Synthesis and characterization of a novel perfluorocyclobutyl aromatic ether-based ABA triblock copolymer

Article abstract of DOI:10.1021/ma0504062

A novel perfluorocyclobutyl aromatic ether-based ABA triblock copolymer (A: polystyrene block; B: perfluorocyclobutyl aromatic ether-based fluoropolymer block) was synthesized by combination of atom transfer radical polymerization (ATRP) of styrene and th

Full text of DOI:10.1021/ma0504062

Macromolecules 2005, 38, 7299-7305
7299
Synthesis and Characterization of a Novel Perfluorocyclobutyl Aromatic
Ether-Based ABA Triblock Copolymer
Xiaoyu Huang,*,† Guolin Lu,† Dan Peng,† Sen Zhang,† and Feng-ling Qing*,†,‡
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese
Academy of Sciences, 354 Fenglin Road, Shanghai 200032, P. R. China, and College of Chemistry and
Chemical Engineering, Donghua University, 1882 Yan’an Road (west), Shanghai 200051, P. R. China
Received February 25, 2005; Revised Manuscript Received June 22, 2005
ABSTRACT: A novel perfluorocyclobutyl aromatic ether-based ABA triblock copolymer (A: polystyrene
block; B: perfluorocyclobutyl aromatic ether-based fluoropolymer block) was synthesized by combination
of atom transfer radical polymerization (ATRP) of styrene and thermal step-growth cycloaddition
polymerization of trifluorovinyl monomer. We first synthesized a new ATRP initiator containing the
trifluorovinyl group, which can initiate ATRP of styrene in a controlled way to obtain well-defined
polystyrene with narrow molecular weight distribution (Mw/Mn < 1.10). The apparent polymerization
rate exhibited first-order relation with respect to the concentration of monomer and the molecular weight
increases linearly with the conversion of monomer. Second, fluoropolymer containing a perfluorocyclobutyl
aromatic ether unit was prepared by solution polymerization and followed by reacting with ATRP initiator
containing a trifluorovinyl group to get ATRP macroinitiator with two initiation groups at both ends.
The macroinitiator-initiated ATRP of styrene to obtain ABA triblock copolymer. The copolymer shows
excellent solubility in conventional solvents.
Introduction
PFCB thermoplastic polymers. Also, thermoset PFCB
polymers were prepared from the monomers containing
three trifluorovinyl groups, which were also synthesized
from 1,3,5-trihydroxybenzene and 1,1,1-tri(4-hydroxy-
phenyl)ethane. So the synthesis strategy using PFCB
combined the flexible, yet thermally robust, aromatic
ethers with fluorocarbon linkage, thereby providing
fluoropolymers which are easily processed from solution
or melt.
Because of much higher polymerization temperature
(>150 °C) and much different polymerization mecha-
nism ([2 + 2] cycloaddition) without any initiator
compared with those of common used monomers, poly-
mer chemists only studied the homopolymerization and
random copolymerization of different trifluorovinyl mono-
mers. Research about combining trifluorovinyl monomer
and common used monomer (styrene, acrylate, etc.) into
block copolymer has never been reported until now. So
the application of PFCB fluoropolymers has been obvi-
ously limited.
Generally, two strategies have been employed to
synthesis block copolymer: sequential feeding of differ-
ent monomers through living polymerization, including
anionic polymerization,10 cationic polymerization,11 group
transfer polymerization,12 living radical polymeriza-
tion,13 etc.; also mechanism transformation strategy14
was used to synthesize block copolymers containing the
blocks with different polymerization mechanisms. Be-
cause the polymerization mechanism of trifluorovinyl
monomer is entirely different from the common used
monomer, only mechanism transformation strategy can
be used to prepare block copolymer from trifluorovinyl
monomer and the common used monomer.
In this paper, we reported the synthesis of a novel
perfluorocyclobutyl aromatic ether-based ABA triblock
copolymer 1 (A: polystyrene block; B: perfluorocyclobu-
tyl aromatic ether-based fluoropolymer block) (Scheme
1) through mechanism transform strategy. This kind of
triblock copolymer is the first example of block copoly-
It is well-known that fluoropolymers have many
advantages compared with general commercial poly-
mers only containing carbon, hydrogen, and oxygen due
to the incorporation of fluorocarbon functionality, in-
cluding increased thermal and oxidative stability, opti-
cal transparency, solvent compatibility, environmental
stability, etc.1 So the application of fluoropolymers with
high performance have taken on great significance in
recent years. However, low processability limited the
use of fluoroplymers.2 Recently, some scientists of The
Dow Chemical Co. obtained fluoropolymers containing
perfluorocyclobutane (PFCB) linkage by step-growth
cycloaddition polymerization of aryl trifluorovinyl ether
monomers.3
PFCB polymers have the conventional properties of
fluoropolymer such as low dielectric constant, low
moisture absorption, low surface energy, high thermal/
oxidative stability, and high chemical resistance, also
possessing many other advantages including optical
transparency, improved processability, and thermal
mechanical properties.4-6 PFCB aromatic ether poly-
mers are generally synthesized by step-growth cyclo-
addition polymerization of trifluorovinyl monomers in
bulk or solution above 150 °C without any initiator and
catalyst. Recent studies of PFCB polymers focused on
the use of the thermal polymerization of different aryl
trifluorovinyl ether monomers to obtain different ho-
mopolymers and random copolymers containing PFCB
aromatic ether linkage.7-9 Monomers containing two
trifluorovinyl groups were synthesized from commer-
cially available raw materials, such as 1,3-dihydroxy-
benzene, 4,4′-biphenol, and 2,2-bis(p-hydroxyphenyl)-
perfluoropropane, and were polymerized to form different
† Chinese Academy of Sciences.
‡ Donghua University.
* To whom correspondence should be addressed: e-mail
xyhuang@mail.sioc.ac.cn or flq@ mail.sioc.ac.cn.
10.1021/ma0504062 CCC: $30.25 © 2005 American Chemical Society
Published on Web 07/23/2005

7300 Huang et al.
Scheme 1. ABA Triblock Copolymer 1
Macromolecules, Vol. 38, No. 17, 2005
Scheme 3. Synthesis of Model Polystyrene 6
Scheme 2. Synthesis of ATRP Initiator 2
aluminum chloride (AlCl3) (3.1268 g, 23.4 mmol). The solution
was heated to reflux for 8 h, then the flask was cooled to 0 °C,
and granular ice was added to terminate the reaction. 1 N HCl
(80 mL) was added, and the organic layer was separated. The
organic layer was washed by brine (50 mL × 3) followed by
drying over MgSO4. A straw yellow solid, ATRP initiator 2,
2-bromo-1-(p-trifluorovinyloxy)phenylpropan-1-one (2.5566 g,
44.0%), was obtained by silica column chromatography. 1H
NMR (300 MHz, CDCl3): δ (ppm): 1.89 (d, J ) 6.3 Hz, 3H),
5.24 (q, J ) 6.6 Hz, 1H), 7.18 (d, J ) 8.7 Hz, 2H), 8.07 (d, J )
9.0 Hz, 2H). 19F NMR (282 MHz, CDCl3): δ (ppm): -119.0 (dd,
1F), -125.6 (dd, 1F), -135.0 (dd, 1F). 13C NMR (300 MHz,
acetone-d6): δ (ppm): 20.2 (-CH3), 42.9 (-CHBr), 116.5, 129.7,
132.0, 132.4, 129.7-136.3 (-CFdCF2), 143.9-152.0 (-CFd
CF2), 159.0, 192.0 (-CdO). FT-IR (KBr): ν (cm-1): 3023, 2983,
2923, 1835 (OCFdCF2), 1689, 1601, 1505, 847. Anal. Calcd
for C11H8F3BrO2: C, 42.75%; H, 2.61%; F, 18.44%; Br, 25.85%.
Found: C, 42.79%; H, 2.64%; F, 18.59%; Br, 25.77%. ESI-MS
(m/z): calcd 309.1; found 309.2.
mer containing perfluorocyclobutyl aromatic ether unit.
All compounds in this paper were characterized by FT-
IR, GPC, 1H NMR, 13C NMR, 19F NMR, MS, and
element analysis in detail.
Experimental Section
Materials. Styrene (St, Aldrich, 99%) was washed with 5%
aqueous NaOH solution to remove inhibitor and then with
water, dried with MgSO4, and distilled twice over CaH2 under
reduced pressure before use. Copper(I) bromide (CuBr, Aldrich,
98%) was purified by stirring overnight over CH3CO2H at room
temperature, followed by washing the solid with ethanol,
diethyl ether, and acetone prior to drying at 40 °C under
vacuum for 1 day. 4,4′-Biphenol (97%) was purchased from
Aldrich and purified by recrystallization before use. 1,2-
Dibromotetrafluoroethane was prepared by condensing equimo-
lar amounts of bromine and tetrafluoroethylene at -195 °C
followed by warming up to 22 °C.15 Granular zinc was activated
by washing in 0.1 N HCl followed by drying at 140 °C under
vacuum for 10 h. Phenol (Aldrich, 99+%), N,N,N′,N′,N′′-
pentamethyldiethylenetriamine (PMDETA, Aldrich, 99%), and
2-bromopropionyl chloride (Acros, 98%) were used as received.
Measurements. FT-IR spectra were recorded on a Nicolet
AVATAR-360 FT-IR spectrophotometer with 4 cm-1 resolution.
1H NMR and 13C NMR were performed on a Varian Mercury
300 spectrometer (300 MHz). 19F NMR was collected on a
Bruker AM-300 spectrometer using trifluoroacetic acid as
external standard. ESI-MS were measured by an Agilent LC/
MSD SL system. Relative molecular weights and molecular
weight distributions (Mw/Mn) were measured by a Waters gel
permeation chromatography (GPC) system equipped with a
Waters 1515 Isocratic HPLC pump, a Waters 2414 refractive
index detector (RI), a Waters 2487 dual λ absorbance detector
(UV), and a set of Waters Styragel columns (HR3, HR4, and
HR5, 7.8 × 300 mm). GPC measurements were carried out at
35 °C using tetrahydrofuran (THF) as eluent with a 1.0 mL/
min flow rate. The system was calibrated with polystyrene
standards. Elemental analysis was carried out on a Carlo-
Erba1106 system. Monomer conversion was determined by GC
using a HP 6890 system with an SE-54 column.
ATRP Initiator 2. ATRP initiator 2 was synthesized
according to Scheme 2 by three steps using phenol as starting
material. Synthesis of (1,2,2-trifluorovinyloxy)benzene (5) was
similar to those reported procedures in previous literature.16
The yield is 47.0%. 1H NMR (300 MHz, CDCl3): δ (ppm): 7.09
(d, J ) 8.4 Hz, 2H), 7.17 (t, J ) 7.2 Hz, 1H), 7.38 (t, J ) 7.2
Hz, 2H). 19F NMR (282 MHz, CDCl3): δ (ppm): -120.5 (dd,
1F), -127.2 (dd, 1F), -134.2 (dd, 1F). Anal. Calcd for
C8H5F3O: C, 55.18%; H, 2.89%. Found: C, 55.15%; H, 2.90%.
ESI-MS (m/z): calcd 174.1; found 174.0.
To a 250 mL dried three-neck round-bottom flask fitted with
a condenser and a thermometer, (1,2,2-trifluorovinyloxy)-
benzene (5) (3.2665 g, 18.8 mmol) and carbon disulfide (CS2)
(50 mL) were added under a N2 atmosphere followed by adding
2-bromopropionyl chloride (2.2 mL, 3.74 g, 21.8 mmol) and
Model Polystyrene 6 Initiated by 2. ATRP of styrene can
be initiated by 2 (Scheme 3) to get polystyrene with narrow
molecular weight distribution. A typical procedure of synthesis
of model polystyrene 6 by bulk polymerization is listed as
follows: to a 25 mL Schlenk flask (flame-dried under vacuum
just before use) sealed with a rubber septum, CuBr (0.1342 g,
0.936 mmol) was charged under a N2 atmosphere. After three
cycles of evacuating and backfilling with N2, styrene (10 mL,
87.0 mmol), PMDETA (0.196 mL, 0.939 mmol), and 2 (0.2889
g, 0.935 mmol) were introduced via a gastight syringe followed
by three cycles of freezing-pumping-thawing. The mixture
was stirred at room temperature for 30 min so that the mixture
became homogeneous. The flask was placed in an oil bath at
110 °C for polymerization. The polymerization was quenched
by immersing the flask in liquid N2 after 8 h. THF was added
to dissolve the viscous crude product, and the solution was
filtered through a short Al2O3 column to remove the catalyst.
The resulting solution was concentrated and precipitated in
methanol. The solid was purified by three times of dissolution
and precipitation, followed by drying under vacuum to obtain
7.9261 g of polystyrene of 87.5% yield, Mn ) 15 100, Mw/Mn )
1.12. FT-IR (KBr): ν (cm-1): 3025, 2983, 2923, 1601, 1493,
1452, 757, 698.
ATRP Kinetics. ATRP kinetics of styrene initiated by 2
was studied in solution polymerization using diphenyl ether
as solvent.17 CuBr (0.0824 g, 0.575 mmol) and diphenyl ether
(10 mL) were charged to a 25 mL Schlenk flask sealed with a
rubber septum under a N2 atmosphere. After three cycles of
evacuating and backfilling with N2, styrene (5 mL, 43.5 mmol),
PMDETA (0.12 mL, 0.575 mmol), and ATRP initiator 2 (0.1778
g, 0.575 mmol) were introduced via a gastight syringe followed
by three cycles of freezing-pumping-thawing. The mixture
was stirred at room temperature for 30 min until the mixture
became homogeneous. Then, the first sample taken as a time
) 0 data point was obtained by withdrawing 0.50 mL of
solution from the flask using a purged syringe and adding to
2.00 mL of THF. The flask was immersed into an oil bath at
110 °C. At every time interval (1.0 h), a 0.50 mL sample
solution was taken and added to 2.00 mL of THF.
Every sample solution in THF taken at different time was
injected into GC to determine the monomer conversion com-
pared with the time ) 0 data point. The remaining solution
was filtered through a short Al2O3 column to remove the
catalyst and then used for GPC measurement to determine
the molecular weight and molecular weight distribution.

Macromolecules, Vol. 38, No. 17, 2005
ABA Triblock Copolymer 7301
Scheme 4. Synthesis of Model Dimer 7
2F), -126.8 (dd, 2F), -134.3 (dd, 2F). Anal. Calcd for
C16H8F6O2: C, 55.50%; H, 2.33%. Found: C, 55.47%; H, 2.30%.
ESI-MS (m/z): calcd 346.2; found 346.3.
ATRP Macroinitiator 11. ATRP macroinitiator 11 was
synthesized through intramolecular [2 + 2] cycloaddition of
the trifluorovinyl ether group of ATRP initiator 2 and the
trifluorovinyl ether end group of propagating chain of poly-
(4,4′-bis(trifluorovinyloxy)biphenyl) at both ends (Scheme 6).
A typical procedure of synthesis of ATRP macroinitiator 11
is listed as follows: To a predried 25 mL Schlenk flask sealed
with a rubber septum, trifluorovinyl monomer 8 (4.0855 g, 11.8
mmol) and diphenyl ether (6 mL) were added under a N2
atmosphere and followed by three cycles of freezing-pump-
ing-thawing. The flask was placed in an oil bath at 200 °C
for polymerization. After 4 h, ATRP initiator 2 (3.9000 g, 12.6
mmol) in 5 mL of diphenyl ether was charged using a gastight
syringe. The reaction lasted for another 6 h and was quenched
by immersing the flask in liquid N2. Dichloromethane (20 mL)
was added to dilute the solution, and the solution was added
to 300 mL of methanol to precipitate the solid product. The
crude product was purified by three times of dissolution and
precipitation to separate any possible dimer 7, followed by
drying under vacuum to obtain 7.2395 g of solid. Mn ) 7500,
Mw/Mn ) 1.31, Br% ) 2.18%. FT-IR (KBr): ν (cm-1) 1693 (-Cd
O), 1607, 1497, 962, 824.
ABA Triblock Copolymer 1. Perfluorocyclobutyl aromatic
ether-based ABA triblock copolymer 1 (A: polystyrene block;
B: perfluorocyclobutyl aromatic ether-based fluoropolymer
block) was synthesized by ATRP of styrene initiated by ATRP
macroinitiator 11 (Scheme 7).
The procedure of synthesis of ABA triblock copolymer
initiated by 11 is similar to that of synthesis of model
polystyrene initiated by 2: ATRP macroinitiator 11 and CuBr
were added to a 25 mL Schlenk flask (flame-dried under
vacuum just before use) sealed with a rubber septum under a
N2 atmosphere. After three cycles of evacuating and backfilling
with N2, styrene, PMDETA, and diphenyl ether were intro-
duced via a gastight syringe followed by three cycles of
freezing-pumping-thawing. The mixture was stirred at room
temperature for 10 min so that the mixture became homoge-
Model Dimer 7. Model dimer 7 was synthesized through
intramolecular [2 + 2] cycloaddition of the trifluorovinyl ether
group of ATRP initiator 2 (Scheme 4).
To a 10 mL predried Schlenk flask, ATRP initiator 2 (0.3740
g, 1.21 mmol) and diphenyl ether (1.50 mL) were added under
a N2 atmosphere followed by three cycles of freezing-pump-
ing-thawing. The solution was heated at 200 °C for 6 h. The
reaction was quenched by immersing the flask in liquid N2.
Model dimer 7 (0.3180 g, 85.0%), a light yellow liquid, was
obtained by silica column chromatography. 1H NMR (300 MHz,
CDCl3): δ (ppm): 1.90 (d, J ) 6.6 Hz, 6H), 5.23 (q, J ) 6.3
Hz, 2H), 7.18 (d, J ) 8.7 Hz, 2H), 7.30 (d, J ) 8.4 Hz, 2H),
8.07 (t, J ) 8.4 Hz, 4H). 19F NMR (282 MHz, CDCl3): δ (ppm):
-127.2 to -132.8 (m, cyclobutyl-F6). 13C NMR (300 MHz,
acetone-d6): δ (ppm): 20.0 (-CH3), 42.2 (-CHBr), 105.0-115.2
(m, cyclobutyl), 116.5, 129.7, 132.0, 132.4, 159.0, 191.7 (-Cd
O). λmax ) 327 nm. Anal. Calcd for C22H16F6Br2O4: C, 42.75%;
H, 2.61%. Found: C, 42.82%; H, 2.57%. ESI-MS (m/z): calcd
618.2; found 618.3.
Trifluorovinyl Monomer 8. Trifluorovinyl monomer 8,
4,4′-bis(trifluorovinyloxy)biphenyl, was synthesized according
to Scheme 5. The procedure was similar to those of previous
literature.18 The product was separated by column chroma-
tography with a yield of 42.8%. Next, it was purified by
recrystallization from ethanol/water to obtain the trifluorovinyl
1
monomer 8 of 99.8% purity measured by GC. H NMR (300
MHz, CDCl3): δ (ppm): 7.19 (d, J ) 9.0 Hz, 4H), 7.55 (d, J )
8.7 Hz, 4H). 19F NMR (282 MHz, CDCl3): δ (ppm): -119.8 (dd,
Scheme 5. Synthesis of Trifluorovinyl Monomer 8
Scheme 6. Synthesis of ATRP Macroinitiator 11

7302 Huang et al.
Macromolecules, Vol. 38, No. 17, 2005
Scheme 7. Synthesis of ABA Triblock Copolymer 1
neous. The flask was placed in an oil bath at 110 °C for
polymerization. The polymerization was quenched by immers-
ing the flask in liquid N2 after 6 h. THF was added to dilute
the solution, and the solution was filtered through a short
Al2O3 column to remove the catalyst. The resulting solution
was concentrated and precipitated in methanol. The solid was
purified by three times of dissolution and precipitation,
followed by drying under vacuum.
0.35% of fluorine and 0.42% of bromine determined by
titration. All these evidences confirmed that model
polystyrene 6 was initiated by 2 and contained a
trifluorovinyl end group.
To make sure whether the polymerization of styrene
initiated by 2 is atom transfer radical polymerization,
we studied polymerization kinetics by GC to obtain a
semilogarithmic plot of ln([M]0/[M]) vs time (Figure 2).
From Figure 2, we can conclude that the apparent
polymerization rate is first order with respect to the
monomer concentration, which is same as the common
ATRP. The apparent rate coefficient (kapp ) 7.3 × 10-5
s-1) is determined from the slope of the kinetic plot.
The evolution of molecular weights and molecular
weight distributions with monomer conversion is shown
in Figure 3. It is obvious that molecular weights
increase linearly with monomer conversion and are very
close to the expected molecular weights (solid line in
Figure 3). Also, the molecular weight distributions
remained low throughout the polymerization (Mw/Mn <
1.15). These two phenomena also accord with the
characteristics of ATRP.
Results and Discussion
ATRP of Styrene Initiated by 2. We used the
traditional method to synthesize compound 5 containing
trifluorovinyl in two steps from commercially available
phenol via fluoroalkylation with BrCF2CF2Br followed
by Zn-mediated elimination.19,20 Next, the ATRP initia-
tion group -COCHBrCH3 was introduced by Friedel-
Crafts reaction so that compound 5 was transformed
into ATRP initiator 2 with trifluorovinyl.
Compound 2 initiated the polymerization of styrene
to obtain model polystyrene 6 with narrow molecular
weight distribution. Model polystyrene 6 was character-
ized by 1H NMR and 19F NMR. As shown in Figure 1A,
we can find the typical 1H NMR signals of polystyrene:
the peaks at 6.60 and 7.09 ppm attributed to the
benzene ring of polystyrene and the peaks at 1.45 and
1.84 ppm attributed to the -CH2- and -CH- units of
polystyrene. We also can find a minor peak at 4.40 ppm,
the signal of -CHBr end group of polystyrene, and a
peak at 0.90 ppm, the signal of methyl of -COCH-
(CH3)-PS. Figure 1B depicts its 19F NMR spectrum of
model polystyrene 6 in CDCl3; the resonance signals of
the -OCFdCF2 group appeared, including -117.6,
-124.3, and -134.3 ppm. We also found that model
polystyrene 6 (Mn ) 15 100, Mw/Mn ) 1.12) comprised
So we can confirm that ATRP of styrene can be
initiated by 2 to obtain polystyrene containing trifluo-
rovinyl end group with narrow molecular weight dis-
tribution.
Synthesis and Characterization of Macroinitia-
tor. Since we must employ a mechanism transformation
Figure 2. Kinetic plot for solution ATRP of styrene initiated
by 2 at 110 °C: [styrene]0 ) 4.35 M, [CuBr]0 ) [PMDETA]0 )
Figure 1. 1H NMR (A) and 19F NMR (B) of model polystyrene
6 in CDCl3.
[initiator]0 ) 0.0575 M, kapp ) 7.3 × 10-5 s-1
.

Macromolecules, Vol. 38, No. 17, 2005
ABA Triblock Copolymer 7303
Figure 5. 19F NMR of model dimer 7 (A) and ATRP initiator
2 (B) in CDCl3.
Figure 3. Dependence of molecular weight (Mn) and molec-
ular weight distribution (Mw/Mn) on monomer conversion for
solution ATRP of styrene initiated by 2 at 110 °C: [styrene]0
) 4.35 M, [CuBr]0 ) [PMDETA]0 ) [initiator]0 ) 0.0575 M.
Figure 6. 13C NMR of macroinitiator 11 (A) and ATRP
initiator 2 (B) in acetone-d6.
which are same as those of ATRP initiator 2 shown in
Figure 4B. We also find two peaks at 7.18 and 7.30 ppm
attributed to other protons of benzene ring close to the
perfluorocyclobutyl. Figure 5A depicts the 19F NMR
spectrum of model dimer 7. A series of peaks between
-127.2 and -132.8 ppm appeared which denoted per-
fluorocyclobutyl; compared with the 19F NMR spectrum
of ATRP initiator 2 shown in Figure 5B, we cannot find
the resonance signals of trifluorovinyl including -119.0,
-125.6, and -134.3 ppm. So we can confirm that ATRP
initiation group, -COCH(CH3)-Br, is stable at 200 °C,
and the trifluorovinyl of compound 2 is easy to run
intermolecular [2 + 2] cycloaddition to form perfluoro-
cyclobutyl by heating.
Next, we synthesized ATRP macroinitiator 11 with
two initiation groups at both ends by reacting ATRP
initiator 2 with propagating chain of trifluorovinyl
monomer 8 according to Scheme 6. Its chemistry
structure was confirmed by 1H NMR and 13C NMR. As
shown in Figure 4C, we still find the minor peaks of
-COCH(CH3)-Br, -COCH(CH3)-Br, and the protons
of benzene ring close to the carbonyl at both ends at
1.88, 5.21, and 8.05 ppm, which are the same as those
of ATRP initiator 2. We also find two new strong peaks
at 7.21 and 7.48 ppm attributed to the protons of
benzene ring of 4,4′-biphenylene perfluorocyclobutyl
ether repeating unit. Figure 6A displays the 13C NMR
spectrum of ATRP macroinitiator 11 in acetone-d6; the
Figure 4. 1H NMR of model dimer 7 (A), ATRP initiator 2
(B), and macroinitiator 11 (C) in CDCl3.
strategy to synthesize perfluorocyclobutyl aromatic
ether-based ABA triblock copolymer (A: polystyrene
block; B: perfluorocyclobutyl aromatic ether-based fluo-
ropolymer block), we need to synthesize perfluorocy-
clobutyl aromatic ether-based prepolymer with ATRP
initiation groups at both ends, which can initiate ATRP
of styrene to obtain the polymer we desired. We de-
signed the synthesis route as shown in Scheme 6, so
the key points are whether the ATRP initiation groups
of compound 2 are stable at a high temperature (200
°C) for some time and whether the trifluorovinyl of
compound 2 can react with the trifluorovinyl of propa-
gating chain at both ends. The easiest way to get
answers is to run model reaction of compound 2 by
heating at 200 °C for 6 h. We obtained a dimeric product
7 containing two ATRP initiation groups at both ends
and perfluorocyclobutyl with high yield (85.0%). The
1
dimeric product 7 was characterized by H NMR and
1
19F NMR. Figure 4A shows the H NMR spectrum of
model dimer 7; the peaks of -COCH(CH3)-Br and
-COCH(CH3)-Br and the protons of benzene ring close
to the carbonyl appeared at 1.90, 5.23, and 8.07 ppm,

7304 Huang et al.
Macromolecules, Vol. 38, No. 17, 2005
Figure 7. GPC curve of macroinitiator 11 (A) and model
dimer 7 (B).
Figure 8. 1H NMR of ABA triblock copolymer 1 in acetone-
d6.
Table 1. Synthesis of ABA Triblock Copolymers 1 by
Solution Polymerizationa
), and 6.53, 6.93 ppm (benzene ring). The polymerization
product was also characterized by FT-IR to find a sharp
band at 962 cm-1 attributed to perfluorocyclobutyl unit,
and the typical signals of polystyrene segment appeared
at 3026, 2924, 2850, 1603, 1495, and 1453 cm-1. Also,
the sharp band at 825 cm-1 demonstrated the para-
disubstituted benzene ring of the PFCB block; other two
sharp peaks at 698 and 757 cm-1 confirmed the mono-
substituted benzene ring of polystyrene block.
c
run
[M]:[I]b
time (h)
temp (°C)
Mn (g/mol)c
Mw/Mn
1
2
3
4
100:1
300:1
300:1
300:1
8
8
17
48
110
110
110
110
8 300
8 900
15 500
17 900
1.34
1.29
1.27
1.24
a Macroinitiator: Mn ) 7500, Mw/Mn ) 1.31, Br ) 2.18%. b The
ratio of the moles of monomer and ATRP initiation group.
c Measured by GPC under 35 °C.
All these evidence confirmed the synthesis of ABA
triblock copolymer 1 (A: polystyrene block; B: perfluo-
rocyclobutyl aromatic ether-based fluoropolymer block).
Solubility Tests. Solubility tests were performed for
ABA triblock copolymer 1 with different molecular
weights in four conventional solvents with low boiling
point: tetrahydrofuran, chloroform, dichloromethane,
and acetone. The results indicated that ABA triblock
copolymer 1 exhibits excellent solubility in the above
four solvents.
peaks at 20.0, 43.0, and 192.0 ppm are attributed to
-CH3, -CHBr, and -CdO, which are the same as those
of ATRP initiator 2 shown in Figure 6B. A series of new
peaks between 105.0 and 115.0 ppm appeared, which
are typical signals of perfluorocyclobutyl. To make sure
whether dimer 7 was separated from macroinitiator 11
after repeated dissolution and precipitation, GPC mea-
surement was run using a UV detector, and the detec-
tion wavelength was set at 327 nm. Only one peak
appeared in the GPC curve (Figure 7A) of macroinitiator
11 (Mn ) 7500), and we cannot find any peak in the
area of lower molecular weight compared with that of
dimer 7 (Figure 7B). This means we obtained a pure
macroinitiator 11 without any dimer 7. FT-IR assured
the presence of -CdO at 1693 cm-1. Also, the titration
result demonstrated that 2.18% of Br existed in the
reaction product (Mn ) 7500, Mw/Mn ) 1.31) of ATRP
initiator 2 with propagating chain of trifluorovinyl
monomer 8, and the titration result is identical with
the theory value (2 × 80/7500 ) 2.13%). Now, we can
make sure that we successfully synthesized perfluoro-
cyclobutyl aromatic ether-based macroinitiator with two
ATRP initiation groups at both ends.
Conclusion
A new ATRP initiator containing a trifluorovinyl
group, which can initiate ATRP of styrene in a con-
trolled way to obtain well-defined polystyrene with
narrow molecular weight distribution (Mw/Mn < 1.10),
was synthesized. Next, a novel perfluorocyclobutyl
aromatic ether-based ABA triblock copolymer (A: poly-
styrene block; B: perfluorocyclobutyl aromatic ether-
based fluoropolymer block) was synthesized by combi-
nation of atom transfer radical polymerization of styrene
and thermal step-growth cycloaddition polymerization
of trifluorovinyl monomer. The copolymer shows excel-
lent solubility in conventional solvents.
Synthesis and Characterization of ABA Triblock
Copolymer. A series of ABA triblock copolymers were
prepared under different polymerization conditions. The
polymerization results are listed in Table 1. We can find
that all products’ molecular weights are higher than
that of macroinitiator, which means styrene is initiated
for polymerization. It is obvious that the molecular
weight increases with lifting of polymerization time and
feed ratio. This is a typical phenomenon of ATRP.
The polymerization products were characterized by
1H NMR and FT-IR. Figure 8 presents a 1H NMR
spectrum of the polymerization product in acetone-d6,
the peaks at 7.14 and 7.50 ppm are attributed to the
protons of benzene ring of 4,4′-biphenylene perfluoro-
cyclobutyl ether repeating unit, and the typical signals
of polystyrene appeared at 1.43 (-CH2-), 1.79 (-CH-
Acknowledgment. Xiaoyu Huang thanks the finan-
cial support from Chinese Academy of Sciences and the
Ministry of Finance of “Hundreds of Talents Project”
and National Natural Science Foundation of China
(Grant 20404017). Feng-ling Qing thanks the financial
support from National Natural Science Foundation of
China of “National Science Foundation for Distin-
guished Young Scholars” and the Ministry of Science
and Technology of “National High Technology Research
and Development Program” (item 2003AA327070).
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