First hydrogen-bonding-induced self-assembled aggregates of a polyfluorene derivative

Article abstract of DOI:10.1021/ma020744s

A convenient approach to a novel polyfluorene derivative (PI) with hydrogen-bonding interactions and another derivative P2 without hydrogen-bonding interactions has been developed. The structure of polymers PI and P2 is verified by FT-IR, ¹H an

Full text of DOI:10.1021/ma020744s

Macromolecules 2003, 36, 323-327
323
First Hydrogen-Bonding-Induced Self-Assembled Aggregates of a
Polyfluorene Derivative
J ia n P ei,*,†,‡ Xia o-Lin g Liu ,† Zh i-Ku a n Ch en ,† Xin -Ha i Zh a n g,† Yee-Hin g La i,† a n d
Wei Hu a n g†
College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China, and
Institute of Materials Research and Engineering and Department of Chemistry,
National University of Singapore, 3 Research Link, Singapore 117602
Received May 15, 2002; Revised Manuscript Received November 22, 2002
ABSTRACT: A convenient approach to a novel polyfluorene derivative (P 1) with hydrogen-bonding
interactions and another derivative P 2 without hydrogen-bonding interactions has been developed. The
structure of polymers P 1 and P 2 is verified by FT-IR, 1H and 13C NMR, and elemental analysis. The
investigation demonstrates that the intramolecular and intermolecular H-bonding interactions play an
important role in the optical properties of P 1 in the dilute solution and in films. P 1 emits different light
in dilute solutions (blue color) and in solid states (yellowish-orange) under the irradiation of UV light.
The time-resolved PL decay dynamics also demonstrate the existence of such interactions in P 1. However,
this phenomenon is not observed in another polymer (P 2) without hydrogen-bonding interactions. The
scanning electron microscopic (SEM) results of P 1 at solid states reveal the formation of entangled
nanostructures induced though the hydrogen-bonding interactions. Therefore, the investigation shows
that the interaction between the nitrogen and the hydroxy group at the 9-position effectively affects the
optical properties of P 1, which might provide a new approach to control over molecular ordering through
interchain interactions, especially the hydrogen bonding.
In tr od u ction
resulting from hydrogen-bonding complexation and
interactions.6 Especially, a series of biomaterials based
on polyacetelyene with chiral amino acid and glucose
as substituents exhibited excellent mesoscopic order and
superstructures through interchain interactions.7
Herein, to understand the effect of the hydrogen-bond-
induced intramolecular and intermolecular interactions
on the optical and electronic properties of conjugated
polymers, which may also be the main driving force in
the mesoscopic order, we designed and synthesized two
polyfluorene compounds. Polyfluorene and derivatives
(PFs), as blue light-emitting polymers, are one class of
the most promising materials, and their chemical and
physical properties have been actively investigated.8
Although they exhibit the high efficiency and good
thermal stability, chain aggregation and excimer forma-
tion tend to degrade the performance of optical and
electrooptical devices.8 Excimers are known to provide
nonradiative relaxation pathways in polyfluorenes,
which lead to reduced emission efficiency relative to
exciton luminescence. In this contribution, within poly-
mer P 1, hydroxide and 5′-methyl-2,2′-bipyridyl-5-methyl
groups were introduced at the 9-position of fluorene
rings. The intramolecular and/or the intermolecular
hydrogen bond between the hydrogen atom of the
hydroxide group and the nitrogen atom of the pyridine
ring may form in the dilute solution and/or in the solid
states, which may affect the molecular structure and
the properties of polymer P 1. Therefore, to further
demonstrate this effect, we also synthesized another
derivative, polymer P 2, in which the hydrogen bond was
interrupted because of the replacement of hydroxy group
by a benzyloxy group at the methylene bridge of the
fluorene ring.
One of the expectations in material science is to
discover surprising properties or functionality of novel
materials. In the past two decades, since conjugated
(semiconducting) polymers serve as highly responsive
optical and electrical platforms for the new generation
of the display technologies, extensive experimental and
theoretical attention has been devoted to studies of
π-conjugated polymers in science and emerging industry
technologies.1 Control of nano- and mesoscopic order in
conjugated systems is a subject of great importance
because it enables the tuning of macroscopic properties
of electrooptical devices such as organic light-emitting
diodes (OLEDs),2 field effect transistors (FET),3 and
chemosensors and biosensors.4 As electrical and optical
functionalities rely on extended conjugated systems, a
lot of work has been devoted to π stacking as the major
driving force for one-dimensional columnar superstruc-
tures.5 However, the concomitant electronic interactions
are not always desired because of substantial and hardly
predictable changes of the molecular properties of the
chromophores. Recently, control over molecular ordering
to nanoscale dimension through hydrogen bonding,
π-stacking, solvatochromic, and other intramolecular
and/or intermolecular interactions is a challenging field
of material research. The optical response of chro-
mophores aggregates provides an important tool in
studies of intermolecular and intramolecular interac-
tions and bonding. Mesoscopic order can be achieved by
applying the self-assembly technique in molecules with
well-defined structures. Superstructures including cy-
lindrical strands have also been achieved and formed
† Peking University.
‡ Institute of Materials Research and Engineering and National
University of Singapore.
Exp er im en ta l Section
In str u m en ta tion . 1H and 13C NMR spectra were obtained
as solutions in deuterated chloroform and recorded on a Bruker
* To whom correspondence should be addressed: e-mail
jianpei@chem.pku.edu.cn; Tel 86-10-62753427; Fax 86-10-62751708.
10.1021/ma020744s CCC: $25.00 © 2003 American Chemical Society
Published on Web 12/21/2002

324 Pei et al.
Macromolecules, Vol. 36, No. 2, 2003
F igu r e 1. Synthetic route to polymers P 1 and P 2.
ACF 300 and AMX 400 spectrometer. TMS was used as
internal reference for all compounds. FT-IR spectra were
obtained as KBr pellets on a Bio-Rad FTS 165 spectrometer.
Elemental analyses were obtained on a Perkin-Elmer 2400
elemental analyzer in the Microanalysis Lab at the National
University of Singapore. Molecular weights of the polymer
were determined by gel permeation chromatography (GPC)
against the standard of polystyrene on a Perkin-Elmer model
200 HPLC system and THF as the eluting solvent. The UV-
vis absorption spectra of the polymer were recorded on a
Shimadzu UV-3101 scanning spectrophotometer. The fluores-
cence spectra were collected on a Perkin-Elmer LS50B lumi-
nescence spectrometer. The scanning electron microscope
results were carried out on a J EDL J SM 6700F field emission
gun scanning electron microscope with 1.0 nm (1.5 kV)
resolution.
150.02, 146.20, 141.51, 140.66, 140.16, 139.73, 139.54, 139.35,
137.76, 133.58, 132.48, 128.89, 128.67, 127.83, 126.60, 123.63,
121.66, 121.06, 120.92, 120.48, 120.01, 88.48, 66.86, 55.84,
43.51, 40.76, 31.87, 30.04, 24.20, 22.98, 18.81, 14.42. Anal.
Calcd for C57H56N2O: C, 87.20; H, 7.19; N, 3.57. Found: C,
86.65; H, 7.36; N, 3.51. FT-IR (λ, cm-1): 3028, 2925, 2853,
1597, 1551, 1459, 1405, 1248, 889, 814, 779, 743, 696.
Resu lts a n d Discu ssion
The structure of polymers P 1 and P 2 is outlined in
Figure 1. The monomers and polymers were prepared
by the multistep synthetic approach. The monomer M1,
9,9-dihexylfluorene-2,7-bis(trimethylene boronate), was
prepared using 2,7-dibromofluorene following the lit-
erature procedures.9 The lithiation of 5,5′-dimethyl-2,2′-
bipyridine reacted with 2,7-dibromo-9-fluorenone af-
forded 2,7-dibromo-9-hydroxy-9-(5′-methyl-2,2′-bipyridyl-
5-methyl)fluorene (monomer M2). The benzylation of
the hydroxide group of monomer M2 afforded compound
3. According to our previous contributions,9c,10 the
Suzuki coupling polymerization with Pd(PPh3)4 as
catalyst was employed to produce the desired polymers
(P 1 and P 2). After careful purification to remove ionic
impurities and catalyst residues, brown fibrous poly-
mers were obtained with a yield of over 85%. The
chemical structure and the purity of the polymers were
verified by FT-IR, 1H and 13C NMR, and elemental
analysis. The number molecular weight (Mn) measure-
ment by GPC against the standard of polystyrene and
THF as eluent was about 7000 with a PD of 1.8 for P 1
and 13 500 with a PD of 1.8 for P 2. The polymers were
readily dissolved in toluene, THF, p-dioxane, chloroform,
NMP, DMF, and pyridine.
P oly[(9,9-d i-n -h exyl-9H-flu or en -2,7-ylen e)-co-a lt-(9-h y-
d r oxy-9-((5′-m eth yl-2,2′-bip yr id yl)-5-yl)m eth yl)-9H-flu o-
r en -2,7-ylen e] (P 1). Under an argon atmosphere, monomers
1 (0.502 g, 1 mmol) and 2 (0.506 g, 1 mmol) were added
together with 1.5 mol % of Pd(PPh3)4, 3 mL of toluene, and
2.5 mL of 2 M aqueous sodium carbonate solution. The mixture
was stirred under vigorous at 80-90 °C for 48 h. The mixture
was poured into stirred 100 mL of methanol to precipitate
plenty of light-yellow solids. The solids were collected by
filtration and washed with methanol and water. The polymer
was washed with refluxing acetone in Soxhlet for 2 days. The
light-yellow solids were dried under vacuum at room temper-
ature. Yield: 80%. 1H NMR (CDCl3, 400 MHz, ppm): 8.06-
7.50 (10H, b), 7.28-7.01 (8H, m), 5.55 (1H, s, OH), 3.77 (2H,
s, Py-CH2), 2.30 (3H, s, Py-CH3), 2.15-0.81 (26H, b). Anal.
Calcd for C50H50N2O: C, 86.42; H, 7.25; N, 4.03. Found: C,
86.29; H, 7.52; N 4.39. FT-IR (λ, cm-1): 3639, 2956, 2859, 1603,
1459, 1435, 1401, 1248, 1231, 886, 860, 814, 770, 698.
P oly[(9,9-di-n -h exyl-9H-flu or en -2,7-ylen e)-co-alt-(9-ben -
zyloxyl-9-((5′-m eth yl-2,2′-bip yr id yl)-5-yl)m eth yl)-9H-flu o-
r en -2,7-ylen e] (P 2). The polymer were also obtained through
the same procedure to produce P 1 utilizing monomers 1 and
The UV-vis absorption and photoluminescence (PL)
spectra of polymers P 1 and P 2 in solution were inves-
tigated. Both polymers exhibited almost the same
absorption spectra in THF solution and peaked at about
382 nm as poly(9,9-dialkylfluorene)s. The fluorescence
spectrum of P 1 in THF solution peaked at about 410
1
3. H NMR (CDCl3, 400 MHz, ppm): 8.58 (1H, s, Py-H), 8.41
(1H, s, Py-H), 8.36-8.29 (2H, q, Py-H), 7.77-7.20 (19H, m,
aromatic-H), 4.17 (2H, s, OCH2), 3.60 (2H, s, Py-CH2), 2.46
(3H, s, Py-CH3), 2.05 (4H, s, CH2), 1.54-0.67 (22H, m). 13C
NMR (CDCl3, 100 MHz, ppm): 154.99, 154.16, 152.28, 151.71,

Macromolecules, Vol. 36, No. 2, 2003
Self-Assembled Aggregates of a Polyfluorene 325
F igu r e 2. Steady-state fluorescence spectra of P 1 in different
solvents: toluene (cycle), THF (square), p-dioxane (diamond),
DMF (cross), NMP (line), and pyridine (triangle).
F igu r e 3. Steady-state fluorescence spectra of polymer 1 in
THF-methanol: from up to down, methanol-THF, v/v ) 0.0,
0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.0, 12.0, 17.0, and 27.0 µL/3
mL.
and 436 nm and exhibited a shoulder at about 468 nm;
however, it also showed a broad band that peaked at
538 nm (spread from 500 to 650 nm) with low intensity,
which was not observed in the emission spectra of P 2
and poly(9,9-dialkylfluorene). In comparison with P 2,
the new emitted peak of P 1 in THF solution may be
due to the possibility of self-assembled structures
through the intra- and/or intermolecular hydrogen-
bonding interactions or π-aggregation or both. From its
structure, we can find that the hydroxy group at the
same position of fluorene ring of P 1 can interact with
the nitrogen atom of bipyridine group at the 9-position
of the fluorene ring to form intra- or interunit hydrogen
bonding in the dilute solution. To investigate this
possibility, we also measured the absorption and fluo-
rescent spectra of P 1 in different solvents, which possess
different hydrogen-bonding ability. Figure 2 exhibits the
PL spectra of P 1 in different organic solvents. It was
observed that a similar broad peak at about 520 nm
emerged in toluene and p-dioxane solutions, which was
also observed in THF solution, although the fluorescent
intensity decreased with increase of the polarity of the
solvents from toluene to THF and p-dioxane. However,
this new fluorescent peak fully disappeared in the PL
spectra in strong hydrogen-bonding solvents such as
DMF and NMP. These observations implied that P 1
formed self-assembled aggregates through hydrogen-
bonding interactions in toluene, p-dioxane, and THF at
room temperature whereas such self-assembly was
totally disrupted by the addition of strong hydrogen-
bonding solvents. Further measurement of the PL
spectrum of P 1 in pyridine solution exhibited that the
broad band was observed with an additional about 20
nm red-shifted in comparison to ones in toluene, p-
dioxane, and THF. We guess that new aggregation
might form between the hydroxide group of P 1 and the
solvent, pyridine, and induce the energy level of their
excited states shifted. As shown in Figure 2, the solution
of P 1 still emitted blue light under the irradiation of
UV light in the different solvents.
the concentration of methanol reached 1% (v/v). The
results further indicated that addition of methanol did
not affect the backbone structure of polymer in the
solution but caused an obvious effect on the interaction
of the hydrogen bonding. Therefore, addition of small
amounts of strong H-bonding solvents such as methanol
to THF solution of P 1 induces a considerable effect on
the forming of the intra- and/or intermolecular H-
bonding.
The absorption and PL spectra in films of polymers
P 1 and P 2 were also measured (as shown in Figure 4).
From both absorption and PL spectra of P 2 in films,
we observed that they were identical with those in dilute
solutions. For P 1, an interesting change occurred in its
fluorescent spectra in the transparent film spin-cast
from toluene solution (2% w/v) although the absorption
spectrum in the film exhibited only a slight red shift in
comparison with that in the solution in THF. We found
that the broad peak at 572 nm appeared more apparent.
Two fluorescent peaks at 415 and 425 nm, which were
slightly red-shifted in comparison with those in the
dilute solution, were also found in very low intensity
(1/10 as that of the main peak at 572 nm). In the dilute
toluene solution, the emission spectrum showed well-
resolved vibronic structure. The thin-film emission
spectrum was generally broad, structureless, and red-
shifted in comparison with solution ones. It implies that
the emission from the singlet excited state of the
1
chromophores A* observed in the dilute solution emis-
sion spectrum did not play a main role in the thin-film
emission. On the contrary, the emission from P 1 might
originate from another chromophores, mainly singlet
1
excimers (AA)*, formed by the intra- and/or interchain
interactions due to the hydrogen bonding and aggrega-
tion, which was not observed in P 2 and other polyfluo-
rene derivatives with disubstituted alkyl groups at the
methylene bridge of the fluorine rings. This physical
degradation usually leads to a red-shifted fluorescence
and reduced intensity by exciton migration and relax-
ation through lower energy excimer traps. The films of
P 1 emitted yellowish-orange light under the irradiation
of UV light. We did not think that this low-energy
emission bands (red-shift of the emission spectra) in our
polymer were due to the formation of keto defect sites
at the methylene bridge as the key role in the fluores-
cence spectra of polyfluorenes,11 since the obvious dif-
ference between the absorption spectra of P 1 in the
We also investigated the behavior of the emission
spectra of P 1 in THF solution with successive addition
of methanol. As shown in Figure 3, although the
bandwidth and fluorescent intensity of two emission
peaks at about 410 and 436 nm and the shoulder peak
at 485 nm were identical, the broad peak at about 500-
650 nm obviously decreased upon the addition of
methanol to the solution (each 0.5 µL of methanol to 3
mL solution in THF) and completely disappeared when

326 Pei et al.
Macromolecules, Vol. 36, No. 2, 2003
F igu r e 4. Absorption (circle) and steady-state fluorescence spectra (diamond) of P 2 and the fluorescence spectrum (square) of
P 1 and in film states spin-casting from xylene solution.
F igu r e 5. Time-resolved photoluminescence decays for solu-
tion of polymer 1 at detection wavelengths of λem ) 538 nm in
THF solution and THF/methanol (100/1) solution.
solutions and the solid films was not observed, and we
suggested that it might be impossible to generate any
defects including keto sites in our polymers (P 1 and P 2)
through forming the fluorenyl anions.11 Actually, the
dominated peak in the emission spectra of P 1 in the
solid states was also red-shifted in comparison with the
polyfluorene derivatives with keto defects sites. Some
results indicated that the introduction of bulky side
chains could effectively prevent the formation of the
aggregation in the solid states, causing the emission
spectra red shift (the low-energy bands), which we
usually observed among the polyfluorene derivatives
bearing slightly less bulky side chains.12 However, these
F igu r e 6. Scanning electron micrographs (SEM) of the thin
low-energy bands did not dominate the fluorescence
spectra like P 1 in the solid states. Meanwhile, the
emission spectra of P 1 in the solutions also exhibited
such low-energy bands, which were not observed from
any polyfluorene derivatives including P 2. Therefore,
our novel results strongly indicated the key role of the
intermolecular and intramolecular hydrogen bonding as
the formation of low-energy bands in P 1, which was due
to the hydroxy substituents at the methylene bridged.
The time-resolved PL decay dynamics further inves-
tigated the PL mechanism of P 1 in dilute solution. P 1
in dilute THF solution all exhibited a single-exponential
decay at three various detection wavelengths, 410, 436,
and 468 nm, which corresponded to three peaks of the
fluorescent spectrum. This indicated that only a single
film of P 1 dropping from toluene solution.
at 436 nm, to 472 ps at 468 nm, respectively. The
corresponding PL decay dynamics of P 1 in dilute THF
solution at 538 nm detection wavelength was fit to be
nonexponential and could be best described by a biex-
ponential with measured lifetimes of 0.3 and 3.1 ns,
indicating different fluorescent species like excimers and
aggregated complexes. While adding 1% of methanol to
the THF solution of P 1, the corresponding PL decay
dynamics at the same detection wavelength appeared
as a single exponential with a measured lifetime of 0.3
ns as shown in Figure 5, which further demonstrated
that the intra- and/or intermolecular hydrogen-bonding
interactions in the dilute THF solution was interrupted
with the addition of methanol, a strong hydrogen-
bonding solvent. Actually, although much theoretical
1
fluorescent species A* was involved in the fluorescence
process at the three various wavelengths. The measured
1
lifetime of A* varied from 420 ps at 410 nm to 439 ps

Macromolecules, Vol. 36, No. 2, 2003
Self-Assembled Aggregates of a Polyfluorene 327
Refer en ces a n d Notes
and experimental work has been done on the photo-
physics of conjugated polymers, including the nature of
the excited states, the origin of luminescence, and the
nature of charge photogeneration, these photophysical
processes in conjugated polymers remain poorly under-
stood and controversial.13 More experiments about the
mechanism are in progress in our laboratory.
(1) (a) Mu¨llen, K.; Wegner, G. Electronic Materials: The Oligo-
mer Approach; Wiley-VCH: Weinheim, Germany, 1998. (b)
Handbook of Conducting Polymers; Skotheim, T. A., Elsen-
baumer, R. L., Reynolds, J ., Eds.; Marcel Dekker: New York,
1997. (c) Swager, T. M. Acc. Chem. Res. 1998, 31, 201. (d)
Heeger, A. J . Solid Commun. 1998, 107, 673.
We also employed scanning electron microscopic
(SEM) to observe the mesoscopic superstructure at dried
films of P 1. After slow evaporation of toluene solution
of P 1, SEM results revealed the formation of entangled
nanostructures, which was induced through the hydro-
gen bonding and aggregation as Figure 6 shows. The
diameters of the cylindrical strands are in the range of
about 10-100 nm, with certain diameters occurring
more frequently, which meant the existence of further
hierarchical organizations. After being exposed to air,
the solid films of P 1 did not exhibit any obvious change.
The folding process of P 1 induced by intra- and/or
intermolecular interactions (hydrogen-bonding and ag-
gregation) can be compared to the superstructure
formation in proteins.14
(2) (a) Burroughes, J . H.; Bradley, D. D. C.; Brown, A. R.; Marks,
R. N.; MacKay, K.; Friend, R. H.; Burn, P. L.; Holmes, A. R.
Nature (London) 1990, 347, 539. (b) Gustafsson, G.; Cao, Y.;
Treasy, G. M.; Klavetter, F.; Colaneri, N.; Heeger, A. J .
Nature (London) 1992, 357, 477. (c) Kraft, A.; Grimsdale, A.
C.; Holmes, A. B. Angew. Chem., Int. Ed. 1998, 37, 402.
(3) (a) Brown, A. R.; Pomp, A.; Hart, C. M.; de Leeuw, D. M.
Science 1995, 270, 972. (b) Horowitz, G. Adv. Mater. 1998,
10, 365. (c) Sirringhaus, H.; Brown, P. J .; Friend, R. H.;
Nielsen, M. M.; Bechgaard, K.; Langeveld-Voss, B. M. W.;
Spiering, A. J . H.; J anssen, R. A. J .; Meijer, E. W.; Herwig,
P.; de Leeuw, D. M. Nature (London) 1999, 401, 685.
(4) McQuade, D. T.; Pullen, A. E.; Swager, T. M. Chem. Rev.
2000, 100, 2537.
(5) (a) Schenning, A. P. H. J .; Benneker, F. G. B.; Geurts, H. P.
M.; Liu, X. Y.; Nolte, R. J . M. J . Am. Chem. Soc. 1996, 118,
8549. (b) van Nostrum, C. F. Adv. Mater. 1996, 8, 1027. (c)
Rohr, U.; Schlichting, P.; Bo¨hm, A.; Gross, M.; Meerhholz,
K.; Bra¨uchle, C.; Mu¨llen, K. Angew. Chem., Int. Ed. 1998,
37, 1434. (d) Adam, D.; Schuhmacher, P.; Ha¨ussling, L.;
Siemensmeyer, K.; Etzbach, K. H.; Ringsdorf, H.; Haarer, D.
Nature (London) 1994, 371, 141.
Con clu sion
In conclusion, a convenient approach to homopoly-
fluorenes with different substituents at the fluorene
ring, which might have special intramolecular and/or
intermolecular interactions through the hydrogen bond-
ing, had been developed in this contribution. It is
possible to prepare a series of polyfluorene derivatives
containing H-bonding or other noncovalent interactions
through a similar approach. The studies on the optical
properties of P 1 demonstrated that it exhibited in-
tramolecular and intermolecular H-bonding in the dilute
solution and in the film. The fluorescent spectra of P 1
showed that the new emission peak at about 525 nm
appeared in the dilute toluene solution, and its intensity
was decreased with increase of the polarity of solvents
and fully disappeared in high hydrogen-bonding sol-
vents or with addition of methanol. In solid films, this
new emission peak red-shifted to 572 nm and became
the maximum although other two peaks at about 410
and 436 nm were also observed with quite low intensity.
It implied that the interactions were strengthened
through the hydrogen bonding. P 1 emitted different
light in dilute solutions (blue color) and in films (yel-
lowish-orange color) under the irradiation of UV light.
The time-resolved PL decay dynamics were also dem-
onstrated the existence of such interactions in P 1.
However, this phenomenon was not observed in another
polymer (P 2) without hydrogen-bonding interactions.
The scanning electron microscopic (SEM) results of P 1
at dried films revealed the formation of entangled
nanostructures induced through the hydrogen-bonding
interactions. Therefore, the investigation showed that
the interaction between the nitrogen and the hydroxy
group at the 9-position occupied an important role in
the optical properties, which might provide a new
approach to control over molecular ordering through
interchain interactions, especially the hydrogen bond-
ing.
(6) Wu¨rthner, F.; Thalacker, C.; Sautter, A. Adv. Mater. 1999,
11, 754.
(7) Tang, B. Z. Polym. News 2001, 26, 262.
(8) (a) Fukuda, M.; Sawada, K.; Yoshino, K. J . Polym. Sci., Part
A: Polym. Chem. 1993, 31, 2465. (b) Pei, Q.; Yang, Y. J . Am.
Chem. Soc. 1996, 118, 7416. (c) Ranger, M.; Rondeau, D.;
Leclerc, M. Macromolecules 1997, 30, 786. (d) Redekcer, M.;
Bradley, D. D. C.; Inbasekaran, M.; Woo, E. P. Appl. Phys.
Lett. 1999, 74, 1400. (e) Bliznyuk, V. N.; Carter, S. A.; Scoot,
J . C.; Klarner, G.; Miller, R. D.; Miller, D. C. Macromolecules
1978, 11, 1800. (f) Klarner, G.; Lee, J . I.; Lee, V. Y.; Chan,
E.; Chen, J . P.; Nelson, A.; Markiewicz, D.; Siemens, R.; Scott,
J . C.; Miller, R. D. Chem. Mater. 1999, 11, 1800.
(9) (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 50, 4467. (b) Takahashi, S.; Kunoyama, Y.; Sonogash-
ira, K.; Hagihara, N. Synthesis 1980, 627. (c) Yu, W.-L.; Pei,
J .; Cao, Y.; Huang, W.; Heeger, A. J . Chem. Commun. 1999,
1837.
(10) (a) Yu, W.-L.; Cao, Y.; Pei, J .; Huang, W.; Heeger, A. J . Appl.
Phys. Lett. 1999, 75, 3270. (b) Yu, W.-L.; Pei, J .; Huang, W.;
Heeger, A. J . Adv. Mater. 2000, 12, 828.
(11) List, E. J . W.; Guentner, R.; de Freitas, P. S.; Scherf, U. Adv.
Mater. 2002, 14, 374.
(12) (a) Setayesh, S.; Grimsdale, A. C.; Weil, T.; Enkelmann, V.;
Mu¨llen, K.; Meghdadi, F.; List, E. J . W.; Leising, G. J . Am.
Chem. Soc. 2001, 123, 946. (b) Marsitzky, D.; Vestberg, R.;
Blainey, P.; Tang, B. T.; Hawker, C. J .; Carter, K. R. J . Am.
Chem. Soc. 2001, 123, 6965.
(13) (a) Heeger, A. J .; Kivelson, S.; Schreiffer, R. J .; Su, W. P. Rev.
Mod. Phys. 1988, 60, 781. (b) Rauscher, U.; Bassler, H.;
Bradley, D. D. C.; Hennecke, M. Phys. Rev. B 1990, 42, 9830.
(c) Frankevich, E. L. Phys. Rev. B 1992, 46, 9320. (d) Hsu, J .
W. P.; Yan, M.; J edju, T. M.; Rothberg, L. J .; Hsieh, B. R.
Phys. Rev. B 1994, 49, 712. (e) Soos, Z. G.; Etemad, S.; Galvao,
D. S.; Ramasesha, S. Chem. Phys. Lett. 1992, 194, 341.
(14) (a) Muthukumar, M.; Ober, C. K.; Thomas, E. L. Science 1997,
277, 1225. (b) Nelson, J . C.; Saven, J . G.; Moore, J . S.;
Wolynes, P. G. Science 1997, 277, 1793.
MA020744S