Fluorinated poly(arylene ether ketone)s for high temperature dielectrics

Article abstract of DOI:10.1016/j.polymer.2015.12.006

There is a need for polymeric capacitors with improved energy storage density and thermal stability. In this work, the effect of polymer molecular structure and symmetry on T_g, breakdown strength, and relative permittivity were investigated. A

Full text of DOI:10.1016/j.polymer.2015.12.006

Polymer 83 (2016) 199e204
Contents lists available at ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Fluorinated poly(arylene ether ketone)s for high temperature
dielectrics
Andrew T. Shaver a, Kezhen Yin b, Hailun Borjigin a, Wenrui Zhang a,
,
Shreya Roy Choudhury a, Eric Baer b, Sue J. Mecham a, J.S. Riffle a *, James E. McGrath a
a Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA, USA
b Center for Layered Polymeric Systems, Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
There is a need for polymeric capacitors with improved energy storage density and thermal stability. In
this work, the effect of polymer molecular structure and symmetry on Tg, breakdown strength, and
relative permittivity were investigated. A systematic series of four amorphous poly(arylene ether ketone)s
were compared. Two of the polymers had symmetric bisphenols while the remaining two had asymmetric
bisphenols. Two contained trifluoromethyl groups while the other two had methyl groups. The symmetric
polymers had Tg's of approximately 160 ꢀC while the asymmetric polymers showed higher Tg's near
180 ꢀC. The symmetric polymers had breakdown strengths near 380 kV/mm at 150 ꢀC. The asymmetric
counterparts had breakdown strengths near 520 kV/mm even at 175 ꢀC, with the fluorinated polymers
performing slightly better in both cases. The non-fluorinated polymers had higher relative permittivities
than the fluorinated materials, with the asymmetric polymers being better in both cases.
© 2015 Elsevier Ltd. All rights reserved.
Received 20 August 2015
Received in revised form
20 November 2015
Accepted 3 December 2015
Available online 11 December 2015
Keywords:
Poly(arylene ether ketone)
Capacitor
Dielectric polymer
1. Introduction
layers [21]. This is advantageous for capacitors because the prop-
erties of two different materials can be combined and each inter-
Today's electronics are involved in many vital functions of
everyday life and capacitors serve key roles in these devices [1e4].
Because of miniaturization and increased energy consumption in
such applications, new dielectric materials must be developed with
higher energy density while maintaining low loss of that energy
[1,4]. Considerable research has been devoted to polymeric
dielectric materials due to their ease of manufacturing, high
breakdown strength, low loss, and self-clearing capabilities [1,5,6].
Biaxially oriented polypropylene is widely regarded as the current
state-of-the-art material and it is well known that many of its
properties originate from the biaxial orientation process [7e10].
However, the use of biaxially oriented polypropylene is limited due
to its poor performance above ~85 ꢀC and low energy density
[8,9,11].
face of the two polymers works to bolster the overall dielectric
properties [12,13]. One of the polymers, the insulating layer with
low dielectric constant, is chosen to have high breakdown strength
and low loss, e.g. poly(ethylene terephthalate) [19], polycarbonate
[12e18], or polysulfone [20]. The other polymer has a high dielec-
tric constant such as poly(vinylidene fluoride) [13,17,20] or it's co-
polymers that can increase the energy density [12,14e16,18,19]. The
layered structure leads to build-up of Maxwell-Wagner-Sillars
interfacial polarization at the interfaces. The charge buildup at
these interfaces allows the films to discharge along the interfaces
and thus results in higher breakdown strengths [19].
In this work, four different poly(arylene ether)s were synthe-
sized to compare symmetric and asymmetric fluorine-containing
structures versus their non-fluorinated counterparts. Prior work
on low dielectric polymers as insulators showed that asymmetric
versus symmetric fluorination could affect a material's overall po-
larization [22]. Therefore, this paper describes poly(arylene ether
ketone)s (PAEKs) with systematic fluorine- and non-fluorine-
containing geometries that could be melt processed for use in ca-
pacitors (Fig. 1). In the future, they could be layered with poly(-
vinylidene fluoride) to explore the effect that fluorination and
symmetry have on the interfaces of the microlayer film
A processing technique under investigation to increase dielec-
tric film performance has been termed forced assembly microlayer
coextrusion [12e20]. In this process, two polymers are multilay-
ered in a film to create a structure with many parallel alternating
* Corresponding author.
E-mail address: judyriffle@aol.com (J.S. Riffle).
http://dx.doi.org/10.1016/j.polymer.2015.12.006
0032-3861/© 2015 Elsevier Ltd. All rights reserved.

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A.T. Shaver et al. / Polymer 83 (2016) 199e204
2.2. Synthesis of BPA, 6FBPA, 3FBPAP and BPAP poly(arylene ether
ketone)s
The procedure for all four polymers was the same. A represen-
tative synthesis of the BPA polymer was adapted from previous
literature [25e29]. For example, bisphenol (67.713 g,
A
296.6 mmol), 4,4'-difluorobenzophenone (65.643 g, 306.4 mmol),
and DMAc (600 mL) were charged to a three-neck flask equipped
with a N2 inlet, mechanical stirrer, and DeaneStark trap. Toluene
(300 mL) and K2CO3 (48.352 g, 349.8 mmol) were added to the flask
and the DeaneStark trap was filled with toluene. The apparatus
was placed in a silicone oil bath that was heated to 155 ꢀC to begin
azeotropic removal of water. After 4 h the toluene and water were
removed from the DeaneStark trap. The oil bath was maintained at
150 ꢀC for 12 h, then the reaction was allowed to cool to room
temperature. The polymer solution was filtered to remove any
excess K2CO3 or by-product salts. The polymer solution was
precipitated into deionized water, then the polymer was stirred in
deionized water at 80 ꢀC to further assist the removal of salts and
solvents. The white polymer was filtered and dried at 110 ꢀC under
vacuum. Yield was 81%.
The values for the remaining three reactions were as follows. For
the 6FBPA polymer the amounts of the materials were: 4,40-Hex-
afluoroisopropylidenediphenol (2.733 g, 8.128 mmol), 4,4'-difluor-
obenzophenone (1.814 g, 8.468 mmol), DMAc (24 mL), toluene
(12 mL), and K2CO3 (1.3800 g, 9.985 mmol). Yield was 92%. For the
3FBPAP polymer the amounts of the materials were: 1,1-bis(4-
Fig. 1. The polymer chemical structures.
architecture. Literature shows that increasing the strength of the
interface can increase the breakdown strength of layered dielectric
films [23]. It was reasoned that added fluorine structures in the
polymers may improve interactions with fluorinated high dielectric
constant materials such as PVDF.
hydroxyphenyl)-1-phenyl-2,2,2-trifluoroethane
(9.960
g,
28.93 mmol), 4,4'-difluorobenzophenone (6.481 g, 30.25 mmol),
DMAc (24 mL), toluene (12 mL), and K2CO3 (6.4370 g, 46.57 mmol).
Yield was 82%. For the BPAP polymer the amounts of the materials
were: 4,4'-(1-phenylethylidene)bisphenol (2.081 g, 7.167 mmol),
4,4'-difluorobenzophenone (1.600 g, 7.469 mmol), DMAc (24 mL),
toluene (12 mL), and K2CO3 (1.2300 g, 8.899 mmol). Yield was 89%.
2. Experimental materials
2.3. Proton nuclear magnetic resonance (NMR) spectroscopy
N,N-Dimethylacetamide (DMAc), dichloromethane, triflic acid,
toluene, 4,4'-(1-phenylethylidene)bisphenol, 2,2,2-trifluoroaceto
phenone, and phenol were purchased from SigmaeAldrich. DMAc
was vacuum distilled from calcium hydride. Triflic acid, toluene,
dichloromethane, 2,2,2-trifluoroacetophenone and phenol were
used as received. 4,4'-(1-Phenylethylidene)bisphenol was dried at
110 ꢀC under vacuum. 4,40-Difluorobenzophenone and bisphenol A
were kindly donated by Solvay and recrystallized from 2-propanol
and toluene, respectively. 4,40-Hexafluoroisopropylidenediphenol
was obtained from Ciba and purified by sublimation, followed by
recrystallization from toluene. Potassium carbonate was purchased
from Fisher Scientific and dried at 150 ꢀC under vacuum.
1H NMR analysis was performed on a Varian Inova spectrometer
operating at 400 MHz. All spectra were obtained from 15% (w/v) 1-
mL solutions in chloroform-d.
2.4. Film-casting
The polymer (0.4 g) was weighed into a small glass vial with a
magnetic stir bar. Chloroform (11 mL) was added to the vial to
obtain a 2.5 wt% solution. The solution was filtered using a 1-mm
syringe filter into a clean glass vial. A 5 ꢁ 500 glass plate was placed
in a base bath for 30 min for surface treatment. The glass plate was
rinsed and dried, then placed on a level surface for casting. The
solution was poured onto the plate and the solution was spread to
the edges of the plate until it covered the whole glass plate. A glass
dome with 2 outlets was used to cover the plate. One outlet was
fitted with a syringe filter and the other was connected to the house
air stream running at 2 SCFH. The plate was left undisturbed for a
minimum of 30 min, then transferred to an oven at 110 ꢀC for an
additional 30 min. The film was removed from the glass plate using
a razor blade by slowly lifting the edges until the film came off.
2.1. Synthesis of 1,1-bis(4-hydroxyphenyl)-1-phenyl-2,2,2-
trifluoroethane (the bisphenol monomer for 3FBPAP)
Phenol (41.32 g, 440 mmol) and 2,2,2-trifluoroacetophenone
(19.32 g, 110 mmol) were charged to a 250-mL, three-neck,
round bottom flask equipped with a magnetic stir bar, N2 inlet,
and an addition funnel fitted with a drying tube and heated to
45 ꢀC. Once a homogeneous solution was achieved, triflic acid
(3.8 mL, 42 mmol) was introduced dropwise while maintaining
the temperature at 45 ꢀC. After 1 h, the slurry was treated with
200 mL of hot deionized water and the product was isolated by
filtration. The pink solid was stirred in 200 mL of hot deionized
water for 30 min, vacuum filtered, and washed with hot water,
then dichloromethane. The product was dried at 80 ꢀC under
vacuum for 24 h. Yield was ~90%. The mp was 215 ꢀC, consistent
with literature [24].
2.5. Size exclusion chromatography (SEC)
SEC was conducted to measure molecular weights and distri-
butions. The mobile phase was DMAc distilled from CaH2 con-
taining dry LiCl (0.1 M). The column set consisted of 3 Agilent PLgel
10-
m
m Mixed B-LS columns 300 ꢁ 7.5 mm (polystyrene/divinyl-
benzene) connected in series with a guard column having the same

A.T. Shaver et al. / Polymer 83 (2016) 199e204
201
stationary phase. The columns and detectors were maintained at
at each temperature.
50 ꢀC. An isocratic pump (Agilent 1260 infinity, Agilent Technolo-
gies) with an online degasser (Agilent 1260), autosampler and
column oven was used for mobile phase delivery and sample in-
jection. A system of multiple detectors connected in series was used
for the analyses. A multi-angle laser light scattering detector
(DAWN-HELEOS II, Wyatt Technology Corp.), operating at a wave-
length of 658 nm, a viscometer detector (Viscostar, Wyatt Tech-
nology Corp.), and a refractive index detector operating at a
wavelength of 658 nm (Optilab T-rEX, Wyatt Technology Corp.)
provided online results. The system was corrected for interdetector
delay and band broadening using a 21,000 g/mole polystyrene
standard. Data acquisition and analysis were conducted using Astra
6 software from Wyatt Technology Corp. Validation of the system
was performed by monitoring the molar mass of a known molec-
ular weight polystyrene sample by light scattering. The accepted
variance of the 21,000 g/mole polystyrene standard was defined as
2 standard deviations (11.5% for Mn and 9% for Mw) derived from a
set of 34 runs. Specific refractive index values were calculated
based on the assumption of 100% recovery.
2.10. Dielectric thermal analysis (DETA)
Dielectric spectroscopy was measured with a frequency sweep
from 0.01 Hz to 10000 Hz at 25 ꢀC at a constant voltage of 1 V using
a Novocontrol (Hundsangen, Germany) spectrometer. Electrodes on
each side of the film were sputtered-coated with gold using an EMS
Q300 T sputter coater (Electron Microscopy Science, Quantum
Technologies, Ashford, Kent, England). The diameter of the gold
electrode was 1 cm. Prior to testing, the films were dried for 24 h at
120 ꢀC. The frequency sweep measurements were carried out at
room temperature and the temperature sweep heating rate was
5 ꢀC/min.
3. Results and discussion
The structures, molecular weights and thermal properties of the
poly(arylene ether ketone)s were characterized by proton NMR,
SEC and DSC. The 1H NMR spectra shown in Fig. 2 confirmed the
expected chemical structures. The integral values were consistent
with the expected structures and no extraneous peaks were
observed.
2.6. Thermogravimetric analysis (TGA)
The SEC results showed that the polymer Mw's were within
close range of each other and that high molecular weights had been
achieved (Table 1 and Fig. 3). The PDI's were all symmetric and
comparable to each other. Step growth polymerization PDI values
should ideally be two. The lower values may be due to lower mo-
lecular weight chains being lost during precipitation as well as the
fact that light scattering calculations of broad molecular weight
polymers tend to overestimate the Mn and thereby reduce the PDI.
The DSC thermograms for the four polymers are shown in Fig. 4.
The two symmetric polymers have Tg's near 160 ꢀC while the two
asymmetric polymers have Tg's near 180 ꢀC. This increase is most
likely caused by increased stiffness of the polymer backbone caused
by introducing a phenyl substituent into the linking group in the
bisphenol monomers. A stiffer backbone requires more energy to
begin long-range segmental motion. Both of the fluorine-
containing polymers have slightly higher Tg's than their non-
fluorinated counterparts. The larger fluorine atom may cause
more steric hindrance than the hydrogen, therefore leading to a
stiffer polymer structure.
The calculated breakdown strengths of each of the materials as
functions of temperature are listed in Table 2. At 25 ꢀC, the trend is
3FBPAP > BPAP > 6FBPA > BPA with a difference of approximately
20 V between each. This can also likely be correlated to stiffness
because breakdown strength has been shown to increase with
Young's modulus [31,32]. As the temperature is increased, the two
asymmetric polymers maintain higher calculated breakdown
strengths, most likely due to their higher Tg's and stiffer backbones.
Even at 175 ꢀC, the calculated breakdown strengths of the asym-
metric polymers are greater than those of the symmetric polymers
at 125 ꢀC.
Thermal stabilities of the polymers were investigated using a TA
Instruments TGA Q5000 under a N2 atmosphere with the N2
running at 25 mL/min. The heating rate was 10 ꢀC/min from room
temperature to 700 ꢀC.
2.7. Differential scanning calorimetry (DSC)
The thermal properties were investigated with a TA Instruments
DSC Q200. The polymers were heated under N2 to ensure an inert
atmosphere at 60 mL/min. The heating rate was 10 ꢀC/min to
350 ꢀC, then the sample was cooled to 0 ꢀC at 10 ꢀC/min. It was
heated once more to 350 ꢀC at 10 ꢀC/min and the reported DSC
thermograms are from the second scans.
2.8. Refractive indices
The refractive indices of PAEK films were characterized using a
2010 Metricon instrument with a 633 nm laser at room tempera-
ture. The PAEK films were brought into contact with the base of a
prism with a known refractive index. The laser beam began hori-
zontal (90ꢀ) to the prism/polymer interface so all light was totally
reflected, and then it rotated until it was normal to the prism/
polymer interface (0ꢀ). At some angle between 90ꢀ and 0ꢀ the re-
flected laser light intensity decreased which indicated the critical
angle. The refractive indices of the films were calculated by Snell's
Law (equation (1))
npsinq ¼ n sinq
(1)
p
f
f
where np and nf are the refractive indices of the prism and the film,
respectively, qp is the critical angle and qf equaled 90ꢀ [30].
The relative permittivity (ε) was measured from 10ꢂ1to104 Hz
(Fig. 5). The trend in relative permittivity for the four polymers is
BPAP > BPA > 3FBPAP > 6FBPA. The differences can be attributed to
their fluorine content, introduction of a phenyl ring, and their
symmetric versus asymmetric structures. Increased fluorine con-
tent in the polymer increases the fractional free volume, and an
increase in fractional free volume decreases the amount of polar-
izable content per unit volume. With less material to be polarized,
the relative permittivity will be lower [33]. Thus, it is reasonable to
expect that 6FBPA and 3FBPAP would have lower relative permit-
tivities than BPA and BPAP, respectively. Xie et al. made a series of
poly(arylene ether ketone)s using 4,4’-difluorobenzophenone
2.9. Breakdown strength
Breakdown strengths of the PAEK films were measured with a
needle-plane electrode. The needle electrode was the positive side
and the diameter of the needle tip was 40 mm. The negative elec-
trode was a 3 ꢁ 10 cm rectangular aluminum plate. A Quadtech
(Marlborough, MA) Guardian 20-kV HiPot tester was used as the
voltage source and the voltage ramp speed was 500 V/s. The
breakdown strength measurements were carried out in an oil bath
at 25, 75, 125, 150, and 175 ꢀC with twenty repetitions for each film

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A.T. Shaver et al. / Polymer 83 (2016) 199e204
Fig. 2. Confirmation of structure via proton NMR.
Table 1
Molecular weights in DMAc with 0.1 M LiCl at 50 ꢀC
Mw (kDa)
PDI
BPA PAEK
78
67
67
62
1.5
1.4
1.5
1.4
6FBPA PAEK
BPAP PAEK
3FBPAP PAEK
Fig. 4. DSC thermograms showing the glass transition temperatures.
Table 2
Calculated breakdown strengths measured via a needle-plane electrode method.
The units of breakdown strength are volts/film thickness (kV/mm).
25 ꢀC
75 ꢀC
125 ꢀC
150 ꢀC
175 ꢀC
BPA PAEK
782 35
803 55
821 45
840 45
563 44
583 20
753 33
765 33
412 52
410 34
651 50
662 49
365 22
396 28
615 27
641 26
e
6FBPA PAEK
BPAP PAEK
3FBPAP PAEK
e
511 36
523 31
Fig. 3. Molecular weights by light scattering SEC.
which showed comparable results to our own. Their non-
fluorinated poly(arylene ether ketone) had an ε of 2.95 at 1 MHz
where as our BPA-based poly(arylene ether ketone) had an ε of
2.94 at 0.1 MHz [34]. Further literature shows that the ε of both our
fluorinated and non-fluorinated PAEK polymers are in the expected
value range. [35e37].

A.T. Shaver et al. / Polymer 83 (2016) 199e204
203
difference gives an indication of the orientation contribution of
the material.
εmaxwell ¼ n2
(2)
In Fig. 6 the left graph compares the measured ε at 1 kHz to the
Maxwell ε of the symmetric PAEK structures. The dashed line is
included to make a better comparison between the two ε values.
The measured ε and Maxwell comparison were extremely close
since BPA and 6FBPA are both symmetric and therefore have no
orientation polarization. The right graph makes the same com-
parison but with the two asymmetric structures. In this case there
is a difference between the measured ε and the Maxwell com-
parison lines. This is expected since the orientation polarization
due to the asymmetric trifluoromethyl group will be greater than
for the asymmetric methyl. This is confirmed since the measured ε
by dielectric spectroscopy has a less negative slope than the
Maxwell comparison. This indicates that orientation polarization
contributes more to the 3FBPAP measured ε than it contributes to
the BPAP ε.
4. Conclusions
Fig. 5. The relative permittivity of each material over varying frequency at 25 ꢀC.
In summary, we were able to make high molecular weight BPA,
6FBPA, BPAP, and 3FBPAP based poly(arylene ether ketone)s via
nucleophilic aromatic substitution step growth polymerization. All
four polymers displayed high Tg's with those of the asymmetric
PAEK's approximately 20 ꢀC higher than their symmetric counter-
parts, most likely due to increases in backbone stiffness. Consistent
with the DSC results, the breakdown strengths of the asymmetric
PAEK's were higher than for the symmetric polymers. The trend in ε
was BPAP > BPA > 3FBPAP > 6FBPA and this was attributed to
fluorine content, replacement of the methyl or trifluoromethyl in
the bisphenol linking groups with the phenyl ring, and the asym-
metric structure. Introduction of fluorine in place of hydrogen re-
sults in increased fractional free volume, and this reduces the
polarizable content per unit volume. The phenyl ring has a superior
polarizability to weight ratio. The asymmetric structure results in
larger dipoles which contribute to orientation polarization. This
was confirmed by comparing the relative permittivities measured
at 1 kHz to the Maxwell model relative permittivities (squares of
the refractive indices). This suggests that asymmetric structures
with higher relative permittivities would be advantageous for
multilayer capacitors with PVDF or its copolymers.
It is reasoned that energy storage density would be improved in
multilayer films with increased interaction at the interface between
the two materials. Thus, our approach has been to design engi-
neering polymers that contain fluorinated groups so that they will
interact positively with PVDF at the interfaces between the layers.
The maximum energy storage density in an insulating material is
proportional to the dielectric constant times the square of the
breakdown strength. The breakdown strengths of these amorphous
poly(arylene ether ketone)s are higher than the aromatic poly-
carbonates that were studied previously. For example, at 125 ꢀC,
bisphenol A polycarbonate had a calculated breakdown strength of
540 kV/mm[13] while 3FBPAP PAEK has a calculated breakdown
strength of 622 kV/mm. Moreover the Tg of bisphenol A poly-
carbonate is 150 ꢀC whereas the Tg of 3FBPAP PAEK is 183 ꢀC, and
both have excellent mechanical properties. Thus, we believe that
these poly(arylene ether ketone)s have potential for incorporation
into multilayered (thin-film) capacitors with PVDF as a high
dielectric constant layer. The processing parameters for making
multilayered capacitors through forced assembly microlayer coex-
trusion and the dielectric properties of those materials with pol-
y(arylene ether ketone)s and high dielectric constant fluorinated
Introduction of a phenyl ring in the bisphenol linking group
increases the relative permittivity because its polarizability to
weight contribution is higher than for the methyl or tri-
fluoromethyl groups. This can be explained using the Vogel model
polarization group contribution values [38]. The phenyl group has a
polarization contribution of 123.5 and a MW of 77 to give a polar-
izability/weight ratio of 1.604. In comparison, the methyl group has
a polarization contribution of 17.66 and a MW of 15 to give a ratio of
1.177. The trifluoromethyl group has a polarization contribution of
86.4 and a MW of 69 to give a ratio of 1.252. The phenyl group
contributes more polarization to the relative permittivity than the
methyl or trifluoromethyl groups, and this can be correlated to its
easily polarized aromaticity [33]. Other poly(ether ketone)s with
highly aromatic structures and ketones have high ε values, thus
showing their structural importance to the polymer ε for dielectric
films [11,39,40].
The higher performance of BPAP and 3FBPAP over their sym-
metric counterparts, BPA and 6FBPA, can be linked to their asym-
metric methyl or trifluoromethyl groups. In the symmetric
polymers the methyl or trifluoromethyl groups have an opposing
group with the same composition so the dipole will be canceled.
Without the opposing group, the asymmetric polymers have a net
dipole and any group with a net dipole will contribute to orienta-
tion polarization (dipole polarization). Orientation polarization is
one of the three main types of polarization that can contribute to
the overall polarizability, which is one of the main factors in
determining the relative permittivity. The three types are elec-
tronic, atomic, and orientation polarization [33].
In order to examine the contribution of incorporating fluorine
in an asymmetric geometry, relative permittivities (ε) measured
by dielectric spectroscopy were compared with the squares of the
refractive indices, also known as the Maxwell ε. Equation (2)
shows the relationship between the refractive index and rela-
tive permittivity. The difference between the measured and
Maxwell ε provides some understanding of the contributions of
orientation polarization to the permittivities in the polymer sys-
tems. This is because the Maxwell model represents the ε at high
frequencies, which is dominated by electronic polarization. The
measured ε by dielectric spectroscopy was at lower frequencies
and has orientation polarization contributions. Therefore the

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A.T. Shaver et al. / Polymer 83 (2016) 199e204
Fig. 6. Comparison of the measured relative permittivity by dielectric spectroscopy versus the squared refractive indices. The left graph is the comparison of the symmetric PAEK
structures and the right graph is the comparison of the asymmetric structures. Relative permittivities were measured by dielectric spectroscopy at 1 kHz.
113702e113702-9.
polymers will be a major focus of a forthcoming publication.
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This research was generously supported by the National Science
Foundation through the Center for Layered Polymeric Systems
(CLiPS) Science and Technology Center Grant (DMR-0423914).
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