Synthesis and characterization of highly fluorinated poly(phthalazinone ether)s based on AB-type monomers

Article abstract of DOI:10.1002/pola.27199

Four different fluorinated methyl- and phenyl-substituted 4-(4-hydroxyphenyl)-2-(pentafluorophenyl)-phthalazin-1(2H)-ones, AB-type phthalazinone monomers, have been successfully synthesized by nucleophilic addition-elimination reactions of methyl- and phenyl-substituted 2-((4-hydroxy)benzoyl)benzoic acid with 1-(pentafluorophenyl)hydrazine. Under mild reaction conditions, the AB-type monomers underwent self-condensation polymerization reactions successfully and gave fluorinated poly(phthalazinone ether)s with high molecular weights. Detailed structural characterization of the AB-type monomers and fluorinated polymers was determined by ¹H NMR, ¹⁹F NMR, FTIR, and GPC. The solubility, thermal properties, mechanical properties, water contact angles, and optical absorption of the polymers were evaluated. The polymers had high T_gs varying from 337 to 349 °C and decomposition temperatures (T_{d, 25} wt %) above 409 °C. Tough, flexible films were cast from THF and chloroform solutions. The films showed excellent tensile strengths ranging from 70 to 85 MPa with good hydrophobicities with water contact angles higher than 95.5 °C. The polymers had absorption edges below 340 nm and very low absorbance per cm at higher wavelengths 500-2500 nm. These results indicate that the polymers are promising as high performance materials, for example, membranes and hydrophobic materials.

Full text of DOI:10.1002/pola.27199

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Synthesis and Characterization of Highly Fluorinated Poly(phthalazinone
ether)s Based on AB-Type Monomers
Xiuhua Li,1,2 Yan Gao,1,2 Qiang Long,1,2 Allan S. Hay3
1School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641, China
2The Key Laboratory of Fuel Cell Technology of Guangdong Province, South China University of Technology,
Guangzhou 510641, China
3Department of Chemistry, McGill University, Montreal, Quebec H3A 2K6
Correspondence to: X. Li (E-mail: lixiuhua@scut.edu.cn) or A. S. Hay (E-mail: allan.hay@mcgill.ca)
Received 4 December 2013; revised 30 March 2014; accepted 1 April 2014; published online 22 April 2014
DOI: 10.1002/pola.27199
ABSTRACT: Four different fluorinated methyl- and phenyl-
substituted 4-(4-hydroxyphenyl)-2-(pentafluorophenyl)-phthalazin-
1(2H)-ones, AB-type phthalazinone monomers, have been suc-
cessfully synthesized by nucleophilic addition–elimination reac-
tions of methyl-substituted and phenyl-substituted 2-((4-
hydroxy)benzoyl)benzoic acid with 1-(pentafluorophenyl)hydra-
zine. Under mild reaction conditions, the AB-type monomers
underwent self-condensation polymerization reactions success-
fully and gave fluorinated poly(phthalazinone ether)s with high
molecular weights. Detailed structural characterization of the AB-
type monomers and fluorinated polymers was determined by 1H
NMR, 19F NMR, FTIR, and GPC. The solubility, thermal properties,
mechanical properties, water contact angles, and optical absorp-
tion of the polymers were evaluated. The polymers had high Tgs
varying from 337 to 349 ꢀC and decomposition temperatures
(Td,
%) above 409 ꢀC. Tough, flexible films were cast from
25 wt
THF and chloroform solutions. The films showed excellent tensile
strengths ranging from 70 to 85 MPa with good hydrophobicities
with water contact angles higher than 95.5 ꢀC. The polymers had
absorption edges below 340 nm and very low absorbance per
cm at higher wavelengths 500–2500 nm. These results indicate
that the polymers are promising as high performance materials,
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for example, membranes and hydrophobic materials.
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52, 1761–1770
KEYWORDS: AB type monomer; fluoropolymers; high performance
polymers; hydrophobic material; step-growth polymerization
age,10 and proton exchange membrane materials for fuel
cells.11,15,19,21–23,26–28,40,41
INTRODUCTION Phthalazinone-containing polymers, a new
class of high-performance polymers containing heterocyclic
moieties, have demonstrated good solubility, high rigidity,
and excellent mechanical and thermal properties. These out-
standing properties are strongly associated with the rigid
unsymmetrical phenyl phthalazinone moieties in the poly-
mers backbones. Poly((1,2-dihydro-1-oxo(2H)-phthalazine-
2,4-diyl)-1,4-phenyleneoxy-1,4-phenylenesulfonyl-1,4-phenyl-
ene), the first phthalazinone-containing polymer, was pub-
lished in 1993.1 Since that time many phthalazinone-
containing high-performance polymers, such as poly(phthala-
zinone ether)s,2–30 polyamides,31–33 polyimides,34 and poly-
formal35 with good solubility and excellent thermal stability
have been synthesized. These high-performance polymers
may have promising applications in passive optical wave-
guides,5,13,14,36 ultrafiltration and nanofiltration mem-
branes,37,38 and functional membranes in the energy field,
such as membranes for lithium-ion batteries,39 anion
exchange membrane materials for vanadium redox flow
battery applications,9,10 thin films for dielectric energy stor-
Highly fluorinated polymers such as polytetrafluoroethylene
(Teflon) are very attractive in many applications, due to their
high thermal and chemical stabilities, excellent optical and
electronic properties, and special surface properties associated
with their very low surface tension. However, the applications
of fully fluorinated polymers usually are restricted by their
poor processability.42 Many partially fluorinated polymers with
improved processability have been investigated.43–49 Among
them, fluorinated poly(arylene ether)s are one of the most
important classes owing to high-Tg, excellent thermo oxidative
stability, and outstanding mechanical properties and have been
applied in the fields of aerospace and electronics industries
where high performance is required.46–49 Some fluorinated
poly(phthalazinone ether)s have been reported in the past few
years.5,7,13,20,24 Xiao reported the preparation of fluorinated
poly(phthalazinone ether)s by reaction of a monofluorinated
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SCHEME 1 Synthesis of poly(phthalazinone ether)s from AB-type phthalazinone monomers 1a–d.
phthalazinone monomer with commercially available aromatic
dihalides and perfluorobiphenyl. All the polymers show good
solubility in common aprotic solvents and have excellent ther-
mal properties. The TE mode refractive indices of the polymers,
ranging 1.5874–1.6888, endow them a potential as materials
for optical waveguides.5 Lu ran the polymerization of 4-(40-
hydroxyaryl)phthalazin-1(2H)-ones with perfluorobiphenyl but
failed to give high molecular weight polymers.24 Photo-cross-
linking,7 cross-linking techniques,13 and self-condensation tech-
niques20 have been applied to improve the properties of the
fluorinated poly(phthalazinone ether)s. Self-condensation of
AB-type monomers is an effective way to synthesize high
molecular weight polymers. We previously synthesized the AB-
type phthalazinone monomers 1a–d (Scheme 1).
sol (>98%), 2,3-xylenol (>97%), 2,6-xylenol (>98%), and o-
phenylphenol (>98%) were purchased from Aldrich Chemi-
cal Co. and used as received. 1-(Pentafluorophenyl) hydra-
zine was purchased from TCI Chemical Co. Anhydrous
potassium carbonate was used as received. Reagent grade
solvents N,N-dimethylformamide (DMF), N,N-dimethylaceta-
mide (DMAc), N-methyl-2-pyrrolidinone (NMP), dimethyl
sulfoxide (DMSO), tetrahydrofuran (THF), 1,1,2,2-tetrachloro-
ethane (TCE), CHCl3, sulpholane, pyridine, ethanol, glacial
acetic acid, benzene, toluene, methanol were obtained from
commercial sources and used as received.
Characterizations
1H NMR and 19F NMR spectra were measured with a Bruker
AVANCE 400S with deutrated dimethyl sulfoxide (DMSO-d6)
or deuterated chloroform (CDCl3) as a solvent, and tetrame-
thylsilane (TMS) and CFCl3 as internal references, respec-
tively. FT-IR spectra were recorded on a Bruker Tensor 27
instrument. Gel permeation chromatography (GPC) analyses
were carried out on a Waters 510 HPLC equipped with 5 lm
phenol gel columns (linear, 43 500 Å) arranged in series
with chloroform as a solvent, a UV detector at 254 nm and
polystyrenes as standards. The system was operated at 25
ꢀC with a flow of 1 mL min21 solvent. Melting points were
taken on a XT4A melting point testing apparatus at 70 ꢀC
per minute. The solubility of the polymers was determined
with 2 mg of a polymer in 3 mL of a solvent. Thermogravi-
metric analysis (TGA) was carried out using with a TAINC
SDT Q600 thermogravimetric analyzer at a heating rate of
20 ꢀC per minute from 30 to 700 ꢀC under a protective
nitrogen atmosphere (100 mL min21). The Tgs of the poly-
mers were obtained using a Netzsch DSC 204C DSC instru-
These AB monomers failed to form high molecular weight
homopolymers 2a–d, even under stringent conditions, because
the high degree of crystallization of the oligomers resulted in
the premature precipitation of the polymers.3 Later, we intro-
duced the fluorine atoms into the AB-type monomer to improve
the solubility of the oligomer to enable formation of the high
molecular weight polymers. The fluorinated poly(phtha1azinone
ether) has good solubility in many common solvents and could
be cast into a clear, transparent, and tough films.20
In this paper, we design a series of new fluorinated AB-type
phthalazinone monomers containing methyl or phenyl side
groups. Herein the synthesis and polymerizations of these
fluorinated AB-type phthalazinone monomers have been
investigated. High molecular weight fluorinated poly(phthala-
zinone ether)s were obtained by the self-condensations of
the AB-type monomers. All these fluorinated poly(phthalazi-
none ether)s have good solubility in some common solvents
and can be cast into clear, transparent, and tough films that
have excellent thermal and mechanical properties, high
hydrophobicity, characteristic optical properties.
21
ꢀ
ment at a heating rate of 20 C min with a heating cooling
heating circle scanning method. The Tg was taken from the
midpoint of the change in slope of the baseline. The mechan-
ical properties of the membranes were measured with a
SANS Electromechanical Universal Testing Machine
EXPERIMENTAL
(UTM6000) at a stretching speed of 50 mm min21 at 25 C.
ꢀ
Materials
2-((4-hydroxy)benzoyl)benzoic acids (3a–d) were synthe-
sized as outlined in Cheng’s work.18 m-Cresol (>98%), o-cre-
The data were evaluated with SANS Power Test-SOOC
software.
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Water Contact Angle
was 89.1%. The solid product was recrystallized from a mix-
ture solution of absolute ethanol/water (3/1(v/v)) to give
light brown needle crystals. 1H NMR (DMSO-d6, d, ppm):
2.19 (s, 3H), 6.92–6.98 (d, 1H), 7.23–7.37 (m, 2H), 7.84–7.90
(d, 1H), 7.99–8.07 (m, 2H), 8.38–8.50 (d, 1H), 9.83 (s, 1H).
19F NMR (DMSO-d6, d, ppm): 2145.8 (2F), 2152.5 (1F), and
ꢀ
The films were vacuum-dried at 100 C for 24 h prior to the
water contact angle measurements. Contact angle was
detected with an Optical Contact Angle Measuring Device
DSA100, and the size of the water droplet is 4 lL. The meas-
urements ran five trials for each membrane.
ꢀ
2161.8 (2F). Mp:233 C.
Optical Absorption
Synthesis of AB-Type Monomer 4-(30-Phenyl-40-
Hydroxyphenyl)-2-(Pentafluorophenyl)-phthalazin-1(2H)-
one (4d)
The optical absorbance was determined using a Perkin
Elmer Lambda 950 UV–vis–NIR spectrophotometer (200–
2500 nm) for free standing films. The measured value of
absorbance was divided by the film thickness to obtain a
value of optical absorbance per cm.
2-(30-Phenyl-40-hydroxybenzoyl)benzoic acid 3d (3.19 g, 0.01
mol) and 1-(pentafluorophenyl) hydrazine (1.98 g, 0.01 mol)
were heated in sulpholane (7 mL) at 125 ꢀC for 23 h in a
flask equipped with a magnetic stirrer and a condenser. After
adding 25 mL of ethanol into the reaction mixture, the reac-
tion mixture was poured into 100 mL of hot water to give
an ochre precipitate. The precipitate was filtered and washed
thoroughly with water. The yield was 80.1%. The solid prod-
uct was recrystallized from H2O/EtOH 5 1/4(v/v) to give a
light brown powder. 1H NMR (DMSO-d6, d, ppm): 7.14–7.16
(d, 1H), 7.30–7.32 (s, 1H), 7.40–7.44 (m, 2H), 7.47–7.52 (d,
2H), 7.60–7.62 (m, 2H), 7.95–8.08 (m, 3H), 8.44–8.46 (m,
1H), 10.14 (s, 1H). 19F NMR (DMSO-d6, d, ꢀppm): 2145.7
(2F), 2152.5 (1F), and 2161.7 (2F). Mp:222 C.
Synthesis of AB-Type Monomer 4-(30,50-Dimethyl-40-
Hydroxyphenyl)-2-(Pentafluorophenyl)phthalazin-1(2H)-
one (4a)
2-(30,50-Dimethyl-40-hydroxybenzoyl)benzoic acid 3a (2.70 g,
0.01 mol) and 1-(pentafluorophenyl) hydrazineꢀ(1.98 g, 0.01
mol) were heated in sulpholane (7 mL) at 125 C for 23 h in
a flask equipped with a magnetic stirrer and a condenser.
After cooling down 15 mL of ethanol was added into the
reaction mixture and the reaction mixture was poured into
80 mL of hot water to give a dark brown precipitate. The
precipitate was filtered and washed with water thoroughly.
The yield was 86.5%. The solid product was recrystallized
from a mixture of DMAc/EtOH 5 1/5(v/v) to give pale yel-
low needle crystals. 1H NMR (DMSO-d6, d, ppm): 2.19–2.28
(s, 6H), 7.20–7.25 (s, 2H), 7.86-7.90 (d, 1H), 7.98–8.08 (m,
2H), 8.25–8.45(d, 1H), 8.73–8.75(s, 1H). 19F NMR (DMSO-d6,
d, ppm): 2145.9 (2F), 2152.3 (1F), and 2161.9 (2F).
Synthesis of Fluorinated Poly(phthalazinone ether) 5a
Initially, a 25 mL dried flask was flushed with nitrogen and
charged with 4-(30,50-dimethyl-40-hydroxyphenyl)-2-(penta-
fluorophenyl)-phthalazin-1(2H)-one 4a 0.4323 g (1 mmol),
K2CO3 0.1036 g (0.75 mmol), DMAc (2.5 mL), and toluene (3
mL). The reaction mixture was heated to 135 ꢀC for 2 h to
remove water generated in the reaction with toluene. Then
toluene was then removed completely with a strong N2 flux.
The reaction mixture temperature was maintained for 2 h.
After cooling, the mixture was diluted with 5 mL DMAc and
poured into 150 mL of methanol containing 5 vol % of
hydrochloric acid to precipitate out the polymer. The result-
ing polymer was dissolved in chloroform (25 mL), filtered
through a thin layer of celite to remove the inorganic salts,
and reversed precipitated into 150 mL of methanol. After fil-
tering, drying in a vacuum oven at 80 ꢀC for 12 h, gave
ꢀ
Mp:266 C.
Synthesis of AB-Type Monomer 4-(20, 30-Dimethyl-40-
Hydroxyphenyl)-2-(Pentafluorophenyl)phthalazin-1(2H)-
one (4b)
2-(20,30-Dimethyl-40-hydroxybenzoyl)benzoic acid 3b (2.70 g,
0.01 mol) and 1-(pentafluorophenyl) hydrazineꢀ(1.98 g, 0.01
mol) were heated in sulpholane (7 mL) at 125 C for 23 h in
a flask equipped with a magnetic stirrer and a condenser.
Working up the reaction mixture by the same procedure
used for 4a gave a pale ochre precipitate 4b. The yield was
76.0%. The solid product was recrystallized from absolute
1
1
0.396 g of white fiber. The yield was 99.5%. H NMR (CDCl3,
ethanol to give light brown needle crystals. H NMR (DMSO-
d, ppm): 2.38(s, 6H), 7.32 (s, 2H), 7.77–7.79 (d, 1H), 7.85–
7.89 (m, 2H), 8.56–8.58 (m, 1H). 19F NMR (CDCl3, d, ppm):
2145.5 (2F), 2158.3 (2F).
d6, d, ppm): 1.99 (s, 3H), 2.14 (s, 3H), 6.80-6.83 (d, 1H), 7.0–
7.04 (d, 1H), 7.36–7.42 (d, 1H), 7.63–8.05 (d, 2H), 8.40–8.46
(d, 1H), 9.64 (s, 1H). 19F NMR (DMSO-d6, d, ppm): 2145.2
(1F), 146.5 (1F), 2152.6 (1F), 2161.7 (1F), and 2162.0
ꢀ
Synthesis of Fluorinated Poly(phthalazinone ether) 5b
Initially, a 25 mL dried flask was flushed with nitrogen and
charged with 4-(20,30-dimethyl-40-hydroxyphenyl)-2-(penta-
fluorophenyl)-phthalazin-1(2H)-one 4b 0.4323 g (1 mmol),
K2CO3 0.1036 g (0.75 mmol), DMAc (2.5 mL), and benzene
(3 mL). The reaction mixture was heated to 110 ꢀC for 2 h
to remove water generated in the reaction with benzene.
After most of benzene was removed, the reaction mixture
was kept weakly refluxing for 4 h. After cooling, the mixture
was diluted with 5 mL DMAc and poured into 150 mL of
(1F). Mp: 218 C.
Synthesis of AB-Type Monomer 4-(30-Methyl-40-
Hydroxyphenyl)-2-(Pentafluorophenyl)-Phthalazin-1(2H)-
one (4c)
2-(30-Methyl-40-hydroxybenzoyl)-benzoic acid 3c (2.56 g,
0.01 mol) and 1-(pentafluorophenyl) hydrazineꢀ(1.98 g, 0.01
mol) were heated in sulpholane (7 mL) at 125 C for 23 h in
a flask equipped with a magnetic stirrer and a condenser.
Working up the reaction mixture by the same procedure
used for 4a gave a pale ochre raw precipitate 4c. The yield
methanol containing
5 vol % of hydrochloric acid to
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SCHEME 2 Synthesis of phthalazinone-containing AB monomers 4a–d.
precipitate out the polymer. The resulting polymer was dis-
solved in chloroform (25 mL), filtered through a thin layer of
celite to remove the inorganic salts, and reversed precipi-
tated into 150 mL of methanol. After filtering, drying in a
zin-1(2H)-one was synthesized by reaction of 2-((4-hydroxy)-
benzoyl)benzoic acid with 1-(pentafluorophenyl)hydrazine at
a reaction temperature of 110 ꢀC for 23 h to give a high
yield of 92.4%.20 Herein the AB-type new monomers 4a-d,
methyl or phenyl substituted 4-(4-hydroxyphenyl)-2-(penta-
fluorophenyl)-phthalazin-1(2H)-one, were synthesized by
reactions of the derivates of 2-((4-hydroxy)benzoyl)benzoic
acid 3a–d with 1-(pentafluorophenyl)hydrazine under vary-
ing reaction conditions (Scheme 2 and Table 1). The key step
in the cyclic reactions is the nucleophilic addition–elimina-
tions between ketone and hydrazine groups. The nucleophilic
addition-elimination activities of the ketone groups are
weakened by the electron donating effect and steric hin-
drance effect of side groups. The yields of 4a–d are a bit
lower than that of the phthalazinone monomer 4-(4-hydroxy-
phenyl)-2-(pentafluorophenyl)-phthalazin-1(2H)-one without
side groups. In the nucleophilic addition-elimination of 3a
and 1-(pentafluorophenyl) hydrazine, the yield of 4a
increases with increases in reaction temperature and reac-
tant concentration until the temperature is higher than 130
ꢀC when the color of 4a deepens with the increasing temper-
ature. The optimum ꢀsynthesis conditions for 4a are reaction
temperature of 125 C, reaction time of 23 h with a reactant
concentration of 1.25 M. 4b–c synthesized under the same
conditions. 4b gave the lowest yield due to the obvious
steric hindrance effect of the methyl group ortho to the
ketone group.
ꢀ
vacuum oven at 80 C for 12 h, gave 0.405 g of white fiber.
1
The yield was 99.6%. H NMR (CDCl3, d, ppm): 2.22 (s, 3H),
2.46 (s, 3H), 6.69–6.78 (s, 1H), 7.14–7.19 (m, 1H), 7.40–7.42
(m, 1H), 7.74–7.90 (s, 2H), 8.59 (s, 1H). 19F NMR (CDCl3, d,
ppm): 2144.0 (1F), 2145.7 (1F), 2154.6 (2F). The other
polymers 5c and 5d were synthesized in the similar way to
5b.
Syntheses of Fluorinated Poly(phthalazinone ether) 5c
Replacing 4b with 4-(30-methyl-40-hydroxyphenyl)-2-(penta-
fluorophenyl)-phthalazin-1(2H)-one 4c 0.4183 g (1 mmol)
ran the self-polycondensation and working up the reaction
mixture similar to the procedure for 5b. The yield was
99.7%. 1H NMR (CDCl3, d, ppm): 2.52 (s, 3H), 6.85–6.89 (d,
1H), 7.38–7.40 (m, 1H), 7.53 (s, 1H), 7.80–7.84 (m, 1H),
7.88–7.89 (m, 2H), 8.58–8.61 (m, 1H). 19F NMR (CDCl3, d,
ppm): 2144.5 (2F), 2154.4 (2F).
Synthesis of Fluorinated Poly(phthalazinone ether) 5d
Replacing 4b with 4-(30-phenyl-40-hydroxyphenyl)-2-(penta-
fluorophenyl)-phthalazin-1(2H)-one 4d 0.4804 g (1 mmol)
and working up the reaction mixture similar way to 5b gave
0.457 g white fibrous polymer 5d. The yield was 99.5%. 1H
NMR (CDCl3, d, ppm): 6.99–7.05 (m, 1H), 7.33–7.45 (m, 2H),
7.52–7.56 (m, 1H), 7.64–7.71 (m, 3H), 7.87 (s, 3H), 8.57–
8.59 (m, 1H). 19F NMR (CDCl3, d, ppm): 2145.1 (2F), -153.7
(2F).
1
Figure 1 displays H NMR and 19F NMR spectra of the fluori-
nated phthalazinones 4a–d. The spectroscopic data are in
agreement with the proposed structures. 1H NMR of 4a
(DMSO-d6): d (ppm) methyl signal 2.19–2.28 (s, 6H), aro-
matic signals 7.20–7.25 (s, 2H), 7.86–7.90 (d, 1H), 7.98–8.08
(m, 2H), 8.25-8.45(d, 1H), hydroxyl signal 8.73–8.75 (s, 1H).
19F NMR spectrum of 4a clearly indicates three kinds of flu-
orine atoms of the pentafluorophenyl group at d 145.9,
d 152.3 and d 161.9 ppm, respectively, in a ratio of 2:1:2. In
the 1H NMR spectrum of 4b the methyl signals divide into
RESULTS AND DISCUSSION
Synthesis of Fluorinated AB-Type Phthalazinone
Monomers 4a–d
In our previous work, the fluorinated AB-type phthalazinone
monomer 4-(4-hydroxyphenyl)-2-(pentafluorophenyl)phthala-
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TABLE 1 The Nucleophilic Addition–Elimination Reactions of
the Derivatives of 2-(Hydroxybenzoyl)benzoic Acid 3a–d and
1-(Pentafluorophenyl)hydrazine
methyl groups. Especially in the case of 4d, hydroxyl signal
appear at the highest chemical shift area because of the elec-
tron withdrawing p–p conjugation of phenyl group.
In the FTIR spectrum of A–B-type monomer 4a (Fig. 2), it
has two kinds of functional groups hydroxyl group and C–F.
The wide signal near 3300 cm21 is contributed by the
absorption of –OH. And the signal assigned to C–F appears
at 1078 cm21. The characteristic signal of AC@NA in the
phthalazinone moiety appears at 1518 cm21 overlapped
with aromatic rings signals. The absorption peak assigned to
AC@O occurs at 1649 cm21. The characteristic signal of
methyl group appears at 2972 cm21. Monomers 4b–c con-
taining methyl groups demonstrate similar absorptions. In
the case of 4d with the phenyl side group, the characteristic
signal of methyl group disappears and the signal of phenyl
Benzoic
acid
Conv.
(m)
Temp.
(ꢀC)
Time
(h)
Yield
(%)
Color of
product
3a
1.25
1.25
1.25
1.00
1.25
1.25
1.25
1.00
1.25
1.00
1.25
120
125
125
125
130
150
125
125
125
125
125
23
23
6
84.6
86.5
85.8
78.2
87.0
87.9
76.0
68.5
89.1
78.1
80.1
Pale yellow
Yellow
Yellow
6
Yellow
23
23
23
6
Light brown
Brown
3b
3c
3d
Light brown
Light brown
Light brown
Light brown
Light brown
23
6
group appears at 3066 cm21
.
23
Synthesis of Fluorinated Poly(phthalazinone ether)s
5a–d
As depicted in Scheme 3, the fluorinated poly(phthalazinone
ether) 5a–d were synthesized via the self-condensations of
new AB-type phthalazinone monomers 4a–d. Herein the new
phthalazinone monomers 4a–d are the derivatives of 4-(4-
hydroxyphenyl)-2-(pentafluorophenyl)-phthalazin-1(2H)-one
with varying side groups. The optimum self-condensation
conditions for 4-(4-hydroxyphenyl)-2-(pentafluorophenyl)-
phthalazin-1(2H)-one to give high molecular weight polymer
has been published in our previous work.20 We ran the self-
condensations of the AB-type new phthalazinone monomers
4a–d under the same conditions as 4-(4-hydroxyphenyl)-2-
(pentafluorophenyl)-phthalazin-1(2H)-one (Table 2). All the
monomers except 4a gave high molecular weight polymers.
Polymer 5d has the lowest molecular weight because the
two groups at d 1.99 (s, 3H) and d 2.14(s, 3H) owing to the
position effects of the electron donating conjugation and the
electron withdrawing effect of the hydroxyl group. Fluorine
signals around d 146 and 161.9 ppm split into two peaks in
19F NMR spectrum of 4b because of the r–p hyperconjugation
of the asymmetrical methyl groups. The ratio of the fluorine
signals is 1:1:1:1:1. Fluorine signals in 19F NMR spectra of
4c–d demonstrate three kinds of fluorine atoms in the penta-
fluorophenyl group in a ratio of 2:1:2 because of the penta-
fluorophenyl groups located at the meta-position of the
methyl and phenyl groups. Hydroxyl signals in the 1H NMR
spectra of 4b–c move to high a chemical shift area due to the
reduced electron donating r–p hyperconjugation of the ortho-
FIGURE 1 1H NMR and 19F NMR spectra of fluorinated phthalazinones 4a–d.
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ene to ruꢀn the polymerization at the higher temperature of
135–140 C, high molecular weight polymer 5a was success-
fully synthesized with a narrow polydispersity of 1.52.
The 1H NMR and 19F NMR spectra of the fluorinated poly(-
phthalazinone ether)s (Fig. 3) were recorded using CDCl3 as
solvent. The spectroscopic data are in agreement with the
proposed structures. Obviously, the hydroxyl signal and the
para fluorine signal disappear in the 1H NMR and 19F NMR
spectra of the polymers respectively. The FTIR spectra of the
polymers are shown in Figure 4. The peaks at 3000–3600
disappeared in the polymer FTIR spectra. This agrees well
1
with the results of the H NMR and 19F NMR.
Solubility
The solubility of the polymers 5a–d in common aprotic
organic solvents is listed in Table 3. They show excellent sol-
ubility in DMAc, THF, CHCl3, TCE, NMP, and pyridine. A rea-
sonable explanation is that the twisted noncoplanar bulky
phthalazinone architectures and flexible ether bonds inter-
fere with the compact packing of the backbones and give a
larger free volume. The other explanation is that the intro-
duction of strong polar moieties pentafluorophenyl group
strengthens the polarity of the polymer backbones. In addi-
tion, the pendant side groups also have effects on the solu-
bility of these polymers because of variations of the
conformation of the polymer backbone. Polymer 5b is solu-
ble in sulpholane and polymer 5c partially soluble, while
FIGURE 2 FT-IR spectra of fluorinated phthalazinones 4a–d.
[Color figure can be viewed in the online issue, which is avail-
able at wileyonlinelibrary.com.]
negative p–p conjugation of the phenyl group lowers the
reactivity of the phenoxide anion. Polymer 5c has the highest
molecular weight due to the positive electron donating r–p
hyperconjugation of the ortho methyl group of the phenol
ring that increase the reactivity of the phenol salt. Polymer
5a has the lowest molecular weight due to the low polymer-
ization temperature. By changing the solvent to DMAc/tolu-
SCHEME 3 Synthesis of Fluorinated Poly(Phthalazinone Ether)s 5a–d.
TABLE 2 Self-Condensation of AB-Type Phthalazinone Monomers 4a–d
Polymerization
tem.(ꢀC) time21 (h)
Polymer
Solvent
Yield (%)
Mn (kg mol21
)
Mw (kg mol21
)
Mw/Mn
5a
105–110/4
135–140/4
105–110/4
105–110/4
105–110/4
DMAc/benzene
DMAc/toluene
DMAc/benzene
DMAc/benzene
DMAc/benzene
98.6
99.5
99.6
99.7
99.5
7,836
42,398
257,607
67,692
171,696
98,541
5.41
1.52
1.30
1.54
2.75
169,739
52,020
111,431
35,815
5b
5c
5d
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FIGURE 3 1H NMR and 19F NMR spectra of fluorinated poly(phthalazinone ether)s 5a–d.
their counterparts 5a and 5b are insoluble. All of these poly-
mers could be cast into tough, flexible, and colorless or
nearly colorless films. These properties are promising for
practical applications in the field of membranes.
indicating that the introduction of the bulky side group
increases the rigidity of the polymer backbones.
The initial weight losses of the fluorinated poly(phthalazinone
ether)s 5a–d were observed in the temperature range of 403–
423 ꢀC, which is significantly lower than that of polymer without
20
ꢀ
side group (491 C). Table 4 also summarizes the decomposi-
tion temperatures of polymers 5a–d as determined by TGA, plot-
ted in Figure 5. Evidently, polymer 5d with a phenyl side group
has a higher Td value than 5a–c containing methyl groups. This
instability could be attributable to the oxidation of the C–H
bonds in the methyl group, followed by decarboxylation and
decarbonylation reactions. Moreover, all the polymers display
char yields above 70% in nitrogen at 600 ꢀC. This excellent ther-
mal stability could be ascribed to crosslinking of these polymers
and the high aromatic ring content of the polymer backbones.
Thermal Properties
All the fluorinated poly(phthalazinone ether)s 5a–d show
high Tgs as listed in Table 4, as measured by a differential
scanning calorimeter. When compared with the fluorinated
poly(phthalazinone ether) without side group, polymers 5a–
d demonstrate a distinct increase in Tg higher than 22 ꢀC
Mechanical Properties
Mechanical properties of the polymers membranes are sum-
marized in Table 5. All the fluorinated poly(phthalazinone
TABLE 3 Solubility of Fluorinated Poly(phthalazinone ether)s
5a–d
DMAc THF CHCl3 TCE NMP Pyridine Sulpholane
5a 11
5b 11
5c 11
5d 11
1
11
11 11
11 11
11 11
11
11
11
11
–
11 11
11 11
11 11
1
6
–
11
1
FIGURE 4 FT-IR spectra of fluorinated poly(phthalazinone
ether)s 5a–d. [Color figure can be viewed in the online issue,
which is available at wileyonlinelibrary.com.]
11, Fully soluble at room temperature; 1, soluble; 6, partially soluble;
2, insoluble.
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TABLE 4 Thermal Properties of Fluorinated Poly(phthalazinone
ether)s 5a–d
Tg
(ꢀC)a
Td (25 wt %)
(ꢀC)a
Td (210 wt %)
(ꢀC)b
600 ꢀC
Residue (%)c
Polymer
5a
342
337
348
349
315
408
415
409
451
491
433
434
433
478
-
71
71
72
77
-
5b
5c
5d
8e20
a
Reported for 5% wt loss at a heating rate 20 ꢀC min21 under nitrogen
flow rate 80 mL min21
b
.
Reported for 10% wt loss at a heating rate 20 ꢀC min21 under nitrogen
flow rate 80 mL min21
.
c
Char yield, calculated as the percentage of the solid residue after heat-
ing from room temperature to 600 ꢀC in nitrogen.
FIGURE 6 Contact angles of fluorinated poly(phthalazinone
ether)s 5a–d (THF).
The water contact angles of the polymer 5a–d films are
higher than 95.5ꢀ, indicating high hydrophobicities.
Optical Absorption
The UV–vis–NIR absorption spectra of the fluorinated poly
(phthalazinone ether)s 5a–d films are shown in Figure 7.
These polymers have similar optical absorption properties.
The absorption edges of these polymers are at wavelengths
below 340 nm and the Abs/cm are very low at higher wave-
lengths 500–2500 nm. They show slight differences in opti-
cal absorption at wavelengths ranging from 340 to 500 nm.
Polymer 5a with two symmetric methyl groups gives the
lowest absorbance per cm.
FIGURE 5 TG curves of fluorinated poly(phthalazinone ether)s
5a–d. [Color figure can be viewed in the online issue, which is
available at wileyonlinelibrary.com.]
CONCLUSIONS
AB-type phthalazinone monomers from methyl or phenyl
substituted 4-(4-hydroxyphenyl)-2-(pentafluorophenyl)ph-
thalazin-1(2H)-one 4a–d have been synthesized by
ether)s 5a–d show high tensile strength ranging from 70 to
85 MPa. Their Young’s moduli vary from 1.83 to 2.46 Gpa.
Elongations at break are below 10.3%. These results indicate
that these polymers have excellent mechanical properties.
Contact Angles
The surface tensions of the fluorinated poly(phthalazinone
ether)s 5a–d films were characterized by water contact
angle measurements, and the results are shown in Figure 6.
The films were coated on glass slides from THF solutions.
TABLE 5 Mechanical Properties of Fluorinated
Poly(phthalazinone ether)s 5a–d
Tensile
strength
(Mpa)
Elongation
Modulus
(Gpa)
Polymer
at break (%)
5a
5b
5c
5d
85.4
74.2
73.2
70.0
10.3
9.62
9.32
4.37
2.46
2.01
2.35
1.83
FIGURE 7 UV–vis–NIR absorption spectra of fluorinated poly
(phthalazinone ether)s 5a–d. [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com.]
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13 Y. Song, J. Wang, G. Li, Q. Sun, X. Jian, J. Teng, H. Zhang,
Polymer 2008, 49, 724–731.
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chloroform solutions by the solution cast method. The
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24 Z. Lu, L. Cheng, J. Li, K. Zhang, S. Yi, J. Qin, J. Polym. Sci.
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The work was supported by the National Natural Science
Foundation of China (NSFC) (Grant 51173045), Research
Fund of the Key Laboratory of Fuel Cell Technology of
Guangdong Province (Grant 201104) and Funds of the
National College Students’ Innovative Entrepreneurial Train-
ing Plan (Grant 201210561055-2601) and Guangdong Prov-
ince College Students’ Innovative Entrepreneurial Training
Plan (Grant 1056112040-405).
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