,
and supercapacitors,3−7 where low bandgaps of the conjugated
polymers are highly preferred. For this reason, a plethora of
strategies were developed to narrow down the bandgap of
PAEs, for example, the introduction of the silole or heterocylic
units into the aromatic systems.1 Among these, PAEs with
electron donor and acceptor moieties are of particular interest
because the intramolecular charge-transfer interactions between
donor and acceptor would lead to a lower bandgap. The main
idea behind this lies in that the highest occupied molecular
orbital (HOMO) energy (EHOMO) level of the donor and the
lowest unoccupied molecular orbital (LUMO) energy (ELUMO
level of the acceptor are closer than those in pristine PAE
)
systems, since the bandgap energy (Eg) may be defined by Eg =
8,9
ELUMO − EHOMO
.
To date, the attainable Eg of PAEs having
donor−acceptor interactions was reported to be as low as 1.8
eV.10−12
To achieve a lower bandgap of PAEs, the strength of both
electron donating and accepting units must be further
increased, which can be accomplished by employing stronger
electron donating groups like dialkylamine on the donor to
raise the HOMO energy level as well as stronger electron
withdrawing groups such as −CN and −NO2 on the acceptor
to reduce the LUMO energy level.8,9 Tetracyanoethylene
(TCNE) is one of the strongest electron acceptors13 but has
sparsely been used for the synthesis of donor−acceptor type
polymers. This is attributed to the difficulty in synthesizing
TCNE derivatives suitable for polymerization. Furthermore, it
should be pointed out that many conventional approaches for
synthesizing conjugated polymers, especially those involved
with the use of metal-ion catalysts (e.g., palladium or nickel),
are not appropriate for the applications in the synthesis of
polymers having TCNE derivatives because these TCNE
RESULTS AND DISCUSSION
■
Synthesis of the Precursor Polymer. As illustrated in
Scheme 1, a π-conjugated PAE precursor having electron-rich
Received: December 15, 2012
Revised: February 18, 2013
Published: March 1, 2013
© 2013 American Chemical Society
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Note
Scheme 1. Reaction Scheme for PBBN−TCBD
Scheme 2. Reaction Scheme for Synthesizing Monomer M-I
dioctylanilino-substituted alkynes in the side chain, which was
referred to as PBBN thereafter, was polymerized via
Sonogashira cross-coupling reaction23 between functional
monomers M-I with terminal acetylenes and M-II with
diiodide, using tetrakis(tripheneylphosphine)palladium and
copper iodide catalysts in a mixed solvent of triethylamine
and tetrahydrofuran (THF) at 50 °C. The electronically rich
N,N-dioctylamino groups in M-I activated the alkynes in the
side chains of M-I, thus making the selective reaction of side-
chain alkynes with TCNE possible in the postfunctionalization
step. Nevertheless, the presence of very strong electron
donating groups on M-I typically has a detrimental effect on
the Pd-catalyzed cross-coupling reactions24 during the polymer-
ization of PBBN. For example, the polymerization of M-I with
1,4-diiodobenzene under the same reaction condition for
PBBN has proven to be less efficient, merely resulting in the
formation of oligomers having an Mn of 4600 and an Mw of
7900 determined by gel permeation chromatography in Figure
S37. This observation prompted us to design M-II having
electron withdrawing (carbonyl) groups, which activated the
functional (iodo) groups in M-II for polymerization and
consequently ensured the formation of PBBN with high
molecular weight.
available 4-iodoaniline (1) to afford N,N-dioctyl-4-iodoaniline
(2). Then, N,N-dioctyl-4-iodoaniline (2) was coupled with
trimethylsilylacetylene via Sonogashira reaction at room
temperature, followed by deprotection under basic condition
(potassium carbonate in a mixed solvent of methanol and
THF) to yield 4-(N,N-dioctylamino)phenylethyne (4). 1,4-
Dibromo-2,5-diiodobenzene (6), which was synthesized by
iodization of 1,4-dibromobenzene (5) using iodine in
concentrated sulfuric acid at 125−135 °C,25 was employed as
the starting building block because the iodo group had a higher
reactivity toward Sonogashira reaction than the bromo group.26
Consequently, 1,4-dibromo-2,5-diiodobenzene (6) was coupled
with trimethylsilylacetylene using PdCl2(PPh3)2/CuI/PPh3 as a
catalyst in a mixed solvent of THF and diisopropylamine at
room temperature in such a way that the iodo group in 1,4-
dibromo-2,5-diiodobenzene (6) was selectively reacted with
trimethylsilylacetylene, while the bromo group remained intact.
The resulting 2,5-bis(trimethylsiylethynyl)-1,4-dibromoben-
zene (7) was then reacted with 4-(N,N-dioctylamino)-
phenylethyne under reflux using the aforementioned catalyst
system, followed by deprotection in the basic condition to
produce M-I.
The reaction scheme for synthesizing M-I is depicted in
Scheme 2, and the detailed experimental procedures and
characterizations are presented in the Supporting Information
(Figures S1−S20). The flexible side chains on M-I were
introduced to ensure good solubility of both monomer and
polymer in organic solvents by alkylation of the commercially
The reaction scheme for the synthesis of M-II is shown in
Scheme 3, and the detailed experimental procedures and
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Note
Scheme 3. Reaction Scheme for Synthesizing Monomer M-II
characterizations are presented in the Supporting Information
(Figures S21−S28). The synthesis of M-II began with p-xylene
(9), which was iodized by iodine and periodic acid in a sulfuric
acid/acetic acid/chloroform solvent system.27 2,5-Diiodo-p-
xylene (10) obtained was then oxidized by potassium
permanganate to obtain 2,5-diiodoterephthalic acid (11),27
which was then chlorinated by thionyl chloride and
subsequently esterified with 1-butanol in the presence of
triethylamine to obtain M-II.
Synthesis of PBBN−TCBD. Referring to Scheme 1, the
precursor PBBN was then subjected to the reaction with
TCNE, which proceeded well in dichloromethane at room
temperature to afford the target PAE having donor−acceptor
type chromophores in the side chains (denoted by PBBN−
TCBD), as evidenced by an immediate color change of polymer
solution from light yellow to red. The cycloaddition/retro-
electrocyclization reaction predominately prevailed over the
electron-rich alkynes in the side chains of PBBN, whereas the
deactivated alkynes in the main chain of PBBN were kept
intact, even in the case of excessive loading of TCNE in the
reaction solution. This may be attributed to both deactivating
effects of carbonyl group and steric hindrance effect of bulky
side chains on the main-chain alkynes in PBBN. Once the
activated alkynes were converted into electron-accepting
TCBD, the reaction of TCNE with main-chain alkynes would
be nearly impossible. It should be noted that an excess amount
of TCNE did not produce any side reactions at this
temperature and it could be readily removed by column
chromatography. As a consequence, we were able to obtain
PBBN−TCBD with a well-defined structure.
Characterization of PBBN and PBBN−TCBD. Both
PBBN and PBBN−TCBD are well soluble in common solvents
such as THF, chloroform, and dichloromethane, owing to the
presence of long flexible side chains along the macromolecular
chains. As a result, polymer films can be easily prepared by
solution-casting method. As determined by gel permeation
chromatography (GPC) shown in Figure 1, PBBN has a
sufficiently high molecular weight (Mn = 26 072, corresponding
to about 50 repeat units of alternating arylene and ethynylene)
and a good polydispersity (Mw/Mn = 1.97), which originate
from the enhanced reactivity of diiodide group in M-II by
carbonyl groups as well as good solubility of the polymer in the
reaction solution. On the other hand, PBBN−TCBD reveals a
reasonable increase in molecular weight (Mn = 31 754) due to
the TCNE adduction and an appreciable decrease in
polydispersity (Mw/Mn = 1.73) because of further purification
by column chromatography upon the completion of reaction, as
compared with those of PBBN. Notice that although the
molecular weights of PBBN and PBBN−TCBD may be
Figure 1. GPC traces of (a) PBBN (dashed line) and (b) PBBN−
TCBD (solid line) using THF as eluent and polystyrenes as standards.
overestimated by GPC measurements owing to their rigid
backbones and bulky side chains, it is useful for relative
comparison.
1
The chemical structure of PBBN was confirmed by H and
13C NMR spectra in Figures S29 and S30 and the FTIR
spectrum in Figure S31, while the chemical structure of
1
PBBN−TCBD was verified by H and 13C NMR spectra in
Figures S32 and S33 and the FTIR spectrum in Figure S34. In
regard to the 1H NMR spectra, a desirable shift for each peak of
PBBN−TCBD relative to that of PBBN is observed in Figure
S35 due to the influence of electron withdrawing TCBD units
in PBBN−TCBD. A close look at the 13C NMR spectra in
Figure S36a reveals two chemical shifts at 85.7 and 93.3 ppm,
which may be assigned to the main-chain and side-chain
alkynes in PBBN, respectively. Upon the reaction of PBBN
with TCNE, the chemical shift of main-chain alkynes has
slightly shifted to 82.3 ppm, while a new chemical shift at 93.3
ppm is attributed to =C(CN)2 groups in PBBN−TCBD.
Furthermore, the presence of TCBD units in PBBN−TCBD
can be confirmed by the existence of −CN at chemical shifts of
112.5, 114.9, 115.9, and 116.9 ppm and CC(CN)2 at
chemical shifts of 161.6 and 168.6 ppm. The following
observations can be made from the FTIR spectra in Figure 2.
PBBN exhibits an absorption peak at 2191 cm−1 for side-chain
alkynes and a shoulder at 2186 cm−1 for main-chain alkynes.
Upon the completion of reaction with TCNE, PBBN−TCBD
shows an absorption peak at 2214 cm−1 for the −CN group and
a shoulder at 2185 cm−1 for main-chain alkynes. Because of the
effect of strong electron accepting TCBD, the carbonyl group
in PBBN at a wavenumber of 1707 cm−1 is red-shifted to 1722
cm−1 for PBBN−TCBD. The aforementioned results clearly
demonstrate that the cycloaddition/retro-electrocyclization
reaction of TCNE with activated alkynes selectively occurred
in the side chains of PBBN.
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Macromolecules
Note
grams in Figure 5. It can be observed from Figure 4a that
PBBN displays the π−π* transitions at 229, 271, 335, and 406
nm. PBBN has a molar absorptivity (ε) of 2.4 × 104 mol−1
L
cm−1 in dichloromethane at λmax,abs = 406 nm. Remarkably, a
shoulder appears at 498 nm with a long tail that decays well
into the visible region, indicative of the strong electron
donating property of the polymer containing dialkylamino
groups.29 Since the onset wavelength (λonset) of PBBN is about
582 nm, the optical bandgap energy of PBBN is determined to
be 2.13 eV. Despite the nonplanarity of TCBD unit, the
efficient intramolecular charge-transfer interactions between
dialkylamino donors and TCBD-containing acceptors are
established for various species.16 Such an intramolecular
charge-transfer interaction is also present in our synthesized
PAE with donor−acceptor type chromophores in the side
chains. As shown in Figure 4b, the UV−vis spectrum of
PBBN−TCBD exhibits broad charge-transfer (CT) bands with
Figure 2. FTIR spectra of (a) PBBN and (b) PBBN−TCBD.
Thermogravimetric analysis in Figure 3 reveals that PBBN
begins to decompose at 181 °C while PBBN−TCBD starts to
a maximum absorption peak at 463 nm (ε = 3.9 × 104 mol−1
L
cm−1) in the visible absorption region. It is noteworthy that the
onset wavelength (λonset) of PBBN−TCBD reaches ca. 780 nm
close to the near-IR region, and correspondingly the optical
bandgap energy (Egopt) is determined to be 1.59 eV, which is
much lower than that of PBBN. The strong intramolecular
charge-transfer interactions in PBBN−TCBD induced such a
low bandgap in the PAE π-conjugated system. In the UV region
of Figure 4b, strong absorption bands at approximately 228,
252, 289, and 344 nm are characteristic of π−π* transitions
located on the phenyl and ethynyl subunits of PBBN−TCBD.
These absorption bands were red-shifted relative to those of
PBBN, indicative of the strong effects of electron withdrawing
TCBD units in PBBN−TCBD.
Figure 3. TGA data of PBBN (dashed line) and PBBN−TCBD (solid
line).
decompose at 267 °C. The remarkable enhancement of thermal
stability by 86 °C may arise from the strong donor−acceptor
interactions in PBBN−TCBD and/or the change of chain
conformation upon the reaction of side-chain alkynes of PBBN
with TCNE. The high thermal stability of PBBN−TCBD is
essential for its practical applications. The differential scanning
calorimetry thermograms in Figure S38 indicate that PBBN
exhibits a glass transition temperature (Tg) at 44.6 °C and a
melting temperature (Tm) at 97.3 °C. In contrast, PBBN−
TCBD only shows a Tg at 53.2 °C, and the increase of Tg by 8.6
°C is attributed to intramolecular charge-transfer interactions
along macromolecular chains, which will be elaborated by UV−
vis spectroscopy and cyclic voltammetry. No Tm can be
identified in PBBN−TCBD, which may be attributed to the
nonplanarity of TCBD units.28
The electrochemical behaviors of PBBN and PBBN−TCBD
are shown by cyclic voltammograms in Figure 5, where the
locations of oxidation and reduction potentials are identified.
All potentials are referenced to the ferricinium/ferrocene (Fc+/
Fc) couple, and they are used as an internal standard following
the literature.30 Specifically, PBBN displays a quasi-reversible
one-electron oxidation step at a half-wave oxidation (E1/2ox) of
0.34 V vs Fc+/Fc, which is attributed to the redox between
ox
amine and amine cation, and the other oxidation step at E1/2
of 0.93 V vs Fc+/Fc, which represents the subsequent oxidation
from amine cation to dication.31 The prefix “quasi” is used
because the cathodic peak current is typically smaller than the
ox
anodic peak current. The irreversible anodic peak at Epa
=
0.70 V may be attributed to the oxidation effect of the neutral
arylene ethynylene backbone in PBBN.1 Figure 5b shows that
Low Bandgap in PBBN−TCBD Induced by Intra-
molecular Charge-Transfer Interactions. The intramolec-
ular charge-transfer interactions in PBBN−TCBD are evi-
denced by UV−vis spectra in Figure 4 and cyclic voltammo-
red
PBBN−TCBD exhibits a half-wave reduction potential (E1/2
)
of −1.04 V vs Fc+/Fc, which is ascribed to the electron
accepting TCBD units in PBBN-TCBD. The large potential
difference (ΔE = 1.26 V) of reduction potential for PBBN−
TCBD between the cathodic and anodic peaks might have
arisen from the conformational changes between the distorted
neutral TCBD and the planar anion of TCBD during the
charge-transfer process.14 It can also be observed from Figure
ox
5b that there exhibits an irreversible anondic peak at Epa
=
0.29 V owing to the oxidation effect of the neutral arylene
ethynylene backbone in PBBN−TCBD. This peak has a shift of
−0.41 V relative to that of PBBN, arising from the strong
electron accepting effect of TCBDs in PBBN−TCBD.
Furthermore, PBBN−TCBD shows a half-wave oxidation
potential (E1/2ox) at 0.89 V vs Fc+/Fc, which can be assigned
to the electron donating N,N-dioctylanilino groups in PBBN−
TCBD.
Figure 4. UV−vis spectra of (a) PBBN and (b) PBBN−TCBD in
dichloromethane.
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Note
Figure 5. Cyclic voltammograms of (a) PBBN and (b) PBBN−TCBD in dichloromethane solution containing 0.1 M nBu4NPF6. Epa and Epc are
anodic and cathodic peak potentials, respectively, with “ox” denoting oxidation and “red” denoting reduction. Red arrows describe the directions of
scans.
It can be seen from Figure 5b that PBBN−TCBD shows an
onset oxidation potential (Φox = 0.74 V) and an onset
reduction potential (Φred = −0.61 V), which were obtained
from the intersection of the two tangents drawn at the rising
current and the baseline charging current of the CV curves.
Under the premise that the energy level of Fc+/Fc is 4.80 eV
below the vacuum level,32 the energy levels of HOMO and
AUTHOR INFORMATION
■
Corresponding Author
*E-mail polymerhuang@yahoo.com; Ph 1-330-622-3807; Fax
1-330-972-5290.
Notes
The authors declare no competing financial interest.
LUMO are estimated to be EHOMO = −5.54 eV and ELUMO
=
ACKNOWLEDGMENTS
−4.19 eV, respectively. Correspondingly, the bandgap energy
(EgCV) of PBBN−TCBD based on cyclic voltammetric results is
1.35 eV. Note that this value is slightly lower than Egopt = 1.59
eV determined by UV−vis spectroscopy. The lower electro-
chemical band gap of PBBN−TCBD relative to its optical band
gap may be interpreted by the ion pairing effects, indicative of a
very low exciton binding energy. Above, we estimated energy
levels of HOMOs and LUMOs by using onset potentials
because reversible oxidation/reduction potentials were not
identified for PBBN−TCBD, while half-wave potentials had to
be used in the rigorous sense. On the basis of the observations
made above, it can be concluded that intramolecular charge-
transfer interactions indeed induced a low bandgap energy in
PBBN−TCBD.
■
The authors acknowledge with gratitude that this study was
supported in part by the National Science Foundation under
Grant CBET-0755763.
REFERENCES
■
(1) Weder, C. Poly(arylene ethynylene)s: From Synthesis to Application;
Springer: New York, 2005.
(2) Bunz, U. H. F. Chem. Rev. 2000, 100, 1605−1644.
(3) Winder, C.; Sariciftci, N. S. J. Mater. Chem. 2004, 14, 1077−1086.
(4) Bundgaard, E.; Krebs, F. C. Solar Energy Mater. Solar Cells 2007,
91, 954−985.
(5) Kulkarni, A. P.; Tonzola, C. J.; Babel, A.; Jenekhe, S. A. Chem.
Mater. 2004, 16, 4556−4573.
(6) Chen, M.; Crispin, X.; Perzon, E.; Andersson, M. R.; Pullerits, T.;
Andersson, M.; Inganas, O.; Berggren, M. Appl. Phys. Lett. 2005, 87,
252105.
̈
CONCLUSION
■
́
(7) Soudan, P.; Lucas, P.; Ho, H. A.; Jobin, D.; Breau, L.; Belanger,
To summarize, we have demonstrated a facile approach toward
the synthesis of a poly(arylene ethynylene) having donor−
acceptor type chromophores in the side chains. A precursor π-
conjugated polymer with reasonably high molecular weight was
obtained by the Sonogashira reaction between one monomer
with terminal acetylenes and the other with activated diiodide.
The selective reaction of TCNE with activated dioctylanilino-
substituted alkynes in the side chains of precursor polymer
afforded the target poly(arylene ethynylene). This unique
polymer shows enhanced thermal stability and exhibits strong
intramolecular charge-transfer interactions, resulting in a very
low bandgap of poly(arylene ethynylene). Along with the
inherent features of poly(arylene ethynylene), this low bandgap
π-conjugated polymer is a promising material for applications in
nonlinear optical devices, organic photovoltaic devices, and
light-emitting diodes.
D. J. Mater. Chem. 2001, 11, 773−782.
(8) Ajayaghosh, A. Chem. Soc. Rev. 2003, 32, 181−191.
(9) Roncali, J. Chem. Rev. 1997, 97, 173−205.
(10) Ashraf, R. S.; Klemm, E. J. Polym. Sci., Part A: Polym. Chem.
2005, 43, 6445−6454.
(11) Morikita, T.; Yamaguchi, I.; Yamamoto, T. Adv. Mater. 2001, 13,
1862−1864.
(12) Palai, A. K.; Mishra, S. P.; Kumar, A.; Srivastava, R.;
Kamalasanan, M. N.; Patri, M. Eur. Polym. J. 2010, 46, 1940−1951.
(13) Miller, J. S. Angew. Chem., Int. Ed. 2006, 45, 2508−2525.
(14) Huang, W.; Han, C. D. Macromolecules 2012, 45, 4425−4428.
(15) Bruce, M. I.; Rodgers, J. R.; Snow, M. R.; Swincer, A. G. J. Chem.
Soc., Chem. Commun. 1981, 271−272.
(16) Kivala, M.; Diederich, F. Acc. Chem. Res. 2009, 42, 235−248.
(17) Kivala, M.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.; Gross, M.;
Diederich, F. Angew. Chem., Int. Ed. 2007, 46, 6357−6360.
(18) Kivala, M.; Stanoeva, T.; Michinobu, T.; Frank, B.; Gescheidt,
G.; Diederich, F. Chem.Eur. J. 2008, 14, 7638−7647.
(19) Michinobu, T.; May, J. C.; Lim, J. H.; Boudon, C.; Gisselbrecht,
J.-P.; Seiler, P.; Gross, M.; Biaggio, I.; Diederich, F. Chem. Commun.
2005, 737−739.
ASSOCIATED CONTENT
■
S
* Supporting Information
Detailed experimental procedures and characterizations of
monomers and polymers. This material is available free of
charge via the Internet at http://pubs.acs.org.
(20) Michinobu, T.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.; Frank,
B.; Moonen, N. N. P.; Gross, M.; Diederich, F. Chem.Eur. J. 2006,
12, 1889−1905.
2036
dx.doi.org/10.1021/ma302576p | Macromolecules 2013, 46, 2032−2037

Macromolecules
Note
(21) Michinobu, T. J. Am. Chem. Soc. 2008, 130, 14074−14075.
(22) Michinobu, T.; Kumazawa, H.; Noguchi, K.; Shigehara, K.
Macromolecules 2009, 42, 5903−5905.
(23) Chinchilla, R.; Naj
(24) Blankenburg, L.; Klemm, E. Des. Monomers Polym. 2003, 6, 57−
65.
́
era, C. Chem. Rev. 2007, 107, 874−922.
(25) Chanteau, S. H.; Tour, J. M. J. Org. Chem. 2003, 68, 8750−8766.
(26) Marsden, J. A.; Miller, J. J.; Shirtcliff, L. D.; Haley, M. M. J. Am.
Chem. Soc. 2005, 127, 2464−2476.
(27) Zhou, Q.; Swager, T. M. J. Am. Chem. Soc. 1995, 117, 12593−
12602.
́
(28) García, R.; Herranz, M. A.; Torres, M. R.; Bouit, P. A.; Delgado,
J. L.; Calbo, J.; Viruela, P. M.; Ortí, E. M. N. J. Org. Chem. 2012, 77,
10707−10717.
(29) Thomas, S. W. I.; Swager, T. M. Macromolecules 2005, 38,
2716−2721.
́
(30) Gagne, R. R.; Koval, C. A.; Lisensky, G. C. Inorg. Chem. 1980,
19, 2854−2855.
(31) Michinobu, T.; Inui, J.; Nishide, H. Org. Lett. 2003, 5, 2165−
2168.
(32) Pommerehne, J.; Vestweber, H.; Guss, W.; Mahrt, R. F.; Bassler,
̈
H.; Porsch, M.; Daub, J. Adv. Mater. 1995, 7, 551−554.
2037
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