Click chemistry as a powerful tool for the construction of functional poly(p-phenyleneethynylene)s: Comparison of pre- and postfunctionalization schemes

Article abstract of DOI:10.1021/ma050484p

1,3-Dipolar cycloadditions have been used to prepare a series of functionalized poly(p-phenyleneethynylene)s (PPEs). This was accomplished by employing a PPE with pendent triisopropylsilylacetylene groups. The triisopropylsilyl groups can be removed in si

Full text of DOI:10.1021/ma050484p

5868
Macromolecules 2005, 38, 5868-5877
Click Chemistry as a Powerful Tool for the Construction of Functional
Poly(p-phenyleneethynylene)s: Comparison of Pre- and
Postfunctionalization Schemes
Brian C. Englert, Selma Bakbak, and Uwe H. F. Bunz*
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
Received March 7, 2005; Revised Manuscript Received April 22, 2005
ABSTRACT: 1,3-Dipolar cycloadditions have been used to prepare a series of functionalized poly(p-
phenyleneethynylene)s (PPEs). This was accomplished by employing a PPE with pendent triisopropyl-
silylacetylene groups. The triisopropylsilyl groups can be removed in situ, exposing free alkynes in the
side chains of the polymer to react with azides in a postpolymerization functionalization strategy in a
1,3-dipolar cycloaddition. The properties of these polymers were explored and compared to polymers of
the same molecular structure but synthesized by a prepolymerization functionalization approach. Polymers
1
of the same structure exhibit identical H NMR, 13C NMR, and IR spectra regardless of whether they
were obtained by a conventional route or by postfunctionalization of a suitable PPE. UV-vis and
fluorescence spectra are similar in solution. Postmodification through click chemistry, when compared
to premodification, is an excellent method to produce functionalized, defect-free PPEs. Reaction of the
azides with the main chain alkyne units is not observed.
Introduction
acetylide is considerably more reactive toward the azide
so that a rate enhancement of the 1,3-dipolar cyclo-
additions results.4 The high yield and the specificity of
this transformation make it appealing, not only for
synthesis of small molecules but as well for the func-
tionalization of polymers as reported recently by Hawker
and Frechet5 in the attachment of dendrons to noncon-
jugated polymers.
The functionalization of an alkyne-appended poly(p-
phenyleneethynylene) (PPE 5 via 6) by 1,3-dipolar
cycloaddition to organic azides 7 is described. The
postpolymerization functionalization of conjugated poly-
mers is a useful technique in which a specific polymer
backbone is postsynthetically altered. Leclerc1 has
executed this concept elegantly in the polythiophene
series by polymerization of an active-ester containing
thiophene monomer, while Holdcroft2 has developed
postpolymerization halogenation of polythiophenes. These
approaches allow introduction of molecular diversity
late, in the final step, of the synthetic sequence and are
therefore efficient compared to the introduction of
functional elements during the synthesis of specific
monomers. Additionally, postfunctionalization schemes
allow the introduction of groups that might not be
compatible with the polymerization conditions. Fast
assembly of libraries of polymers and introduction of
different and potentially sensitive functional groups are
some of the advantages of postpolymerization function-
alization. The caveat with postfunctionalization is the
requirement of high yielding and specific reactions;
errors in the functionalization of monomers can be
corrected by the appropriate purification steps, while a
polymer synthesized by postfunctionalization processes
cannot be purified further.
Results and Discussion
PPEs are valuable due to their dramatic chromic
responses.6-9 They have been utilized in sensory schemes
and in semiconductor devices including to light-emitting
diodes7a,b and photodiodes.8 However, postfunctional-
ization schemes on PPEs have only sparsely been
carried out.6 It is of significant interest to develop an
efficient platform that could allow the manipulation of
PPE’s properties in a postpolymerization modification
approach (Figure 1). In this contribution a PPE scaffold,
6, is introduced that allows to “click on” different
functional groups by a 1,3-dipolar cycloaddition. The
polymers 8 made by the postmodification approach were
compared to those of the same structure but made by a
conventional approach (Figure 1). This allowed the
evaluation of the click process as tool to functionalized
conjugated polymers. Important (specific) questions are
if the postfunctionalization process selects the alkyne
appendage over the backbone alkynes, if the conversion
of the appended alkynes is complete, and if it occurs
with a similar regiochemical 1,4-control as reported for
the copper-catalyzed 1,3-dipolar cycloaddition (Figure
1).
Huisgen and Szeimies3 investigated the 1,3-dipolar
cycloaddition of azides to alkynes. Triazoles are the only
product of this reaction. Sharpless recognized the
potential of this transformation and retooled the dipolar
cycloaddition as “click chemistry” for the construction
of biologically active molecules. The most effective
variant uses terminal alkynes in combination with
copper sulfate and sodium ascorbate. The sodium ascor-
bate reduces copper sulfate to Cu+, which will form a
copper acetylide under these conditions. The copper
Synthesis and Characterization of Polymers 5
and 6. Reaction of diiodohydroquinone (1) with the
propargylic bromide 2 in the presence of excess potas-
sium carbonate furnished 3 in 82% yield. The copolym-
erization of 3 with the diyne 4 under standard condi-
tions with 0.7 mol % Pd-catalyst furnished polymer 5
in 87% yield as a yellow, reasonably soluble, fibrous
material with a degree of polymerization (Pn) of 64 (gel
* Corresponding author: e-mail uwe.bunz@chemistry.gatech.edu;
fax +1-404-385-1795.
10.1021/ma050484p CCC: $30.25 © 2005 American Chemical Society
Published on Web 06/15/2005

Macromolecules, Vol. 38, No. 14, 2005
Functional Poly(p-phenyleneethynylene)s 5869
Figure 1. Post- and prepolymerization functionalization strategies.
Scheme 1. Synthesis of the Polymer Platform 6
permeation chromatography, Mn ) 65 × 103, Mw/Mn )
PDI ) 4.4). Polymer 5 is characterized by its 1H NMR,
13C NMR, and IR spectra that are in excellent agree-
ment with the proposed structure.
Reaction of the polymer 5 with tetrabutylammonium
fluoride furnishes a considerably less soluble polymer
(6) in almost quantitative (95%) yield as a deep yellow
powder. Gel permeation chromatography (GPC) shows
a decrease of Pn to 46 (Mn ) 24 × 103, PDI ) 1.6). We
believe that the decreased solubility of 6 as compared
to that of 5 was due to a removal of higher molecular
weight polymer chains during the filtration step that
is necessary for the preparation of GPC samples. Ag-
gregated and/or insoluble but finely suspended parts of
the polymer are retained by the utilized GPC ultrafil-
ters, yellowish in appearance after use and supporting
our notion that significant amounts of 6 were retained.
We were able to obtain 1H NMR and 13C NMR spectra
of 6. The proton NMR spectrum of 6 resembles that of
5 but (a) does not show a signal for the TIPS groups,
(b) features an additional signal for the free alkyne
groups at δ ) 2.58 ppm, and (c) displays a shift in the
arene protons that are now spaced and resonate at 7.17
and 7.40 ppm. The IR spectrum of 6 shows a strong
band at 3301 cm-1, which is diagnostic for the presence
of a terminal alkyne. Additionally, two bands at 2202
and 2122 cm-1 can be attributed to the C≡C stretch of
the backbone and the free alkyne, respectively. It was
possible to obtain a 13C NMR spectrum of 6 with a
reasonable signal-to-noise ratio if chromium acetyl-
acetonate (cracac) was added as relaxating agent.
Figure 2. UV-vis and emission spectra of polymer 5 (top)
and polymer 6 (bottom) in chloroform solution and in the solid
state (absorption and emission maxima, see Table 1).
The optical spectra of 5 and 6 in solution are similar
and typical for PPEs (Figure 2 and Table 1). The solid-

5870 Englert et al.
Macromolecules, Vol. 38, No. 14, 2005
Table 1. Optical Properties, Yields, Degree of Polymerization, and Degree of Functionalization of 5, 6, and 8
yield
(%)
deg of post-
absorption
absorption
emission
emission
(film) [nm]
quantum
yield (Φfl)
polymer
Mn (PDI)
functionalization (%) (CHCl3) [nm] (film) [nm] (CHCl3) [nm]
5
87
95
91
92
91
82
94
93
76
93
82
75
96
63.6 × 103 (4.43)
24.4 × 103 (1.64)
13.7 × 103 (5.24)
8.5 × 103 (3.20)
25.5 × 104 (4.25)
71.7 × 103 (4.44)
25.4 × 103 (2.56)
24.5 × 103 (1.01)
22.6 × 103 (2.39)
16.2 × 104 (7.70)
10.8 × 104 (1.49)
71.8 × 103 (2.10)
22.6 × 103 (2.39)
na
>95
na
>95
>95
na
>95
na
>95
na
>95
na
ca. 50
422
420
415
413
406
416
418
421
424
408
412
416
412
450, 426
462, 438
434
448
447
448
448
447
449
448
454
454
452
450
450
450
462, 490, 512
533
0.99
0.89
0.98
0.98
0.87
0.92
0.97
0.94
0.98
0.96
0.93
0.97
0.91
6
8a pre
8a post
12
463
437
485
410
450
8b pre
8b post
8c pre
8c post
8d pre
8d post
8e pre
8e post
422
483
435
479
433
470
431
470, 523
470
416
426
452, 470
460
473
428
436
Scheme 2. In Situ Generation of 6 and Its Reaction with Azides 7a-e Yielding 8a-e and Prefunctionalization
Approach toward 8a-e
state spectra of 5 and 6 are strikingly different. The
removal of the TIPS groups leads to a 12 nm red shift
(577 cm-1) in absorption. This red shift could be a sign
either of increased planarization or of interchromophore
interaction that would give testimony to the formation
of weak electronic aggregates between PPE chains on
top of a significant contribution of chain planarization
(1475 cm-1). The solid-state emission of 6 shows an
excimer band at 533 nm that is not present in the solid-
state spectrum of 5, reinforcing the notion of some
interchain interactions existing in thin films of 6 in the
excited state.9
Synthesis of Functionalized Polymers 8a-e. The
successful formation of 6 allowed its reaction with
different azides. In a first experiment, direct reaction
of 6 with dodecyl azide 7a was performed under
microwave irradiation, but the low solubility of polymer
6 in organic solvents led to material that was only to a
moderate extent triazole-functionalized. It was found
that an in situ deprotection of 5 with tetrabutyl-
ammonium fluoride (TBAF) and coupling procedure was
a better way of obtaining the 1,3-dipolar cycloadducts.
Reaction of 5 with the azides 7a-e in the presence of
copper sulfate, TBAF, and sodium ascorbate in wet THF
(5% water) as solvent gave the functionalized PPEs
8a-e in yields of 75-96% after 48 h at 40-60 °C.
Without the addition of copper sulfate and sodium
ascorbate the reaction did not proceed as well. As a
consequence, postmodification reactions were always
executed in the presence of copper sulfate and sodium
ascorbate. Workup is performed by 3-fold precipitation
of the polymer into methanol to remove the starting
azide reagent. The yields of the postfunctionalization
reactions are high and shown in Table 1.
functionalized, according to 1H NMR, 13C NMR, and IR
spectroscopies. This was confirmed by the synthesis of
the same polymers 8a-d by a conventional approach
(Scheme 2). These “premodified” polymers offer a stan-
dard the postmodified PPEs can be compared to. In
completely postmodified polymers 8a-d, there were no
1
peaks in the H NMR at 2.55 for the terminal alkyne
(Figure 3). Signals for the newly formed triazoles are
present at 7.5-8.0 ppm. Signals from the carbons of the
triazole nuclei are visible at 140-150 and 120-130 ppm
in the 13C NMR spectrum of the functionalized poly-
mers. The peak at 3294 cm-1 has disappeared in the
postfunctionalized 8. The excess of azide reagent 7 was
removed completely by the 3-fold precipitation of the
polymers 8 into methanol. According to IR spectroscopy
the strong azide band at 2100 cm-1 (Figure 4) had
disappeared. In situ deprotection and reaction of poly-
mer 5 with azide dendron 7e afforded a polymer 8e
which contained ≈10% of unreacted terminal alkyne
1
according to H NMR spectroscopy and comparison of
its spectral data to those of conventionally prepared 8e.
Partial functionalization is not surprising, as Frechet
and Hawker have observed similar results for the
functionalization of nonconjugated polymeric systems.5
Reaction of 9 with azides 7a, c, d, and e afforded
monomers 10a, c, d, and e. Reaction with diyne 4 under
standard conditions furnished the polymers 8a,c-e in
excellent yields (Table 1, Scheme 2). Monomer 10b was
also obtained by this method. It is insoluble and could
neither be characterized nor purified. An alternate
approach employing the reaction of 3 with azide 7b
under thermal conditions afforded monomer 11 (Scheme
3). Polymerization of 11 with 4 under standard condi-
tions accessed 12 in almost quantitative yields. The
presence of the triisopropylsilyl groups was confirmed
by two signals recorded between δ ) 10-20 ppm in the
Reactions carried out with azides 7a-e afforded
polymers 8a-e, of which 8a-d were fully and 8e mostly

Macromolecules, Vol. 38, No. 14, 2005
Functional Poly(p-phenyleneethynylene)s 5871
Figure 3. 1H NMR of polymers 5, 6, 8a (post), and 8a (pre) (top to bottom).
13C NMR spectrum of 12. Deprotection of 12 with TBAF
yielded polymer 8b as a moderately soluble yellow solid.
Overall, the 13C NMR spectra of the polymers 5, 6, and
8a-e are very similar and easily interpreted. The
resonances due to the backbone carbon atoms and the
triazoles are almost superimposable for all of the
investigated polymers.
from monomer to polymer, we are not able to assess the
regiochemistry of the triazole units in polymer 8 at all
by NMR spectroscopy and cannot give any testimony
with respect to the regioselectivity of the postfunction-
alization process (Figure 5). In the formation of the
sterically hindered monomer 11 high regioselectivity is
observed, and only the 1,4-product is formed.
Regioisomers. At room temperature, the copper-
catalyzed process is typically regioselective, favoring the
1,4-triazole. We opted to perform these copper-catalyzed
reactions between 40 and 60 °C as we observed im-
proved yields in monomers and higher degree of func-
tionalization in polymeric systems. Under these condi-
tions 10a and 10c-e were obtained as approximate 2:1
mixtures of the 1,4- and the 1,5-regioisomers as can be
seen in the spectroscopic data for 10a (Figure 5). The
regioisomers were not separable by flash chromatogra-
phy and therefore used as mixtures.
Characterization of Functionalized Polymers
8a-e. It was of interest to study the influence of
postmodification on the molecular weight of 8. We find
PPEs decrease in molecular weight (5, 63.6 × 103; 6,
25.4 × 103 > 8 > 8.5 × 103) and polydispersity (5: 4.4
to between 3.2 > 8 > 1.5) when comparing 8 to platform
polymer 5 (Table 1). This is possibly due to differences
in solubility between 5 and the postfunctionalized
polymers 8. Material is lost during the filtration step
required for GPC due to aggregated and/or insoluble
parts of 8, similarly to the case discussed for polymer
6. GPC ultrafilters are yellowish in appearance after
filtration of solutions of 8a-e, and the decreased
polydispersity is an excellent indication for the loss of
high molecular weight fractions during filtration.
1
The H NMR spectra of the conventionally prepared
polymer 8a and its twin made by the postfunctional-
ization of 5 are shown in Figure 3. The polymers are
spectroscopically indistinguishable from each other.
When one inspects the NMR spectra of the polymer 8a
(conventional), the spectral features of the regioisomers
that are well resolved in the spectra of the monomer
10a are not resolved at all in the spectra of the polymer
8a. Because of this decrease in resolution, when going
To rule out the possibility of diyne formation, i.e.,
cross-linking, as a reason for observed insolubility, we
treated polymer 6 with TBAF, copper sulfate, and
sodium ascorbate in wet THF (5% water) in the presence
of air. Only after heating to reflux for 24 h did we

5872 Englert et al.
Macromolecules, Vol. 38, No. 14, 2005
Figure 4. IR of polymers 5, 6, 8a (post), and 8a (pre) (top to bottom). The blue arrows point to the bands of the terminal alkynes.
Scheme 3. Synthesis of Polymer 8b via a Prefunctionalized Strategy Starting from Monomer 3
observe a material containing some diyne linkages. The
material was still soluble, and the amount of cross-
linking must have been moderate. The signals of the
diyne groups are however visible the in 13C NMR due
to their shorter relaxation time as compared to the
signals attributed to the alkyne carbons of the main
chain. Signals assignable to diyne formation were not
observed in any of the postfunctionalized polymers 8a-e
because those were synthesized in a nitrogen atmo-
sphere, under scrupulous exclusion of oxygen.
The possibility of incorporation of triazole groups into
the backbone of the PPEs as a cause for the decreased
solubility was also considered. Control experiments were
performed in which didodecyl-PPE was treated at 40
°C for 16 h with an excess of dodecyl azide under
standard postfunctionalization conditions. After pre-

Macromolecules, Vol. 38, No. 14, 2005
Functional Poly(p-phenyleneethynylene)s 5873
Figure 5. 13C NMR of monomer 10a showing 1,4-triazoles (blue arrows) and 1,5-triazoles (red arrows).
Figure 6. UV-vis and emission spectra of polymer 8b (conventional) and polymer 12 in chloroform (left) and in the solid state
(right). The only difference is the TIPS group attached to the triazole units.
cipitation into methanol only unfunctionalized PPE was
Optical Properties of Functionalized Polymers
8a-e. The optical properties of polymers 8a-e were
examined and compared with those of their premodified
counterparts. In solution, absorption and fluorescence
maxima of structurally identical polymers 8a-e occur
at similar wavelengths ((2 nm). The largest difference
in absorption is found when comparing platform poly-
mer 6 to functionalized polymers 8 and 12. For all
polymers 8, both pre- and postfunctionalized, blue shifts
in absorption are observed when compared to 6 (Table
1). Polymer 12 with TIPS groups attached to the
pendant triazole moieties is an extreme case and has a
solution absorption maximum of 406 nm, which is blue-
shifted by 6-24 nm of the absorption maxima of
polymers 8a-e (Figure 6). The solid-state emission of
12 is almost unchanged to that obtained in solution. We
assume that the increased steric demand of the TIPS
groups forces the backbone of this PPE into a nonplanar
ground state.12,13
1
isolated according to H NMR, 13C NMR, and UV-vis
spectroscopy. Attack on the backbone-ynes is not favored
under those reaction conditions.
There is precedence for decreased solubility of click-
functionalized polymers: Kluger et al. performed post-
functionalization of poly(oxynorbornenes)10 and noted
dramatic differences in solubility between polymers
functionalized with 1,4-triazoles and those not. In some
cases, GPC data for these polymers could not be
obtained due to limited solubility. Matyjaszewski et al.
have recently modified polymers of acrylonitrile with
click-type chemistry to form tetrazoles and also noted
marked differences in solubility between polymers
modified by click chemistry and their unmodified pre-
cursors.11 It is, however, surprising that the attachment
of dodecyl chains or Frechet-type dendrons leads to a
decrease in solubility of 8 in our case. A possible
explanation is that the presence/incorporation of the
triazole group per se reduces the solubility of any
polymer.
All of the investigated polymers 5, 6, 8, and 12 have
the same backbone. In the solid state, i.e., in thin films,

5874 Englert et al.
Macromolecules, Vol. 38, No. 14, 2005
their absorption spectra vary considerably. Polymer 6
shows an absorption maximum at 462 nm, while the
TIPS-substituted 12 has a solid-state absorption maxi-
mum located at 410 nm. All of the other triazole-
functionalized polymers, 8, show absorption maxima
ranging from 416 to 436 nm. The red shift in the
absorption spectra of 8a-e, when going from solution
into the solid state is quite small, only 6-17 nm. That
is unusual because the precursor polymer 6 shows a
shift of 42 nm when going from solution into the solid
state. The differences in the thin film UV spectra
between pre- and postfunctionalized polymers 8a-e of
identical structure are small, and as a rule the absorp-
tion of the postfunctionalized samples is 8-13 nm red-
shifted.
The introduction of the triazole unit into the side
chains of the PPEs 8 and the PPE 12 influences their
absorption insofar as a more twisted conformation of
the main chain must be assumed. In the case of 12 the
large TIPS substituent will probably lead to an ad-
ditional twist of the main chain, and the conformations
of 12’s backbone in solution and in the solid state will
be very similar. The subtle differences between the
absorption of the pre- vs the postfunctionalized triazole-
substituted PPEs 8a-e is possibly due to difficult-to-
be-detected differences in the ratio of 1,4- and 1,5-
isomers.
to completely functionalize PPE 6 via a postmodification
strategy into 8a-d. In the case of azide 7e, this
approach provided a polymer 8e, which was up to 90%
functionalized. While all of these triazole-functionalized
polymers aggregate, their absorption spectra are quite
insensitive to this aggregation process, which suggests
that water-soluble triazole-functionalized PPEs may
findattractiveapplicationsinbiologicalsensingschemes.14
Experimental Section
Instrumentation. The 1H and 13C NMR spectra were taken
on a Varian 300 MHz or a Bruker 400 MHz spectrometer using
1
a broadband probe. The H chemical shifts are referenced to
the residual proton peaks of CDCl3 at δ 7.24 and DMSO at δ
2.49. The 13C resonances are referenced to the central peak of
CDCl3 at δ 77.0 and DMSO at δ 39.5. Chromium(III) acety-
lacetonate was used when obtaining 13C NMR data for all
polymers. UV-vis measurements were made with a Shimadzu
UV-2401PC recording spectrophotometer. Fluorescence data
were obtained with a Shimadzu RF-5301PC spectrofluoropho-
tometer. A Headway Research model PWM32 instrument was
used to spin-coat dilute chloroform solutions of polymers onto
quartz slides for thin film experiments. 1,4-Diiodo-2,5-dihyd-
roquinone,13 1,4-diethynyl-2,5-bis(2-ethylhexyl)benzene (4),13
dodecyl azide (7a),10 and 912 were prepared and characterized
in accordance with published procedures.
General Procedure for Conversion of Halide to Azide.
In a round-bottom flask the corresponding organic halide was
dissolved in acetone; 10 equiv of sodium azide was added, and
the mixture was heated to reflux for 24 h and cooled to room
temperature, and the solvent was removed under vacuum.
Following aqueous work-up, the crude products were purified
by column chromatography on silica gel with dichloromethane:
hexane as an eluent.
Synthesis of 3. 1,4-Hydroxy-2,5-diiodobenzene (4.73 g, 13.1
mmol), potassium carbonate (18.1 g, 131 mmol), and 2 (9.00
g, 32.7 mmol) were dissolved in acetone (150 mL). The mixture
was heated to reflux for 24 h, allowed to cool to room
temperature, then diluted with dichloromethane, and washed
with 1 N HCl (2 × 150 mL). The solvent was removed under
vacuum. The crude solid was purified by chromatography on
silica gel (1:1, dichloromethane:hexane) to yield 3 as a colorless
crystalline solid (8.05 g, 82%). 1H NMR (CDCl3): δ 7.47 (m
2H), 4.73 (m, 4H), 1.20 (m, 6H), 1.03 (m, 36H). 13C NMR
(CDCl3): δ 152.2, 124.6, 101.2, 90.8, 86.4, 59.0, 18.9, 11.4. IR:
v 2953, 2735, 2610, 2461, 2183, 2081, 1999, 1901, 1821, 1469,
1372, 1272, 1217, 1068, 1003, 915; mp 80-82 °C. Calcd: C,
48.00; H, 6.44. Found: C, 48.07; H, 6.52.
Synthesis of Polymer 5. Monomer 3 (10.0 g, 13.3 mmol)
and 2,5-ethylhexyl-1,4-diethynylbenzene (4) (4.72 g, 13.5
mmol) were dissolved in tetrahydrofuran (26 mL) and piperi-
dine (26 mL) in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times after
which (Ph3P)2PdCl2 (65 mg, 93 µmol) and CuI (10 mg, 53 µmol)
were added. The mixture was allowed to stir at room temper-
ature for 48 h, after which the solvent was removed and the
mixture was dissolved in dichloromethane and washed with
1 N HCl, 1 N NH4OH, and water. The organic layer was dried
over MgSO4 and the solvent removed. The resulting polymer
was redissolved in dichloromethane and precipitated out of
methanol (three times 1 L) to yield 6 (9.81 g, 87%) as a yellow
solid. 1H NMR (CDCl3): δ 7.29 (m, 2H), 7.24 (m, 2H), 4.79 (m,
4H), 2.74 (m, 2H), 1.75 (m, 2H), 1.52 (m, 16H), 1.25 (m, 6H),
1.02 (m, 36H), 0.82 (m, 6H). 13C NMR (CDCl3): δ 152.4, 141.2,
133.2, 123.1, 118.6, 114.5, 101.7, 94.7, 90.1, 58.0, 40.3, 38.4,
32.4, 28.8, 25.6, 23.0, 22.2, 20.5, 18.4, 16,4, 13.9, 11.1, 10,7.
IR: v 2957, 2943, 2920, 2911, 2883, 2860, 2846, 2361, 2159,
1507, 1498, 1489, 1481, 1464, 1457, 1442, 1415, 1344, 1280,
1251, 1196, 1185, 1038, 1032, 1023, 1015, 1008, 983, 879, 665,
647. GPC (polystyrene standards): Mn ) 63.6 × 103, PDI )
4.42. Calcd: C, 79.56; H, 10.01. Found: C, 79.03; H, 9.94.
Synthesis of Polymer 6. Polymer 5 (0.250 g, 0.296 mmol)
was dissolved in THF (50 mL) under nitrogen purge in an
We examined the fluorescence quantum yields of 5,
6, and 8a-e in solution (Table 1). There are no
significant differences between the quantum yields of
the conventional and the click-functionalized PPEs. The
deprotected polymer 6 and the polymer 12 have the
lowest quantum yields (0.89 and 0.87). The postfunc-
tionalization therefore does not seem to disturb the
backbone of the PPE.
DSC of Functionalized Polymers 8a-e. The ther-
mal behavior of polymers 8a-e was investigated be-
tween 0 and 250 °C by differential scanning calorimetry
(DSC). Polymers 5, 6, 8b, 8c, 8d, and 8e show slow
decomposition and no phase transitions. Polymer 8a,
obtained by a premodification strategy, shows an endo-
thermic transition beginning at 66 °C and ending at 126
°C.5b A reproducible isotropic transition at 200 °C upon
heating and cooling was also observed. Polymer 8a
synthesized by a postmodification strategy showed only
slow decomposition. When comparing polymers synthe-
sized by a post- and premodification strategy, it is
important to note that the conventional and the click
polymers 8 often have different degrees of polymeriza-
tion but identical substitutents and are therefore ex-
pected to behave differently. Longer polymer chains
would melt at higher temperatures. As discussed above,
slightly differing polymer structures such as the pres-
ence of 1,5-triazoles would also be expected to cause
differences in the solid-state properties of these poly-
mers.
Conclusions
We have produced a series of PPEs (8a-e) by em-
ploying click chemistry in both pre- and postpolymer-
ization functionalization approaches. In examples where
the structural repeat unit of the polymer was the same,
the optical properties of these polymers in solution
proved to be identical. Differing thin-film optical and
thermal properties result from differening degrees of
polymerization and perhaps a different distribution of
triazole regioisomers. Click chemistry provided a means

Macromolecules, Vol. 38, No. 14, 2005
Functional Poly(p-phenyleneethynylene)s 5875
oven-dried Schlenk flask. Under nitrogen tetrabutylammo-
nium fluoride (1 mL, 1 M solution in THF, containing ca. 5%
water) was added slowly over 5 min. The mixture was allowed
to stir at room temperature for 12 h. The solvent was removed,
and the mixture was dissolved in dichloromethane and washed
with 1 N HCl, 1 N NH4OH, and water. The organic layer was
dried over MgSO4 and the solvent removed. The product was
dissolved in dichloromethane and precipitated out of methanol
(200 mL) to yield polymer 6 (0.149 g, 95%) as a deep yellow
solid. 1H NMR (CDCl3): δ 7.38 (m, 2H), 7.19 (m, 2H), 4.80 (m,
4H), 2.75 (m, 4H), 2.55 (m, 2H), 1.76 (m, 2H), 1.55 (m, 16H),
1.28 (m, 6H), 0.84 (m, 6H). 13C NMR (TCE): δ 152.8, 141.5,
133.4, 123.2, 118.3, 114.9, 95.2, 89.9, 57.4, 40.4, 38.4, 32.5, 28.8,
25.7, 23.1, 14.0, 10.8. IR: v 3752, 3663, 3309, 2960, 2921, 2864,
2200, 2135, 1545, 1507, 1455, 1416, 1371, 1262, 1202, 1033,
(CDCl3): δ 7.57 (m, 2H), 7.26 (m, 4H), 5.31 (m, 4H), 4.30 (m,
4H), 2.72 (m, 4H), 1.85 (m, 12H), 1.56 (m, 46H), 0.82 (m, 18H).
13C NMR (CDCl3): δ 153.0, 143.82, 141.1, 133.0, 124.8, 121.9,
117.8, 114.5, 94.4, 89.7, 89.7, 63.9, 50.0, 40.0, 38.1, 32.0, 29.0,
26.0, 22.6, 13.6, 10.4. IR: v 3602, 3083, 2954, 2841, 2434, 2196,
2028, 1688, 1529, 1499, 1361, 1212, 890, 824, 777, 600. GPC
(polystyrene standards) Mn ) 13.7 × 103, PDI ) 5.24.
Synthesis of Polymer 8b (Postpolymerization Func-
tionalization). Polymer 5 (0.100 g, 0.118 mmol) and azide
7b (0.231 g, 0.471 mmol) were dissolved in THF (15 mL) under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which CuSO4 (0.5 mg, 2 µmol), sodium ascorbate (4 mg, 19
µmol), and tetrabutylammonium fluoride (0.25 mL, 1 M
solution in THF, containing ca. 5% water) were added. The
mixture was allowed to stir at 60 °C for 48 h. The solvent was
removed under vacuum. The mixture was redissolved in
dichloromethane and washed with 1 N HCl, 1 N NH4OH, and
water. The organic layer was dried over MgSO4, and the
solvent was removed. The resulting polymer was dissolved in
dichloromethane and precipitated out of methanol to yield 8b
(0.168 g, 94%) as a yellow solid. 1H NMR (CDCl3): δ 7.64 (m,
2H), 7.26 (m, 2H), 7.17 (m, 2H), 5.34 (m, 4H), 4.64 (m, 4H),
2.82 (m, 4H), 1.25 (m, 20H), 0.84 (m, 12H). 13C NMR (CDCl3):
δ 153.0, 144.5, 141.2, 133.2, 122.2, 118.2, 114.9, 110.6, 94.8,
90.1, 63.8, 57.9, 42.3, 40.3, 38.3, 32.3, 31.7, 29.7, 28.6, 25.5,
22.9, 18.3, 13.8, 11.0, 10.6. IR: v 3311, 3259, 2961, 2443, 2204,
1702, 1592, 1505, 1456, 1415, 1356, 1316, 1258, 1076, 1015,
924, 892, 854, 674, 632. GPC (polystyrene standards) Mn
)
24.4 × 103, PDI ) 1.64. Calcd: C, 85.67; H, 8.32. Found: C,
85.73; H,8.46.
Synthesis of Polymer 8a (Postpolymerization Func-
tionalization). Polymer 5 (0.100 g, 0.118 mmol) and azide
7a (62 mg, 0.295 mmol) were dissolved in THF (15 mL) under
a nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen and frozen and evacuated three times,
after which CuSO4 (0.5 mg, 1.9 µmol), sodium ascorbate (4 mg,
19 µmol), and tetrabutylammonium fluoride (0.25 mL, 1 M
solution in THF, containing ca. 5% water) were added. The
mixture was allowed to stir at 40 °C for 48 h. The THF was
removed under vacuum, and the mixture was dissolved in
dichloromethane and washed with 1 N HCl, 1 N NH4OH, and
water. The organic layer was dried over MgSO4 and the solvent
removed. The resulting polymer was dissolved in dichlo-
romethane and precipitated out of methanol to yield 8a (0.104
887, 799, 752, 707, 658. GPC (polystyrene standards) Mn
)
25.4 × 103, PDI ) 2.56.
Synthesis of 11. Diiodo compound 3 (1.00 g, 1.33 mmol)
and azide 7b (2.93 g, 5.99 mmol) were dissolved in o-xylene
under nitrogen purge in an oven-dried Schlenk flask. The
mixture was allowed to stir at reflux for 48 h. The solvent was
removed under vacuum, and the crude product was purified
by chromatography on silica gel (1:3, ethyl acetate:hexane) to
yield 11 as a colorless solid and single regioisomer (2.01 g,
1
g, 92%) as a yellow solid. H NMR (CDCl3): δ 7.58 (m, 2H),
7.28 (m, 4H), 5.33 (m, 4H), 4.31 (m, 4H), 2.72 (m, 4H), 1.87
(m, 12H), 1.58 (m, 46H), 0.86 (m, 18H). 13C NMR (CDCl3): δ
152.8, 143.9, 141.2, 133.2, 123.1, 122.0, 118.1, 114.9, 94.7, 89.9,
64.1, 50.2, 40.2, 38.3, 32.3, 31.7, 30.0, 29.2, 26.3, 25.5, 22.7,
13.8, 10.6. IR: v 3136, 2948, 2851, 2729, 2673, 2418, 2201,
2094, 1599, 1507, 1461, 1446, 1418, 1378, 1334, 1277, 1212,
1007, 861, 722. GPC (polystyrene standards) Mn ) 8463, PDI
) 3.20.
1
86%). H NMR (CDCl3): δ 7.25 (s, 2H), 5.06 (s, 4H), 4.74 (t,
4H), 3.04 (m, 4H), 1.43 (m, 6H), 1.09 (m, 36H). 13C NMR
(CDCl3): δ 152.4, 142.3, 137.0, 123.0, 85.8, 60.8, 40.7, 31.8,
18.8, 18.5, 11.5, 1.1. 19F NMR (CDCl3): -82.1, -115.4, -123.0,
-123.2, -124.1, -124.5, -127.5. IR: v 3090, 2947, 2867, 2725,
2464, 2363, 2105, 2002, 1692, 1467, 1458, 1375, 1352, 1233,
1207, 1150, 1055, 1000, 883, 848, 711, 647. MS calcd for
[C50H56F34I2N6O2Si2], 1728.9; found: 1729.4; mp 146-150 °C.
Calcd: C, 34.73; H, 3.26. Found: C, 34.24; H, 3.25.
Synthesis of 10a. Diiodo compound 9 (1.00 g, 2.28 mmol)
and azide 7a (1.93 g, 9.13 mmol) were dissolved in THF under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which CuSO4 (6 mg, 22.8 µmol) and sodium ascorbate (45 mg,
228 µmol) were added. The mixture was allowed to stir at 50
°C for 48 h. The solvent was removed, and the mixture
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4.
The solvent was removed under vacuum, and the crude
product was purified by chromatography on silica gel (1:1,
ethyl acetate:hexane) to yield 10a as a light yellow crystalline
Synthesis of Polymer 12 (Prepolymerization Func-
tionalization). Monomer 11 (single regioisomer) (1.00 g, 0.574
mmol) and 2,5-ethylhexyl-1,4-diethynylbenzene (4) (0.203 g,
0.579 mmol) were dissolved in dichloromethane (2 mL) and
piperidine (2 mL) in an oven-dried Schlenk flask. The flask
was flushed with nitrogen, frozen, and evacuated three times,
after which (Ph3P)2PdCl2 (20 mg, 29 µmol) and CuI (6 mg, 29
µmol) were added. The mixture was allowed to stir at room
temperature for 48 h. The solvent was removed, and the
mixture was dissolved in dichloromethane and washed with
1 N HCl, 1 N NH4OH, and water. The organic layer was dried
over MgSO4 and the solvent removed. The resulting polymer
12 was dissolved in dichloromethane and precipitated out of
methanol three times to yield a yellow solid (1.42 g, 91%). 1H
NMR (CDCl3): δ 7.26 (m, 4H), 7.18 (m, 2H), 5.35 (m, 4H), 4.66
(m, 4H), 2.80 (m, 4H), 1.24 (m, 18H), 1.01 (m, 42H) 0.82 (m,
12H). 13C NMR (CDCl3): δ 152.7, 141.9, 141.4, 137.4, 133.2,
122.5, 117.3, 114.7, 113.2, 110.5, 95.6, 88.8, 60.4, 44.8, 40.4,
38.1, 32.2, 31.6, 28.6, 25.4, 22.8, 18.3, 13.7, 11.3, 10.5. IR: v
2962, 2867, 2726, 2357, 2205, 1506, 1460, 1412, 1367, 1259,
1092, 1018, 872, 797, 658. GPC (polystyrene standards): Mn
) 25.5 × 104, PDI ) 4.25.
1
solid (1.74 g, 89%). H NMR (CDCl3): δ 7.66 (s, 2H), 7.35 (s,
2H), 5.19 (s, 4H), 4.34 (t, 8H), 3.89 (m, 4H), 1.91 (m, 4H), 1.24
(m, 36H), 0.84 (t, 6H). 13C NMR (CDCl3): δ 152.7, 143.7, 135.3,
125.1, 123.9, 122.8, 86.8, 65.0, 50.8, 32.5, 32.2, 30.6, 29.9, 29.8,
29.7, 29.6, 29.3, 26.8, 26.7, 23.7, 23.0, 14.5. IR: v 3179, 2947,
2844, 2428, 2121, 1900, 1650, 1573, 1485, 1409, 1341, 1204,
1142, 1072, 1038, 892, 840, 802, 723, 647. MS calcd for
[C36H58I2N6O2]: 860.69; found: 860.3; mp 113-115 °C.
Synthesis of Polymer 8a (Prepolymerization Func-
tionalization). Monomer 10a (0.500 g, 0.581 mmol) and 2,5-
ethylhexyl-1,4-diethynylbenzene (4) (0.205 g, 0.586 mmol) were
dissolved in dichloromethane (2 mL) and piperidine (2 mL) in
an oven-dried Schlenk flask. The flask was flushed with
nitrogen, frozen, and evacuated three times, after which
(Ph3P)2PdCl2 (4 mg, 6 µmol) and CuI (1 mg, 6 µmol) were
added. The mixture was allowed to stir at room temperature
for 48 h. The solvent was removed, and the mixture was
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4
and the solvent removed. The resulting polymer was dissolved
in dichloromethane and precipitated out of methanol three
times to yield 8a (0.511 g, 91%) as a yellow solid. 1H NMR
Synthesis of Polymer 8b (Prepolymerization Func-
tionalization). Polymer 12 (0.500 g, 0.331 mmol) was dis-
solved in THF (50 mL) under nitrogen purge in an oven-dried
Schlenk flask. Under nitrogen, tetrabutylammonium fluoride
(3 mL, 1 M solution in THF, containing ca. 5% water) was
added slowly over 5 min. The mixture was stirred for 24 h.
The solvent was removed under vacuum, and the resulting

5876 Englert et al.
Macromolecules, Vol. 38, No. 14, 2005
solid was dissolved in dichloromethane and washed with
water. The organic layer was dried under MgSO4 and filtered,
and the solvent was removed to afford 8b as a yellow solid
27.8, 24.9, 21.9, 13.2, 10.2. IR: v 3577, 3454, 3258, 3126, 2956,
2924, 2806, 2710, 2201, 1960, 1644, 1598, 1513, 1466, 1401,
1279, 1213, 1163, 1023, 991, 870, 804. GPC (polystyrene
standards): Mn ) 24.5 × 104, PDI ) 1.01.
1
(0.398 g, 96%). H NMR (CDCl3): δ 7.65-7.51 (m, 2H), 7.25
(m, 2H), 7.18 (m, 2H), 5.32 (m, 4H), 4.63 (m, 4H), 2.82 (m,
4H), 1.24 (m, 20H), 0.83 (m, 12H). 13C NMR (CDCl3): δ 152.7,
140.8, 132.9, 122.8, 117.1, 114.3, 112.7, 100.7, 94.5, 89.6, 67.5,
63.1, 42.0, 40.0, 37.8, 31.8, 28.2, 25.0, 22.5, 17.9, 13.5, 10.2.
IR: v 2959, 2863, 2206, 1691, 1614, 1463, 1223, 1027, 883,
744, 709, 652. GPC (polystyrene standards): Mn 71.7 × 103,
PDI ) 4.44.
Synthesis of Polymer 8d (Postpolymerization Func-
tionalization). Polymer 5 (0.100 g, 0.188 mmol) and azide
7d (0.116 g, 0.375 mmol) were dissolved in THF under nitrogen
purge in an oven-dried Schlenk flask. The flask was flushed
with nitrogen, frozen, and evacuated three times, after which
CuSO4 (0.5 mg, 1.9 µmol), sodium ascorbate (4 mg, 18.7 µmol),
and tetrabutylammonium fluoride (0.25 mL, 1 M solution in
THF, containing ca. 5% water) were added. The mixture was
allowed to stir at 40 °C for 48 h. The solvent was concentrated,
and the polymer precipitated out of methanol:H2O (50:50) twice
Synthesis of Polymer 8c (Postpolymerization Func-
tionalization). Polymer 5 (0.100 g, 0.118 mmol) and azide
7c (88.4 mg, 0.355 mmol) were dissolved in THF (15 mL) under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen and frozen and evacuated three times,
after which CuSO4 (0.5 mg, 2 µmol), sodium ascorbate (4 mg,
19 µmol), and tetrabutylammonium fluoride (0.25 mL, 1 M
solution in THF, containing ca. 5% water) were added. The
mixture was stirred at 50 °C for 48 h. The solvent was
removed, and the mixture was dissolved in dichloromethane
and washed with 1 N HCl, 1 N NH4OH, and water. The organic
layer was dried over MgSO4, and the solvent was removed
under vacuum. The resulting polymer was dissolved in hot
DMSO and precipitated out of methanol (three times) to yield
8c (0.093 g, 76%) as a yellow solid. 1H NMR (DMSO): δ 7.56-
7.50 (m, 4H), 7.41 (m, 2H), 5.73 (m, 2H), 4.92 (m, 2H), 4.59
(m, 6H), 4.01 (m, 12H), 3.18 (m, 12H), 1.91 (m, 32H), 1.73 (m,
6H), 1.55 (m, 16H), 1.25 (m, 6H), 0.84 (m, 12H). 13C NMR
(TCE): δ 152.6, 141.7, 132.6, 124.6, 117.5, 102.8, 93.9, 90.3,
76.4, 72.9, 69.8, 67.0, 60.8, 57.3, 48.1, 30.1, 27.8, 24.8, 22.6,
18.7, 13.2, 10.3. IR: v 3544, 3309, 2948, 2866, 2528, 2200, 2102,
1730, 1625, 1436, 1382, 1203, 1118, 1076, 1041, 862, 740, 555,
453, 412. GPC (polystyrene standards): Mn ) 22.6 × 103, PDI
) 2.39.
Synthesis of 10c. Diiodo compound 9 (1.00 g, 2.28 mmol)
and azide 7c (2.00 g, 4.79 mmol) were dissolved in THF under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which CuSO4 (6 mg, 22.8 µmol) and sodium ascorbate (45 mg,
228 µmol) were added. The mixture was allowed to stir at 50
°C for 48 h. The solvent was removed, and the mixture was
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4.
The solvent was removed under vacuum, and the crude
product was purified by chromatography on silica gel (1:1,
ethyl acetate:dichloromethane) to yield 10c as a colorless
crystalline solid (1.81 g, 62%). 1H NMR (CDCl3): δ 7.78 (s, 2H),
7.41 (s, 2H), 7.24 (s, 2H), 5.15 (m, 6H), 4.49 (m, 12H), 3.95 (m,
4H), 3.68 (m, 4H), 1.97 (m, 24H). 13C NMR (CDCl3): δ 170.3,
169.8, 169.1, 169.0, 152.5, 143.1, 124.2, 123.7, 100.4, 86.5, 72.3,
71.8, 70.8, 68.1, 67.6, 64.4, 61.6, 50.1, 20.7, 20.5. IR: v 3557,
3479, 3454, 3086, 2955, 2876, 2739, 2450, 2419, 2109, 2028,
1961, 1916, 1732, 1645.17, 1482, 1320, 1172, 993, 952, 907,
854, 795, 753, 696, 649, 602. MS calcd for [C44H54I2N6O22]:
1272.74; found: 1273.1; mp 156-160 °C.
Synthesis of Polymer 8c (Prepolymerization Func-
tionalization). Monomer 10c (0.230 g, 0.251 mmol) and 2,5-
ethylhexyl-1,4-diethynylbenzene (4) (0.088 g, 0.251 mmol) were
dissolved in dichloromethane (2 mL) and piperidine (2 mL) in
an oven-dried Schlenk flask. The flask was flushed with
nitrogen, frozen, and evacuated three times, after which
(Ph3P)2PdCl2 (3 mg, 5 µmol) and CuI (1 mg, 5 µmol) were
added. The mixture was allowed to stir at room temperature
for 48 h. The solvent was removed, and the mixture was
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4
and the solvent removed. The solvent was concentrated and
the polymer precipitated out of H2O (50:50) twice to yield 13
(0.241 g, 93%). 1H NMR (DMSO): δ 7.56 (m, 2H), 7.50 (m,
2H), 7.41 (m, 2H), 5.72 (m, 2H), 4.91 (m, 2H), 4.59 (m, 6H),
4.01 (m, 12H), 3.18 (m, 12H), 1.91 (m, 32H), 1.70 (m, 6H), 1.54
(m, 16H), 1.26 (m, 6H), 0.87 (m, 6H). 13C NMR (DMSO): δ
152.7, 141.9, 140.7, 132.6, 124.5, 122.3, 117.7, 113.7, 111.9,
102.7, 93.8, 85.9, 76.48, 73.0, 69.9, 66.6, 61.0, 58.1, 49.4, 31.5,
1
to yield 8d (0.149 g, 82%). H NMR (CDCl3): δ 8.01 (m, 1H),
7.63 (m, 1H), 7.38 (m, 2H), 6.86 (m, 2H), 4.80 (m, 4H), 4.13
(m, 8H), 3.89 (m, 8H), 3.73 (m, 16H), 2.75 (m, 4H), 2.55 (m,
2H), 1.76 (m, 2H), 1.55 (m, 16H), 1.28 (m, 6H), 0.84 (m, 6H).
13C NMR (TCE): δ 153.5, 150.0, 144.9, 141.7, 133.6, 130.6,
120.7, 118.1, 114.3, 112.5, 107.1, 94.9, 90.1, 70.4, 69.6, 64.5,
53.23, 40.4, 38.5, 32.4, 28.8, 25.6, 22.6, 14.0, 10.9. IR: v 3642,
3561, 3515, 3412, 2930, 2857, 2351, 2205, 1644, 1592, 1504,
1445, 1263, 1138, 1130. GPC (polystyrene standards): Mn )
108.4 × 103, PDI ) 1.49.
Synthesis of 10d. Diiodo compound 9 (0.500 g, 1.14 mmol)
and azide 7d (1.05 g, 3.39 mmol) were dissolved in THF under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which CuSO4 (3 mg, 11 µmol) and sodium ascorbate (23 mg,
114 µmol) were added. The mixture was allowed to stir at 50
°C for 48 h. The solvent was removed, and the mixture was
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4.
The solvent was removed under vacuum, and the crude
product was purified by chromatography on silica gel (10:1,
ethyl acetate:hexane) to yield 10d as a colorless crystalline
1
solid (0.651 g, 53%). H NMR (CDCl3): δ 7.77 (m, 2H), 7.23
(m, 2H), 7.56 (m, 4H), 6.78 (t, 2H), 5.14 (m, 4H), 4.11 (m, 8H),
3.87 (m, 8H), 3.61 (m, 16H). 13C NMR (CDCl3): δ 152.9, 135.5,
130.1, 124.8, 124.4, 118.5, 114.8, 111.4, 107.4, 86.8, 78.9, 71.9,
71.0, 69.9, 61.1, 58.2. IR: v 3259, 2954, 2871, 2360, 2115, 1734,
1600, 1518, 1455, 1349, 1223, 1021, 801. MS calcd for
[C40H46I2N6O12]: 1056.6; found: 1057.2; mp 162-164 °C.
Synthesis of Polymer 8d (Prepolymerization Func-
tionalization). Monomer 10d (0.301 g, 0.280 mmol) and 2,5-
ethylhexyl-1,4-diethynylbenzene (4) (99.2 mg, 0.283 mmol)
were dissolved in dichloromethane (2 mL) and piperidine (2
mL) in an oven-dried Schlenk flask. The flask was flushed with
nitrogen, frozen, and evacuated three times, after which
(Ph3P)2PdCl2 (10 mg, 14 µmol) and CuI (3 mg, 14 µmol) were
added. The mixture was allowed to stir at room temperature
for 48 h. The solvent was removed; and the mixture was
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4
and the solvent removed. The resulting polymer was dissolved
in dichloromethane and precipitated out of methanol three
times to yield 8d (0.309 g, 93%) as a yellow solid. 1H NMR
(CDCl3): δ 8.01 (m, 2H), 7.26 (m, 10H), 5.39 (m, 4H), 4.14 (m,
16H), 3.75 (m, 16H), 2.68 (m, 4H), 1.24 (m, 16H), 0.84 (m, 12H).
13C NMR (CDCl3): δ 153.0, 144.4, 142.6, 141.2, 135.0, 133.0,
131.7, 130.3, 120.4, 117.2, 113.2, 112.0, 106.3, 95.0, 89.8, 70.7,
70.7, 68.8, 63.7, 40.1, 38.0, 32.1, 30.5, 28.4, 25.2, 22.7, 13.8,
10.5. IR: v 2958, 2207, 1604, 1510, 1453, 1261, 1101, 1018,
933, 802. GPC (polystyrene standards): Mn ) 16.2 × 104, PDI
) 7.70.
Synthesis of 7e. 3,4-Dibenzyloxybenzyl chloride (0.500 g,
1.48 mmol) and sodium azide (0.959 g, 14.8 mmol) were
dissolved in acetone in an oven-dried Schlenk flask. The
mixture was allowed to stir at reflux for 48 h. The solvent was
removed, and the mixture was dissolved in dichloromethane
and washed with water. The organic layer was dried over
MgSO4. The solvent was removed under vacuum, and the
crude product was purified by chromatography on silica gel
(2:1, dichloromethane:hexane) to yield 7e as a light yellow
1
crystalline solid (0.430 g, 84%). H NMR (CDCl3): δ 7.39 (m,

Macromolecules, Vol. 38, No. 14, 2005
Functional Poly(p-phenyleneethynylene)s 5877
10H), 6.85 (m, 3H), 5.19 (s, 4H), 4.23 (s, 2H). 13C NMR
(CDCl3): δ 149.3, 149.2, 137.4, 134.3, 128.7, 128.1, 128.1, 127.6,
127.5, 121.8, 115., 3, 115.1, 71.6, 71.5, 54.9. IR: v 3337, 3027,
2897, 2838, 2445, 2079, 1599, 1413, 1304, 1248, 1201, 1057,
988, 940, 839, 767, 670, 633. MS calcd for [C21H19N3O2]:
345.39; found: fragmentation; mp 82-85 °C. Calcd: C, 57.46;
H, 4.11. Found: C, 57.29; H, 4.62.
31.4, 30.6, 29.0, 28.3, 27.3, 25.1, 24.5, 23.3, 22.7, 20.3, 13.7,
10.4. IR: v 2944, 2938, 2723, 2597, 2396, 2204, 1955, 1602,
1445, 1268, 1125, 1004, 803. GPC (polystyrene standards): Mn
) 71.8 × 103, PDI ) 2.10.
Acknowledgment. We thank the Department of
Energy (DE-FG02-04ER46141) for generous funding.
Synthesis of Polymer 8e (Postpolymerization Func-
tionalization). Polymer 5 (0.100 g, 0.118 mmol) and azide
7e (163 mg, 0.471 mmol) were dissolved in THF (10 mL) under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which CuSO4 (0.5 mg, 2 µmol), sodium ascorbate (4 mg, 19
µmol), and tetrabutylammonium fluoride (0.25 mL, 1 M
solution in THF, containing ca. 5% water) were added. The
mixture was stirred at 60 °C for 48 h. The solvent was
removed, and the mixture was dissolved in dichloromethane
and washed with 1 N HCl, 1 N NH4OH, and water. The organic
layer was dried over MgSO4, and the solvent was removed
under vacuum. The resulting polymer was dissolved in dichlo-
romethane and precipitated out of methanol (three times) to
Supporting Information Available: 13C NMR of poly-
mers 5, 6, 8a (post), and 8a (pre) and bar chart of 13C NMR
spectra of polymers 5, 6, and 8a-e. This material is available
free of charge via the Internet at http://pubs.acs.org.
References and Notes
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1
yield 8e (0.139 g, 96%) as a yellow solid. H NMR (CDCl3): δ
7.37 (m, 2H), 7.25 (m, 28H), 4.79 (m, 16H), 2.74 (m, 4H), 2.54
(m, 2H), 1.74 (m, 2H), 1.54 (m, 16H), 1.29 (m, 6H), 0.84 (m,
6H). 13C NMR (TCE): δ 152.3, 141.4, 133.4, 132.0, 128.4, 127.8,
127.3, 123.1, 118.2, 115.2, 94.2, 89.5, 71.3, 57.4, 40.4, 38.4, 32.4,
28.7, 25.7, 23.0, 14.0, 10.8. IR: v 3306, 2957, 2918, 2864, 2200,
2122, 1948, 1638, 1599, 1505, 1456, 1419, 1259, 1204, 1025,
804. GPC (polystyrene standards): Mn ) 22.6 × 103, PDI )
2.39.
Synthesis of 10e: Diiodo compound 9 (0.400 g, 0.913 mmol)
and azide 7e (1.26 g, 3.65 mmol) were dissolved in THF under
nitrogen purge in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which CuSO4 (2 mg, 9 µmol) and sodium ascorbate (18 mg,
97.3 µmol) were added. The mixture was allowed to stir at 50
°C for 48 h. The solvent was removed, and the mixture was
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4.
The solvent was removed under vacuum, and the crude
product was purified by chromatography on silica gel (1:1,
ethyl acetate:dichloromethane) to yield 10e as a colorless solid
(0.830 g, 80%). 1H NMR (CDCl3): δ 7.56 (s, 2H), 7.46 (m, 22H),
7.12 (m, 6H), 5.64 (d, 4H), 5.39 (m, 4H), 5.10 (d, 8H). 13C NMR
(CDCl3): δ 152.5, 149.2, 149.0, 138.7, 136.7, 136.6, 128.4, 127.8,
127.2, 127.0, 123.7, 122.5, 121.3, 114.7, 114.7, 86.6, 71.2, 64.6,
54.0. IR: v 3060, 3031, 2927, 2867, 2088, 1953, 1753, 1728,
1595, 1513, 1348, 1263, 1217, 1135, 1054, 1021, 846, 698, 616.
MS calcd for [C52H42I2N6O6]: 1100.74; found: fragmentation;
mp 155-157 °C.
Synthesis of Polymer 8e (Prepolymerization Func-
tionalization). Monomer 10e (0.600 g, 0.532 mmol) and 2,5-
ethylhexyl-1,4-diethynylbenzene (4) (0.188 g, 0.537 mmol) were
dissolved in THF (2 mL) and piperidine (2 mL) in an oven-
dried Schlenk flask. The flask was flushed with nitrogen,
frozen, and evacuated three times, after which (Ph3P)2PdCl2
(19 mg, 27 µmol) and CuI (5 mg, 27 µmol) were added. The
mixture was allowed to stir at room temperature for 48 h. The
solvent was removed, and the mixture was dissolved in
dichloromethane and washed with 1 N HCl, 1 N NH4OH, and
water. The organic layer was dried over MgSO4 and the solvent
removed. The resulting polymer was dissolved in dichlo-
romethane and precipitated out of methanol three times to
yield 8a (0.493 g, 75%) as a yellow solid. 1H NMR (CDCl3): δ
7.36 (m, 2H), 7.23 (m, 28H), 4.80 (m, 16H), 2.74 (m, 4H), 2.54
(m, 2H), 1.74 (m, 2H), 1.54 (m, 16H), 1.29 (m, 6H), 0.83 (m,
6H). 13C NMR (CDCl3): δ 160.6, 152.8, 148.8, 143.9, 141.1,
136.4, 133.0, 131.1, 128.1, 127.5, 127.0, 123.9, 122.3, 121.0,
117.5, 114.4, 94.6, 89.9, 70.8, 63.5, 53.6, 45.7, 40.0, 38.0, 31.9,
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MA050484P