Comparison of precursor polymer routes to and electronic properties of a new phenylacetylene derivatised poly[2-(2'-ethylhexyloxy)-1,4- phenylenevinylene]

Article abstract of DOI:10.1039/a904274a

We have prepared poly[2-(2'-ethylhexyloxy)-5-phenylethynyl-1,4- phenylenevinylene] (PAPPV) 13 via, S-methyl xanthate 10, chloro 11, and O- ethyl xanthate 12 precursor polymers. All three precursor polymers could be thermally converted to give films of 13. We found that the UV-VIS and photoluminescence (PL) spectra, and PL quantum yields (11-14%) were similar when 13 was prepared from either the S-methyl xanthate or chloro precursor polymers. In contrast, the UV-VIS and PL spectra of 13 prepared via the O- ethyl xanthate precursor polymer were observed to be blue-shifted and the PL quantum yield was much lower (2%).

Full text of DOI:10.1039/a904274a

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J O U R N A L O F
Comparison of precursor polymer routes to and electronic properties
of a new phenylacetylene derivatised poly[2-(2'-ethylhexyloxy)-1,4-
phenylenevinylene]
Shih-Chun Lo,a Anna K. Sheridan,b Ifor D. W. Samuelb and Paul L. Burn*a
C H E M I S T R Y
aThe Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford, UK OX1
3QY
bDepartment of Physics, University of Durham, South Road, Durham, UK DH1 3LE
Received 27th May 1999, Accepted 25th October 1999
We have prepared poly[2-(2'-ethylhexyloxy)-5-phenylethynyl-1,4-phenylenevinylene] (PAPPV) 13 via, S-methyl
xanthate 10, chloro 11, and O-ethyl xanthate 12 precursor polymers. All three precursor polymers could be
thermally converted to give ®lms of 13. We found that the UV±VIS and photoluminescence (PL) spectra, and
PL quantum yields (11±14%) were similar when 13 was prepared from either the S-methyl xanthate or chloro
precursor polymers. In contrast, the UV±VIS and PL spectra of 13 prepared via the O-ethyl xanthate precursor
polymer were observed to be blue-shifted and the PL quantum yield was much lower (2%).
Poly(1,4-phenylenevinylene) (PPV) and its derivatives have
been studied extensively with particular emphasis in recent
years on their use as the light-emitting layers in light-emitting
diodes (LEDs).1 The main derivatives of PPV usually have one
or more alkoxy or alkyl substituents of varying lengths
attached to the phenyl ring.2 Other phenyl substituents that
have also been studied include halogen,1b,3 thioether,4 aryl,5
styryl,6 and silyl.1b However, the effects of a side-chain
acetylene group on the electronic properties of a PPV derivative
have yet to be explored although there have been studies on
poly(1,4-phenylacetylene)s.7 The two main synthetic routes to
PPV have involved the synthesis of soluble conjugated
derivatives, which are normally substituted with long lipophilic
groups, or a precursor polymer route which generally leads to
insoluble polymers. Of the two main synthetic routes we have
concentrated on the latter as it gives rise to materials which can
be easily incorporated into multilayer LEDs. Here, we describe
problematic. Introduction of the iodo group onto 2 was ®rst
attempted using iodine in a mixture of periodic acid, glacial
acetic acid and aqueous sulfuric acid. Under these conditions a
small amount (27%) of the desired iodonated compound 3 was
isolated. In addition to 3 we also formed an inseparable
mixture of 14 and 15 which were not only iodonated on the
aromatic ring but also on one benzylic position and these were
isolated in yields of around 34%. Although 14 and 15 could be
re-acetylated in good yield this approach was inef®cient. We
have found that excellent yields of 3 can be achieved by
treatment of a chloroform solution of 2 with iodine and silver
acetate at room temperature. Under these mild conditions 3
can be formed in yields of up to 97%. Addition of the
phenylacetylene moiety to give 4 was achieved by reacting 3
with an excess of copper(I) phenylacetylide. Under these
conditions 4 could be formed in a 93% yield. The acetate
protecting groups were then removed by treating 4 with
aqueous hydroxide to give 5 in 96% yield. The bis-S-methyl
xanthate monomer 6 was formed in 56% yield by sequential
treatment of 5 with sodium hydride followed by carbon
disul®de, and then methyl iodide. 5 was also converted to the
bis-chloro monomer 7 in up to 90% yield by reaction with a
mixture of DMAP, p-toluenesulfonyl chloride and triethyl-
amine. Finally, to prepare the O-ethyl xanthate monomer 9, 5
was ®rst transformed with phosphorus tribromide to the bis-
bromo monomer 8 (in 49% yield) which was then reacted with
potassium O-ethyl xanthate to give 9 in 96% yield.
the syntheses of
a phenylacetylene substituted polymer,
poly{[2-(2'-ethylhexyloxy)-5-phenylacetylenyl-1,4-phenylenevi-
nylene]} (PAPPV) 13, via chloro, S-methyl xanthate, and O-
ethyl xanthate precursor polymers, and compare its electronic
properties with the unsubstituted parent poly[2-(2'-ethylhex-
yloxy)-1,4-phenylenevinylene] (EHPPV)8 prepared via the
equivalent precursor polymers.
Polymerisations and conversions
The polymerisations of all three polymers were carried out
under similar conditions (Scheme 2). The general procedure
involved the treament of a 0.13 M tetrahydrofuran solution of
monomer with ca. 0.9 equivalents of a 0.18±0.19 M tetrahy-
drofuran solution of potassium tert-butoxide. The reactions
were stirred with ice-bath cooling for 1 h before being
quenched by precipitation into methanol. Under these condi-
tions the S-methyl xanthate polymer 10, the chloro polymer 11,
and the O-ethyl xanthate polymer 12 were formed in yields of
ca. 26, 80 and 60%, respectively. The molecular weights of
dilute solutions of the three precursor polymers were analysed
by gel-permeation chromatography (GPC) (against polystyr-
ene standards) immediately on dilution and after equilibration.
The samples were equilibrated by being treated in an ultrasonic
Results and discussion
Monomer syntheses
The strategies for the syntheses of the three monomers for the
preparation of PAPPV 13 are shown in Scheme 1. The ®rst step
in all three syntheses was acetylation of bis-hydroxy 18 which
was done to facilitate the handling of the products in the next
two steps. 1 was acetylated in a 97% yield using acetic
anhydride in pyridine heated at re¯ux. The next step in the
synthesis was the addition of iodine and this proved to be more
J. Mater. Chem., 2000, 10, 275±281
This journal is # The Royal Society of Chemistry 2000
275

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Scheme 1 Reagents and conditions: i, acetic anhydride, pyridine, heat, N2 ; ii, I2, AgOAc, CHCl3, room temp.; iii, PhCCCu, pyridine, heat, N2; iv,
NaOH, H2O, MeOH, CH2Cl2, room temp., Ar; v, NaH, diethyl ether, heat, then CS2, heat, then MeI, heat, Ar; vi, DMAP, tosyl chloride,
triethylamine, CH2Cl2, room temp., N2; vii, PBr3, diethyl ether, room temp., Ar; viii, potassium O-ethyl xanthate, (n-Bu)4NBr, CH2Cl2, Ar, room
temp.
ꢀ
bath for 10 min. Under these equilibration conditions we
ꢀ
observed a drop in Mw for the chloro and O-ethyl xanthate
precursor polymers without any polymer degradation whilst
the S-methyl xanthate precursor polymer 10 showed little
found to have an Mw of 2.96105 and polydispersity of 2.2
which is signi®cantly higher than that observed for the S-
3
ꢀ
methyl xanthate precursor polymer to EHPPV (Mw of 8.5610
and a polydispersity of 1.8) indicating that the phenylacetylene
is enhancing the polymerisation process. In comparing the
syntheses of 10, 11 and 12 with their counterparts for the
preparation of EHPPV two trends are notable.8 First, the
choro and O-ethyl xanthate monomers give higher yields of
their respective precursor polymers than the S-methyl xanthate
monomers, and second, the molecular weights of the precursor
ꢀ
change. The decrease in Mw observed by GPC analysis for 11
and 12 on dilution and equilibration is similar to that seen for
some other precursor polymers which have been used to
prepare PPV derivatives and we believe this occurs owing to the
dissociation of polymer aggregates or physical networks.8,9
Interestingly, the S-methyl xanthate precursor polymer 10 was
Scheme 2 Reagents and conditions: i, KOBut, THF, Ar; ii, heat, vacuum.
J. Mater. Chem., 2000, 10, 275±281
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polymers follow the same trend with the S-methyl xanthate and
chloro monomers forming the polymers of lowest and highest
observed molecular weights, respectively. In addition, all three
precursor polymers were found to be soluble in tetrahydro-
furan and chloroform with the xanthate precursor polymers
being much more soluble than the chloro precursor polymer.
Thermogravimetric analysis (TGA) of polymers 10, 11 and
12 was carried out with a heating rate of 5 ³C min21 under
nitrogen and we assign the ®rst weight loss observed by TGA to
the elimination of the leaving group. For the S-methyl xanthate
polymer 10, the xanthate group was found to eliminate at
134 ³C, with the ®rst weight loss occurring at ca. 120 ³C. The
weight loss observed for 10 at this temperature was 21%, which
is close to the 25% that is expected from the precursor polymer,
which has low levels of conjugation. Similarly, TGA of the
chloro precursor polymer 11 indicated that hydrogen chloride
was eliminated at 255 ³C with the elimination beginning at ca.
234 ³C. We found that the weight loss for 11 was 9% which is
near to that expected (10%) for the fully saturated precursor
polymer. Finally, analysis of 12 indicated that the O-ethyl
xanthate group was being eliminated at 229 ³C with an onset of
elimination of ca. 210 ³C. The weight loss was 23% which was
close to the 27% expected for the elimination of the O-ethyl
xanthate groups from the precursor polymer.
Given that different precursor polymers to the same
conjugated polymer can result in polymers with similar
chemical structures but different electronic properties we
were interested to determine the properties of PAPPV prepared
by the three different precursor polymers. All three precursor
polymers and the conjugated polymers formed after thermal
conversion were studied by UV±VIS and IR spectroscopy. The
UV±VIS spectrum of PPV derivatives generally consists of two
components; a UV absorption which corresponds to localised
p±p* transitions and an absorption in the visible region which
is due to delocalised p±p* transitions. In addition, the ratio of
absorption intensity of UV to the visible components can often
give an indication of the level of conjugation in the converted
polymer with the smaller the ratio the better the conjugation.
All three precursor polymers were thermally converted in the
temperature range 211±213 ³C under vacuum overnight.
The IR spectra of the S-methyl xanthate precursor polymer
10 and conjugated polymer 13 formed under these conditions
are shown in Fig. 1. The important feature to note is that the
absorptions at 1061 and 1214 cm21 which we assign to the S-
methyl xanthate leaving group are absent in the sample of 13.
Instead we observe a strong absorption at 964 cm21 which
corresponds to the trans-vinylene CH out-of-plane bend and an
absorption at 3058 cm21 which corresponds to a vinylene CH
stretch. The IR spectra of the chloro precursor polymer 11 and
13 formed from 11 are shown in Fig. 2. Again the two
absorptions at 964 and 3058 cm21 are observed in the
thermally treated sample indicating that conversion has
taken place. Finally, the O-ethyl xanthate polymer 12 was
converted to 13 and their spectra are shown in Fig. 3. The
absorption at 1048 cm21 which we assign to the xanthate
leaving group in 12 was absent in the formed 13 and in their
place we observed the absorptions which correspond to trans-
vinylene units. At ®rst sight the IR spectra of 13 prepared from
the three different precursors look similar. However, close
examination of the IR spectra of 13 formed from each of the
precursor polymers shows that there are differences which are
most striking in 13 prepared from 12. The differences arise in
the relative intensity of the absorption near or at 964 cm21
which is one of the strong indicators of trans-vinylene links.
When 13 was prepared from 10 or 11 the intensity of this
absorption, relative to the other absorptions in the spectra, was
similar (Fig. 1 and 2). In contrast, when 13 was prepared from
12 the relative intensity of the trans-vinylene absorption is
signi®cantly less relative to the other absorptions in the spectra
(Fig. 3). In addition to the absorption at 964 cm21 each of the
samples also has an absorption at or near 861 cm21 which is
close to the absorption that was assigned to cis-vinylene
linkages in PPV prepared from an O-ethyl xanthate precursor
polymer.10 Therefore, as the ratio of the absorptions at 967 and
863 cm21 in 13 prepared from 12 is signi®cantly smaller than in
the samples of 13 which were prepared from 10 and 11 we
conclude that 13 prepared from the O-ethyl xanthate precursor
polymer has a greater proportion of cis-linkages.
The thin ®lms of 13 for UV±VIS and photoluminescence
analysis were prepared so that the absorption associated with
the delocalised p±p* transitions had an optical density of
around one. The effect of the different synthetic routes used on
the absorption spectrum of 13 is shown in Fig. 4 which
compares the absorption of thin ®lms of 13 prepared from 10,
11 and 12. The spectrum of 13 prepared from 10 and 11 shows a
strong absorption in the region of 470 nm, and a shorter
wavelength peak in the region of 300 nm. For comparison the
analogue of polymer 13 without the phenylacetylene sub-
stituent, EHPPV, has an absorption maximum at 450 nm, and
the feature at 300 nm is absent.8 This observation suggests that
the 300 nm feature is due to a localised transition associated
with the diphenylacetylene moiety and is consistent with the
absorption spectra of the diphenylacetylene monomers. We
consider that the small red-shift to 470 nm in the absorption of
the phenylacetylene substituted polymer is due to a modest
increase in electron delocalisation due to the phenylacetylene
groups.
The absorption spectrum of 13 prepared from 12 differs from
that obtained by the other two precursor routes: both the onset
and ®rst peak of the absorption are blue-shifted by between 40
and 50 nm (0.2±0.3 eV). Two possible reasons for this blue-shift
are that the polymer has an increased level of cis-linkages or
that there has only been partial conversion of 12 to 13. Both
explanations would lead to reduced electron delocalisation and
hence a blue-shifted spectrum. The IR analysis of 13 from 12
would suggest that the conversion had gone essentially to
completion. However, the IR analysis was carried out on a ®lm
prepared by depositing a solution of the polymer onto a KBr
disc and then allowing the solvent to evaporate. The sample for
UV±VIS analysis was spin-coated from solution and hence the
®lm would be expected to be thinner than that used for the IR
analysis. Given that trapped elimination products, which might
occur in thicker ®lms, can act as catalysts for elimination of
remaining leaving groups11 we also investigated a thin ®lm of
13 prepared by converting 12 which had been spin-coated onto
a KBr disc under the same conditions used for the preparation
of the UV±VIS sample. IR analysis of the `spin-coated' sample
of 13 also showed that the xanthate leaving group had been
eliminated and we therefore propose that the blue shift in the
UV±VIS absorption spectra is due to increased cis-linkages.
This is in contrast to the synthesis of EHPPV where the UV±
Fig. 1 IR spectra of ®lms of 10 and 13 formed from 10.
J. Mater. Chem., 2000, 10, 275±281
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Fig. 4 UV±VIS absorption spectra of ®lms of 13 formed from 10, 11
and 12.
Fig. 2 IR spectra of ®lms of 11 and 13 formed from 11.
VIS absorption spectra was the same whether the EHPPV was
prepared from the chloro or O-ethyl xanthate route and this
clearly shows that the phenylacetylene moiety is having an
important effect on the conversion process.
emission in conjugated polymers arises from both intra- and
inter-molecular excited states, with interconversion between
them.13 This model provides a possible framework for under-
standing the observed behaviour. It may be that substantial
intermolecular emission is observed in 13 prepared from 10 and
11, whereas as in 13 prepared from 12 there is much more light
emission from an intramolecular excited state. The differences
in the observed spectra would then be due to differences in the
arrangement of the polymer chains due to the syntheses used.
In the case of 13 prepared from 12 the higher density of cis-
linkages may reduce contact between polymer chains, thereby
impeding the formation of intermolecular excitations. Further
photophysical studies would be needed to con®rm this
conjecture.
Finally, we have also studied the effect of synthetic route on
the ef®ciency of PL from the resulting polymer. The PL
quantum yields of PAPPV 13 formed from 10, 11 and 12 are
14¡2, 11¡2, and 2¡1%, respectively. These quantum yields
are signi®cantly lower than those observed for EHPPV
prepared from the S-methyl xanthate (37¡4%), chloro
(55¡5%) and O-ethyl xanthate (17¡2%) precursor polymers,8
suggesting that the phenylacetylene moiety may in some way
assist in quenching the luminescence. It is also worth noting
that the O-ethyl xanthate precursor polymer forms the least
luminescent EHPPV and PAPPV.
Photoluminescence (PL) spectra give further information
about the electronic structure of polymers. The samples of 13
for the PL studies were prepared by heating the precursor
polymers at 220 ³C at v0.001 mBar for 15.5 h. PL spectra of 13
prepared by each of the three precursor routes are shown in
Fig. 5. All the spectra are very broad (150 nm full width at half
maximum) with only weak structure. The spectrum of 13
prepared from 11 peaks at 680 nm (1.8 eV), close to the peak of
665 nm (1.9 eV) for 13 prepared from 10. In contrast, the use of
precursor 12 to make 13 leads to a large blue-shift of the PL
which then peaks at 580 nm (2.1 eV). The blue-shift in the UV±
VIS absorption and PL spectra of 13 prepared from 12 are of
similar size.
The PL spectra are also remarkably different from those of
EHPPV, which does not have the phenylacetylene substitution,
prepared from the analogues of 10±12. The unsubstituted
materials showed pronounced vibronic structure with peaks/
shoulders close to 555, 600 and 650 nm.8 The PL of 13 prepared
from 10 and 11 is much redder than that of EHPPV with the
red shift in PL being larger than the red shift in the absorption
spectra. In fact the position and shape of the emission spectra
of 13 prepared from 10 or 11 resemble the emission from a
dihexyloxycyano-substituted PPV (CN-PPV) which has a
broad structureless emission peaking at 690 nm,12 although
the phenylacetylene materials give a little more emission at
short wavelengths (v550 nm).
In conclusion, we have synthesised a new phenylacetylene
substituted 2-alkoxyPPV, PAPPV, via a chloro and two
different xanthate precursor polymer routes and again clearly
demonstrated that the electronic properties of PPV derivatives
are very sensitive to the mode of preparation and the
attachment of functional groups.
It has been shown that the broad, red-shifted and long-lived
PL from CN-PPV ®lms is due to an intermolecular excited state
such as an excimer.12 In general it has been proposed that light
Fig. 5 Photoluminescence spectra of ®lms of 13 formed from 10, 11
and 12.
Fig. 3 IR spectra of ®lms of 12 and 13 formed from 12.
278
J. Mater. Chem., 2000, 10, 275±281

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washed with an aqueous solution of sodium metabisul®te
(7.9 M, 100 cm3), dried over anhydrous magnesium sulfate,
®ltered, and the solvent completely removed to give a yellow
oil. The residue was puri®ed by column chromatography over
silica using ethyl acetate±light petroleum (60±80 ³C) (0 : 1 to
1 : 30) as eluent to give a colourless oil of 3 (22.0 g, 97%), which
crystallised on cooling, mp 34 ³C; (Found: C, 50.4; H, 6.1.
C20H29IO5 requires C, 50.4; H, 6.1%); nmax/cm21 1737 (CLO);
Experimental
Measurements
NMR spectra were recorded on Bruker AM500, AMX500 or
DPX400 MHz spectrometers.13C NMR spectra were fully
decoupled. IR spectra were recorded on a Perkin-Elmer
Paragon 1000 Infrared spectrometer in chloroform unless
otherwise stated. UV±VIS spectra were recorded on a Perkin-
Elmer UV±VIS (Lambda 14P) spectrophotometer and unless
otherwise stated all spectra were recorded as a solution in
distilled dichloromethane. Mass spectra were recorded on a VG
Autospec spectrometer, the mode of ionisation being stated in
each case. Melting points were determined on a BuÈchi 510
melting point apparatus and are uncorrected. Microanalyses
were carried out in the Inorganic Chemistry Laboratory,
Oxford. Gel permeation chromatography was carried out using
PLgel 20 mm Mixed-A columns (600 mmz300 mm lengths,
7.5 mm diameter) from Polymer Laboratories calibrated with
l
max/nm 290 (e/dm3 mol21 cm21 2382); dH(500 MHz, CDCl3)
0.89±0.94 (6 H, m, 26Me), 1.29±1.35 (4 H, m, 26CH2), 1.39±
1.52 (4 H, m, 26CH2), 1.70±1.76 (1 H, m, CH), 2.11 (3 H, s,
COMe), 2.15 (3 H, s, COMe), 3.86±3.91 (2 H, m, ArOCH2),
5.09 (2 H, s, ArCH2), 5.10 (2 H, s, ArCH2), 6.93 (1 H, s, ArH)
and 7.73 (1 H, s, ArH); dC(125 MHz, CDCl3) 11.1, 14.0, 20.92,
20.94, 23.0, 23.9, 29.1, 30.5, 39.3, 60.7, 70.1, 70.4, 86.2, 112.8,
126.6, 139.2, 139.5, 157.4, 170.6 and 170.7; m/z [CI(NH3)] 494
(MNH4z) and 476 (Mz).
6
ꢀ
polystyrene narrow standards (Mp~1,300±15.4610 ) in tetra-
1,4-Bis(acetoxymethyl)-2-(2'-ethylhexyloxy)-5-(phenylethynyl)-
benzene 4
hydrofuran with toluene as ¯ow marker. The samples for GPC
were ®ltered through a Te¯on membrane (0.45 mm). The
tetrahydrofuran was degassed with helium and pumped at a
rate of 1 mL min21. The PL spectra of thin ®lms were measured
using a CCD spectrograph following excitation by an argon ion
laser at 476 nm. The absolute photoluminescence quantum
yield was measured in air using an integrating sphere to collect
the light emitted in all directions14 with excitation at 476 nm
provided by an argon ion laser. The thermogravimetric analysis
was carried out on a Rheometric Scienti®c STA 1500. For each
run the sample was held at 25 ³C for 30 min and then heated
from 25 to 600 ³C at 5 ³C min21 with analysis done under
nitrogen.
A mixture of 3 (5.73 g, 476 mmol), copper(I) phenylacetylide15
(5.33 g, 32.4 mmol) and distilled pyridine (75 cm3) was heated
at re¯ux for 9.5 h under nitrogen. The reaction mixture was
allowed to cool and then the solvent was removed. The residue
was dissolved in dichloromethane (100 cm3) and passed
through a plug of silica using dichloromethane as eluent.
The ®ltrate was collected and the solvent completely removed.
The residue was puri®ed by column chromatography over silica
using ethyl acetate±light petroleum (60±80 ³C) (1 : 40 to 1 : 30)
as eluent to afford a yellowish oil of 4 (5.01 g, 93%) (Found: C,
74.8; H, 7.8. C28H34O5 requires C, 74.6; H, 7.6%); nmax/cm21
(neat) 1739 (CLO); lmax/nm 296 (e/dm3 mol21 cm21 34817) and
314 (28263); dH(400 MHz, CDCl3) 0.90±0.97 (6 H, m, 26Me),
1.31±1.37 (4 H, m, 26CH2), 1.40±1.56 (4 H, m, 26CH2), 1.71±
1.80 (1 H, m, CH), 2.13 (3 H, s, COMe), 2.14 (3 H, s, COMe),
3.93±3.95 (2 H, m, ArOCH2), 5.15 (2 H, s, ArCH2), 5.34 (2 H, s,
ArCH2), 6.95 (1 H, s, ArH), 7.33±7.38 (3 H, m, 36Ar'H), and
7.51±7.54 (3 H, m, 26Ar'H and ArH); dC(100 MHz, CDCl3)
11.2, 14.1, 21.0, 23.0, 23.9, 29.1, 30.5, 39.4, 61.2, 64.8, 70.4, 86.4
(CMC), 92.9 (CMC), 111.4, 114.4, 123.3, 124.6, 128.4, 128.3,
131.4, 133.2, 139.1, 157.2 (CLO), and 170.8 (CLO); m/z
[CI(NH3)] 468 (MNH4z) and 450 (Mz).
1,4-Bis(acetoxymethyl)-2-(2'-ethylhexyloxy)benzene 2
A mixture of 1,4-bis(hydroxymethyl)-2-(2'-ethylhexyloxy)ben-
zene 18 (10.13 g, 38.02 mmol), acetic anhydride (7.9 cm3,
83.64 mmol), and distilled pyridine (22.8 cm3) was heated
under nitrogen at re¯ux for 4.5 h. After being cooled, the
reaction mixture was added to a mixture of diethyl ether
(70 cm3) and hydrochloric acid (3.0 M, 50 cm3). The organic
layer was separated and washed with a saturated aqueous
sodium hydrogen carbonate solution (2650 cm3). The aqueous
layer was collected and extracted with diethyl ether (70 cm3).
The combined organic layers were dried over magnesium
sulfate, ®ltered, and the solvent completely removed to give a
brown oil (13.16 g). The residue was puri®ed by column
chromatography over silica using ethyl acetate±light petroleum
(60±80 ³C) (1 : 30 to 1 : 15) as eluent to give 2 as an oil (12.95 g,
97%) (Found: C, 68.3; H, 8.3. C20H30O5 requires C, 68.5; H,
8.6%); nmax/cm21 (neat) 1743 (CLO); lmax/nm 282 (e/dm3
mol21 cm21 3043); dH(400 MHz, CDCl3) 0.89±0.95 (6 H, m,
26Me), 1.28±1.37 (4 H, m, 26CH2), 1.37±1.57 (4 H, m,
26CH2), 1.68±1.77 (1 H, m, CH), 2.10 (3 H, s, COMe), 2.11 (3
H, s, COMe), 3.86±3.94 (2 H, m, ArOCH2), 5.09 (2 H, s,
ArCH2), 5.15 (2 H, s, ArCH2), 6.88 (1 H, s, ArH), 6.93 (1 H, dd,
J 1.0 and 7.6 Hz, ArH) and 7.30 (1 H, d, J 7.6 Hz, ArH); dC(125
MHz, CDCl3) 11.2, 14.1, 21.00, 21.02, 23.0, 23.9, 29.1, 30.6,
39.4, 61.7, 66.2, 70.1, 111.0, 119.9, 124.3, 129.8, 137.5, 157.3,
170.8 and 170.9; m/z [CI(NH3)] 368 (MNH4z).
1,4-Bis(hydroxymethyl)-2-(2'-ethylhexyloxy)-5-(phenylethynyl)-
benzene 5
A mixture of 4 (3.57 g, 7.92 mmol), aqueous sodium hydroxide
(10%, 51 cm3), dichloromethane (10 cm3) and methanol
(118 cm3) was stirred at room temperature for 5 h under
argon. The solvent was removed and the residue was dissolved
in dichloromethane (100 cm3). The organic layer was washed
with water (2660 cm3), dried over anhydrous magnesium
sulfate, ®ltered, and the solvent completely removed to give a
brown oil (3.08 g). The residue was puri®ed by column
chromatography over silica using ethyl acetate±light petroleum
(60±80 ³C) (1 : 16 to 1 : 10 to 1 : 7) as eluent to give a white solid
of 5 (2.78 g, 96%), mp 71.5±72 ³C (Found: C, 78.3; H, 8.6.
C24H30O3 requires C, 78.65; H, 8.25%); nmax/cm21 3606 (OH);
l
max/nm 297 (e/dm3 mol21 cm21 30420) and 314 (25655);
dH(400 MHz; CDCl3) 0.88±0.96 (6 H, m, 26Me), 1.28±1.36
(4 H, m, 26CH2), 1.38±1.52 (4 H, m, 26CH2), 1.71±1.80 (1 H,
m, CH), 2.50 (1 H, t, J 6.4 Hz, OH), 2.57 (1 H, t, J 6.2 Hz, OH),
3.94±3.95 (2 H, m, ArOCH2), 4.67 (2 H, d, J 6.4 Hz, ArCH2),
4.89 (2 H, d, J 6.2 Hz, ArCH2), 7.03 (1 H, s, ArH), 7.32±7.37 (3
H, m, 3 x Ar'H), 7.45 (1H, s, ArH) and 7.48±7.51 (2 H, m,
Ar'H); dC(100 MHz, CDCl3) 11.1, 14.1, 23.0, 24.0, 29.0, 30.6,
39.3, 61.4, 63.7, 70.5, 86.7 (CMC), 92.9 (CMC), 109.6, 112.5,
123.3, 128.2, 128.4, 131.3, 131.9, 143.9 and 157.3; m/z
[CI(NH3)] 366 (Mz) and 349 (M2OH).
2,5-Bis(acetoxymethyl)-4-(2'-ethylhexyloxy)iodobenzene 3
A solution of 2 (16.7 g, 47.6 mmol) in chloroform (20 cm3) was
added to a mixture of silver acetate (8.87 g, 53.3 mmol) iodine
(13.4 g, 53.3 mmol), and chloroform (64 cm3) which had been
stirred at room temperature for 1 h under nitrogen. The
reaction mixture was stirred at room temperature for 3.5 h
before being passed through a plug of silica gel using
dichloromethane as eluent. The ®ltrate was collected and
J. Mater. Chem., 2000, 10, 275±281
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1,4-Bis[(methylthio)thiocarbonyloxymethyl]-2-(2'-
ethylhexyloxy)-5-(phenylethynyl)benzene 6
71.5; H, 7.0. C24H28Cl2O requires C, 71.5; H, 7.0%); lmax/nm
297 (e/dm3 mol21 cm21 29997) and 316(sh) (22239);
dH(400 MHz, CDCl3) 0.92±1.00 (6 H, m, 26Me), 1.33±1.40
(4 H, m, 26CH2), 1.42±1.63 (4 H, m, 26CH2), 1.76±1.85 (1 H,
m, CH), 3.98 (2 H, d, J 5.4 Hz, ArOCH2), 4.63 (2 H, s, ArCH2),
4.84 (2 H, s, ArCH2), 7.02 (1 H, s, ArH), 7.34±7.40 (3 H, m,
Ar'H), and 7.54±7.58 (3 H, m, 26Ar'H and ArH);
dC(100 MHz, CDCl3) 11.2, 14.1, 23.0, 24.0, 29.1, 30.6, 39.4,
40.7, 44.7, 70.6, 86.0 (CMC), 93.6 (CMC), 112.0, 114.6, 123.1,
126.4, 128.3, 128.4, 131.5, 134.1, 140.8 and 157.2; m/z
[CI(NH3)] 403, 405 and 407 (MHz).
A solution of 5 (2.00 g, 5.46 mmol) in dry diethyl ether (23 cm3)
was added to sodium hydride (60% in oil, 655 mg, 16.4 mmol)
in dry diethyl ether (23 cm3) under argon. The reaction mixture
was heated at re¯ux for 1 h and then carbon disul®de (1.3 cm3,
21.8 mmol) was added. The reaction mixture was heated at
re¯ux for 2.7 h and then iodomethane (2.0 cm3, 32.7 mmol) was
added. The reaction mixture was heated at re¯ux for further
2.7 h and then allowed to cool. The reaction mixture was
passed through a plug of silica using diethyl ether as eluent and
the ®ltrate was collected and the solvent completely removed to
give a yellow oil. The residue was puri®ed by column
chromatography and chromatotron over silica using ethyl
acetate±light petroleum (60±80 ³C) (1 : 30 and 1 : 90 respec-
tively) to give an oil of 6, which solidi®ed on cooling (1.67 g,
56%), mp 53 ³C (Found: C, 61.6; H, 6.3. C28H34O3S4 requires
C, 61.5; H, 6.3%); nmax/cm21 1067 and 1207; lmax/nm 282 (e/
dm3 mol21 cm21 40710), 297(sh) (32811), and 316(sh) (21874);
dH(400 MHz, CDCl3) 0.90±0.96 (6 H, m, 26Me), 1.31±1.36 (4
H, m, 26CH2), 1.40±1.54 (4 H, m, 26CH2), 1.71±1.79 (1 H, m,
CH), 2.59 (6 H, s, 26SMe), 3.95 (2 H, d, J 5.4 Hz, ArOCH2),
5.66 (2 H, s, ArCH2), 5.85 (2 H, s, ArCH2), 7.00 (1 H, s, ArH),
7.33±7.37 (3 H, m, Ar'H), 7.49±7.53 (2 H, m, Ar'H) and 7.58 (1
H, s, ArH); dC(125 MHz, CDCl3) 11.2, 14.1, 19.08, 19.13, 23.0,
23.9, 29.1, 30.6, 39.3, 70.2, 70.6, 73.6, 86.1 (CMC), 93.5 (CMC),
111.9, 114.7, 123.1, 123.9, 128.26, 128.33, 131.5, 134.0, 138.6,
157.4, 215.4 (CLS) and 215.6 (CLS).
Poly{[2-(2'-ethylhexyloxy)-5-(phenylethynyl)-1,4-phenylene-
vinylene](1-chloroethylene)} 11
A solution of potassium tert-butoxide in tetrahydrofuran
(0.19 M, 217 mg, 1.93 mmol, 10 cm3) was added to a solution
of 7 in tetrahydrofuran (0.13 M, 840 mg, 2.08 mmol, 16.4 cm3)
which had been cooled with an ice-bath under argon. The
reaction mixture was stirred for 1 h with ice-bath cooling and
then poured into methanol (34 cm3). The mixture was then
centrifuged at 4500 rpm for 10 min. The supernatant was
removed and the precipitate was dissolved in tetrahydrofuran
(55 cm3) and then poured into propan-2-ol (63 cm3). The
mixture was then centrifuged at 4500 rpm for 10 min and the
the precipitate of 11 (ca. 612 mg, ca. 80%) was collected and
dissolved in tetrahydrofuran (85 cm3), nmax(®lm on KBr disc)/
cm21 2209 (CMC); dH(400 MHz, CDCl3) 0.78±0.93 (6 H, br s,
26Me), 1.17±1.51 (8 H, br m, 46CH2), 1.63±1.77 (1 H, br s,
CH), 3.14±3.38 (1 H, br d, ArCH2), 3.38±3.62 (1 H, br d,
ArCH2), 3.64±3.95 ( 2 H, br m, ArOCH2), 5.81 (1 H, br s,
ArCHCl), 7.00±7.11 (1 H, br m, ArH) and 7.19±7.51 (6 H, br
Poly([2-(2'-ethylhexyloxy)-1,4-phenylene]{1-[(methylthio)-
thiocarbonyloxy]ethylene}) 10
m, ArH and Ar'H); GPC (0.53 mg cm23
,
24.0 ³C),
A solution of potassium tert-butoxide in tetrahydrofuran
(0.18 M, 201 mg, 1.79 mol, 10 cm3) was added to a solution of 6
in tetrahydrofuran (0.13 M, 1.06 g, 1.94 mmol, 14.5 cm3)
cooled in an ice-bath under argon. The reaction mixture was
stirred for 1 h with ice-bath cooling and then poured into
methanol (30 cm3). The mixture was centrifuged at 4500 rpm
for 10 min, the supernatant was removed and the residue was
dissolved in tetrahydrofuran (20 cm3). The solution was added
to propan-2-ol (30 cm3) and the mixture was centrifuged at
4500 rpm for 10 min. The supernatant was removed and the
orange precipitate of 10 (ca. 218 mg, ca. 26%) was dissolved in
tetrahydrofuran (14 cm3), nmax(®lm on KBr disc)/cm21 1061,
1214 and 2208 (CMC); dH(400 MHz, CDCl3) 0.80±0.96 (6 H, br
m, 26Me), 1.20±1.55 (8 H, br m, 46CH2), 1.62±1.71 (1 H, br
s, CH), 2.40±2.51 (3 H, br s, SMe), 3.17±3.33 (1 H, br m,
ArCH2), 3.39±3.59 (1H, br m, ArCH2), 3.65±3.80 (2 H, br m,
ArOCH2), 6.75 (1 H, br m, ArCH), 7.07±7.18 (1 H, br s, ArH),
7.20±7.39 (4 H, br m, ArH and Ar'H) and 7.44±7.55 (2 H, br m,
Mnw2.46106, Mww7.66106, polydispersity index ca. 3.1,
and Mn~3.96105, Mw~8.86105, polydispersity index~2.3
after equilibration; thermogravimetric analysis: 255 ³C (weight
loss: 9%; expected: 10%).
1,4-Bis(bromomethyl)-2-(2'-ethylhexyloxy)-5-(phenylethynyl)-
benzene 8
A solution of 5 (700 mg, 1.91 mmol), diethyl ether (46 cm3),
and phosphorus tribromide (0.4 cm3, 4.20 mmol) was stirred at
room temperature under argon for 1 h. The reaction mixture
was poured onto an ice-water mixture (30 cm3) and the organic
layer was separated, washed with water (2620 cm3), dried over
anhydrous sodium sulfate, ®ltered, and the solvent was
complete removed to give a yellowish oil. The residue was
puri®ed by chromatotron chromatography over silica using
ethyl acetate±light petroleum (60±80)³C (1:90) as eluent to give
a colourless solid of 8 (464 mg, 49%), mp 85±86 ³C (Found: C,
58.5; H, 6.1. C24H28Br2O requires C, 58.6; H, 5.7%); lmax/nm
258 (e/dm3 mol21 cm21 33913) and 301 (32272); dH(400 MHz,
CDCl3) 0.92±1.00 (6 H, m, 26Me), 1.33±1.43 (4 H, m,
26CH2), 1.44±1.65 (4 H, m, 26CH2), 1.76±1.86 (1 H, m, CH),
3.97 (2 H, d, J 5.3 Hz, ArOCH2), 4.51 (2 H, s, ArCH2), 4.72 (2
H, s, ArCH2), 6.96 (1 H, s, ArH), 7.34±7.41 (3 H, m, Ar'H),
7.53 (1 H, s, ArH) and 7.55±7.59 (2 H, m, Ar'H); dC(125 MHz,
CDCl3) 11.2, 14.1, 23.0, 24.0, 27.5, 29.1, 30.6, 31.9, 39.5, 70.6,
86.0 (CMC), 94.0 (CMC), 112.6, 115.1, 123.2, 126.9, 128.35,
128.4, 131.5, 134.6, 141.2 and 157.2; m/z [CI(NH3)] 491, 493
and 495 (MHz).
Ar'H); GPC (0.65 mg cm23
,
23.8 ³C), Mn~1.36105,
Mw~2.96105, polydispersity index 2.2, and Mn~1.36105,
Mw~2.36105, polydispersity index 1.8 after equilibration;
thermogravimetric analysis: 136 ³C (weight loss: 21%; expected:
25%).
1,4-Bis(chloromethyl)-2-(2'-ethylhexyloxy)-5-(phenylethynyl)-
benzene 7
DMAP (592 mg, 4.85 mmol), p-toluenesulfonyl chloride
(2.52 g, 13.2 mmol) and distilled triethylamine (1.1 cm3,
8.12 mmol) were added sequentially to a solution of 5
(862 mg, 2.35 mmol) in dichloromethane (16 cm3) under
nitrogen at room temperature. The reaction mixture was
stirred at room temperature for 3 h and then passed through a
plug of silica using dichloromethane as eluent. The ®ltrate was
collected and the solvent competely removed to leave a yellow
oil. The residue was puri®ed by column chromatography over
silica using light petroleum (60±80 ³C) as eluent giving a
colourless solid of 7 (850 mg, 90%), mp 36±37 ³C (Found: C,
1,4-Bis[ethoxy(thiocarbonyl)thiomethyl]-2-(2'-ethylhexyloxy)-5-
(phenylethynyl)benzene 9
A mixture of 8 (341 mg, 0.692 mmol), tetra(n-butyl)ammonium
bromide (63 mg, 0.194 mmol) and potassium O-ethylxanthate
(277 mg, 1.73 mmol) in dry dichloromethane (8 cm3) was
stirred at room temperature under argon for 18 h. The reaction
mixture was passed through a plug of silica gel using
280
J. Mater. Chem., 2000, 10, 275±281

View Article Online
dichloromethane as eluent and the ®ltrate was collected and the
solvent completely removed to give a pale yellow oil (427 mg).
The residue was puri®ed by column and chromatotron
chromatography over silica using ethyl acetate±light petroleum
(1 : 90 and 0 : 1 respectively) to give a colourless oil of 9
(381 mg, 96%) (Found: C, 62.6; H, 6.6. C30H38O3S4 requires C,
62.7; H, 6.7%); nmax/cm21 (neat) 1046 and 1211; lmax/nm 286 (e/
dm3 mol21 cm21 57942), 298(sh) (52722) and 318(sh) (34452);
dH(500 MHz, CDCl3) 0.93±0.99 (6 H, m, 26Me), 1.32±1.38 (4
H, m, 26CH2), 1.41±1.57 (10 H, m, 26OCH2CH3 and
26CH2), 1.73±1.80 (1 H, m, CH), 3.91 (2 H, d, J 5.4 Hz,
ArOCH2), 4.35 (2 H, s, ArCH2), 4.61 (2 H, s, ArCH2), 4.65±
4.70 (4 H, m, 26OCH2CH3), 7.00 (1 H, s, ArH), 7.33±7.38 (3
H, m, Ar'H), 7.51±7.53 (2 H, m, Ar'H) and 7.55 (1 H, s, ArH);
dC(125 MHz, CDCl3) 11.2, 13.8, 14.1, 23.0, 24.0, 29.1, 30.6,
34.9, 39.4, 70.0, 70.1, 70.5, 87.0 (CMC), 93.8 (CMC), 112.3,
114.8, 123.3, 124.3, 128.2, 128.3, 131.4, 134.1, 139.1, 157.0,
214.3 (CLS) and 214.5 (CLS); m/z (HRMS) found: 574.1721;
C30H38O3S4 requires 574.1703.
discussions and carrying out the thermogravimetric analyses.
We also thank Dr C. D. Bain and S. A. Haydock for carrying
out the infrared analysis of the spin-coated 13 prepared from
12.
References
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Poly([2-(2'-ethylhexyloxy)-5-(phenylethynyl)-1,4-phenylene]{1-
[ethoxy(thiocarbonyl)thio]ethylene}) 12
A solution of potassium tert-butoxide in tetrahydrofuran
(0.19 M, 21 mg, 0.19 mmol, 1.0 cm3) was added to a solution of
9 in tetrahydrofuran (0.13 M, 118 mg, 0.21 mmol, 1.6 cm3)
which had been cooled with an ice-bath under argon. The
reaction mixture was stirred for 1 h with ice-bath cooling and
then poured into a solution of methanol (3 cm3) and water
(0.3 cm3). The mixture was then centrifuged at 4500 rpm for
10 min. The supernatant was removed and the precipitate was
dissolved in tetrahydrofuran (3.5 cm3) and then poured into
propan-2-ol (3 cm3). The mixture was then centrifuged at
4500 rpm for 10 min to give a yellow precipitate of 12 (ca.
56 mg, ca. 60%) which was dissolved in tetrahydrofuran
(3.5 cm3), nmax(®lm on KBr disc)/cm21 1048, 1237 and 2209
(CMC); dH(400 MHz, CDCl3) 0.80±1.00 (6 H, br s, 26Me),
1.08±1.60 (11 H, br, 46CH2 and OCH2CH3), 1.68±1.83 (1 H,
br m, CH), 3.00±3.40 (2 H, br m, ArCH2), 3.70±3.92 (2 H, br m,
ArOCH2), 4.20±4.47 (2H, br m, OCH2Me), 5.62 (1 H, br s,
ArCH), 6.80±6.95 (1 H, br, ArH) and 7.20±7.50 (6 H, br, ArH
and Ar'H); GPC (0.26 mg cm23, 23.8 ³C), Mn~4.06105,
Mw~6.86105, polydispersity index~1.7 and Mn~2.16105,
Mw~3.36105, polydispersity index~1.6 after equilibration;
thermogravimetric analysis: 229 ³C (weight loss: 23%; expected:
27%).
3
4
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7
8
9
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Poly[2-(2'-ethylhexyloxy)-5-(phenylethynyl)-1,4-
phenylenevinylene] 13
Method 1. Thin ®lms of 10 were heated at 213 ³C at
0.01 mmHg for 15 h to give 13; nmax (®lm on KBr disc)/cm21
861, 964, 2204 and 3058; lmax(thin ®lm)/nm 297 and 470.
10 S. Son, A. Dodabalapur, A. J. Lovinger and M. E. Galvin,
Science, 1995, 269, 376.
11 P. L. Burn, A. B. Holmes, A. Kraft, D. D. C. Bradley, A. R. Brown,
R. H. Friend and R. W. Gymer, Nature, 1992, 356, 47.
12 I. D. W. Samuel, G. Rumbles and C. J. Collison, Phys. Rev. B,
1995, 52, 11573.
Method 2. Thin ®lms of 11 were heated at 211 ³C at
0.01 mmHg for 15.5 h to give 13; nmax (®lm on KBr disc)/cm21
861, 964, 2206 and 3058; lmax(thin ®lm)/nm 290 and 470.
13 I. D. W. Samuel, G. Rumbles and R. H. Friend, Luminescence
ef®ciency and time-dependence: insights into the nature of the
emitting species in conjugated polymers. Primary photoexcitations
in conjugated polymers: molecular exciton versus semiconductor
band model, ed. N. S. Sariciftci, World Scienti®c, Singapore, 1997,
140.
Method 3. Thin ®lms of 12 were heated at 213 ³C at
v0.01 mmHg for 15 h to give 13; nmax (®lm on KBr disc)/cm21
863, 967, 2207 and 3054; lmax(thin ®lm)/nm 301 and 422.
Acknowledgements
14 N. C. Greenham, I. D. W. Samuel, R. T. Phillips,
Y. A. R. R. Kessner, S. C. Morratti, A. B. Holmes and
R. H. Friend, Chem. Phys. Lett., 1995, 241.
S.-C.L. is a Swire Scholar and holds an Overseas Research
Student Award. I.D.W.S. is a Royal Society University
Research Fellow. We thank Corning Cables for provision of
a studentship (A.K.S.) and Dr M. G. RuÈther for helpful
15 R. D. Stephens and C. E. Castro, J. Org. Chem., 1963, 28, 3313.
Paper a904274a
J. Mater. Chem., 2000, 10, 275±281
281