Utilization of N,N-diethyl-3,5-difluorobenzene sulfonamide to prepare functionalized poly(arylene ether)s

Article abstract of DOI:10.1016/j.polymer.2012.11.072

A series of poly(arylene ether)s carrying a pendant diethyl sulfonamide group was prepared by the meta activated nucleophilic aromatic substitution reaction of a new aryl difluoride monomer, N,N-diethyl-3,5-difluorobenzene sulfonamide. The synthesis of N,N-diethyl-3,5-difluorobenzene sulfonamide was achieved via the one-step reaction of diethyl amine with commercially available 3,5-difluorobenzenesulfonyl chloride. Model reactions and NMR data indicated that the fluoride atoms were sufficiently activated by the sulfonamide group, located in the meta position, to provide access to high molecular weight poly(arylene ether)s. The corresponding poly(arylene ether)s, were prepared by reaction of N,N-diethyl-3,5-difluorobenzene sulfonamide with bisphenol A, bisphenol AF, 4,4′-biphenol, hydroquinone, resorcinol, and 4,4′-dihydroxydiphenyl ether. The polymers were characterized via NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. The sulfonamide based poly(arylene ether)s displayed moderate thermal stability with 5% weight loss temperatures ranging from 366 to 385 °C, but possessed relatively low glass transition temperatures, 72-142 °C.

Full text of DOI:10.1016/j.polymer.2012.11.072

Polymer 54 (2013) 530e535
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Polymer
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Utilization of N,N-diethyl-3,5-difluorobenzene sulfonamide to prepare
functionalized poly(arylene ether)s
*
Ryan Selhorst, Eric Fossum
Department of Chemistry, Wright State University, 202 Oelman Hall, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of poly(arylene ether)s carrying a pendant diethyl sulfonamide group was prepared by the meta
activated nucleophilic aromatic substitution reaction of a new aryl difluoride monomer, N,N-diethyl-3,5-
difluorobenzene sulfonamide. The synthesis of N,N-diethyl-3,5-difluorobenzene sulfonamide was ach-
ieved via the one-step reaction of diethyl amine with commercially available 3,5-
difluorobenzenesulfonyl chloride. Model reactions and NMR data indicated that the fluoride atoms
were sufficiently activated by the sulfonamide group, located in the meta position, to provide access to
high molecular weight poly(arylene ether)s. The corresponding poly(arylene ether)s, were prepared by
reaction of N,N-diethyl-3,5-difluorobenzene sulfonamide with bisphenol A, bisphenol AF, 4,40-biphenol,
hydroquinone, resorcinol, and 4,40-dihydroxydiphenyl ether. The polymers were characterized via NMR
spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning
calorimetry. The sulfonamide based poly(arylene ether)s displayed moderate thermal stability with 5%
weight loss temperatures ranging from 366 to 385 ꢀC, but possessed relatively low glass transition
temperatures, 72e142 ꢀC.
Received 27 July 2012
Received in revised form
13 November 2012
Accepted 17 November 2012
Available online 1 December 2012
Keywords:
Poly(arylene ether)s
Nucleophilic aromatic substitution
Meta activation
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
allow NAS reactions to proceed at reasonable rates. Indeed, the
number of reports of meta activated NAS polycondensation reac-
Poly(arylene ether)s, PAEs, are a class of engineering thermo-
plastics that possess excellent chemical and thermal resistance
making them the material of choice for a wide variety of applica-
tions. PAEs are typically prepared via the nucleophilic aromatic
substitution (NAS) polycondensation reaction of aryl difluorides or
chlorides, which are activated toward NAS by the presence of
a strong electron-withdrawing group located in the ortho or para
position, with the para position being the more widely utilized, and
bisphenolates prepared from the corresponding bis-phenols [1,2]. A
number of activating groups have been employed such as the
traditional sulfone [1e7], ketone [2,8e11], and phosphoryl groups
[12e20], however, a wide variety of alternative activating groups
have also been successfully employed including: azomethine [21],
thianthrene [22], a number of heterocycles [23e32] and, more
recently, the N,N-dimethylsulfonamide group [33].
tions has increased in recent years. Our group has reported the
synthesis of PAEs based on fluoro displacement of 3,5-
difluorodiphenyl sulfone, 1 [34], 3,5-difluorobenzophenone, 2
[35], and 3,5-difluorotriphenylphosphine oxide, 3 [36]. In each
case the activating group ends up as a pendant group rather than
directly in the backbone and the polymers can be considered
simply geometric isomers of the more common PAEs prepared
from 4,40-difluorodiphenyl sulfone, 4,40-difluorobenzophenone,
and 4,40-difluorotriphenylphosphine oxide, respectively. Kim et al
have also prepared biphenyl-based PAEs via the use of a meta
trifluoromethyl group activated displacement of nitro groups [37e
41]. A number of other examples of PAEs in which the activating
group resides pendant to the backbone, have been reported,
however, the orientation of the activating group was always ortho
to the leaving group, typically fluoride [42e50].
1.2. Functional groups
1.1. Meta activated NAS reactions
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 either be introduced at the
monomer stage (“pre”) or after the polymer has been prepared
(“post”). Functional groups that are introduced “pre” must be able
In principle, a strong electron-withdrawing group, located in
the meta position, should also provide sufficient activation to
* Corresponding author.
E-mail address: eric.fossum@wright.edu (E. Fossum).
0032-3861/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.polymer.2012.11.072

R. Selhorst, E. Fossum / Polymer 54 (2013) 530e535
531
to withstand the rather rigorous conditions utilized in NAS reac-
tions and not result in any side reactions. The introduction of
functional groups, via a “post” procedure, must not disturb the
polymer backbone or lead to any crosslinking. The ideal functional
group would be one that could be carried into the polymer and be
subsequently converted to a variety of additional moieties.
In this report we will describe our efforts to prepare PAEs that
carry a pendant sulfonamide moiety, located in the meta position
relative to the ether bonds. Thus, the synthesis, characterization,
and polymerization behavior of N,N-diethyl-3,5-difluorobenzene
sulfonamide, 4, will be described. Since the sulfonamide group in
the 3,5-difluorobenzene sulfonamide is located in the meta posi-
tion, relative to both fluorine atoms, it is anticipated that a wide
variety of N-substitutions, with potentially bulky groups, could
provide a useful method to introduce a multitude of functional
groups to the resulting PAEs. For example, a N,N-diaryl-3,5-
difluorobenzene sulfonamides could be utilized to introduce aryl
bromide or iodide moieties. Alternatively, N-propargyl sulfonamide
structures would provide access to “clickable” systems.
of-flight (MALDI-TOF-TOF) was performed at the Mass Spectrom-
etry & Proteomics Facility at The Ohio State University, Columbus,
OH, on a Bruker Daltonics ultrafleXtremeÔ (Bruker Daltonics,
Breman, Germany) mass spectrometer operated in reflectron,
positive ion mode with a N2 smartbeam IIÔ laser. Laser power was
used at the threshold level required to generate signal and acquired
at 1000 Hz until suitable data was obtained. The instrument was
calibrated with the Peptide Calibration Standard II purchased from
Bruker Daltonics which contains Angiotensin II, Angiotensin I,
Substance P, Bombesin, ACTH clip 1-17, ACTH clip 18-39, Somato-
statin 28, Bradykinin Fragment 1e7, Renin Substrate Tetradeca-
peptide porcine with a covered mass range: w700 Da to 3200 Da.
Samples were prepared in THF to approximately 50 pmol/
Dihydroxybenzoic acid (DHB) was used as the matrix prepared as
a saturated solution in THF. Allotments of 5 L of matrix and 1 L of
mL. 2,5-
m
m
sample were thoroughly mixed together; 0.5 mL of this was spotted
on the target plate and allowed to dry.
2.2.1. Synthesis of (N,N-diethyl)-3,5-difluoro-benzenesulfonamide (4)
To
a
250 mL Erlenmeyer flask were added 3,5-
2. Experimental
difluorobenzenesulfonyl chloride (5.00 g, 23.5 mmol) and 50 mL
of dichloromethane. A 26% solution of diethylamine (5.0 mL,
52.7 mmol) in water was added to the flask followed by DI water
(40.0 mL). The solution was heated to 40 ꢀC for 24 h with vigorous
stirring. The reaction mixture was then extracted twice with 25 mL
portions of dichloromethane and the organic layer was subse-
quently washed with 50.0 mL of 5% HCl solution, DI water, 50.0 mL
of 0.1 M NaOH solution, and finally water. The organic layer was
then evaporated under reduced pressure to yield a yellow solid,
which was then recrystallized from hexanes to afford 3.5 g (61%) of
the title compound as a light yellow crystalline solid (m.p. 50e
2.1. Materials
Powdered K2CO3 (Sigma Aldrich) was dried at 130 ꢀC in an oven
before use. 3,5-Difluorobenzene sulfonyl chloride was purchased
from Oakwood Products and was used as received. Bisphenol A
(Sigma Aldrich), 4,40-biphenol (Sigma Aldrich), 4,40-dihydrox-
ydiphenyl ether (Sigma Aldrich), DPE, Resorcinol (Sigma Aldrich)
and Bisphenol AF (TCI America) were recrystallized from toluene,
followed by drying under vacuum prior to use. Hydroquinone
(Sigma Aldrich) was recrystallized from methanol/water, followed
by drying under vacuum prior to use. N-methylpyrrolidone (Sigma
Aldrich), NMP, was dried over and distilled from calcium hydride
under a nitrogen atmosphere prior to use. 4-tert-Butylphenol
(Sigma Aldrich) and diethyl amine (Sigma Aldrich) were used as
received.
51 ꢀC). 1H NMR (CDCl3,
d): 7.4e7.5 (m, 2 H), 7.00 (tt, 1 H), 3.2-3.3
(q, 4 H), 1.2e1.3 (t, 6 H); 13C NMR (CDCl3, d): 14 (s), 42 (s), 107 (t), 110
(dd), 143 (t), 162.9 (dd) all with respect to TMS at 0.0 ppm; 19F NMR
(DMSO-d6,
d
): ꢁ106.3. GC/MS: m/z: 249. Elemental analysis: Calc.
Anal. for C10H13F2NSO2: C, 48.16; H, 5.26; Found: C, 48.07; H, 5.13.
2.2.2. Model reaction of (4)
2.2. Instrumentation
To a 25 mL round-bottomed flask were added 4 (0.300 g,
1.2 mmol), K2CO3 (0.497 g, 3.6 mmol), t-butylphenol (0.360 g,
2.4 mmol) and NMP (1.875 mL). The resulting mixture was heated
to 185 ꢀC for 21 h with stirring and was monitored by removing
aliquots for GC/MS analysis, which indicated nearly quantitative
displacement of the fluorides. The solution was then diluted to
100 mL in CHCl3 and extracted 3 times with both 10% HCl solution
and saturated NaHCO3. The solution was then stirred in water
overnight, dried over MgSO4 and dried under vacuum to yield
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 (w30 mg/0.7 mL). GC/MS analyses were per-
formed using a HewlettePackard (HP) 6890 Series GC and a HP
5973 Mass Selective Detector/Quadrupole system. DSC and TGA
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/ 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
0.352 g (60%) of an off-white solid, 5. 1H NMR (CDCl3,
H), 1.25 (s, 18 H), 3.12 (q, 4H), 6.70 (t, 1H), 6.88 (d, 4 H), 6.99 (d, 2 H),
7.29 (d, 4 H); 13C NMR (CDCl3,
): 14.1, 31.5, 34.4, 42.0, 110.3, 111.3,
d): 1.02 (t, 6
d
119.1, 126.9, 142.9, 147.5, 153.2, 159.6.
2.2.3. General procedure for polymerization reactions (7aef)
A typical polymerization reaction will be described using
Bisphenol A, 6a. To a 25 mL round-bottomed flask, equipped with
a stir bar, reflux condenser, and gas inlet, was added 4 (0.500 g,
2.0 mmol), K2CO3 (0.832 g, 6.30 mmol), 6a (0.472 g, 2.07 mmol)
and NMP (3.0 mL). The reaction mixture was heated to 185 ꢀC for
21 h at which point it was cooled to w100 ꢀC and slowly poured
into water (400 mL) with vigorous stirring. The solution was
allowed to stir for another 30 min before filtering and drying the
resulting solid under vacuum. The polymer was dissolved in
a minimum amount of THF and then re-precipitated in ethanol/
water (400 mL:40 mL) containing a few drops of concentrated HCl.
The resulting white precipitate, 0.66 g (68%) was isolated via
VE3580 refractive index detector. Two Polymer Laboratories 5 mm
PL gel Mixed C columns (heated to 35 ꢀC) were used with tetra-
hydrofuran as the eluent and a Thermoseparation Model P1000
pump operating at 1.0 mL/min. Number average molecular weights,
Mn, were determined with the light scattering and refractive index
(RI) detectors and the dispersity was determined using 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. Matrix assisted laser desorption/ionization time-

532
R. Selhorst, E. Fossum / Polymer 54 (2013) 530e535
filtration and dried under vacuum prior to analysis. 1H NMR (CDCl3,
Fluorobenzene, which is considered to be unreactive in NAS reac-
tions, has a 19F NMR chemical shift of ꢁ112 ppm.
d
): 1.08 (t, 6 H), 1.68 (b, 6 H), 3.18 (q, 4 H), 6.82 (t, 1 H), 6.93 (d, 4 H),
7.06 (d, 2 H), 7.22 (d, 4 H). 13C NMR (CDCl3, d): 14.1, 31.0, 42.1, 42.4,
110.6, 111.8, 119.1, 128.4, 143.0, 146.8, 153.6, 159.4.
Polymerization reactions with the remaining bis-phenols were
carried out in a similar fashion.
The 19F NMR chemical shift for the fluorine atoms in compound 4
was found to be ꢁ106.3 ppm. For comparison purposes, the 19F NMR
chemical shifts for the fluorine atoms in N,N-dimethyl-2,4-
difluorobenzene sulfonamide, which was also successfully con-
verted to a PAE, were ꢁ103.08 (para) and ꢁ104.82 (ortho) ppm,
respective to the sulfonamide group [33]. The fluorine data indicate
that the fluorine atoms in 4 were considerably less reactive than
those located in the ortho and para positions, however, given that the
19F NMR chemical shift of the fluorine atoms in 4 is similar to that of
4,40-difluorobenzophenone (ꢁ106.1 ppm) they should still be
readily displaceable by phenoxide nucleophiles. The relative ease of
displacement of the fluorine atoms in 4 was confirmed experi-
mentallybycarryingout a model reaction, using 4-t-butylphenoxide
as the nucleophile, as outlined in Scheme 1. Displacement of both
fluorine atoms, as confirmed by GC/MS analysis, was completed
after 21 h at 185 ꢀC, which indicated a high potential for the
successful preparation of the corresponding poly(arylene ether)s.
7b (64%): 1H NMR (CDCl3,
d
): 1.11 (t, 6 H), 3.22 (q, 4 H), 6.94 (t,
1H), 7.02 (d, 4 H), 7.21 (d, 2H), 7.41 (d, 4 H); 13C NMR (CDCl3,
): 13.1,
42.1,112.6,113.6,118.7,120.6 (q, CF3),129.6,132.1,143.9,156.6,158.2.
d
7c (64%): 1H NMR (CDCl3,
d): 1.12 (t, 6 H), 3.22 (q, 4 H), 6.91 (t, 3
H), 7.12 (d, 4 H), 7.15 (d, 2 H), 7.56 (d, 4 H); 13C NMR (CDCl3,
42.2, 111.0, 112.2, 128.8, 136.9, 143.4, 155.3, 159.4.
d): 14.3,
7d (70%): 1H NMR (CDCl3,
d): 1.11 (t, 6 H), 3.21 (q, 4 H), 6.78 (t, 1
H), 7.04 (b, 8 H), 7.06 (d, 2 H); 13C NMR (CDCl3,
110.8, 120.3, 121.3, 143.2, 151.0, 154.0, 159.8.
d): 14.2, 42.1, 110.0,
7e (41%): 1H NMR (CDCl3,
d): 1.11 (t, 6 H), 3.22 (q, 4 H), 6.84 (t, 3
H), 7.06 (s, 4 H), 7.10 (d, 2 H); 13C NMR (CDCl3,
111.5, 121.3, 143.5, 152.2, 159.4.
d): 14.1, 42.1, 110.6,
7f (38%): 1H NMR (CDCl3,
d): 1.03 (t, 6 H), 3.14 (q, 4 H), 6.67 (t, 3
H), 6.73 (dd, 2 H), 6.78 (t, 1 H), 7.29 (t, 1H); 13C NMR (CDCl3,
42.1, 110.7, 111.8, 112.7, 114.9, 131.2, 143.6, 157.3, 158.5.
d): 14.1,
3.2. Polymer synthesis
As outlined in Scheme 2 a series of PAEs was prepared from 4
and a variety of bis-phenols in N-methylpyrrolidinone (NMP) with
potassium carbonate utilized to prepare the corresponding
bisphenolate in situ. In order to be consistent, all of the reactions
were carried out at 185 ꢀC for 21 h, followed by precipitating the
reaction mixture into a large excess of water to afford the corre-
sponding polymer as an off-white solid. The polymer was isolated
via filtration and dried prior to being analyzed by Size Exclusion
Chromatography (SEC), 1H and 13C NMR spectroscopy, Thermog-
ravimetric Analysis (TGA), and Differential Scanning Calorimetry
(DSC).
3. Results and discussion
3.1. Monomer synthesis and characterization
The synthesis of N,N-diethyl-3,5-difluorobenzene sulfonamide,
4, was achieved via the one-step procedure outlined in Scheme 1.
Reaction of commercially available 3,5-difluorobenzenesulfonyl
chloride with an excess of diethylamine afforded the desired
compound in 61% yield after recrystallization twice from hexanes.
Confirmation of the structure of 4 was provided by a combination of
1H, 13C, and 19F NMR spectroscopy, gas chromatography/mass
spectrometry (GC/MS), and elemental analysis. The 13C NMR
spectrum of 4 is presented in Fig. 1.
Due to spinespin coupling with the two fluorine atoms present
on the ring, carbon atoms aed all experience some degree of
splitting and the coupling constants vary with their position rela-
tive to the CeF bonds. Carbon a gives rise to a triplet at 107 ppm,
the resonance for carbon c is a doublet of doublets centered at
110 ppm, carbon d, at 143 ppm, appears as a triplet, and carbon
b gives rise to a doublet of doublets at 162.9 ppm. The signals for
carbon atoms e and f were identified as singlets and were found at
42 and 14 ppm, respectively.
The 13C NMR spectrum of polymer 7a is presented in Fig. 2 and
indicates that 4 was successfully converted to the desired polymer.
The triplets, representing carbon atoms a and d, and doublets of
doublets, arising from carbon atoms b and c, resulting from fluorine
coupling in 4, have been reduced to singlets after conversion to the
corresponding aryl ether system.
In addition, the signals arising from the carbon atoms, labeled
gel, in the Bisphenol-A component are now present.
3.3. Cyclic oligomer formation
The reactivity of the electrophilic sites in 4, toward NAS reac-
tions, was probed via a combination of 13C and 19F NMR spectros-
copy as well as model reactions (Scheme 1). A number of authors
have utilized NMR spectroscopy as a guide for determining the
ability of fluoride atoms to be displaced by nucleophiles. [33,51,52]
In general, more reactive species exhibit both 13C and 19F NMR
chemical shifts that are considerably more downfield than those
from less reactive species. For example, the 19F NMR chemical shifts
of 4,40-difluorodiphenyl sulfone and 4,40-difluorobenzophenone
are reported as ꢁ104.1 and ꢁ106.1 ppm, respectively.
In previous polycondensation reactions with 3,5-difluoro
aromatic systems it was observed that the formation of linear
polymer was always accompanied by the formation of cyclic olig-
omeric species and the current monomer showed similar behavior.
Fig. 3 displays the SEC traces of the crude polymer 7a, the polymer
after reprecipitation from ethanol/water (90:10) and the ethanol/
water soluble material. In the trace of the crude material there is
evidence of some discrete sized oligomeric material in the lower
molecular weight region while, after the reprecipitation process,
their presence was much less apparent. The trace of the ethanol/
Scheme 1. Synthetic procedure for the synthesis of 4 and subsequent model reaction for determination of the reactivity of its electrophilic sites.

R. Selhorst, E. Fossum / Polymer 54 (2013) 530e535
533
Fig. 1. 75.5 MHz 13C (CDCl3) NMR spectrum of monomer 4.
Fig. 2. 75.5 MHz 13C (CDCl3) NMR spectrum of polymer 7a.
water soluble fraction indicated that at least two discernable
species along with some of the lower molecular weight, presum-
ably linear, material had been removed.
of 3.2 (7c). The much lower Mn value (6300 Da) observed for the
resorcinol system (7f), may result from the meta orientation of the
reactive groups found in both 4 and resorcinol, leading to a higher
percentage of cyclic species, as well as the lower reactivity of the
phenoxide groups. Despite the reasonably high Mn values of poly-
mers 7ae7f, they were found to be soluble in a wide variety of
solvents including chloroform, tetrahydrofuran (THF), and N-
methylpyrolidinone (NMP), but were insoluble in water and
alcohols.
The ethanol/water soluble material was further analyzed via
mass spectrometry and the spectrum is shown in Fig. 4. The spec-
trum clearly shows the presence of cyclic species with the dimer
(m/z ¼ 913.327, n ¼ 2 þ Kþ), trimer (m/z ¼ 1350.434, n ¼ 3 þ Kþ),
and tetramer (m/z ¼ 1787.566, n ¼ 4 þ Kþ) predominating, although
some higher molecular weight cyclic species are also present. All of
the signals corresponded to the mass of a discrete cyclic species
plus a potassium ion. The regular spacing between the signals
corresponds exactly to the repeat unit formula weight of one
Bisphenol A and one monomer 4.
3.5. Thermal properties
The thermal properties of polymers 7aef were evaluated by
a combination of Thermogravimetric Analysis (TGA) and Differen-
tial Scanning Calorimetry. The TGA thermograms for polymers 7a
and 7b, under nitrogen, are shown in Fig. 5. Under a nitrogen
atmosphere all of the polymers exhibited a two-stage decomposi-
tion profile with the first stage being attributed to the loss of the
diethyl sulfonamide group. In fact, the percentage weight loss for
the first step very closely approximated the percentage, by weight,
of the diethyl sulfonamide group relative to the repeat unit of the
polymer. For example, the calculated weight percentages of diethyl
sulfonamide in the Bis-A (7a) and Bis-AF (7b) polymers were 31.1
and 25.0%, respectively, while the experimental% losses, under
3.4. Molecular weight determination
The number average molecular weights, Mn, of polymers 7aef
were determined via SEC using the light scattering and refractive
index detectors and the data is summarized in Table 1. The samples
were evaluated after removing the low molecular weight cyclic
species. All of the polymers, with the exception of the resorcinol-
based material, 7f, possessed Mn values above 20,000 Daltons
(Da). The Bisphenol-AF material (7b) had a Mn value of 85,500 Da
and the hydroquinone polymer (7e) had a Mn of 20,400 Da, which
correspond to 157 and 64 repeat units, respectively. The dispersity
values for 7ae7f, determined using a conventional calibration on
the refractive index detector, ranged from a low of 1.9 (7a) to a high
Scheme 2. Reaction scheme for polycondensation reactions of monomer
4
with
Fig. 3. SEC traces of polymer 7a: (a) crude, (b) reprecipitated from ethanol/water
a variety of bis-phenols.
(90:10), and (c) the ethanol/water soluble material.

534
R. Selhorst, E. Fossum / Polymer 54 (2013) 530e535
Table 2
Calculated and experimental values for the percentage weight loss of the diethyl
sulfonamide group in polymers 7aef. The experimental data was determined from
the 1st derivative plots of weight percent versus temperature curves.
Polymer
Weight% SO2NEt2
1st Step% loss
(N2)
1st Step% loss
(air)
7a
7b
7c
7d
7e
7f
31.1
25.0
34.3
33.9
42.6
42.6
27.0
22.9
29.1
31.6
41.3
42.8
29.2
25.2
29.7
40.4
43.5
41.1
Fig. 4. MALDI-TOF MS spectrum of the ethanol/water soluble material from the reaction
utilized to prepare 7a. The repeat unit formula weight was calculated as 437.18 g/mol.
Table 1
Reaction conditions, percentage yield, molecular weight, dispersity, and thermal
analysis data for polymers prepared from monomer 4 and various bis-phenols.
Polymer Bisphenol % yield Mna (Da) Dispersity Tg (ꢀ) Td (5%) Td (5%)
b
c
c
N2 (ꢀC) air (ꢀ)
7a
7b
7c
7d
7e
7f
6a
6b
6c
6d
6e
6f
66
64
64
70
48
38
27,900
85,500
30,300
39,600
20,500
6300
1.9
2.2
3.2
2.2
2.3
1.9
117
136
142
102
102
72
388
395
400
396
381
382
381
385
388
366
381
382
a
Determined via SEC analysis.
Heating rate of 10 ꢀC/min.
Heating rate of 10 ꢀC/min.
b
c
Fig. 6. Differential scanning calorimetry traces of polymers 7aef, under a nitrogen
atmosphere at a heating rate of 10 ꢀC/min.
nitrogen, during the first step of degradation were 27.0 and 22.9%.
Similar results were observed under air atmospheres and the
weight percent data for all of the polymers is summarized in
Table 2.
The DSC traces (Fig. 6) for 7aef indicated that completely amor-
phous polymers had been prepared with only glass transition
temperatures, Tg, being observed in heating traces up to 300 ꢀC. The
highest Tg value was 142 ꢀC for the more rigid, biphenyl-based poly-
mer (7c) while the lowest was only 72 ꢀC for the resorcinol-based
polymer (7f). However, the very low Tg value (72 ꢀC) observed for 7f
might be attributed, in part, to its low molecular weight, 6300 g/mol.
For comparison purposes the Tg values of the biphenyl-based PAE
materials prepared from 3,5-difluorodiphenyl sulfone, 1, 3,5-
difluorobenzophenone, 2, and 3,5-difluorotriphenylphosphine
oxide, 3, were 175, 126, and 175 ꢀC, respectively.
The backbones of the diphenyl ether and hydroquinone systems,
7d and 7e, can be considered as geometric isomers of poly(1,4-
phenylene oxide), which has a Tg of 95 ꢀC. The Tg values of 7d and
7e were both found to be 102 ꢀC, only slightly higher than that of
poly(1,4-phenylene oxide). The presence of the diethylsulfonamide
group most likely increases the free volume in the systems, which
should lead to a lower Tg. However, it appears that the free volume
effects are offset by the strong intermolecular forces resulting from
the polarity of the sulfonamide group, which hinder backbone
rotation, leading to a Tg value similar to that of the relatively flexible
poly(1,4-phenylene oxide).
4. Conclusions
The synthesis and application of N,N-diethyl-3,5-difluor-
obenzene sulfonamide, 4, has been evaluated as a route to
synthesize poly(arylene ether)s with pendant sulfonamide groups.
The synthesis of 4 was achieved in relatively high yield via
a straightforward one-step process using commercially available
reagents. While the electrophilic sites in 4 were shown to be
considerably less reactive than those activated by a sulfonamide
located in the ortho and para positions, they were sufficiently
reactive to prepare high molecular weight poly(arylene ether)s. The
reaction of 4 with a variety of bis-phenols, under typical NAS
conditions, afforded completely amorphous poly(arylene ether)s
bearing a pendant diethylsulfonamide group located meta to the
newly formed ether bonds. Number average molecular weights as
high as 85,500 Da were achieved. The poly(arylene ether)s
Fig. 5. Thermogravimetic analysis data, weight percentage and first derivative of
weight percent, for polymers 7a and 7b, under nitrogen.

R. Selhorst, E. Fossum / Polymer 54 (2013) 530e535
[17] Connell JW, Smith J,JG, Hergenrother PM. Polymer 1995;36:5e11.
535
possessed relatively low glass transition temperatures (Tg) which
ranged from 72 to 142 ꢀC, but displayed relatively good thermal
stability with the 5% weight loss temperatures ranging from 381 to
400 ꢀC in nitrogen. The thermal decomposition of the polymers
followed a two-step pathway in which the first step was assigned to
the loss of the sulfonamide group, followed by backbone degra-
dation. Further work involving the introduction of more sterically
demanding substituents on the sulfonamide moiety is ongoing.
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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.
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