Facile one-pot synthesis and thermal cyclopolymerization of aryl bistrifluorovinyl ether monomers bearing reactive pendant groups

Article abstract of DOI:10.1002/pola.23953

A diverse pool of aryl bistrifluorovinyl ether (BTFVE) compounds with reactive pendant groups were prepared in a facile, high yielding three step "one-pot" synthesis from commercial 4-bromo(trifluorovinyloxy)benzene. Monomers were confirmed from ATR-FTIR,

Full text of DOI:10.1002/pola.23953

Facile One-Pot Synthesis and Thermal Cyclopolymerization of Aryl
Bistrifluorovinyl Ether Monomers Bearing Reactive Pendant Groups
KAIZHENG ZHU,1,2* SCOTT T. IACONO,1,2y STEPHEN M. BUDY,1,2z JIANYONG JIN,3 DENNIS W. SMITH, Jr.1,2
1Department of Chemistry, Clemson University, Clemson, South Carolina 29634
2Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University,
Clemson, South Carolina 29634
3Tetramer Technologies, L.L.C., Pendleton, South Carolina 29631
Received 12 November 2009; accepted 22 January 2010
DOI: 10.1002/pola.23953
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: A diverse pool of aryl bistrifluorovinyl ether (BTFVE)
compounds with reactive pendant groups were prepared in a
facile, high yielding three step ‘‘one-pot’’ synthesis from com-
mercial 4-bromo(trifluorovinyloxy)benzene. Monomers were
confirmed from ATR–FTIR, 1H, 13C, and 19F NMR, and HRMS
analysis. Aryl BTFVE compounds were thermally polymerized to
afford perfluorocyclobutyl (PFCB) aryl ether polymers with high
number–average molecular weight (Mn) for homopolymers
(17,050–27,090) and copolymers with 4,40-bis(trifluorovinyloxy)-
biphenyl monomers (27,860–56,500). The PFCB aryl ether homo-
and copolymers collectively possess high thermal stability
(>299 ꢀC in N2) and are readily solution processable producing
optically transparent films. The thermal polymerization was
achieved and reactive moieties remained intact, aside from
those functionalized with acrylates. In the case with acrylate
functionalized polymers, orthogonal polymerization was
achieved by first photopolymerizing the acrylates followed by
thermal curing of the aryl trifluorovinyl ether endgroups. Prelim-
inary results in this study produced the successful preparation of
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photodefinable PFCB aryl ether material. 2010 Wiley Periodi-
cals, Inc. J Polym Sci Part A: Polym Chem 48: 1887–1893, 2010
KEYWORDS: aryl trifluorovinyl ethers; fluoropolymers; litho-
graphy; PFCB aryl ether polymers; polyethers
INTRODUCTION The introduction of fluorine in polymers
continues to be important in the development of advanced
materials exhibiting high thermal and thermo-oxidative sta-
bility, chemical resistance, and superior electrical insulating
ability.1 Perfluorocyclobutyl (PFCB) aryl ether polymers are a
unique and versatile class of partially fluorinated linear and
network polymers used for photonics,2–6 electro-optics,5,7,8
proton exchange membranes,9,10 hybrid composites,11–14
atomic oxygen (AO) resistance,15,16 and liquid crystalline
materials.17,18 Consolidated reviews on PFCB aryl ether poly-
mers have been recently reported.19,20 Most notably, PFCB
aryl ether polymers retain many desired properties of fluoro-
polymers, including low optical attenuation and high thermal
performance, while offering many advantages, such as highly
tailorable refractive index for the core and cladding, and
excellent solution and melt processibility.2 PFCB aryl ether
polymers are traditionally prepared from the thermal [2þ2]
cyclopolymerization of the aryl trifluorovinyl ether (TFVE)
monomers without the need for a catalyst or initiator, result-
ing in conversions in nearly quantitative yield.21 The kinetics
of the step-growth cycloaddition polymerization has been
reported using Raman spectroscopy22 and, more recently,
evidence for the biradical intermediate has been identified
by electron paramagnetic resonance (EPR) spectroscopy.23
Traditionally, aryl TFVE containing monomers are prepared
in two steps starting from phenolic precursor via alkylation
with 1,2-dibromotetrafluoroethane (BrCF2CF2Br), followed
by zinc-mediated dehalogenation. This was established by
Babb et al.21 at The Dow Chemical Company who first
reported the synthesis of 3-trifluorovinyloxy-a,a,a-trifluoroto-
luene, 1,3-bis(trifluorovinyloxy)benzene, 4,40-bis(trifluorovi-
nyloxy)biphenyl and 1,1,1-(trifluorovinyloxyphenyl)ethane
from phenolic feedstocks.
There are limited commercial phenolic precursors available
in order to produce a functionally diverse pool of aryl TFVE
ether monomers. Therefore, a methodology was established
by Neilson and Smith et al.19,24 that utilized 4-bromo(tri-
fluorovinyloxy)benzene, now commercially available, for the
preparation of diverse aryl TFVE monomers tailored for
Additional Supporting Information may be found in the online version of this article.
*Present address: Department of Chemistry, University of Oslo, Oslo, Norway.
†Present address: U.S. Air Force, Patrick Air Force Base, Florida 32925.
‡Present address: Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721.
Correspondence to: D. W. Smith, Jr. (E-mail: dwsmith@clemson.edu)
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Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 1887–1893 (2010) 2010 Wiley Periodicals, Inc.
FACILE ONE-POT SYNTHESIS, ZHU ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
specific material applications. By employing halogen–metal
exchange, the Grignard (or lithiated) of 4-(trifluorovinyloxy)-
benzene can be reacted with a collection of electrophiles
installing carboxylic acid, acyl chloride, aldehyde, alcohol,
and amine groups in very good yields with retention of the
fluoroolefin.25 Furthermore, it has been shown 4-bromo(tri-
fluorovinyloxy)benzene is also tolerant to Suzuki cross-cou-
pling conditions affording terphenyl,17 4,6-disubstituted pyri-
midines,26 and hexa-peri-hexabenzocoronene monomers.3
Therefore, this methodology has become general utility for
the modular preparation of a vast pool of monomers tailored
for specific applications.
in a desiccator prior to use. All reagent manipulations were
performed in nitrogen.
Instrumentation
Column chromatography was performed using Sorbent Silica-
gel (230–450 mesh, Sorbent Technologies). Thin layer chro-
matography (TLC) was carried out on polyester support
plates coated with silica gel 60F254 (Aldrich). Visualization
1
was achieved using a UV lamp. H, 19F, and 13C NMR spectra
were recorded on a JEOL Eclipseþ 300 and chemical shifts
were recorded in ppm (d) with reference to internal tetrame-
thylsilane (0 ppm), CDCl3 (77 ppm), and CFCl3 (0 ppm) for
1H, 13C, and 19F NMR, respectively. Attenuated total reflec-
tance Fourier transform infrared (ATR–FTIR) analysis of neat
samples was performed on a Thermo-Nicolet Magna 550
FTIR spectrophotometer with a diamond ATR attachment.
High resolution mass spectrometry (HRMS) data were
obtained at the University of Illinois Mass Spectrometry Lab-
oratory (Urbana-Champaign, IL) on a Micromass Q-TOF
Ultima Mass spectrometer using electrospray ionization (ESI)
in positive mode as the source. Differential scanning calorim-
etry (DSC) analysis was performed on a TA Q1000 instru-
ment in nitrogen at a heating rate of 10 ꢀC/min up to
200 ꢀC. The glass transition temperature (Tg) was obtained
from a second heating cycle using TA Universal Analysis
2000 software suite. Thermal gravimetric analysis (TGA) was
performed on a Mettler-Toledo 851 instrument in nitrogen at
a heating rate of 10 ꢀC/min up to 800 ꢀC. Gel permeation
chromatography (GPC) data were collected in CHCl3 from a
Waters 2690 Alliance System with photodiode array detec-
tion. GPC samples were eluted in series through Polymer
Labs PLGel 5 mm Mixed-D and Mixed-E columns at 35 ꢀC.
Molecular weights were obtained using polystyrene as a
standard (Polymer Labs Easical PS-2).
Kuo and Liu27 reported the one-pot preparation of tertiary
alkyl carboxylates and sulfonates from ketones. The aryl lith-
ium reagent was initially added to the carbonyl compound;
without quenching the lithium alkoxide to give the tertiary
alcohol, the desired tertiary carboxylate ester was prepared
by adding the acyl chloride in situ. This one-pot procedure is
remarkable from an industrial point of view: it is simple and
efficient, affording an overall yield considerably higher than
those obtained from a traditional two-step process. We ini-
tially attempted to repeat this procedure by trapping methyl
acetate with a solution of 4-lithium(trifluorovinyloxy)ben-
zene, yielding the tertiary alcohol. However, this tertiary
alcohol was not stable and rapidly dehydrated. Realizing the
potential utility of an analogous alcohol monomer, we began
a study to synthesize the trifluoromethyl (ACF3) analog,
which was predicted to be stable against dehydration. The
Grignard reagent, rather than a lithium reagent, derived
from the commercial 4-bromo(trifluorovinyloxy)benzene was
successfully prepared and quenched with methyl trifluoro-
acetate. On the basis of these results, we have developed a
new three-step ‘‘one-pot’’ synthetic procedure for the synthe-
sis of new aryl bistrifluorovinyl ether (BTFVE) derivatives
with reactive pendant moieties. This one-pot process is
operationally simple, high yielding, and tolerant to function-
ally diverse electrophiles affording a new series of aryl
BTFVE derivatives. Their synthesis, characterization, and
thermal cyclopolymerization to PFCB aryl ether polymers are
discussed.
General Procedure for Synthesis of Monomers (M1–M5)
To a flame dried 100-mL three-neck round bottom flask fit-
ted with a condenser and a nitrogen inlet side-neck, were
added magnesium (1.2 g, 48 mmol) and freshly distilled
THF (50 mL). A small crystal of I2 and a few drops of 4-
bromo(trifluorovinyloxy)benzene were added and the reaction
was carefully spot heated (heat gun) to initiate the Grignard
reaction. After initiation, the remaining 4-bromo(trifluorovi-
nyloxy)benzene (10.12 g, 40 mmol) was added drop wise
over 15 min to maintain reflux, followed by reflux for addi-
tional 2 h, and then cooled to 0 ꢀC. Methyltrifluoroacetate
EXPERIMENTAL
Materials and Methods
ꢀ
Chemicals and solvents used were purchased from Sigma
Aldrich or Alfa Aesar and used without purification unless
otherwise stated. 4-Bromo(trifluorovinyloxy)benzene and
4,40-bis(4-trifluorovinyloxy)biphenyl (BP) were donated by
Tetramer Technologies, L.L.C. (Pendleton, SC) and are avail-
able commercially through Oakwood Chemicals, Inc. (Colum-
bia, SC). The following acyl chlorides were used to prepare
monomers M1–M5: acryloyl chloride (M1), methacryloyl
chloride (M2), cyclopropanecarbonyl chloride (M3), cyclo-
butanecarbonyl chloride (M4), and 6-bromohexanoyl chloride
(M5). HPLC grade THF was dried and deoxygenated using a
Pure-Solv solvent purification system from Innovative Tech-
nologies. All glassware was flame dried and allowed to cool
(1.34 mL, 13.3 mmol) was added drop wise at 0 C over 10
min and then slowly warmed to 50 ꢀC for another 1 h. The
reaction mixture was then cooled to 0 ꢀC and appropriate
acyl chloride (40 mmol) was added drop wise over a period
of 30 min. The reaction mixture was warmed slowly to room
temperature and stirred for 24 h. The organic products were
extracted into CH2Cl2 (50 mL), washed with DI H2O (2 ꢁ 50
mL), dried over anhydrous MgSO4, and vacuum filtered. After
rotary evaporation, the crude oil was purified by column
chromatography on silica gel using 100% hexanes, then 80%
hexanes–20% CH2Cl2 (v/v) for elution (Rf typically 0.3).
NOTE: For the acrylate containing monomers (M1 and M2),
solvent evaporation was conducted below 40 ꢀC and the
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ARTICLE
glass reaction vessels were covered with Al foil to avoid
thermal and UV initiated polymerization.
ACHA), 2.32–2.25 (m, 4H, ACH2A), 2.10–2.00 (m, 2H,
ACH2A); 19F NMR (283 MHz, CDCl3) d ꢂ70.9 (s, ACF3, 3F),
ꢂ119.0 (dd, cis-CF¼¼CF2, 2F, Fa), ꢂ125.6 (dd, trans-CF¼¼CF2,
1,1-Bis(4-(1,2,2-trifluorovinyloxy)phenyl)-2,2,2-
trifluoroethyl Acrylate (M1)
2F, Fb), ꢂ134.1 (dd, ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac
¼
59.2 Hz, Jbc ¼ 108.5 Hz); 13C NMR (75.5 MHz, CDCl3)
d 171.5, 155.3, 147.0 (td, ACF¼¼CF2, 1J ¼ 274.0, 2J ¼ 66.5
Hz), 133.5 (dt, ACF¼¼CF2, 1J ¼ 257.3 Hz, 2J ¼ 47.2 Hz),
132.4, 130.3, 126.0, 122.1, 115.5, 84.3 (q, J ¼ 28.9 Hz,
ACF3), 38.7, 25.0, 18.4; HRMS (ESI–TOF) (m/z) [M þ Na]þ
calcd. for C23H15O4F9, 549.0724; found, 549.0750.
M1 was obtained as a pale yellow oil in 65% yield. ATR–
FTIR (neat) t 3024, 1830, 1753, 1630, 1606, 1508, 1314,
1165, 827; 1H NMR (300 MHz, CDCl3) d 7.50–7.48 (d, J ¼
8.9 Hz, 4H), 7.14–7.11 (d, J ¼ 8.9 Hz, 4H), 6.52–6.46 (d, 1H,
ACH¼¼CH2), 6.28–6.19 (d, 1H, trans-CH¼¼CH2), 5.98–5.95 (d,
1H, cis-CH¼¼CH2); 19F NMR (283 MHz, CDCl3) d ꢂ71.2 (s,
ACF3, 3F), ꢂ119.0 (dd, cis-CF¼¼CF2, 2F, Fa), ꢂ125.5 (dd,
[1,1-Bis(4-(1,2,2-trifluorovinyloxy)phenyl)-2,2,2-
trifluoroethyl]-6-bromohexanoate (M5)
trans-CF¼¼CF2, 2F, Fb), ꢂ134.2 (dd, ACF¼¼CF2, 2F, Fc) (Jab
¼
95.4 Hz, Jac ¼ 59.2 Hz, Jbc ¼ 111.8 Hz); 13C NMR (75.5 MHz,
M5 was obtained as a pale yellow oil in 45% yield. ATR–
FTIR (neat) t 3043, 2958, 2930, 1830, 1768, 1610, 1508,
1
2
CDCl3) d 162.5, 155.4, 146.9 (td, ACF¼¼CF2, J ¼ 274.0, J ¼
1
2
1
66.5 Hz), 133.1 (dt, ACF¼¼CF2, J ¼ 257.3 Hz, J ¼ 47.2 Hz),
133.0, 131.7, 130.5, 128.1, 125.9, 122.1, 115.5, 85.3 (q, J ¼
28.9 Hz, ACF3); HRMS (ESI–TOF) (m/z) [M þ Na]þ calcd. for
1314, 1165, 828; H NMR (300 MHz, CDCl3) d 7.45–7.48 (d,
J ¼ 8.9 Hz, 4H), 7.14–7.11 (d, J ¼ 8.9 Hz, 4H), 3.39 (t, J ¼
6.5 Hz, 2H, ACH2Br), 2.51 (t, J ¼ 7.2 Hz, 2H, ACOCH2A),
1.88–1.83 (m, 2H, ACH2A), 1.60–1.55 (m, 2H, ACH2A),
1.40–1.38 (m, 2H, ACH2A); 19F NMR (282.8 MHz, CDCl3) d
ꢂ70.9 (s, ACF3, 3F), ꢂ119.0 (dd, cis-CF¼¼CF2, 2F, Fa), ꢂ125.5
(dd, trans-CF¼¼CF2, 2F, Fb), ꢂ134.1 (dd, ACF¼¼CF2, 2F, Fc)
(Jab ¼ 95.4 Hz, Jac ¼ 59.2 Hz, Jbc ¼ 108.5 Hz); 13C NMR
C21H11O4F9, 521.0411; found, 521.042.
1,1-Bis(4-(1,2,2-trifluorovinyloxy)phenyl)-2,2,2-
trifluoroethyl Methacrylate (M2)
M2 was obtained as a pale yellow oil in 60% yield. ATR–
FTIR (neat) t 3024, 1832, 1753, 1636, 1610, 1508, 1315,
1165, 827; 1H NMR (300 MHz, CDCl3) d 7.50–7.47 (d, J ¼
8.9 Hz, 4H), 7.14–7.11 (d, J ¼ 8.9 Hz, 4H), 6.28 (s, cis-
CH¼¼CH2, 1H), 5.73 (s, trans-CH¼¼CH2, 1H), 1.98 (s,
AC(CH3)¼¼CH2, 3H); 19F NMR (283 MHz, CDCl3) d ꢂ71.2 (s,
ACF3, 3F), ꢂ119.0 (dd, cis-CF¼¼CF2, 2F, Fa), ꢂ125.6 (dd,
1
(75.5 MHz, CDCl3) d 169.7, 155.3, 147.6 (td, ACF¼¼CF2, J ¼
274.0, 2J ¼ 66.5 Hz), 133.5 (dt, ACF¼¼CF2, 1J ¼ 257.3 Hz,
2J ¼ 47.2 Hz), 132.2, 130.4, 125.9, 122.1, 115.5, 84.6 (q, J ¼
28.9 Hz, ACF3), 34.9, 33.3, 32.4, 27.5, 23.9; HRMS (ESI–TOF)
(m/z) [M þ Na]þ calcd. for C24H18O4F9Br, 643.0142; found,
643.0157.
trans-CF¼¼CF2, 2F, Fb), ꢂ134.1 (dd, ACF¼¼CF2, 2F, Fc) (Jab
¼
95.4 Hz, Jac ¼ 59.2 Hz, Jbc ¼ 108.5 Hz); 13C NMR (75.5 MHz,
General Polymerization and Copolymerization Procedure
Specified amounts of monomers were charged in a glass am-
poule previously flame-dried under vacuum. The ampoule
was vacuum sealed and then placed in a sand bath pre-
heated to 165 ꢀC or 175 ꢀC for 48 h. After cooling to room
temperature, the ampoule was then cracked and the crude
solid was dissolved into a minimum amount of THF and
then precipitated into a large excess of methanol, vacuum fil-
tered, washed liberally with MeOH, and dried in a vacuum
1
2
CDCl3) d 163.7, 155.4, 146.7, (td, ACF¼¼CF2, J ¼ 274.0, J ¼
66.5 Hz), 136.2, 133.7 (dt, ACF¼¼CF2, 1J ¼ 257.3 Hz, 2J ¼
47.2 Hz), 131.8, 130.5, 127.5, 126.0, 122.1, 115.5, 85.3 (q,
J ¼ 28.9 Hz, ACF3); GC–EIMS (70 eV) m/z (% relative inten-
sity) 512 (15, Mþ), 427 (30), 232 (30), 183 (35), 183 (35),
104 (10), 69 (100).
1,1-Bis(4-(1,2,2-trifluorovinyloxy)phenyl)-2,2,2-trifluoroethyl
Cyclopropanecarboxylate (M3)
ꢀ
M3 was obtained as a pale yellow oil in 50% yield. ATR–
FTIR (neat): t 3043, 2930, 1830, 1753, 1606, 1510, 1313,
1165, 827; 1H NMR (300 MHz, CDCl3) d 7.47–7.44 (d, J ¼
8.9 Hz, 4H), 7.14–7.11 (d, J ¼ 8.9 Hz, 4H), 1.82–1.77 (m, 1H,
ACHA), 1.04–0.93 (m, 4H, ACH2A); 19F NMR (283 MHz,
CDCl3) d ꢂ71.20 (s, ACF3, 3F), ꢂ119.0 (dd, cis-CF¼¼CF2, 2F,
Fa), ꢂ125.6 (dd, trans-CF¼¼CF2, 2F, Fb), ꢂ134.1 (dd,
ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac ¼ 59.2 Hz, Jbc ¼ 108.5
Hz); 13C NMR (75.5 MHz, CDCl3) d 171.1, 155.3, 147.3 (unre-
solved splitting of ACF¼¼CF2), 132.1, 130.4, 126.0, 122.0,
115.4, 84.5 (unresolved splitting of ACF3), 13.8, 9.0; HRMS
(ESI–TOF) (m/z) [M þ Na]þ calcd. for C22H13O4F9, 535.0568;
found, 535.0594.
oven at 60 C for 24 h.
PFCB Aryl Ether Polymer (P3)
ATR–FTIR (neat) t 3020, 1755, 1610, 1508, 1217, 955; 1H
NMR (300 MHz, CDCl3) d 7.44–7.38 (m, 4H), 7.06–7.04 (d,
J ¼ 8.3 Hz, 2H), 7.19–7.17 (d, J ¼ 8.3 Hz, 2H), 1.78–1.73 (m,
1H, ACHA), 0.96–0.90 (m, 4H, ACH2CH2A); 19F NMR (283
MHz, CDCl3) d ꢂ71.2 (s, ACF3, 3F), ꢂ119.0 (dd, residual cis-
CF¼¼CF2, 2F, Fa), ꢂ125.5 (dd, trans-CF¼¼CF2, 2F, Fb), ꢂ134.1
(dd, residual ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac ¼ 59.2 Hz,
Jbc ¼ 108.5 Hz), ꢂ127.3–(ꢂ132.7) (m, cyclobutyl-F6).
PFCB Aryl Ether Polymer (P4)
ATR–FTIR (neat) t 3020, 1750, 1608, 1508, 1217, 957; 1H
NMR (300 MHz, CDCl3) d 7.42–7.38 (m, 4H), 7.06–7.04 (d, J
¼ 6.9 Hz, 2H), 7.19–7.16 (d, J ¼ 8.6 Hz, 2H), 3.29–3.26 (m,
1H, ACHA), 2.26–2.21 (m, 4H, ACH2A), 1.98–1.85 (m, 2H,
ACH2A); 19F NMR (283 MHz, CDCl3) d ꢂ70.80 (s, ACF3, 3F),
ꢂ118.9 (dd, residual cis-CF¼¼CF2, 2F, Fa), ꢂ125.6 (dd, resid-
ual trans-CF¼¼CF2, 2F, Fb), ꢂ134.1 (dd, residual ACF¼¼CF2,
1,1-Bis(4-(1,2,2-trifluorovinyloxy)phenyl)-2,2,2-trifluoroethyl
Cyclobutanecarboxylate (M4)
M4 was obtained as a pale yellow oil in 51% yield. ATR–
FTIR (neat) t 3043, 2958, 1832, 1762, 1608, 1508, 1314,
1165, 830; 1H NMR (300 MHz, CDCl3) d 7.46–7.43 (d, J ¼
8.6 Hz, 4H), 7.13–7.10 (d, J ¼ 8.6 Hz, 4H), 3.35–3.30 (m, 1H,
FACILE ONE-POT SYNTHESIS, ZHU ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
SCHEME 1 One-pot synthesis of aryl bis-
trifluorovinyl ether (BTFVE) monomers.
Reagents and chemicals: (i) Mg/THF; (ii)
CF3COOCH3, 0–50 ꢀC, 1 h; (iii) RCOCl, 0 ꢀC,
r.t., 24 h.
2F, Fc) (Jab ¼ 95.4 Hz, Jac ¼ 59.2 Hz, Jbc ¼ 108.5 Hz),
ꢂ127.3–(ꢂ132.7) (m, cyclobutyl-F6).
ACH2A), 1.40–1.38 (m, 2H, ACH2A); 19F NMR (283 MHz,
CDCl3) d ꢂ70.9 (s, ACF3, 3F), ꢂ119.0 (dd, residual cis-
CF¼¼CF2, 2F, Fa), ꢂ125.5 (dd, residual trans-CF¼¼CF2, 2F, Fb),
PFCB Aryl Ether Polymer (P5)
ꢂ134.1 (dd, residual ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac
¼
ATR–FTIR (neat) t 3043, 2958, 1763, 1608, 1508, 1217,
955; 1H NMR (300 MHz, CDCl3) d 7.43–7.37 (m, 4H), 7.20–
7.17 (d, J ¼ 7.9 Hz, 2H), 7.08–7.05 (d, J ¼ 8.3 Hz, 2H), 3.35
(t, J ¼ 6.5 Hz, 2H, ACH2Br), 2.46 (t, J ¼ 7.2 Hz, 2H,
ACOCH2A), 1.84–1.80 (m, 2H, ACH2A), 1.64–1.60 (m, 2H,
ACH2A), 1.46–1.43 (m, 2H, ACH2A); 19F NMR (283 MHz,
CDCl3) d ꢂ70.84 (s, ACF3, 3F), ꢂ119.0 (dd, residual cis-
CF¼¼CF2, 2F, Fa), ꢂ125.4 (dd, residual trans-CF¼¼CF2, 2F, Fb),
59.2 Hz, Jbc ¼ 108.5 Hz), ꢂ127.3–(ꢂ132.7) (m, cyclobutyl-
F6).
RESULTS AND DISCUSSION
Aryl BTFVE compounds M1–M5 were synthesized from a
three-step ‘‘one-pot’’ procedure as shown in Scheme 1. The
sequence protocol followed (i) preparation of Grignard rea-
gent using 4-bromo(trifluorovinyloxy)benzene, (ii) quenching
with methyltrifluoroacetate, and (iii) addition of acyl chloride
to the Grignard adduct. This yielded pendent BTFVE com-
pounds M1–M5 in nearly quantitative yield based on conver-
sion using 19F NMR analysis (vide infra). Pendant groups in-
stalled on the monomers include reactive acrylates (M1 and
M2), strained cycloalkanes (M3 and M4), and 1-bromoalkane
(M5). Overall isolated yield of pure products using column
chromatography were moderate to good (45–65%). Elucida-
tion of all compounds was confirmed by 1H, 13C, and 19F
NMR, ATR–FTIR, and HRMS.
ꢂ134.1 (dd, residual ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac
¼
59.2 Hz, Jbc ¼ 108.5 Hz), ꢂ127.2–(ꢂ132.7) (m, cyclobutyl-
F6).
PFCB Aryl Ether Copolymer P(3-co-BP)
ATR-FTIR (neat): t 3043, 2958, 1762, 1608, 1508, 1217,
957; 1H NMR (300 MHz, CDCl3) d 7.44–7.38 (m), 7.06–7.04
(m), 7.19–7.17 (m), 1.78–1.73 (m, 1H, ACHA), 0.96–0.90 (m,
4H, ACH2CH2A); 19F NMR (283 MHz, CDCl3) d ꢂ70.7 (s,
ACF3, 3F), ꢂ119.2 (dd, residual cis-CF¼¼CF2, 2F, Fa), ꢂ125.7
(dd, residual trans-CF¼¼CF2, 2F, Fb), ꢂ134.2 (dd, residual
ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac ¼ 59.2 Hz, Jbc ¼ 108.5
Hz), ꢂ127.1–(ꢂ132.5) (m, cyclobutyl-F6).
1
Characteristic H, 13C, and 19F NMR peak shifts and splitting
patterns of compounds M1–M5 agreed with the reported
structures; this data is available in the Supporting Informa-
tion. From proton NMR spectra, the aromatic regions demon-
strate ABA’B0 system peaks characteristic of the 1,4-benzene
rings (J ¼ 8.9 Hz). The other proton peaks agree with pend-
ent groups attached to the carbon linkage via the carboxyl
ester. For 13C NMR, peak shifts at ca. 170.0 ppm support the
successful introduction of the carbonyl group (C¼¼O) of the
ester bond. The singlet at ꢂ71.0 ppm in the 19F NMR spectra
attributed to the ACF3 group attached to the carbon linkage
between the two benzene rings. The yield of the pendent
products was determined using this characteristic peak by
19F NMR, as its chemical shift was different from the tertiary
alcohol compound and methyltrifluoroacetate with diagnostic
peaks at ꢂ74.4 and ꢂ74.0 ppm, respectively (vide supra).
PFCB Aryl Ether Copolymer P(4-co-BP)
ATR–FTIR (neat): t 3043, 2958, 1766, 1608, 1508, 955; 1H
NMR (300 MHz, CDCl3) d 7.45–7.38 (m), 7.06–7.04 (m),
7.19–7.16 (m), 3.29–3.26 (m, 1H, ACHA), 2.26–2.21 (m, 4H,
ACH2A), 1.98–1.85 (m, 2H, ACH2A); 19F NMR (283 MHz,
CDCl3) d ꢂ70.9 (s, ACF3, 3F), ꢂ119.0 (dd, residual cis-
CF¼¼CF2, 2F, Fa), ꢂ125.5 (dd, residual trans-CF¼¼CF2, 2F, Fb),
ꢂ134.1 (dd, residual ACF¼¼CF2, 2F, Fc) (Jab ¼ 95.4 Hz, Jac
¼
59.2 Hz, Jbc ¼ 108.5 Hz), ꢂ127.3–(ꢂ133.7) (m, cyclobutyl-
F6).
PFCB Aryl Ether Copolymer P(5-co-BP)
ATR–FTIR (neat): t 3043, 2958, 1750, 1608, 1508, 1217,
956; 1H NMR (300 MHz, CDCl3) d 7.48–7.45 (m), 7.14–7.11
(m), 3.42–3.37 (m, 2H, ACH2Br), 2.53–2.49 (m, 2H,
ACOCH2A), 1.88–1.83 (m, 2H, ACH2A), 1.60–1.55 (m, 2H,
The aryl trifluorovinyl functional groups produce
a
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ARTICLE
FIGURE 2 ATR–FTIR (neat) overlay of (a) BTFVE monomer M3
conversion to (b) PFCB aryl ether homopolymer P3.
SCHEME 2 Thermal [2þ2] cyclopolymerization of BTFVE mono-
mers M3–M5 producing PFCB aryl ether homopolymers P3–P5
and copolymers (P(3-co-BP)-P(5-co-BP)).
approximately ꢂ74.0 ppm for all substrates that corre-
sponded to the ACF3 moiety of the tertiary alcohol com-
pound. The formation of this trace peak (<3–5%) appeared
at about ꢂ71.0 ppm. Furthermore, isolation of this minor
product by column chromatography proved difficult and its
characteristic AMX pattern at ꢂ119, ꢂ125, and ꢂ132 ppm
(JAM ¼ 59.2 Hz, JMX ¼ 95.4 Hz, JAX ¼ 108.5 Hz). Furthermore,
the molecular formula of all monomers was confirmed from
HRMS.
Attempts to install more sterically hindered substrates
such as 2,3,4,5,6-perfluorobenzene-carbonyl-, carbazole-9-
carbonyl-, fluorene-9-carbonyl-, or benzyl group via the
three-step ‘‘one pot’’ methodology was unsuccessful. Addition
of the corresponding acyl chlorides and upon aqueous work-
up only afforded the tertiary alcohol compound in quantita-
tive yield. These results were confirmed by 19F NMR that
only showed the exclusive formation of the single peak at
FIGURE 1 19F NMR overlay of (a) BTFVE monomer M3 conver-
sion to (b) PFCB aryl ether homopolymer P3 in CDCl3.
FIGURE 3 SEM (top) and optical microscope (bottom) images of
grating structure fabrication by direct photolithography of M1.
FACILE ONE-POT SYNTHESIS, ZHU ET AL.
1891

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
TABLE 1 Selected Properties of PFCB Aryl Ether Homopolymers and Copolymers
Polymer
Molar Feed Ratio 3–5:BP
Calculated Compositiona
Mn (PDI)b
Tg (ꢀC)c
Td (ꢀC)d
P3e
P4e
P5e
P(3-co-BP)f
P(4-co-BP)f
P(5-co-BP)f
a
1:0
1:0
17,050 (1.85)
27,090 (1.95)
12,700 (2.85)
56,100 (2.75)
56,500 (2.36)
27,860 (2.82)
108
108
58
397
363
299
387
372
302
1:0
1:0
1:0
1:0
1:1.4
1:1.4
1:1.4
1:1.3
1:1.38
1:1.6
d
86
90
64
Based on 1H NMR integration.
TGA onset (10 ꢀC/min) of chain extended polymers in nitrogen.
b
c
e
f
GPC in CHCl3 using polystyrene as standard.
DSC (10 ꢀC/min) in nitrogen determined by second heating cycle.
165 ꢀC for 48 h.
175 ꢀC for 48 h.
identity remains unclear. Therefore, we attribute the inability
to introduce these electrophiles is possibly due to their
highly hindered structure in addition to the less reactive
Grignard adduct.28
M1 was used to initially prepare photodefinable materials.
Preliminary studies showed M2 undergoes bulk photopoly-
merization to produce insoluble polymers that where shown
to swell in CHCl3 and toluene. Photodefinable core layers
were then prepared using a liquid, bulk mixture of monomer
M1 and 3 wt % 2,2-diethoxyacetophenone (DEAP) as the
photoinitiator. A spin cast film on a Si wafer was exposed to
an UV light (k ¼ 365 nm, 5.8 mJ/s) through the photomask
for 200 s. The pattern was finally developed by washing off
the unreacted monomer with hexanes. The resulting pattern
was postcured at 90 ꢀC for 2 h and at 200 ꢀC for 2 h. The
final pattern structures are shown in Figure 3. The grating
has a width of 15 lm and spacing of 40 lm. This prelimi-
nary study showed the successful preparation of photodefin-
able PFCB aryl ether material utilizing acrylate functionality.
Future work to optimize the system is ongoing.
Aryl BTFVE monomers (M3–M5) were then thermally homo-
ꢀ
polymerized in bulk at 165 C for 48 h to afford high mole-
cular weight PFCB aryl ether polymers (P3–P5) (Scheme 2).
Homopolymerization in excess of 180 ꢀC at extended reac-
tions times greater than 24 h produced insoluble gels. On
the other hand, the aryl BTFVE monomers were also copoly-
merized at 175 ꢀC with 4,40-bis(4-trifluorovinyloxy)biphenyl
(BP) to afford the respective PFCB aryl ether copolymers
P(3-co-BP)–P(5-co-BP). The linear cyclopolymerization was
monitored by 19F NMR and ATR–FTIR spectroscopy. 19F
NMR showed the quantitative conversion of the aryl trifluoro-
vinyl ether AMX pattern to the PFCB aryl ether ring multi-
plets (Figure 1). The multiplet for the PFCB aryl ether ring
afforded predominately head-to-head formation of stereoran-
dom isomers.21,29 Also, the polymerization was followed by
ATR–FTIR as shown in Figure 2. The overlay clearly shows the
disappearance of the fluoroolefin stretch at about 1830 cmꢂ1
and formation of the characteristic PFCB aryl ether breathing
Table 1 shows selected physical properties of PFCB aryl
ether homopolymers (P3–P5) and copolymers (P(3-co-BP)–
P(5-co-BP)). The linear, step-growth polymers and copoly-
mers were produced in moderate to high number-average
molecular weight (Mn) each with a narrow polydispersity
index (PDI). The resulting polymers are solution processable
in common organic solvents (e.g., CHCl3, THF, and acetone)
to produce optically transparent, free-standing films. The
nature of the stereorandom PFCB aryl ether polymer
afforded entirely amorphous polymers with glass transition
1
mode vibration at 960 cmꢂ1. Both H and 19F NMR and ATR–
FTIR indicated the conversion to PFCB aryl ether polymers or
copolymers with functional groups intact.
The direct polymerization of acrylate-containing monomers
(M1 and M2) or even copolymerization with 4,40-bis(trifluoro-
vinyloxy)biphenyl (BP) was unsuccessful. Even polymeriza-
tions at lower temperatures (150 ꢀC) produced insoluble mate-
rial indicating the possibility of a network structure. DSC
analysis showed monomers M1 and Mꢀ2 displayed two discrete
ꢀ
temperatures (Tg) ranging 58–108 C. Copolymerization with
BP showed significantly lower Tg’s compared with the homo-
polymers. The introduction of pendant functional groups did
not appear to jeopardize the thermal stability of the poly-
mers as the thermal decomposition at onset (Td) in nitrogen
is comparable to typical PFCB aryl ether polymer systems.
ꢀ
exothermic peaks at 110 C and 150 C which may be attrib-
uted to the thermal activation of the acrylate group
(ACH¼¼CH2) and fluoroolefin (ACF¼¼CF2), respectively (see
Supporting Information, Figure S9). It is well known that aryl
TFVEs, in general, do not appreciably undergo high molecular
weight polymerization through free radical initiation.30,31
CONCLUSIONS
We prepared five functionally diverse aryl BTFVE monomers
with reactive pendant moieties by way of a simple, facile
three step ‘‘one-pot’’ procedure in moderate to good isolated
yields. These monomers underwent bulk homo- and copoly-
merization to afford high molecular weight, thermally robust
PFCB aryl ether polymers. The ability to solution process
these polymers into transparent, free-standing films makes
them attractive for a multitude of patterning and optical
applications. In particularly, pendant acrylate aryl BTFVE
Another strategy was considered by first initiating side-chain
acrylate polymerization of monomers M1 (or M2) followed
by post-PFCB aryl ether polymerization. An analogous strat-
egy has been reported by others for the preparation of PFCB
aryl ether polymers in concomitant atom transfer radical poly-
merization (ATRP).32,33 In the present study, liquid monomer
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ARTICLE
15 Jin, J.; Smith, D. W., Jr.; Topping, C. M.; Suresh, S.; Chen,
S.; Foulger, S. H.; Rice, N.; Nebo, J.; Mojazza, B. H. Macromole-
cules 2003, 36, 9000–9004.
monomers can be used in photolithography templating fol-
lowed by thermal curing producing PFCB aryl ether cross-
linked networks. Furthermore, pendant cycloalkanes and the
1-bromoalkane PFCB aryl ether polymers are anticipated to
undergo postfunctionalization by nucleophilic substitution.
This strategy is the focus of our continued work.
16 Jin, J. Y.; Topping, C. M.; Suresh, S.; Foulger, S. H.;
Rice, N.; Mojazza, B. H.; Smith, D. W. Polymer 2005, 46,
6923–6932.
17 Jin, J. Y.; Smith, D. W.; Glasser, S.; Perahia, D.; Foulger, S.
H.; Ballato, J.; Kang, S. W.; Kumar, S. Macromolecules 2006,
39, 4646–4649.
This work was supported by the Defense Advanced Research
Projects Agency (DARPA) and the National Science Foundation
(DMR 9985160). J.J. would like to thank Dr. Gregory Nordin
(BYU) for providing the photolithography facility.
18 Smith, D. W.; Boone, H. W.; Traiphol, R.; Shah, H.; Perahia,
D. Macromolecules 2000, 33, 1126–1128.
19 Iacono, S. T.; Budy, S. M.; Jin, J.; Smith, D. W. J Polym Sci
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