Benzyl bromide functionalized poly(phenyleneethylene)s: A novel approach toward conjugated polymers with a well-defined chemical reactivity

Article abstract of DOI:10.1021/ma0302311

The palladium(0)-copper(I)-catalyzed polymerization of 1,4-diethynyl-2,5-bis(decyloxy)-benzene (I), 1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene (IIA), 1-(6-(4-(hydroxymethyl)phenoxy)hexyloxy)-2,5-diiodo-4-methoxybenzene (III), and iodobenzene (IV) yielded

Full text of DOI:10.1021/ma0302311

6716
Macromolecules 2003, 36, 6716-6721
Benzyl Bromide Functionalized Poly(phenyleneethynylene)s: A Novel
Approach toward Conjugated Polymers with a Well-Defined Chemical
Reactivity
Ma r tin Wa gn er a n d Osk a r Nu yk en *
Lehrstuhl fu¨r Makromolekulare Stoffe, Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching b. Mu¨nchen, Germany
Received April 17, 2003; Revised Manuscript Received J une 17, 2003
ABSTRACT: The palladium(0)-copper(I)-catalyzed polymerization of 1,4-diethynyl-2,5-bis(decyloxy)-
benzene (I), 1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene (IIA), 1-(6-(4-(hydroxymethyl)phenoxy)hexyloxy)-
2,5-diiodo-4-methoxybenzene (III), and iodobenzene (IV) yielded a highly soluble, exclusively para-linked
poly(phenyleneethynylene) (P P E2A). Thereby, statistically every fourth phenyleneethynylene unit bore
a benzyl alcohol group predetermined by the molar ratio of the monomers. The monofunctional monomer
IV was used as molar mass limiter, since preliminary investigations on the polymerization of I and IIA
had revealed that the solubility of alkoxy-substituted poly(phenyleneethynylene)s consisting of more than
40 phenyleneethynylene units decreases drastically. The maximum effective conjugation length was
attained at approximately 12 phenyleneethynylene repeating units. Furthermore, a partially meta-linked
benzyl alcohol functionalized poly(phenyleneethynylene) (P P E2B) was synthesized employing 1,3-
diiodobenzene (IIB) instead of IIA. Both conjugated polymers (P P E2A and P P E2B) could be converted
quantitatively into benzyl bromide functionalized poly(phenyleneethynylene)s (P P E3A and P P E3B)
applying triphenylphosphine and tetrabromomethane. Comparison of the polymers by means of GPC
and UV/vis spectroscopy before and after the bromination showed no significant differences and thus no
impairment of the delocalized π-electron system.
In tr od u ction
molecular weight distributions, a precondition to the
comparability of such materials. However, such pro-
ceeding requires conjugated polymers with a defined
chemical reactivity in order to successfully achieve the
controlled polymer analogous conversion.
The exceptional properties of conjugated polymers are
reflected in a variety of potential applications.1,2 Because
of their electrical conductivity, these materials might
be used in field effect transistors3 as well as conductivity
agents and antistatic coatings.4 Another field of applica-
tion represents the shielding of electromagnetic radia-
tion,5 especially the absorption of radar beams. The UV/
vis absorption and fluorescence behavior of conjugated
polymers enables their use in solid-state lasers6,7 as well
as chemical sensors.8,9 In particular, conjugated poly-
mers attract a great deal of attention as emitting layers
in organic light-emitting diodes.10-12 Furthermore, in-
vestigations on the suitability of conjugated polymers
in photovoltaic cells13,14 and microactuators15 are pub-
lished.
In this contribution the synthesis and characteriza-
tion of benzyl bromide functionalized poly(phenylene-
ethynylene)s are presented. The use of poly(phenylene-
ethynylene)s should ensure the straightforward prepara-
tion as well as interesting properties of the products.19,20
The benzyl bromide groups should provide defined
reaction centers, which might be employed to modify
these materials by polymer analogous methods.
Resu lts a n d Discu ssion
One important precondition for the successful polymer
analogous modification of poly(phenyleneethynylene)s
is their complete solubility, which is known to be
considerably increased by means of flexible side chains
at the skeletal structure.19-21 Hence, the use of decyloxy
and 2-ethylhexyloxy side chains should provide suf-
ficient solubility of the desired benzyl bromide func-
tionalized poly(phenyleneethynylene)s. Additionally, the
solubility of poly(phenylenethynylene)s is strongly in-
fluenced by the degree of polymerization.22 Therefore,
the targeted conjugated polymers should consist of just
as many repetition units as necessary to attain the
maximum effective conjugation length. The appropriate
number of phenyleneethynylene units was determined
by means of the palladium(0)-copper(I)-catalyzed po-
lymerization of 1,4-diethynyl-2,5-bis(decyloxy)benzene
(I) and 1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene (IIA)
(Scheme 1). The syntheses of the monomers as well as
the polymerization were accomplished according to the
literature.23,24
The properties of conjugated polymers can be adjusted
by means of various substituents attached to their main
chains; e.g., their solubility was increased by fixing long
alkoxy chains onto the skeletal structure,1,2 or the
helical conformation of conjugated polymers was in-
duced by chiral groups.16,17 Improved photo- and elec-
troluminescent properties of a triphenylamine-bearing
poly(phenylenevinylene)18 as well as the application of
a cyclophane-substituted poly(phenyleneethynylene) as
chemical sensor9 are described. Usually, substituents
are already introduced into the monomers. An alterna-
tive procedure would be the linkage of substituents to
conjugated polymers after the polymerization step. This
method would allow not only the introduction of func-
tionalities which are incompatible with the polymeri-
zation system but also the synthesis of different
substituted conjugated polymers featuring identical
* Corresponding author: e-mail oskar.nuyken@ch.tum.de.
10.1021/ma0302311 CCC: $25.00 © 2003 American Chemical Society
Published on Web 08/09/2003

Macromolecules, Vol. 36, No. 18, 2003
Poly(phenyleneethynylene)s 6717
Sch em e 1. Syn th esis of th e Alk oxy-Su bstitu ted
P oly(p h en ylen eeth yn ylen e) (P P E1) To Deter m in e th e
Cor r ela tion betw een th e Degr ee of P olym er iza tion
a n d th e Ma xim u m Effective Con ju ga tion Len gth
erization of 1,4-diethynyl-2,5-bis(decyloxy)benzene (I)
and 1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene (IIA) a
steep increase of the effective conjugation length (Figure
1). At approximately 24 phenyleneethynylene units
GPC/PS
(Mn
) 10 000 g mol-1) the correlation curve
converges to λ20% ) 476 nm, indicating the achievement
of the maximum effective conjugation length. In con-
sideration of the molar mass overestimation by GPC,
the real number of phenyleneethynylene units amounted
to approximately 12. Gelation of the alkoxy-substituted
poly(phenyleneethynylene) (P P E1) was observed on
) 30 000 g mol-1
.
GPC/PS
exceeding Mn
The solubility of poly(phenyleneethynylene)s is also
affected by the type of linkage between the phenylene-
ethynylene units (para, meta, ortho) due to the influence
of this parameter on the symmetry of the conjugated
polymer.22 Therefore, it was intended to synthesize the
desired functionalized poly(phenyleneethynylene)s not
only exclusively para-linked leading to the largest
maximum effective conjugation length but also partly
meta-bridged increasing solubility.
During the course of the polymerization samples were
taken from the solution in time intervals of 3 h and
subsequently investigated by GPC vs polystyrene cali-
bration as well as UV/vis spectroscopy. However, it must
be considered that the molar mass determination of
poly(phenyleneethynylene)s via polystyrene calibrations
results in an overestimation by a factor of approximately
2 in most cases due to the different hydrodynamic
behavior of the flexible, coiled polystyrene and the rigid,
rodlike conjugated polymer.25-27 The UV/vis absorption
of conjugated polymers correlates directly with their
effective conjugation length: The expansion of the
delocalized π-electron system leads to a shift of the
absorption maximum toward lower energy. Thus, the
correlation between the UV/vis absorption maximum
and the degree of polymerization of the poly(phen-
yleneethynylene)s provides their maximum effective
conjugation length. Usually, the UV/vis absorption
behavior is characterized by the wavelength of the
intensity maximum at lowest energy (λmax). However,
this variable did not prove to be suitable for the above-
described purpose, since the UV/vis absorption spectra
changed their shape on the transition from monomer
to oligomer to polymer (Figure 1). Besides, the broad
and oblate absorption maxima made the assignment of
The benzyl bromide functionalized poly(phenylene-
ethynylene)s should be prepared on the basis of the
synthesis of P P E1. A further monomer was required
in order to introduce functional groups into the polymer.
For this purpose, 1-(6-(4-(hydroxymethyl)phenoxy)hexyl-
oxy)-2,5-diiodo-4-methoxybenzene (III) was chosen, as
the benzyl alcohol group can easily be converted into a
benzyl bromide (Scheme 2). This additional step was
necessary because the auxiliary base (triethylamine) of
the palladium(0)-copper(I)-catalyzed polymerization
reaction was incompatible with benzyl bromides. The
hexamethylene spacer ensured the decoupling of the
functional groups from the delocalized π-electron system
in the conjugated polymer. The benzyl alcohol substi-
tuted monomer (III) was synthesized in three steps. The
starting material was 4-methoxyphenol, which was
etherified with 1,6-dibromohexane to obtain 1-(6-bro-
mohexyloxy)-4-methoxybenzene (78%). This intermedi-
ate was treated with iodine in the presence of an
oxidant, resulting in 1-(6-bromohexyloxy)-2,5-diiodo-4-
methoxybenzene (82%). The subsequent etherification
with 4-hydroxybenzyl alcohol gave 1-(6-(4-(hydroxy-
methyl)phenoxy)hexyloxy)-2,5-diiodo-4-methoxyben-
zene (III) in 86% yield.
The synthesis of the functionalized poly(phenylene-
ethynylene)s is summarized in Scheme 2. Initially, the
monomers 1,4-diethynyl-2,5-bis(decyloxy)benzene (I),
1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene (IIA) (and
1,3-diiodobenzene (IIB)), 1-(6-(4-(hydroxymethyl)phe-
noxy)hexyloxy)-2,5-diiodo-4-methoxybenzene (III), and
iodobenzene (IV) as molar mass limiter were polymer-
ized using tetrakis(triphenylphosphine)palladium(0),
copper(I) iodide, and triethylamine in toluene at 60 °C
for 24 h. The molar ratio of I:IIA/IIB:III:IV was
adjusted to 1:0.45:0.45:0.2. Assuming quantitative con-
version, these conditions should result in an average
number of phenyleneethynylene units of 16,28,29 ensur-
ing high solubility as well as the maximum effective
conjugation length. Furthermore, the molar ratio of the
monomers led to the benzyl alcohol functionalization of
every forth phenyleneethynylene unit in P P E2A and
P P E2B. A too large content of the polar hydroxy groups
in the conjugated polymers was supposed to cause
insolubility23 and was therefore avoided. After termina-
tion the obtained benzyl alcohol functionalized poly-
(phenyleneethynylene)s P P E2A and P P E2B were pu-
λ
max difficult. Hence, the variable λ20% was defined: λ20%
corresponds to the wavelength at lowest energy, which
attains 20% of the intensity at λmax. The plot of λ20% vs
the molar mass and the number of phenyleneethynylene
units respectively shows at the beginning of the polym-
F igu r e 1. Correlation between the UV/vis absorption and the
degree of polymerization of the alkoxy-substituted poly(phe-
nyleneethynylene) (P P E1).

6718 Wagner and Nuyken
Macromolecules, Vol. 36, No. 18, 2003
Sch em e 2. Tw o-Sta ge Syn th esis of Ben zyl Br om id e F u n ction a lized P oly(p h en ylen eeth yn ylen e)s (P P E3A, P P E3b)
via Ben zyl Alcoh ol Su bstitu ted P oly(p h en ylen eeth yn ylen e)s (P P E2A, P P E2b) a s In ter m ed ia tes
1
rified by GPC followed by freeze-drying from benzene.
Cutouts of the H NMR spectra of P P E2A and P P E2B
4.49 ppm in the H NMR spectra of the functionalized
poly(phenyleneethynylene)s. However, the benzylic car-
bon of P P E2A and P P E2B corresponds to the 13C NMR
resonance at δ ) 64.8 ppm, which completely dis-
appeared after the bromination reaction, indicating
quantitative conversion. The benzylic carbon of the
benzyl bromide functionlized polymers P P E3A and
P P E3B was unambiguously assigned to the 13C NMR
signal at δ ) 34.5 ppm (Figure 3).
1
are shown in Figure 2. The average number of phen-
yleneethynylene units of these polymers was calculated
from the intensity ratio of the resonances pertaining to
the end-capping phenyl group and the aromatic repeti-
tion units. Thus, P P E2A consisted of 16 phenylene-
ethynylene units at an average corresponding with the
requirement. In the case of the partly meta-linked poly-
(phenyleneethynylene) P P E2B the average number of
phenyleneethynylene units amounted to 12. This value
was slightly lower than expected. However, super-
imposition of further signals in the resonance range of
the end-group protons may result in an underestima-
tion.
In a second step, the benzyl bromide functionalized
poly(phenyleneethynylene)s P P E3A and P P E3B were
prepared from P P E2A and P P E2B by means of tetra-
bromomethane and triphenylphosphine in dichloro-
methane at room temperature for 1.5 h (Appel reac-
tion).30,31 This method allows the conversion of alcohols
into bromides to the exclusion of Bronsted acids, which
would affect the conjugated system. The purification of
P P E3A and P P E3B occurred by GPC (removal of
molecules < 1000 g mol-1). The exchange of the hydroxy
group by the bromine atom resulted in an only slight
shift of the benzylic protones from δ ) 4.56 ppm to δ )
The analysis of the benzyl alcohol functionalized poly-
(phenyleneethynylene)s by GPC vs polystyrene calibra-
GPC/PS
tion led to Mn
Mn
) 8200 g mol-1 (P P E2A) and
) 9800 g mol-1 (P P E2B) (Table 1, Figure 4).
GPC/PS
The average number of phenyleneethynylene units
(P P E2A: 20; P P E2B: 28) derived from these data
shows the molar mass overestimation of this GPC
method as mentioned before. Comparison of the GPC
traces before and after the hydroxy-bromine exchange
did not reveal any significant alteration (Table 1, Figure
4).
The UV/vis absorption behavior of the synthesized
polymers is summarized in Table 1 and Figure 5. The
wavelength λ20% ) 475.5 nm of the exclusively para-
linked P P E2A corresponds to the range of the conver-
gence value, indicating maximum effective conjugation
length (Figure 1). In the case of P P E2B the replacement
of IIA by the meta-substituted monomer IIB resulted

Macromolecules, Vol. 36, No. 18, 2003
Poly(phenyleneethynylene)s 6719
F igu r e 2. 1H NMR spectra of the benzyl alcohol functionalized poly(phenyleneethynylene)s P P E2A and P P E2B.
F igu r e 3. Cutouts of the 13C NMR spectra before (P P E2A)
and after (P P E3A) the hydroxy-bromine exchange.
F igu r e 4. Molar mass distributions of the poly(phenylene-
ethynylene)s before (P P E2A, P P E2B) and after (P P E3A,
P P E3B) the hydroxy-bromine exchange (GPC in CHCl3 vs
polystyrene calibration).
Ta ble 1. Ch a r a cter iza tion of th e Ben zyl Alcoh ol a n d
Ben zyl Br om id e F u n ction a lized
P oly(p h en ylen eeth yn ylen e)s Con cer n in g Mola r Ma sses
a n d UV/vis Absor p tion
NMR
GPC/PS
Mn
,
Mn
,
g mol-1
g mol-1
λ20%
,
λmax
,
c
c
b
polymer
(PE units)a
(PE units)b
PDIGPC/PS
nm
nm
P P E2A
P P E3A
P P E2B
P P E3B
6700 (16)
4400 (12)
8200 (20)
8800 (20)
9800 (28)
10000 (28)
2.0
2.2
2.0
2.7
475.5
475.5
465.0
465.0
445.0
443.0
418.0
418.0
a
b
Determined by 1H NMR. Determined by GPC in CHCl3 vs
polystyrene calibration. c Determined by UV/vis spectroscopy in
CHCl3.
F igu r e 5. UV/vis absorption of the poly(phenyleneethy-
nylene)s before (P P E2A, P P E2B) and after (P P E3A, P P E3B)
the hydroxy-bromine exchange (UV/vis spectroscopy in CHCl3).
in 10 nm shifted wavelength λ20% ) 465.0 nm. Both
polymers did not change their λ20% after the bromina-
tion. The absorption maximum λmax of P P E2A amounts
to 445.0 nm, in contrast to the 27 nm lower λmax of
P P E2B. Furthermore, the absorption maximum of the
partly meta-linked polymer is considerably broader
compared to those of the linear poly(phenyleneeth-
ynylene)s. Although the UV/vis spectra of P P E2A and
P P E3A seems to be congruent, λmax diverges about 2
nm. emphasizing the difficult assignment of λmax due
to the oblate absorption maxima.
Con clu sion
The exclusively para-linked and the partly meta-
linked benzyl bromide functionalized poly(phenylene-
ethynylene) were prepared in a two-stage synthesis via
benzyl alcohol functionalized poly(phenyleneethynylene)s.
This additional step was necessary because the auxiliary
base of the palladium(0)-copper(I)-catalyzed polymer-
ization reaction is incompatible with benzyl bromides.

6720 Wagner and Nuyken
Macromolecules, Vol. 36, No. 18, 2003
1-(6-(4-Hyd r oxym eth yl)p h en oxy)h exyloxy)-2,5-d iiod o-
4-m eth oxyben zen e (III). 1-(6-Bromohexyloxy)-2,5-diiodo-4-
methoxybenzene (31.3 g, 58 mmol), 4-hydroxybenzyl alcohol
(10.8 g, 87 mmol), potassium carbonate (11.5 g, 87 mmol), and
DMSO (300 mL) were stirred at 60 °C for 12 h. Afterward,
the reaction mixture was poured into ice water (1000 mL) and
extracted with diethyl ether (2 × 400 mL). The solvent of the
combined organic layers was removed by means of a rotary
evaporator, and the residue was purified using column chro-
matography (silica gel, toluene/ethyl acetate 4:1, Rf ) 0.5) to
yield a highly viscous, colorless liquid (29.1 g, 50.0 mmol, 86%).
1H NMR (CDCl3): δ ) 7.26 (pd, 3J H,H ) 8.7 Hz, 2H, CarHCarCH2-
The structure and the degree of polymerization of the
poly(phenyleneethynylene)s were adjusted to ensure
high solubility. Investigations of the conjugated poly-
mers by GPC and UV/vis spectroscopy did not reveal
any impairment of the delocalized π-electron system,
resulting from the hydroxy-bromine exchange. The
benzyl groups might be used as starting point for further
modifications of these conjugated polymers.
Exp er im en ta l Section
Ma ter ia ls a n d In str u m en ta tion . All reagents and sol-
vents were purchased from Sigma-Aldrich or Deutero in
analytical grade (except for toluene: puriss. over molecular
sieve, H2O < 0.005%, under Ar) and used as received except
triethylamine, which was dried over CaH2 and distilled under
a N2 atmosphere. Cross-linked polystyrene (Bio-Beads S-X1)
for the preparative gel permeation chromatography (GPC) was
acquired from Bio-Rad. NMR spectra were recorded on a
Bruker ARX300 (1H/300 MHz, 13C/75 MHz). UV/vis spectra
were obtained from a Varian Cary 3. Elemental analysis was
performed on an Elementar Vario EL. Analytical GPC was
obtained from a Waters 510 equipped with a Waters 410
differential refractometer and Polymer Laboratories Gel Mixed
B columns. CHCl3 was used as eluent, and the calibration
occurred by means of polysytrene (PS) standards.
Mon om er Syn th esis: 1,4-Bis(2-eth ylh exyloxy)-2,5-d i-
iod oben zen e (I) a n d 1,4-d ieth yn yl-2,5-bis(d ecyloxy)ben -
zen e (IIA) were prepared according to the literature.23
1-(6-Br om oh exyloxy)-4-m eth oxyben zen e. 4-Methoxyphe-
nol (12.4 g, 100 mmol), 1,6-dibromohexane (73.2 g, 300 mmol),
potassium carbonate (19.8 g, 150 mmol), and DMSO (300 mL)
were stirred at room temperature for 16 h. Subsequently, the
reaction mixture was poured into ice water (1000 mL) and
extracted with diethyl ether (500 mL). The organic layer was
collected, and the solvent was removed by means of a rotary
evaporator. The residue was taken up in toluene, and the
solution was passed through a short plug of neutral aluminum
oxide using toluene as eluent. After evaporation of the solvent,
excess 1,6-dibromohexane still remaining in the product was
removed by vacuum distillation. The residue was recrystallized
from hexane/toluene (20:1) to yield colorless crystals (22.4 g,
78.0 mmol, 78%). 1H NMR (CDCl3): δ ) 6.81 (s, 4H, CHar),
3.89 (t, 3J H,H ) 6.4 Hz, 2H, OCH2), 3.75 (s, 3H, OCH3), 3.40 (t,
3J H,H ) 6.7 Hz, 2H, CH2Br), 1.95-1.83 (m, 2H, CH2CH2Br),
1.83-1.70 (m, 2H, CH2CH2O), 1.60-1.42 ppm (m, 4H, CH2).
13C{1H} NMR (CDCl3): δ ) 153.72 (CarOCH3), 153.19 (CarOCH2),
115.42 (CarHCarOCH3), 114.62 (CarHCarOCH2), 68.36 (OCH2),
55.72 (OCH3), 33.76 (CH2CH2Br), 32.67 (CH2Br), 29.18 (CH2-
CH2O), 27.91 (CH2CH2CH2Br), 25.29 ppm (CH2CH2CH2O).
3
OH), 7.17 (s, 2H, CHarCarI), 6.87 (pd, J H,H ) 8.7 Hz, 2H,
CarHCarHCarOCH2OH), 4.60 (s, 2H, CH2OH), 4.02-3.89 (m,
4H, OCH2), 3.81 (s, 3H, OCH3), 1.90-1.75 (m, 4H, CH2CH2O),
1.66-1.48 ppm (m, 4H, CH2). 13C{1H} NMR (CDCl3): δ )
158.72 (CH2CH2OCarCarHCarH), 153.28 (CarOCH3), 152.88
(CarICarOCH2), 132.94 (CarCH2OH), 128.61 (CarHCarCH2-
OH), 122.94 (CarICarHOCarCH2), 121.48 (CarHOCarCH3),
114.56 (CarHCarHCarOCH2OH), 86.36 (CarICarOCH2), 85.42
(CarICarOCH3), 70.16 (CH2OCarCarHCarH), 67.82 (CH2OCarCarI),
65.07 (CH2OH), 57.16 (OCH3), 29.14 and 29.04 (CH2CH2O),
25.79 and 25.68 ppm (CH2CH2CH2O). C20H24I2O4 (582.21):
Calcd (%) C, 41.26; H, 4.15. Found (%): C, 41.70; H, 4.21.
P olym er Syn th esis: P P E1. 1,4-Diethynyl-2,5-bis(decyl-
oxy)benzene (I) (461 mg, 1.05 mmol), 1,4-bis(2-ethylhexyloxy)-
2,5-diiodobenzene (IIA) (586 mg, 1.00 mmol), tetrakis(tri-
phenylphosphine)palladium(0) (46 mg, 0.04 mmol), copper(I)
iodide (6 mg, 0.03 mmol), toluene (20 mL), and triethylamine
(5 mL) were stirred at 60 °C to the exclusion of moisture and
oxygen. Samples (1 mL) were taken from the reaction mixture
every 3 h. Iodobenzene (0.1 mL) and CHCl3 (2 mL) were added
immediately to each sample followed by analysis using GPC
vs polystyrene and UV/vis spectroscopy.
P P E2A. 1,4-Diethynyl-2,5-bis(decyloxy)benzene (I) (978 mg,
2.23 mmol), 1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene (IIA)
(586 mg, 1.00 mmol), 1-(6-(4-hydroxmethyl)phenoxy)hexyloxy)-
2,5-diiodo-4-methoxybenzene (III) (582 mg, 1.00 mmol), iodo-
benzene (IV) (92 mg, 0.45 mmol), tetrakis(triphenylphosphine)-
palladium(0) (92 mg, 0.08 mmol), copper(I) iodide (11 mg, 0.06
mmol), toluene (40 mL), and triethylamine (10 mL) were
stirred at 60 °C for 24 h to the exclusion of moisture and
oxygen. After addition of iodobenzene (1 mL) the reaction
mixture was stirred at 60 °C for another 15 min. The
precipitate that originated during the course of polymerization
was filtered off, and the volume of the residual solution was
reduced by means of a rotary evaporator. Subsequently, the
polymer solution were purified using GPC (stationary phase:
cross-linked polysytrene (Bio-Beads S-X1, Bio-Rad); height: 30
cm; diameter: 3 cm; eluent: toluene). The fraction from 105
to 165 mL eluent was collected, and the solvent was evapo-
rated. Finally, the residue was taken up in benzene and freeze-
dried to yield an orange solid (1.19 g, 70%). 1H NMR (C2D2-
Cl4): δ ) 7.57-7.44 (m, I ) 1.17, CarH/end group), 7.41-7.32
C
13H19BrO2 (287.19): Calcd (%) C, 54.37; H, 6.67. Found (%):
C, 55.28; H, 6,73.
1-(6-Br om oh exyloxy)-2,5-diiodo-4-m eth oxyben zen e. Wa-
ter (40 mL), acetic acid (300 mL), concentrated sulfuric acid
(8 mL), 1-(6-bromohexyloxy)-4-methoxybenzene (21.5 g, 75
mmol), potassium iodate (6.4 g, 30 mmol), and iodine (19.0 g,
75 mmol) were stirred at reflux for 3 h. After cooling to room
temperature, the excess of iodine was destroyed using an
aqueous sodium sulfite solution (10%), and the reaction
mixture was poured into ice water (1000 mL). The aqueous
phase was extracted with diethyl ether (2 × 300 mL), and the
solvent of the combined organic layers was evaporated.
Purification of the residue by means of column chromatogra-
phy (silica gel, hexane/toluene 3:1, Rf ) 0.5) resulted in a
3
(m, I ) 1.32, CarH/end group), 7.24 (pd, J H,H ) 7.8 Hz, I )
2.26, CarHCarCH2OH), 7.11-6.93 (m, I ) 8.00, CarHCarO), 6.85
(pd, 3J H,H ) 7.8 Hz, I ) 2.29, CarHCarHCarOCH2OH), 4.56 (s, I
) 2.02, CH2OH), 4.20-3.70 (m, I ) 19.75, OCH2, OCH3), 2.00-
1.70 (m, I ) 14.49, CH, CH2CH2O), 1.70-1.10 (m, I ) 88.66,
CH2), 1.05-0.72 (m, I ) 26.29, CH3) ppm. UV/vis (CHCl3): λ20%
) 475.5 nm, λmax ) 445.0 nm. GPC (CHCl3, RI det, PS): Mn )
8240 g/mol, PDI ) 2.0. Repeating unit: C102H148O10 (1534.29).
P P E2B. This synthesis was accomplished as described for
P P E2A using 1,3-diiodobenzene (IIB) instead of IIA. On
purification by GPC the fraction from 90 to 150 mL eluent was
collected. P P E2B was obtained as orange solid (1.37 g, 82%).
1H NMR (C2D2Cl4): δ ) 7.73 (s, I ) 1.00, CarH/meta), 7.59-
7.45 (m, I ) 3.22, CarH/meta, CarH/end group), 7.43-7.32 (m,
I ) 2.46, CarH/meta, CarH/end group), 7.24 (pd, 3J H,H ) 8.0 Hz,
I ) 2.04, CarHCarCH2OH), 7.09-6.98 (m, I ) 6.00, CarHCarO),
6.85 (pd, 3J H,H ) 8.0 Hz, I ) 1.96, CarHCarHCarOCH2OH), 4.56
(s, I ) 1.91, CH2OH, 4.15-3.85 (m, I ) 15.12, OCH2, OCH3),
1.99-1.71 (m, I ) 12.28, CH2CH2O), 1.70-1.10 (m, I ) 67.74,
CH2), 0.94-0.80 ppm (m, I ) 13.26, CH3). UV/vis (CHCl3): λ20%
) 465.0 nm, λmax ) 418.0 nm. GPC (CHCl3, RI det, PS): Mn )
1
colorless solid (33.0 g, 61.2 mmol, 82%). H NMR (CDCl3): δ
3
) 7.17 (s, 2H, CHar), 3.93 (t, J H,H ) 6.1 Hz, 2H, OCH2), 3.81
3
(s, 3H, OCH3), 3.42 (t, J H,H ) 6.7 Hz, 2H, CH2Br), 1.95-1.85
(m, 2H, CH2CH2Br), 1.85-1.75 (m, 2H, CH2CH2O), 1.62-1.43
ppm (m, 4H, CH2). 13C{1H} NMR (CDCl3): δ ) 153.32
(CarOCH3), 152.84 (CarOCH2), 122.96 (CarHCarOCH2), 121.48
(CarHCarOCH3), 86.34 (CarICarOCH2), 85.42 (CarICarOCH3),
70.08 (OCH2), 57.16 (OCH3), 33.75 (CH2CH2Br), 32.65 (CH2-
Br), 28.94 (CH2CH2O), 27.80 (CH2CH2CH2Br), 25.28 ppm (CH2-
CH2CH2O). C13H17BrI2O2 (538.98): Calcd (%) C, 28.97; H, 3.18.
Found (%): C, 28.89; H, 3.21.

Macromolecules, Vol. 36, No. 18, 2003
Poly(phenyleneethynylene)s 6721
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9830 g/mol, PDI ) 2.0. Repeating unit: C86H116O8 (1277.86).
P P E3A. Tetrabromomethane (265 mg, 0.8 mmol) and
triphenylphosphine (210 mg, 0.8 mmol) were added to a
solution consisting of P P E2A (833 mg, 0.5 mmol -CH2OH)
and CH2Cl2 (15 mL) to the exclusion of moisture. The reaction
mixture was stirred at room temperature for 1.5 h and finally
diluted with toluene (20 mL). After reducing the volume of
the polymer solution by evaporation followed by filtration, the
volume of the residual solution was diminished again. Sub-
sequently, the solution was passed through a GPC column
(stationary phase: cross-linked polysytrene (Bio-Beads S-X1,
Bio-Rad); height: 30 cm; diameter: 3 cm; eluent: toluene).
The fraction from 80 to 170 mL eluent was collected in order
to remove only components with a molar mass lower than 1000
g/mol. Subsequently, the solvent was evaporated and the
residue freezed-dried from benzene to yield an orange solid
(827 mg, 96%). 1H NMR (C2D2Cl4): δ ) 7.59-7.47 (m, I ) 1.14,
CarH/end group), 7.40-7.32 (m, I ) 1.28, CarH/end group), 7.29
3
(pd, J H,H ) 8.4 Hz, I ) 2.38, CarHCarCH2Br), 7.12-6.93 (m, I
) 8.00, CarHCarO), 6,82 (pd, 3J H,H
)
8.4 Hz, CarHCarHCarOCH2-
Br), 4.49 (s, I ) 1.93, CH2Br), 4.20-3.70 (m, I ) 19.63, OCH2,
OCH3), 1.98-1.70 (m, I ) 14.30, CH, CH2CH2O), 1.70-1.10
(m, I ) 88.36, CH2), 1.05-0.75 ppm (m, I ) 26.64, CH3). UV/
vis (CHCl3): λ20% ) 475.5 nm, λmax ) 443.0 nm. GPC (CHCl3,
RI det, PS): Mn ) 8820 g/mol, PDI ) 2.2. Repeating unit:
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C
102H147BrO9 (1597.18).
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P P E3B. This synthesis was carried out as described for
P P E3A using P P E2B (708 mg, 0.5 mmol of -CH2OH) instead
of P P E2A to result in an orange solid (699 mg, 96%). 1H NMR
(C2D2Cl4): δ ) 7.73 (s, I ) 1.05, CarH/meta), 7.61-7.46 (m, I
) 3.09, CarH/meta, CarH/end group), 7.43-7.33 (m, I ) 2.53,
CarH/meta, CarH/end group), 7.28 (pd, 3J H,H ) 8.4 Hz, I ) 2.12,
CarHCarCH2Br), 7.12-6.96 (m, I ) 6.00, CarHCarO), 6.82 (pd,
3J H,H ) 8.4 Hz, I ) 2.02, CarHCarHCarOCH2Br), 4.49 (s, I )
1.91, CH2Br), 4.15-3.80 (m, I ) 15.26, OCH2, OCH3), 2.00-
1.70 (m, I ) 12.24, CH2CH2O), 1.70-1.10 (m, I ) 67.18, CH2),
0.96-0.77 ppm (m, I ) 13.22, CH3). UV/vis (CHCl3): λ20%
465.0 nm, λmax ) 418.0 nm. GPC (CHCl3, RI det, PS): Mn
)
)
9960 g/mol, PDI ) 2.7. Repeating unit: C86H115BrO7 (1340.72).
(26) Francke, V.; Mangel, T.; Mu¨llen, K. Macromolecules 1998,
31, 2447.
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& Sons: New York, 1991; pp 78-82.
(29) Pn ) (1 + r)/(1 - r), r ) nI/(nIIA + 2nIV).
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Ack n ow led gm en t. This research was financially
supported by the Deutschen Forschungsgemeinschaft,
the Stiftung Stipendienfonds des Verbandes der Che-
mischen Industrie, and the Bundesministerium fu¨r
Bildung und Forschung.
Refer en ces a n d Notes
(1) Skotheim, T. A., Elsenbaumer, R. L., Reynolds, J ., Eds.
Handbook of Conducting Polymers, 2nd ed.; Marcel Dekker:
New York, 1997.
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