Poly(arylene ether)s with pendent 3-iodophenyl sulfonyl groups: Synthesis, characterization, and modification

Article abstract of DOI:10.1021/ma400519q

A series of poly(arylene ether)s carrying truly pendent functional groups were prepared by the meta activated nucleophilic aromatic substitution (NAS) polycondensation reaction of a new aryl difluoride monomer, 3,5-difluoro-1-((3- iodophenyl)sulfonyl)benzene, followed by Suzuki-Miyaura and Heck cross-coupling reactions. The synthesis of 3,5-difluoro-1-((3-iodophenyl)sulfonyl)benzene was achieved via the one-step reaction of 3,5-difluorodiphenyl sulfone with N-iodosuccinimide. Model reactions and NMR data indicated that the carbon-iodine functionality was stable to NAS conditions, thus allowing the synthesis of the desired iodo functional poly(arylene ether sulfone), I-PAES. The iodo moiety was then subjected to palladium-catalyzed cross-coupling reactions with phenyl, naphthyl, and 4-acetylphenyl boronic acids as well as styrene in order to prepare the corresponding phenyl, naphthyl, 4-acetyl phenyl, and 2-phenylvinyl analogues. The polymers were characterized via NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. The polymers exhibited moderate thermal stability in air, with 5% weight loss temperatures ranging from 404 to 482 C, while the glass transition temperatures ranged from 131 to 165 C.

Full text of DOI:10.1021/ma400519q

Article
pubs.acs.org/Macromolecules
Poly(arylene ether)s with Pendent 3‑Iodophenyl Sulfonyl Groups:
Synthesis, Characterization, and Modification
Mehmet Tatli, Ryan Selhorst, and Eric Fossum*
Department of Chemistry, Wright State University, 3640 Colonel Glenn Hwy., Dayton, Ohio 45435, United States
S
* Supporting Information
ABSTRACT: A series of poly(arylene ether)s carrying truly
pendent functional groups were prepared by the meta activated
nucleophilic aromatic substitution (NAS) polycondensation
reaction of a new aryl difluoride monomer, 3,5-difluoro-1-((3-
iodophenyl)sulfonyl)benzene, followed by Suzuki−Miyaura
and Heck cross-coupling reactions. The synthesis of 3,5-
difluoro-1-((3-iodophenyl)sulfonyl)benzene was achieved via the one-step reaction of 3,5-difluorodiphenyl sulfone with N-
iodosuccinimide. Model reactions and NMR data indicated that the carbon−iodine functionality was stable to NAS conditions,
thus allowing the synthesis of the desired iodo functional poly(arylene ether sulfone), I-PAES. The iodo moiety was then
subjected to palladium-catalyzed cross-coupling reactions with phenyl, naphthyl, and 4-acetylphenyl boronic acids as well as
styrene in order to prepare the corresponding phenyl, naphthyl, 4-acetyl phenyl, and 2-phenylvinyl analogues. The polymers were
characterized via NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning
calorimetry. The polymers exhibited moderate thermal stability in air, with 5% weight loss temperatures ranging from 404 to 482
°C, while the glass transition temperatures ranged from 131 to 165 °C.
sulfonation reaction provides sulfonic acid groups on the
electron-rich phenyl rings while a “pre”-polymerization
sulfonation of the activated aromatic dihalide monomer results
in sulfonic acid groups present on the electron-poor diphenyl
sulfone component.4
INTRODUCTION
■
Poly(arylene ether)s, PAE, are a class of engineering thermo-
plastics that possess excellent chemical and thermal resistance,
making them the materials of choice for a wide variety of
applications. Poly(arylene ether sulfone), PAES, is a completely
amorphous material that is one of the most notable members of
the PAE class as it possesses excellent thermal and chemical
resistance.1−3 The synthesis of PAES is typically achieved via
the nucleophilic aromatic substitution, NAS, polycondensation
reaction between bisphenol A, or a similar bisphenol, and 4,4′-
dichlorodiphenyl sulfone.1−3 The introduction of functional
groups into PAES provides the opportunity to tailor the
chemical and physical properties to meet a specific need.
Functional groups can be introduced either after the polymer
has been prepared (“post”) or at the monomer stage (“pre”).
The introduction of functional groups, via a “post” procedure,
must not disturb the polymer backbone or lead to any cross-
linking. Functional groups that are introduced “pre” must be
able to withstand the rather rigorous conditions utilized in NAS
reactions and not result in any side reactions. Both “pre” and
“post” pathways have been utilized for PAES, and a wide range
of functional groups have been incorporated including: sulfonic
acids,4−10 aldehydes,11 amines,12 alcohols,11 amides,11 ke-
tones,11 and phosphonic acids.13
Many of the post-polymerization modification reactions
require rather stringent conditions; however, two unique
systems in which a “masked” functional group was introduced
via the bisphenol moiety were reported by Hay and Guiver.
Subsequent “post”-polymerization modification reactions, via
transimidization14 and NAS chemistry,15 provided efficient
access to a wide variety of functional groups. More recently, the
use of an iridium-catalyzed C−H activation/borylation
procedure followed by a Suzuki−Miyaura reaction was
employed to directly introduce functional groups into
commercially available PAES.11 While these methods represent
significant improvements, in terms of synthetic ease, the
modifications result in substantial changes to the backbone of
the polymer, often leading to significant changes in the thermal
and mechanical properties of the materials.
The recent development of PAEs based on meta-activated
NAS polycondensation reactions of 3,5-difluoro aromatic
monomers provides an alternative and powerful platform for
the introduction of functional groups into PAE systems.16−19
The meta activated fluoro displacement reaction of 3,5-
difluorodiphenyl sulfone, 1, gives rise to a PAE in which the
phenylsulfonyl activating group ends up as a pendant group
The functional groups can be incorporated on the more
electron-rich bisphenol component or the more electron-poor
diphenyl sulfone unit. In general, when the functional group is
present on the electron-rich aromatic rings, it was introduced
using a “post”-polymerization method, while functional groups
present on the electron-poor ring are introduced at the
monomer (“pre”) stage. For example, a “post”-polymerization
Received: March 11, 2013
Revised: May 13, 2013
© XXXX American Chemical Society
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Scheme 1. Comparison of the Effects of Incorporating Functional Groups via Traditional PAE Syntheses and Activated 3,5-
Difluoro Aromatics Syntheses
min. Size exclusion chromatography (SEC) analysis was performed
using a system consisting of a Viscotek Model 270 dual detector
(viscometer and light scattering) and a Viscotek Model VE3580
refractive index detector. Two Polymer Laboratories 5 μm PL gel
Mixed C columns (heated to 35 °C) were used with tetrahydrofuran
as the eluent and a Thermoseparation Model P1000 pump operating
at 1.0 mL/min. Number-average molecular weights, Mn, and the
dispersity were determined with the RI signal (calibrated with
polystyrene standards). Melting points were determined on a MEL-
TEMP apparatus and are uncorrected. Elemental analyses were
obtained from Midwest Microlabs, Inc., Indianapolis, IN.
Synthesis of 3,5-Difluoro-1-((3-iodophenyl)sulfonyl)benzene, 2.
Into a 50 mL RB flask, equipped with a stir bar, were added 4.00 g
(15.7 mmol) of 3,5-difluorodiphenyl sulfone (1) and 20 mL of
concentrated H2SO4. To the vigorously stirred solution was slowly
added 4.40 g (24.7 mmol) of N-iodosuccinimide (NIS), and the
resulting mixture was allowed to react for 12 h at room temperature, at
which point the mixture was slowly poured into a large excess of water
and the resulting solid was isolated via filtration. The solid was
redissolved in ∼50 mL of dichloromethane and then washed with a
dilute sodium bisulfite solution. The organic layer was dried over
MgSO4, and the solvents were removed via rotary evaporation,
resulting in 5.6 g of a light yellow solid. The crude product was
recrystallized from isopropanol to afford 3.3 g (60%) of 3,5-DFDPS-I
with a melting point of 158−159 °C. 1H NMR (CDCl3, δ): 7.05 (tt, 1
H), 7.28 (t, 1 H), 7.48 (m, 2 H), 7.91 (ddd, 1 H), 7.96 (dt, 1 H), 8.27
(t, 1 H). 13C NMR (CDCl3, δ): 94.5 (ArC−I), 109.4 (t), 111.4 (d), 127
(s), 131 (s), 136.4 (s), 142.0 (s), 142.9 (s), 144.3 (s), 162.9 (dd). 19F
NMR (DMSO-d6, δ): −105.2. MS (EI): m/z calculated for
C12H7F2O2SI, 380.15; found 380. Elemental Analysis Calcd Anal. for
C12H7F2O2SI: C, 37.91; H, 1.86. Found: C, 37.93; H, 1.82.
Synthesis of the Iodo Model Compound, 3. Into a 25 mL RB flask,
equipped with a magnetic stir bar, condenser, and gas inlet were placed
300 mg (0.789 mmol) of 3,5-DFDPS-I (2), 237 mg (1.58 mmol) of
tert-butylphenol, 327 mg (2.37 mmol) of K2CO3, and 3 mL of NMP.
The resulting mixture was stirred at 150 °C for 4 h, at which point
GC/MS and NMR spectroscopy indicated quantitative conversion to
the desired product. The reaction mixture was precipitated from water
to obtain a white solid (3) in 60% isolated yield (mp = 138−139 °C).
1H NMR (CDCl3, δ): 1.26 (s, 18 H), 6.69 (t, 1 H), 6.85 (d, 4 H), 7.10
(d, 2 H), 7.16 (t, 1 H), 7.31 (d, 4 H), 7.76 (m, 1 H), 7.84 (m, 1 H),
8.11 (t, 1 H). 13C NMR (CDCl3, δ): 31.4 (s), 34.4 (s), 94.3 (ArC−I),
110.0 (s), 112 (s), 119 (s), 127 (s), 131 (s), 136 (s), 142 (s) 143 (s),
143.2 (s), 147.8 (s), 152.8 (s), 160 (s). Elemental Analysis Calcd Anal.
for C32H33IO4S: C, 60.00; H, 5.19. Found: C, 59.21; H, 5.44.
rather than directly in the backbone, and the polymer can be
considered simply a geometric isomer of the more common
PAES prepared from 4,4′-dichlorodiphenyl sulfone (or 4,4′-
difluorodiphenyl sulfone). The potential advantages (Scheme
1) of exploiting the pendant site for functionalization include
(1) a truly pendent functional group, (2) enhanced accessibility
to the functionality, and (3) essentially no change in the
backbone structure as a result of either “pre”- or “post”-
modification chemistry.
In this report the synthesis, characterization, and modifica-
tion of polymers based on 3,5-difluoro-3′-iododiphenyl sulfone,
2, will be described. Since the resulting iodinated poly(arylene
ether sulfone), I-PAES, possesses the iodo group on a pendent
phenylsulfonyl group, it provides a facile route to introduce a
multitude of functional groups, via Suzuki−Miyaura,20,21
Heck,22 and similar cross-coupling reactions, to the resulting
PAES, without any direct alteration of the backbone structure.
EXPERIMENTAL SECTION
■
Materials. Powdered K2CO3 was dried at 130 °C in an oven before
use. 3,5-Difluorodiphenylsulfone, 1, was synthesized via the previously
reported route.16 Bisphenol A was purchased from Sigma-Aldrich and
recrystallized from toluene and dried under vacuum prior to use.
Palladium(II) acetate, Pd (OAc)2, phenylboronic acid, 2-naphthylbor-
onic acid, and 4-acetylphenylboronic acid were purchased from Sigma-
Aldrich and used as received. N-Iodosuccinimide, NIS, was used as
received from Acros Chemicals. 4-tert-Butylphenol (Sigma-Aldrich)
was used as received. N-Methylpyrrolidone (Sigma-Aldrich), NMP,
was dried over and distilled from calcium hydride under a nitrogen
atmosphere prior to use. Tetrahydofuran (Sigma-Aldrich), THF, was
used as received. Styrene (Sigma-Aldrich), inhibited with 10−20 ppm
of 4-tert-butylcatechol, was used as received.
Instrumentation. 1H and 13C nuclear magnetic resonance (NMR)
spectra were acquired using a Bruker AVANCE 300 MHz instrument
operating at 300 and 75.5 MHz, respectively. 19F NMR spectra were
obtained using a Bruker Avance 400 MHz instrument operating at
376.5 MHz using 10% CFCl3 as an external standard with the
instrument set relative to the lock signal. Samples were dissolved in an
appropriate deuterated solvent (DMSO-d6 or CDCl3) at a
concentration of (∼30 mg/0.7 mL). GC/MS analyses were performed
using a Hewlett-Packard (HP) 6890 Series GC and a HP 5973 mass
selective detector/quadrupole system. DSC and TGA analysis were
carried out on TA Instruments DSC Q200 (under nitrogen) and TGA
Q500 (under nitrogen or air), respectively, at a heating rate of 10 °C/
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Synthesis of I-PAES, 4. In a 50 mL RB flask, equipped with a stir
bar, condenser, and nitrogen gas inlet, were placed 4.1 mL of NMP,
1.1 g (7.96 mmol) of potassium carbonate, 1.00 g (2.63 mmol) of 2,
and 0.600 g (2.63 mmol) of Bisphenol A. The reaction flask was
immersed in an oil bath and stirred vigorously at 150 °C for 15 h. The
solution was left to cool to room temperature. The polymer was
precipitated by slowly pouring the reaction mixture into acidic water
(pH ∼ 3−4), and the resulting powdery gray precipitate was isolated
by filtration. The solid was dissolved in THF, precipitated from
ethanol, filtered, and dried to afford 1.15 g (72%) of 4 as an off-white
solid. 1H NMR (CDCl3, δ): 1.69 (s, 6 H), 6.81 (t, 1 H), 6.91 (d, 4 H),
7.19 (m, 2 H), 7.24 (m, 5 H), 7.83 (m, 1 H), 7.87 (m, 1 H), 8.15 (b, 1
H). 13C NMR (CDCl3, δ): 31.0, 42.4, 94.3 (ArC−I), 111.0, 112.5,
119.2, 127.0, 128.5, 130.9, 136.2, 142.4, 142.9, 143.3, 147.0, 153.0,
159.7.
RESULTS AND DISCUSSION
Monomer Synthesis and Characterization. The syn-
thesis of 3,5-difluoro-1-((3-iodophenyl)sulfonyl)benzene, 2,
was achieved via the one-step procedure outlined in Scheme
2. Reaction of 3,5-difluorodiphenyl sulfone, 1, with a slight
■
Scheme 2. Synthetic Procedure for the Synthesis of 2 and
Subsequent Model Reaction for Determination of the
Stability of the C−I Bond to Typical Nucleophilic Aromatic
Substitution Conditions
General Procedure for Post-Polymerization Modification via
Suzuki−Miyaura Reaction. A slightly modified version of the
phosphine-free procedure reported by Novak was used for the
Suzuki−Miyaura reaction.23 A typical “post”-modification reaction of I-
PAES will be described using phenylboronic acid. In a 25 mL Schlenk
flask, equipped with a stir bar, were placed 200 mg (0.352 mmol of
iodo groups) of 4, 85.8 mg (0.704 mmol) of phenylboronic acid, and 5
mL of THF. Another Schlenk flask was charged with 291 mg (2.10
mmol) of K2CO3, 210 μL of a 0.033 M solution of Pd (OAc)2 in
acetone (2 mol %), and 1 mL of water. The Schlenk flasks were
degassed three times using freeze−pump−thaw cycles and backfilled
with nitrogen, and the contents were combined through a cannula.
The resulting mixture was allowed to react for 2 h at 60 °C followed
by addition of an extra 10% of the boronic acid and heating for an
additional 24 h. The reaction mixture was diluted with ∼10 mL of
THF and washed with brine, and the layers were separated. The
organic layer was dried with MgSO4; the volume was decreased to ∼5
mL under pressure and precipitated from methanol to obtain 134 mg
excess of N-iodosuccinimide (NIS) in concentrated sulfuric
acid afforded the desired compound in 60% yield after multiple
recrystallizations from isopropanol. Confirmation of the
1
structure of 2 was provided by a combination of H, 13C
(Figure 1), and 19F NMR spectroscopy, gas chromatography/
mass spectrometry (GC/MS), and elemental analysis.
In order to determine the stability of the carbon−iodine (C−
I) bond in 2, to typical NAS conditions (K2CO3, NMP, heat), a
model reaction was carried out using 4-tert-butylphenol as the
nucleophilic reaction partner (Scheme 2). After heating to 150
°C for 4 h, GC/MS analysis of an aliquot indicated complete
displacement of both aryl fluorides in 2. The robustness of the
C−I bond was explored by comparing the 13C NMR spectra of
the monomer, 2, and model reaction product, 3, as shown in
Figure 1. The key feature of both spectra is the signal for the
carbon atom to which the iodo group is attached, which
appears as a singlet (labeled g) present at 94.5 ppm in 2, with
the same signal (94.3 ppm) in the spectrum of 3, thus
confirming that the iodo group was stable under the NAS
conditions utilized. The multiplets (a−d), due to coupling with
the fluorine atoms present on the ring, were also reduced to
singlets upon conversion to the aryl ether bonds. The
remaining signals were assigned, in a straightforward manner,
to the carbon atoms in the ring possessing the iodo group (e−j)
and those arising from the carbon atoms in the tert-
butylphenoxy groups (k−n).
1
of 5a (74%): H NMR (CDCl3, δ): 1.65 (s, 6 H), 6.78 (t, 1 H), 6.90
(d, 4 H), 7.19 (d, 4 H), 7.25 (d, 2 H), 7.41 (m, 3 H), 7.53 (m, 3 H),
7.79 (m, 2 H), 8.07 (t, 1 H). 13C NMR (CDCl3, δ): 30.9, 42.4, 111.0,
112.5, 119.2, 126.0, 126.7, 127.0, 128.5, 129.0, 129.8, 132.0, 139.0,
141.7, 142.7, 144.0, 146.8, 153.0, 159.7.
1
5b (55%): H NMR (CDCl3, δ): 1.50 (s, 6 H), 6.69 (t, 1 H), 6.79
(d, 4 H), 7.06 (d, 4 H), 7.19 (d, 2 H), 7.42 (m, 2 H), 7.47 (t, 1 H),
7.57 (m, 1 H), 7.79 (m, 5 H), 7.92 (b, 1 H), 8.12 (t, 1 H). 13C NMR
(CDCl3, δ): 30.9, 42.4, 111.0, 112.5, 119.2, 124.8, 126.3 (d), 126.7 (d),
127.6, 128.2, 128.4, 128.9, 129.8, 132.2, 133.0, 133.5, 136.2, 141.7,
142.7, 144.0, 146.8, 153.0, 159.7.
1
5c (55%): H NMR (CDCl3, δ): 1.66 (s, 6 H), 2.62 (s, 3 H), 6.78
(t, 1 H), 6.87 (d, 4 H), 7.20 (d, 4 H), 7.24 (d, 2 H), 7.57 (t, 1 H), 7.64
(d, 2 H), 7.81 (m, 1 H), 7.85 (m, 1 H), 8.03 (d, 2 H), 8.10 (t, 1 H).
13C NMR (CDCl3, δ): 26.7, 30.9, 42.4, 111.0, 112.5, 119.1, 126.2,
127.2, 127.4, 128.5, 129.0, 130.0, 132.1, 136.7, 141.4, 142.0, 143.4,
143.8, 146.9, 153.2, 159.7, 197.3.
Synthesis of Iodinated PAES, I-PAES. As outlined in
Scheme 3, the desired iodo-functionalized PAES, I-PAES (4),
was prepared from 2 and Bisphenol A in N-methylpyrrolidi-
none (NMP) with potassium carbonate utilized to prepare the
corresponding bisphenolate in situ. Reactions were carried out
at 150 °C for 15 h; the longer reaction time, compared to the
model reaction, was necessary to afford polymers with relatively
high molecular weights.
2-Phenylvinyl-Modified PAES via Heck Reaction, 6. To a 100 mL
round-bottomed flask, equipped with a reflux condenser with a
nitrogen inlet, were added I-PAES, 4 (0.250 g, 0.440 mmol of iodo
groups), NaHCO3 (0.220 g, 2.64 mmol), and tetrabutylammonium
bromide (0.057 g, 0.180 mmol) in NMP (5 mL). The mixture was
stirred under N2 atmosphere for 10 min, at which point styrene (0.32
mL, 2.8 mmol) was added in excess. The mixture was heated to 70 °C,
and Pd(OAc)2 (0.010 g, 0.044 mmol) was added. The mixture was
heated and stirred for 24 h. The mixture was diluted with 10 mL of
CHCl3 and washed with water three times. The resulting organic layer
was collected, dried over MgSO4, and concentrated to ∼5 mL. The
concentrated solution was passed through a short plug of silica gel with
additional CHCl3, and the polymer was isolated by precipitation from
300 mL of methanol. The resulting off-white solid was dried under
The 13C NMR spectrum of polymer 4 is also presented in
Figure 1, and it clearly indicates the presence of the desired
iodo group (signal labeled g), despite the longer reaction time.
1
The H NMR spectrum of polymer 4 (Figure 2) shows a
distinct resonance at 8.15 ppm for the proton located between
the sulfonyl and iodo groups (labeled f). By comparing the
integration of the isopropylidene group (1.70 ppm, labeled i) in
the main chain to the signal at 8.15 ppm (f), it was possible to
determine that essentially no iodo groups were lost during the
polymerization process.
1
vacuum to afford 0.150 g (60%) of polymer 6. H NMR (CDCl3 δ):
1.57 (s, 6H), 6.7 (t, 1H), 6.83 (d, 4H), 7.4−7.0 (m, 14H), 7.6 (t, 2H),
7.92 (s, 1H). 13C NMR (CDCl3 δ): 31.1, 42.5, 111.2, 112.5, 119.2,
125.4, 126.5, 126.6, 126.9, 128.6, 129.0, 129.8, 131.3, 131.6, 136.5,
139.1, 141.7, 144.1, 147.0, 153.4, 159.7.
C
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Figure 1. Aromatic regions of the 75.5 MHz 13C (CDCl3) NMR spectra of the iodo monomer, 2, model reaction product, 3, and Bis-A-based iodo-
containing PAES, 4.
Scheme 3. Synthetic Routes to Iodo-Containing Poly(arylene ether sulfone), I-PAES, and Subsequent Modification via Suzuki−
Miyaura and Heck Cross-Coupling Reactions
Polymer Modification Reactions. Two cross-coupling
reactions, Suzuki−Miyaura and Heck, were applied to
investigate the accessibility and reactivity of the iodo groups
present in polymer 4 (Scheme 3). The Suzuki−Miyaura
reactions were carried out with phenyl, naphthyl, and 4-
acetylphenylboronic acid using Pd(OAc)2 as the catalyst in a
mixture of THF and water. The Heck reaction employed
styrene as the reactant and Pd(OAc)2; however, NMP was used
as the solvent. Confirmation of the successful cross-coupling
reactions was provided by 13C NMR spectroscopy; as an
example, the 13C NMR spectra of polymers 5a and 4 are given
in Figure 3. The spectra clearly indicate significant changes
D
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1
Figure 2. The 300 MHz H NMR spectrum (CDCl3) of polymer 4.
Figure 3. The 75.5 MHz 13C NMR spectra (CDCl3) of polymers 4 and 5a.
Table 1. Reaction Conditions, Molecular Weight, Dispersity, and Thermal Analysis Data for Polymers Prepared from Monomer
2
polymer
R group
Mn (Da)
dispersity
Tg (°C)
Td (5%) N2 (°C)
Td (5%) air (°C)
4
I
17 700
18 200
18 300
18 000
16 700
2.0
2.1
1.7
1.9
2.0
144
131
149
165
140
427
492
507
466
447
404
478
482
454
412
5a
5b
5c
6
phenyl
2-naphthyl
4-acetylphenyl
2-phenylvinyl
upon conversion of 4 to 5. The presence of the signals q, r, s,
and t confirms the presence of the biphenyl unit and a
successful cross-coupling reaction. One of the key spectral
changes is the loss of the signal for the carbon atom to which
the iodo group was attached (g) and a new signal, present at
139 ppm, corresponding to the same carbon atom in the
biphenyl moiety, also labeled g. The signal for the carbon atom
located between the sulfonyl and iodo groups (f) is shifted ∼10
ppm upfield after going from 4 to 5. In addition, the signal for
the carbon atom para to the sulfonyl group and ortho to the
E
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iodo groups (h) in 4 also undergoes a significant upfield shift
after the biphenyl unit is installed. Similar results were obtained
for polymers 5b, 5c, and 6, thus confirming their nearly
quantitative cross-coupling reactions.
The number-average molecular weights, Mn, of polymers 4,
5a−c, and 6 were determined via size exclusion chromatog-
raphy (SEC), and the data are summarized in Table 1. The
SEC traces (Figure 4) of the modified materials were little
Figure 5. TGA thermograms of polymers 4, 5a−c, and 6, under a
nitrogen atmosphere, at a heating rate of 10 °C/min.
Figure 4. SEC traces (RI signal) of polymers 4, 5a−c, and 6.
changed from the starting iodo polymer, indicating only subtle
differences in molecular weight and that significant cross-
linking or chain extension did not occur during the
modification process. Since the groups installed were not
substantially different in molecular weight than the original
iodo group, major changes in Mn were not expected, and
indeed, the observed values bear this out. For example, upon
converting the iodo group in 4 to a naphthyl group (polymer
5b), the Mn only increased from 17 700 to 18 300 Da.
Thermal Properties. The thermal properties of the iodo
and modified polymers were evaluated by a combination of
thermogravimetric analysis (TGA) and differential scanning
calorimetry (DSC), with the data depicted in Figures 5 and 6,
respectively. The I-PAES displayed a distinct two-step
degradation pattern; the first step, beginning just below 400
°C, involved a weight loss of ∼24% and is assigned to the loss
of the iodo groups, which have a weight % of 22.3 in the repeat
unit. The second step follows a pattern similar to those
observed for the modified polymers and is indicative of
backbone degradation. Upon conversion to a phenyl or
naphthyl group, the thermal stability increased significantly, as
measured by the 5% weight loss temperatures, Td‑5%, with
values of 492 and 507 °C, respectively. Both the 4-acetylphenyl
and 2-phenylvinylene derivatives were found to be less stable
(466 and 447 °C, respectively), in part due to the presence of
the nonaromatic acetyl and vinyl groups, respectively.
Figure 6. Differential scanning calorimetry traces, second heat, for
polymers 4, 5a−c, and 6 at a heating rate of 10 °C/min.
in Tg for the phenyl derivative, in part, may be to the result of
an increase in free volume; however, the increase in Tg for the
4-acetylphenyl derivative is most likely attributed to the
presence of strong intermolecular forces resulting from the
acetyl group.
CONCLUSIONS
■
In summary, we have developed a straightforward and versatile
method for the introduction of functional groups to a
poly(arylene ether sulfone) analogue. The synthesis of 3,5-
difluoro-1-((3-iodophenyl)sulfonyl)benzene, 2, was achieved in
good yield, and the iodo functional monomer provides a
versatile platform for both “pre”- and “post”-modification of
PAES systems, without directly altering the composition of the
backbone. The polymerization of 2 with Bisphenol A resulted
in the formation of a moderate molecular weight PAES
analogue carrying a pendent 3-iodophenylsulfonyl group, I-
1
All of the polymers were found to be completely amorphous
with only glass transition temperatures, Tg, being observed in
DSC analyses carried out up to 400 °C (see Figure 6). The Tg
values (Table 1) cover a narrow range from 131 °C for the
phenyl derivative to 165 °C for the 4-acetylphenyl derivative,
while the I-PAES itself possessed a Tg of 144 °C. The decrease
PAES. H and 13C NMR spectroscopy indicated that the iodo
groups were stable to nucleophilic aromatic substitution
conditions and were quantitatively carried into the polymer.
Subsequent application of palladium-catalyzed cross-coupling
chemistries afforded a series of PAES with a variety of pendent
functional groups, without any detrimental cross-linking or
F
dx.doi.org/10.1021/ma400519q | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
(20) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457−2483.
chain extension being observed. Since the functional groups do
not reside directly on the backbone, there was little change in
the thermal properties of the materials as evidenced by the
narrow range of Tg values for phenyl, naphthyl, iodo, 2-
phenylvinyl, and 4-acetylphenyl groups. Given the large number
of potential reactions that can be carried out with aryl iodides,
there are many possibilities for further property modifications
of I-PAES.
(21) Suzuki, A. J. Organomet. Chem. 1999, 576, 147−168.
(22) Heck, R. F.; Nolley, J. P. J. Org. Chem. 1972, 37, 2320−2322.
(23) Wallow, T. L.; Novak, B. M. J. Org. Chem. 1994, 59, 5034−5037.
ASSOCIATED CONTENT
■
S
* Supporting Information
13C NMR spectra of polymers 5b, 5c, and 6. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: eric.fossum@wright.edu (E.F.).
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This material is based upon work supported by the National
Science Foundation under CHE-1012392. Dr. Tanya Young
from the NMR Center at The Ohio State University
Department of Chemistry is acknowledged for her assistance
with 19F NMR spectroscopy.
REFERENCES
■
(1) Johnson, R. N.; Farnham, A. G.; Clendinning, R. A.; Hale, W. F.;
Merriam, C. N. J. Polym. Sci., Part A-1: Polym. Chem. 1967, 5, 2375−
2398.
(2) Attwood, T. E.; Newton, A. B.; Rose, J. B. Br. Polym. J. 1972, 4,
391−399.
(3) Atwood, T. E.; Barr, D. A.; Feasey, G. G.; Leslie, V. J.; Newton, A.
B.; Rose, J. B. Polymer 1977, 18, 354−358.
(4) Harrison, W. L.; Hickner, M. A.; Kim, Y. S.; McGrath, J. E. Fuel
Cells 2005, 5, 201−212.
(5) Kim, Y. S.; Hickner, M.; Dong, L.; Pivovar, B. S.; McGrath, J. E. J.
Membr. Sci. 2004, 243, 317−326.
(6) Lafitte, B.; Karlsson, L. E.; Jannasch, P. Macromol. Rapid
Commun. 2002, 23, 896−900.
(7) Sankir, M.; Bhanu, V. A.; Harrison, W. L.; Ghassemi, H.; Wiles,
K. B.; Glass, T. E.; Brink, A. E.; Brink, M. H.; McGrath, J. E. J. Appl.
Polym. Sci. 2006, 100, 4595−4602.
(8) Taeger, A.; Vogel, C.; Lehmann, D.; Lenk, W.; Schlenstedt, L.;
Meier-Haack, J. Macromol. Symp. 2004, 210, 175−184.
(9) Wang, F.; Hickner, M.; Kim, Y. S.; Zawodzinski, T. A.; McGrath,
J. E. J. Membr. Sci. 2002, 197, 231−242.
(10) Lafitte, B.; Puchner, M.; Jannasch, P. Macromol. Rapid Commun.
2005, 26, 1464−1468.
(11) Jo, T. S.; Kim, S. H.; Shin, J.; Bae, C. J. Am. Chem. Soc. 2009,
131, 1656−1657.
(12) Guiver, M. D.; Robertson, G. P.; Foley, S. Macromolecules 1995,
28, 7612−7621.
(13) Lafitte, B.; Jannasch, P. J. Polym. Sci., Part A: Polym. Chem. 2005,
43, 273−286.
(14) Herbert, C. G.; Ghassemi, H.; Hay, A. S. J. Polym. Sci., Part A:
Polym. Chem. 1997, 35, 1095−1104.
(15) Li, Z.; Ding, J.; Robertson, G. P.; Guiver, M. D. Macromolecules
2006, 39, 6990−6996.
(16) Kaiti, S.; Himmelberg, P.; Williams, J.; Abdellatif, M.; Fossum, E.
Macromolecules 2006, 39, 7909−7914.
(17) van Beek, D.; Fossum, E. Macromolecules 2009, 42, 4016−4022.
(18) Tienda, K.; Yu, Z.; Constandinidis, F.; Fortney, A.; Feld, W. A.;
Fossum, E. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 2908−2915.
(19) Selhorst, R.; Fossum, E. Polymer 2013, 54, 530−535.
G
dx.doi.org/10.1021/ma400519q | Macromolecules XXXX, XXX, XXX−XXX