Synthesis and properties of organosoluble polyimides based on novel perfluorinated monomer hexafluoro-2,4-toluenediamine

Article abstract of DOI:10.1016/j.jfluchem.2011.01.008

New highly fluorinated aromatic polyimides based on hexafluoro-2,4- toluenediamine and commercially available dianhydrides (6FDA and ODPA) were synthesized by one-pot high temperature polycondensation in benzoic acid melt. Owing to the CF₃ group and fluorine atoms in the meta-linked phenylenediamine fragment, these polyimides combine good solubility in organic solvents including such a low boiling point solvent as chloroform with high glass transition temperatures (330-345 °C), thermal and thermooxidative stability (T₅ is >500 °C). The highly fluorinated polyimide films (hydrogen content is ≤1%) exhibit good dielectric properties and low water absorption as well as excellent optical transparency in the UV-vis region (cut-off wavelength is 311 nm for 6FDA-based and 357 nm for ODPA-based polyimides), which is very important for optoelectronic materials.

Full text of DOI:10.1016/j.jfluchem.2011.01.008

Journal of Fluorine Chemistry 132 (2011) 207–215
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis and properties of organosoluble polyimides based on novel
perfluorinated monomer hexafluoro-2,4-toluenediamine
Inna K. Shundrina, Tamara A. Vaganova, Soltan Z. Kusov, Vladimir I. Rodionov,
*
Elena V. Karpova, Evgenij V. Malykhin
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Lavrentiev Avenue 9, 630090 Novosibirsk, Russian Federation
A R T I C L E I N F O
A B S T R A C T
Article history:
New highly fluorinated aromatic polyimides based on hexafluoro-2,4-toluenediamine and commercially
available dianhydrides (6FDA and ODPA) were synthesized by one-pot high temperature polyconden-
sation in benzoic acid melt. Owing to the CF3 group and fluorine atoms in the meta-linked
phenylenediamine fragment, these polyimides combine good solubility in organic solvents including
such a low boiling point solvent as chloroform with high glass transition temperatures (330–345 8C),
thermal and thermooxidative stability (T5 is >500 8C). The highly fluorinated polyimide films (hydrogen
content is ꢀ1%) exhibit good dielectric properties and low water absorption as well as excellent optical
transparency in the UV–vis region (cut-off wavelength is 311 nm for 6FDA-based and 357 nm for ODPA-
based polyimides), which is very important for optoelectronic materials.
Received 22 December 2010
Accepted 20 January 2011
Available online 26 January 2011
Keywords:
Highly fluorinated polyimides
Hexafluoro-2,4-toluenediamine
Solubility
Thermal stability
ß 2011 Elsevier B.V. All rights reserved.
Dielectric properties
Optical transparency
1. Introduction
imidized form provides the necessary processability. As a rule, the
listed properties are hardly compatible in the same material.
The design of highly fluorinated aromatic polyimides (PIs) for
optoelectronic applications aims at giving a complex of properties
to polymeric materials, first of all, good optical and dielectric
characteristics, hydrophobicity [1–3]. The replacement of hydro-
gen atoms in the PI structure by fluorines is of principal importance
for high transparency and low optical transmission losses in the
UV–vis and near-IR regions. These properties provide the
application of fluorinated PIs as waveguides in optoelectronic
integrated circuits, transmission medium for the most widely used
lasers, multichip interconnections, and orientation films in liquid
crystal display devices. Low water absorption of fluorinated PIs
stabilizes the optical losses and improves the dielectric perfor-
mance of materials at the wavelengths of optical communications.
Good dielectric characteristics also hold promise for the use in
high-speed microelectronic packaging devices. Along with these
key features, PIs should have good thermal properties and
solubility in relatively low boiling point organic solvents. High
glass transition temperatures Tg, low thermal expansion coeffi-
cient, and high polymer decomposition temperatures Td are
needed both for manufacturing these devices (which includes
short-term processes at temperatures of up to 300–400 8C) and
maintaining their steady operation. The solubility of PIs in the fully
In most cases the incorporation of fluorine into PIs is carried
out by the insertion of pendant CF3 groups or hexafluoroisopro-
pylidene linkages; this results in improvement of the essential
properties, including the solubility in organic solvents [2–4]. The
use of unsymmetrical CF3-containing diamines especially
enhances processability of PIs [5]. An increase in the F/H ratio
can be achieved by incorporation of bulky fluorinated pendant
groups (oxyaliphatic [6,7], aliphatic [7], and oxyaromatic [8]), as
well as bridging perfluoroalkylene groups [9], which improve the
solubility of PIs, but impairs the thermal properties. Contrastingly,
replacement of hydrogen by fluorine in aromatic backbone does
not affect the good thermal properties of aromatic PIs [1–4].
However, synthesis of highly fluorinated aromatic PIs is compli-
cated by the marginal reactivity of polyfluorinated diamines, on
the one hand, and the unavailability of commercial monomers, on
the other. The known PIs containing the perfluoroaromatic
fragments in the main chain were synthesized from tetrafluoro-
para- [10] and -meta-phenylenediamines [11], octafluorobenzi-
dine [10], hexafluoro-2,6- and -2,7-naphthylenediamines [12], as
well as 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluoroben-
zene dianhydride [11]. These PIs exhibit promising optical
properties, low dielectric permittivity, good thermooxidative
stability, but they are insufficiently soluble in organic solvents
and poorly processable in fully imidized form. The insertion of CF3
group into perfluoroaromatic fragments can enhance the PIs
solubility.
* Corresponding author. Fax: +7 383 3309752.
E-mail address: malykhin@nioch.nsc.ru (E.V. Malykhin).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.01.008

208
I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
Recently we elaborated a convenient method of selective
surements were performed with an observational angle 108 and a
Commission International de l’Eclairage (CIE)-D50 illuminant. A CIE
LAB color difference equation was used. Precise molecular weights
of ions were determined by high resolution mass spectrometry
on Thermo Scientific DFS instrument, ionizing energy of 70 eV.
Thermogravimetric (TGA) and differential scanning calorimetry
(DSC) analyses were performed on NETZSCH STA 409 instrument.
The Tgs of the PIs were determined using DSC at a heating rate of
20 8E/min under He flow. The short-term thermal stability of PIs
was estimated from the 5% and 10% weight loss temperatures Td5
and Td10 using TGA with a heating rate of 10 8C/min in an inert
(He) or oxidative (He:?2 = 80:20) atmosphere. To avoid the
influence of absorbed water and residual solvents, the samples
were preheated to 350 8E and cooled down to room temperature;
the second heating scans were recorded. Dielectric constants and
preparation and high purity isolation of polyfluorinated diamines,
having various (het)aromatic frameworks and substituents,
through direct amination of commercially available perfluoro
(het)arenes with anhydrous ammonia [13,14]. This makes
perfluoroaromatic diamines-monomers, including those contain-
ing CF3 groups, accessible for designing new PIs. The aims of the
present work are the synthesis and characterization of highly
fluorinated aromatic PIs based on hexafluoro-2,4-toluenediamine
(6FTDA), and 2,2-bis(30,40-dicarboxyphenyl)hexafluoropropane
dianhydride (6FDA) or 4,40-oxydiphthalic dianhydride (ODPA).
The combination of asymmetrically located CF3 group with
aromatic fluorine atoms in the meta-diamine structure is expected
to provide an excellent balance of all PI properties. In this work
special conditions needed for the polycondensation of perfluori-
nated diamines were found. The novel polyimides 6FTDA/6FDA
dissipation factors were measured on thin films (ꢃ35
mm) by
(PI-1) and 6FTDA/ODPA (PI-2) were characterized by FTIR and 19
F
the parallel-plate capacitor method using Instek LCR 816 Meter
instrument at 23 8E at the frequency 1 kHz. Samples were
preconditioned at 23 8E and 50% relative humidity or dried at
150 8E under reduced pressure for 12 h. Elemental analyses were
determined by a Eurovector model EA 3000 CHN analyzer. Fluorine
content was determined by spectrophotometric analysis [16]. The
NMR spectroscopy, inherent viscosity, and elemental analysis; also
their thermal, dielectric, optical properties and solubility were
studied.
2. Experimental
values of inherent viscosity (hinh) were determined byan Ubbelohde
2.1. Materials
viscosimeter at concentration 0.5 g dLꢂ1 in NMP at 25 8C.
Solubility was determined qualitatively as follows: 50 mg of PI
was mixed with 0.5 mL of solvent and the mixture was
mechanically stirred at room temperature or upon heating. Water
uptake was determined by immersing the polyimide film
(3 cm ꢁ 1 cm) in water at 25 8C for 24 h, which was then dried
immediately by blotting with a paper towel and weighed.
4,40-Oxydiphthalic dianhydride (ODPA) was purified by double
sublimation at 240–260 8C/5 Torr. 2,2-Bis(30,40-dicarboxyphenyl)-
hexafluoropropane dianhydride (6FDA) was dried in vacuum oven
at 140 8C for 6 h. Tetrafluorophthalic anhydride (4FPA) was
obtained by dehydration of tetrafluorophthalic acid prepared by
analogy to the method [15]. Phthalic anhydride (PA) was purified
by sublimation. N-methyl-2-pyrrolidinone (NMP) and N,N-
dimethylacetamide (DMA) were purified by distillation over
2.3. Synthesis of model imide compounds (Scheme 1)
˚
P2O5 under reduced pressure and stored over 3 A molecular sieve;
2.3.1. Mono- and diimide derivatives of 6FTDA
residual moisture <0.02%. Benzoic acid (BA) was purified by
sublimation under reduced pressure.
Hexafluoro-2,4-toluenediamine (1.3 mmol, 0.3 g) and tetra-
fluorophthalic anhydride (2.6 mmol, 0.57 g) were placed into a
round-bottom flask and NMP (10 mL) was added upon stirring
under an argon atmosphere. The solution was stirred for 30 h at
130 8C, and then solvent was removed at heating under the
reduced pressure (30 Torr). Mixture of isomeric monoimides and
individual diimide were isolated from the residue thus obtained
using fractional sublimation.
The mixture of N-(30-amino-20,50,60-trifluoro-40-trifluoro-
methylphenyl)-3,4,5,6-tetrafluorophthalimide and N-(30-amino-
20,40,50-trifluoro-60-trifluoromethylphenyl)-3,4,5,6-tetrafluor-
ophthalimide (isomeric MIs), 2:1; 19F NMR (acetone-d6): the first
Hexafluoro-2,4-toluenediamine (6FTDA, 2,5,6-trifluoro-4-tri-
fluoromethyl-1,3-phenylenediamine) was prepared according to
the data [13]. Octafluorotoluene (0.4 mol, 100 g) was placed into a
steel autoclave and liquid NH3 (300 mL) was added; than the
autoclave was sealed. The reaction mixture was stirred, heated to
120 8C, and kept for 48 h. After completion of the reaction, the
autoclave was cooled and gaseous NH3 was slowly vented. The
reaction mixture was extracted with CH2Cl2 (3ꢁ 200 mL), the
combined extract was dried over MgSO4, and the extractant was
evaporated to give the crude product, which was purified by
crystallization from pentane. Purity of 6FTDA 99%, mp 31.5–
32.5 8C, spectral characteristics are given in [13].
set of signals (integrated intensity 1)
d
ꢂ55.7 (d, 3F, CF3), ꢂ140.7,
ꢂ142.7, ꢂ152.5 (all m, all 1F, aromatic fluorines of toluene
fragment), ꢂ136.3 (m, 2F, F-3, F-6), ꢂ143.5 (m, 2F, F-4, F-5); the
2.2. Measurements
second set of signals (integrated intensity 2)
d
ꢂ56.3 (d, 3F, CF3),
ꢂ138.3, ꢂ144.3, ꢂ158.5 (all m, all 1F, aromatic fluorines of toluene
fragment), ꢂ136.7 (m, 2F, F-3, F-6), ꢂ143.7 (m, 2F, F-4, F-5); HRMS
calcd 450.1941, C15H4F10N2O3, found 450.1937.
19F NMR spectra were recorded on NMR spectrometer Bruker
AV-300 (282.36 MHz) using C6F6
(
d
= ꢂ163 ppm from CCl3F) as
internal standard; 1H and 13C NMR spectra were recorded on NMR
spectrometer Bruker DRX-500 (500.13 and 125.76 MHz, respec-
1,3-Bis(30,40,50,60-tetrafluorophthalimido)-2,4,5-trifluoro-6-tri-
fluoromethylbenzene (DI), mp 314–315 8C; IR (KBr):
n 1802 (C55O
tively) using peaks of pyridine-d5
for 13C from tetramethylsilane) as internal standard;
(
d
= 7.19 ppm for 1H and 123.5
are given in
asym. stretching); 1747 (C55O sym. stretching); 724 (C55O bending)
d
cmꢂ1
;
19F NMR (acetone-d6), letter symbols of fluorines are given
ppm, J are given in Hz. Solid PI samples for registration of NMR
spectra were dissolved to concentration ꢃ5% in NMP. Signals in the
spectra of PIs were assigned by using the spectral data of the model
in Scheme 1 and Fig. 1a:
d
ꢂ56.9 (d, 3F, J = 22, CF3(a0)), ꢂ119.0 (d,
1F, J = 12, F-2(d0)), ꢂ127.0 (d, 1F, J = 22, F-4(c0)), ꢂ135.7 (m, 1F, F-
5(b0)), ꢂ135.2, ꢂ136.0 (both m, both 2F, F-30, F-60), ꢂ142.4, ꢂ142.6
compounds. To estimate Mn, the signals of CF3 group in the range
(both m, both 2F, F-40, F-50); HRMS calcd 633.9629, C23O4N2F14
found 633.9336.
,
¯
from
d
ꢂ50 to ꢂ65 ppm were used; signal/noise ratio ꢄ 40, relative
error ꢃ4%. Fourier transform infrared (FTIR) spectra were recorded
on Bruker Vector-22 instrument for KBr disks. Ultraviolet–visible
(UV–vis) spectra and color intensity of the polymer films were
measured on Varian spectrophotometer Cary 5000. Color mea-
2.3.2. 1,3-Bis-phthalimido-2,4,5-trifluorobenzene (DI-H)
The mixture of hexafluoro-2,4-toluenediamine (1.3 mmol,
0.3 g), phthalic anhydride (2.6 mmol, 0.39 g), and benzoic acid

I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
209
Scheme 1. Synthesis of model mono- and diimides.
(2 g) was heated at 150 8E in a sealed tube for 20 h. Benzoic acid
was removed by sublimation and the crude product thus obtained
was recrystallized from chloroform, yield 70%. Mp 292–293 8C;
(6FTDA + 3FPDA)/ODPA co-polyimide (co-PI-2), portions of di-
amine fragments 70/30. IR spectrum is indistinguishable from
those of the PI-2 (see below); 19F NMR (NMP + acetone-d6), letter
symbols of fluorines are similar to those of co-PI-1, ratios of
IR(KBr): n 3103, 3074 (aromatic C–H stretching); 1789 (C55O asym.
stretching); 1732 (C55O sym. stretching); 881 (C–H absorption in
integrated intensities are given in Table 1:
d
ꢂ54.8, ꢂ55.4 (CF3-f),
polyfluoroaromatic ring); 796, 768 (aromatic C–H absorption), 717
ꢂ56.9 (CF3-a), ꢂ120.3 (F-d), ꢂ124.2 (F-i), ꢂ128.9 (F-c), ꢂ135.99 (F-
h), ꢂ136.8 (F-b), ꢂ139.5 (F-g). Anal. calcd for (C22H6.3F4.6N1.8O5)n:
C, 57.0; H, 1.36; F, 18.9; N, 5.44. Found: C, 55.6; H, 2.05; F, 18.0; N,
5.04.
Variant A0. The reagents mentioned above were placed into a
glass tube under an argon atmosphere, the tube was sealed and
underwent a stepped heating for 50 h at 160 8E and for 20 h at
190 8E. On completion of the reaction polymer was isolated as
described in the method A
(C55O bending) cmꢂ1; 1H NMR (pyridine-d5):
d 7.66, 7.69, 7.90, 7.93
(all m, 8H, 2H40, 2H50, 2H60, 2H70), 7.99 (ddd, 1H,
JHF = 10, JHF = 8, JHF = 7, H6); 13C NMR (pyridine-d5):
d 167.5,
1
166.7 (C10, C30), 152.4 (d, JCF = 257, C2), 148.5, 147.9 (both dd
2
2
[1JCF = 258, JCF = 15], [1JCF = 247, JCF = 12] C4, C5), 137.6, 137.1
(C40, C70), 133.3, 133.1 (C80, C90), 126.3, 125.9 (C50, C60), 121.6 (d,
2JCF = 21, C6), 118.2, 113.0 (both dd [2JCF = 14, JCF = 10],
[2JCF = 17, JCF = 14], C1, C3); 19F NMR (pyridine-d5), letter symbols
of fluorines are given in Scheme 1 and Fig. 1e:
d
ꢂ123.2 (dd, 1F,
(6FTDA + 3FPDA)/6FDA co-polyimide (co-PI-10), portions of
diamine fragments 40/60. IR spectrum is indistinguishable from
those of the PI-1 (see below); 19F NMR shifts are similar to those of
co-PI-1, ratios of integrated intensities are given in Table 1. Anal.
calcd for (C24.5H6.5F9.6N1.7O4)n: C, 51.4; H, 1.14; F, 31.9; N, 4.17.
Found: C, 49.4; H, 1.02; F, 30.2; N, 4.33.
JFF = 13, JFH = 7, F-2(i0)), ꢂ136.0 (dd, 1F, JFF = 23, JFH = 8, F-4(h0)),
ꢂ138.9 (ddd, 1F, JFF = 13, 23, JFH = 10, F-5(g0)); EIMS, 70 eV, m/z (rel.
int.): 422 [M]+ (100), 378 [M–CO2]+ (66), 334 [M–2CO2]+ (10), 104
[C6H4CO]+ (35), 76 [C6H4]+ (51); HRMS calcd 422.0509,
C22H9O4F3N2, found 422.0508.
Variant B (with azeotropic removing of water). A 50 mL round-
bottomed flask equipped with a magnetic stirrer bar, argon gas
inlet tube and downtake condenser was charged with 5 mL
toluene, 5 mmol (1.15 g) of the diamine (6FTDA), equimolar
amounts of (2.22 g of 6FDA or 1.55 g of ODPA) and BA (20 g). The
reaction mixture was heated up to the boiling point of toluene and
kept at this temperature until toluene was distilled off (ꢃ2 h). Then
the reactor was equipped with a short air condenser with a calcium
chloride outlet tube; reaction was kept on at stepped heating under
an argon atmosphere for 4 h at 150 8E and for 10–20 h at 190 8E.
On completion of the reaction polymers were isolated and purified
as described in the method A.
2.4. One-pot synthesis of polyimides and co-polyimides in benzoic
acid melt (Scheme 2)
Variant A. A 100 mL round-bottomed flask equipped with
a magnetic stirrer bar was charged with 5 mmol (1.15 g) of
the diamine (6FTDA), equimolar amount of dianhydride (2.22 g
of 6FDA or 1.55 g of ODPA), and BA (20 g) under argon current.
The flask was tightly closed; the mixture was kept upon stirring
at 135 8E for 3 h. Then the reactor was equipped with an
argon gas inlet tube and a short condenser with a calcium
chloride outlet tube; reaction was kept on at stepped heating
under an argon atmosphere: for 6 h at 150 8E and for 20 h
at 190 8E. On completion of the reaction BA was extracted
with EtOH (3ꢁ 20 mL), polymer residue was washed with
hot EtOH (20 mL). The polymer was dissolved in DMA and
the solution obtained (10 wt%) was poured upon stirring
6FTDA/6FDA polyimide (PI-1). IR (KBr):
n 3132, 3086 (aromatic
C–H stretching); 1802 (C55O asym. stretching); 1749 (C55O sym.
stretching); 782, 766 (aromatic C–H absorption); 720 (C55O
;
bending) cmꢂ1 19F NMR (NMP + acetone-d6), letter symbols of
fluorines are given in Fig. 1c, ratios of integrated intensities are
given in Table 1:
into ethanol (10-fold excess) to form
a
precipitate. The
d
ꢂ54.8, ꢂ55.5 (CF3-f), ꢂ57.0 (CF3-a), ꢂ118.8 (F-
precipitate was washed with ethanol and dried in vacuo at
150 8E for 6 h.
(6FTDA + 3FPDA)/6FDA co-polyimide (co-PI-1), portions of di-
amine fragments 85/15. IR spectrum is indistinguishable from
those of the PI-1 (see below); 19F NMR (NMP + acetone-d6), letter
symbols of fluorines are given in Fig. 1d, ratios of integrated
d), ꢂ127.4 (F-c), ꢂ136.6 (F-b). Anal. calcd for (C26H6F12N2O4)n: C,
48.9; H, 0.94; F, 35.7; N, 4.39. Found: C, 49.8; H, 0.98; F, 35.6; N,
4.32.
6FTDA/ODPA polyimide (PI-2). IR(KBr):
n 3105, 3046 (aromatic
C–H stretching); 1796 (C55O asym. stretching); 1742 (C55O sym.
stretching); 773, 740, 700 (aromatic C–H absorption); 712 (C55O
;
bending) cmꢂ1 19F NMR (NMP + acetone-d6), letter symbols of
intensities are given in Table 1:
d
ꢂ54.8, ꢂ55.5 (CF3-f), ꢂ57.0 (CF3-
a), ꢂ118.8 (F-d), ꢂ123.3 (F-i), ꢂ127.4 (F-c), ꢂ135.0 (F-h), ꢂ136.6
(F-b), ꢂ138.8 (F-g). Anal. calcd for (C25.5H6.2F11.3N1.9O4)n: C, 49.5;
H, 0.99; F, 34.7; N, 4.30. Found: C, 48.4; H, 0.96; F, 33.5; N, 3.67.
fluorines are given in Fig. 1b, ratios of integrated intensities are
given in Table 1:
ꢂ54.8, ꢂ55.4 (CF3-f), ꢂ56.9 (CF3-a), ꢂ120.3
(F-d), ꢂ128.9 (F-c), ꢂ136.8 (F-b). Anal. calcd for (C23H6F6N2O5)n: C,
d

210
I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
Fig. 1. 19F NMR spectra of PIs and model compounds: (a) DI; (b) PI-2; (c) PI-1; (d) co-PI-1 and (e) DI-H.
54.8; H, 1.19; F, 22.6; N, 5.56. Found: C, 54.6; H, 1.22; F, 22.1;
N, 5.52.
150 8C for 12–24 h up to constant weight. The thickness of the
obtained films (10–100 m) was controlled by adjusting concen-
m
tration of the polymer solution.
3. Results and discussion
3.1. Synthesis of polyimides
2.5. Preparation of PI films
PI samples were dissolved in DMA at concentrations of 20–
50 wt%. The solutions were filtered through a 0.5
mm Teflon
membrane filter. The filtered solutions were spin-coated on glass
wafer substrates. After coating, the substrates were placed on a hot
plate and kept at 70 8C for 4 h to gently evaporate the solvent. The
semidried films were placed into a vacuum oven and dried at
Exhaustive fluorination of the benzene ring is known
to decrease the reactivity of phenylenediamines for acylation
by a factor of ꢃ10ꢂ5 [1] because of the total effect of high

I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
211
Scheme 2. Synthesis of PIs.
electronegative fluorines. The resulting low nucleophilicity of
polyfluoroaromatic diamines impedes their effective interaction
with dianhydride and the formation of high-molecular weight
poly(amic acid)s. To prepare PIs based on highly fluorinated
diamines [10,12], the condensation in a solution at 80–130 8C with
the formation of low-weight oligomers and subsequent high-
temperature solid-state chain extension up to 250 8C were used.
Under these conditions the formation of amic acid fragments is
accompanied by their cyclodehydration and polymer chain growth
proceeds via polyaddition of completely cyclized PI oligomers
having amino and anhydride end groups. In the case of the least
reactive monomers, the solid-state cure was carried out using a
cyclic procedure [10] (2-3-fold redissolving of the already cured
soluble material, redrying, and recurring). PIs with perfluoroaro-
matic fragments thus obtained had molecular weight less then
10,000.
practically form at the solution stage. In addition, water, which
forms during cyclodehydration of amic acids, hydrolyses anhydride
groups thus interrupting the acylation of amino groups. Carrying out
thecyclicsolid-statechainextensionprocedure(3cycles)atthefinal
curing temperature Tc 250–300 8C results in the formation of
¯
macromolecules having Mn ꢃ 10; 000 for 6FDA-based PI and ꢃ3500
for ODPA-based PI. Increaseinthenumberofcyclesbringstoa lossof
solubility, which does not make it possible to use this method for
obtaining polymers with higher molecular weights.
Method of one-step high-temperature polycondensation in
high boiling point solvents (o-dichlorobenzene, m-cresol and
chlorinated phenols) at 150–200 8C with using catalytic additives
of organic and mineral acids is considered more practical for
polymerization of low reactive monomers [18]. In the works [19–
21] the melt of aromatic carboxylic acid–benzoic or salicylic was
used as an effective catalytic medium for the one-step preparation
of completely cyclized PIs. The rates of polymerization of low-
reactive diamines in this medium are higher than in amide
solvents [20]. Besides, melts of these acids are a non-toxic medium
as compared with dichlorobenzene and chlorinated phenols and
they can be easily separated from polymer on completion of the
reaction. As to our knowledge, there are no examples of using this
method to prepare polymers based on perfluoroaromatic dia-
mines. In the present work reactivity of 6FTDA in these conditions
was studied and special technique for synthesis of 6FTDA-based PIs
in the benzoic acid (BA) melt was developed.
We tested the possibility to use the cyclic chain extension
procedure for synthesis of PIs based on 6FTDA. Control of the
process was carried out by using 19F NMR. This method is valuable
in providing the needed information [17] on the extent and type of
the occurring transformations, purity and structural regularity of
¯
the growing polymer, Mn value, and presence of active end groups.
Signals in 19F NMR spectra of oligo- and polyimides were assigned
using the spectral characteristics of specially synthesized model
compounds (Scheme 1, Section 2.3).
It was found that 6FTDA interacts with 6FDA and ODPA rather
slowly: condensation solutions prepared at 80 8C for 75 h contain
the initial diamine (up to 15%) and 6FTDA derivatives comprising
one modified amino group, i.e. isomeric monoamic acids and
monoimides. No molecules containing two modified amino groups
Two techniques of PI synthesis in the carboxylic acid melt were
reported [19–21]: in open and closed vessels without removing
water. Taking into account a relatively high volatility of 6FTDA, the
initial stage of the polycondensation in BA melt (up to the complete
Table 1
Characteristics of 6FTDA-based polyimides and copolyimides.
Dianhydride Polyimide Yield Content of F
Structural characteristics (19F NMRa)
hinh (dL gꢂ1
)
The residual
anhydride groups
bond in FTIR
spectrum
(%)
(%, elemental
analysis)
Ratio of diamine/ Portions of 6FTDA/ Ratio of internal/ Number average
dianhydride
fragmentsb
3FPDA
terminal PI
unitsd
molecular
¯
internal
fragmentsc
weight Mn
6FDA
co-PI-1
co-PI-10
PI-1
86
80
85
84
87
33.3
30.1
35.5
18
0.95
0.85
1
85/15
40/60
100/ꢂ
70/30
100/ꢂ
+
+
0.16
0.30
0.25
0.28
29
28
19,000
14,500
ꢂ
+
ODPA
co-PI-2
PI-2
22.1
ꢂ
a
Signals of fluorines used for an evaluation are showed in Fig. 1.
b
c
S(b, c, d, g, h, i)/e
P
S(b, c, d)/ (g, h, i)
d
a/Sf.

212
I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
conversion of monomers into non-volatile oligomers) was
performed in a closed reactor, then the reactor was equipped
with a short condenser and the process was continued in an argon
atmosphere with gradually rising temperature up to 190 8C
(variant A, Scheme 2).
Fig. 1b and c, Section 2) testify to the homogeneous structure of the
macromolecules. In particular, the fluorine content fits its
calculated value, which confirms the retention of CF3 group.
Judging by these results, the variant B makes it possible to retain
the stoichiometric ratio of monomers and to prepare PIs with
relatively high molecular weight. As to co-PIs prepared by the
variants A and A0, in their 19F NMR spectra there are no signals of
the terminal 6FTDA and 3FPDA fragments excepting low-intensity
CF3 group signal, and stoichiometry of the diamine and dianhy-
dride fragments of macromolecules is distorted. For these reasons,
19F NMR characteristics of polymers obtained by the variant A
testify to the presence in their structure of two types of
polyfluoroaromatic fragments (Fig. 1d). The first type contains
CF3 group and has signals a, b, c, and d, which are similar to the
signals of the model DI (Fig. 1a). Three additional signals of
aromatic fluorine atoms (g, h, and i) belong to the second type of
internal fragments, which have no CF3 group. This follows from the
smaller integrated intensity of the CF3 group signal a in comparison
with the total intensity of aromatic fluorine atom signals (b, c, d, g,
h, i) (Table 1). Appearance of the modified fragments in the
polymers can be caused by hydrolysis of CF3 group and subsequent
decarboxylation, occurring at a high temperature under the action
of water onto monomer, oligomer or polymer. Examples of such a
transformation of CF3 group in polyfluoroaromatic compounds are
known [22]. Realization of this process during the polycondensa-
tion results in the formation of co-polyimides containing two types
of diimide fragments, derived from 6FTDA and 2,4,5-trifluorophe-
nylenediamine (3FPDA) (Fig. 1d). Judging by the 19F NMR data, co-
PI-1 contains 85% of internal 6FTDA fragments, and co-PI-2 – only
70% (Table 1).
the Mn values of co-PIs cannot be evaluated using 19F NMR. Judging
¯
by the inherent viscosity values (hinh) (Table 1), co-PIs have lower
molecular weights than PIs 1 and 2.
Thus, the results obtained demonstrate the possibility of the
6FTDA-based PIs preparation by one-step high temperature
polycondensation in BA melt. This method is practically feasible
and effective mode of preparing PIs based on low reactive
perfluorinated diamines.
3.2. Polyimide properties
The solubility of PIs was investigated qualitatively in different
organic solvents at room temperature or upon heating. The results
are reported in Table 2.
All PIs obtained at 190 8E are soluble in amide-type solvents, m-
cresol, DMSO, and c-hexanone. Besides, they show the good
solubility in such a low boiling point organic solvent as chloroform;
this is a distinctive feature improving the processability of
polymers. Films cast from solutions of PI-1 and PI-2 and cured
at 350 8E for an hour do lose solubility. Only 6FDA-based PI-1
remains partially soluble due to the joint influence of the structural
hexafluoroisopropylidene (6F) fragment. Co-PIs are less soluble
because of the lower content of 6FTDA fragments in their structure.
The glass transition temperatures of the PIs were determined
using differential scanning calorimetry. All PIs exhibit no
crystallization or melting transition in DSC measurements. The
Tg values of PIs and co-PIs (Table 3) depend on the structure of both
dianhydride and diamine fragments. ODPA-based PI-2 has a lower
Tg value than 6FDA-based PI-1 (328 vs. 346 8E) due to the presence
of a flexible ether linkage in the PI backbone. The same Tgs ratio
was reported for PIs prepared from these dianhydrides and various
diamines [25–28].
A model reaction of 6FTDA with phthalic anhydride (PA) in BA
melt at 150 8C, which was carried out in a sealed glass tube
(Scheme 1, Section 2.3), confirms the possibility of CF3 group
hydrolysis and subsequent decarboxylation in these conditions.
The 19F NMR spectral characteristics of DI-H (Fig. 1e) correspond to
those of the modified co-PI fragments, derived from 3FPDA
(Fig. 1d).
Accordingly, composition of co-PIs depends on the reaction
conditions. The polymerization of 6FTDA and 6FDA carried out in a
sealed tube (variant A0) caused a considerable decrease in the
portion of the internal 6FTDA fragments in co-PI-10 – down to 40%.
The elemental analysis data agree with the assumed way of
structural modification: the fluorine content in copolymers
reduces in going from co-PI-1 to co-PI-10 (Table 1). Besides, the
NMR data indicate a distortion in the stoichiometry of the diamine
and dianhydride fragments in copolymers in favor of the latter.
Apparently, at the first stage of polymerization
a part of
perfluorinated diamine decomposes under the action of water at
the high temperature.
Both PI-1 and PI-2 have higher Tgs than PIs prepared from
unsubstituted meta-phenylenediamine (MPDA, Table 3) and from
phenylenediamines containing long side polyfluorinated aliphatic
or oxyaliphatic groups (the range of Tgs for 6FDA-based polyimides
is 190–270 8E [6,7]). There are two structural factors, which
distinguish 6FTDA from MPDA: aromatic fluorine atoms and CF3
group. It was shown [10] that incorporation of either one or four
fluorine atoms into para-linked phenylenediamine fragment does
not change the Tg. If this is also true for meta-linked fragments, CF3
group should be regarded as a factor responsible for the relatively
high Tgs of 6FTDA-based PIs. Judging by the data [2], CH3 and CF3
groups have a similar effect upon the Tg of PIs, direction and size of
which depend strongly on the isomerism of the phenylenediamine
To prevent the undesirable destruction, polycondensation was
carried out in the open reactor with the addition of toluene (variant
B). Owing to this modification of the reaction conditions, the water,
which formed intensively at the initial stage, was effectively
removed by means of azeotropic distillation. After all toluene was
distilled off, the process was kept on under the conditions similar
to those provided for the variant A. The synthesis of 6FDA-based PI-
1 was stopped after the reaction mixture split into two phases; and
the synthesis of PI-2, based on the less reactive ODPA – after the
growth of macromolecules stopped. The elemental analysis data
and 19F NMR characteristics of PI-1 and PI-2 thus obtained (Table 1,
Table 2
Solubility of polyimidesa.
b
PI (dianhydride)
PI-1 (6FDA)
Tmax (8C)
m-Cresol
NMP
DMAA
DMF
DMSO
c-Hexanone
Acetone
CHCl3
EtOH
190
350c
190
350c
+
+ꢂh
+
+
+ꢂh
+
+
+ꢂh
+
+
+ꢂh
+
+
+
+ꢂh
ꢂh
+
+ꢂh
+
ꢂh
ꢂh
ꢂh
ꢂh
ꢂh
+
ꢂh
+
PI-2 (ODPA)
+ꢂh
ꢂh
ꢂh
ꢂh
ꢂh
ꢂh
ꢂh
ꢂh
ꢂh
a
Qualitative solubility was determined visually as: completely soluble (+), partially soluble (+ꢂ), insoluble (ꢂ), heating (h).
b
c
The maximal curing temperature.
PI films.

I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
213
Table 3
Glass transition temperatures (8C) of polyfluorinated polyimides and their H-analogs.
Dianhydride
Diamine
F
N
N
N
N
N
N
CH3
TDA
F
CF3
F
MPDA
6FTDA
6FTDA / 3FPDA
MPDA
TDA
6FTDA
346
6FTDA/3FPDA
6FDA
ODPA
332 (85/15)
327 (40/60)
318 (70/30)
285 [23]
260 [24]
342 [23]
278 [24]
328
fragment. The replacement of MPDA fragment by 2,4-toluenedia-
mine (TDA) fragment, which is a structural analog of 6FTDA,
increases Tgs of both 6FDA- and ODPA-based PIs by 57 and 18 8E,
respectively (Table 3). The same tendency, even more pronounced
(>60 8E for both PIs), occurs in going from MPDA-based PIs to
6FTDA-based PI-1 and PI-2. Accordingly, the co-PI samples,
containing 3FPDA fragments along with 6FTDA fragments, have
lower Tg values. The data of Table 3 show the decrease of Tgs with a
diminution in the portion of the CF3 containing fragments.
The considered tendencies confirm the presence of CF3 group at
position 4 of meta-linked phenylenediamine fragment to be an
These observations can be of importance for the design of new PI
materials.
Co-PIs 1, 10, and
2 have worse thermal and especially
thermoxidative stability. It can be caused by the distortion of
macromolecules stoichiometry resulting in excess of the lower
thermostable anhydride end groups.
The dielectric constants, dissipation factors and water absorp-
tion of PI-1 and PI-2 were measured on thin films (35
mm). The
films were preconditioned at 50% relative humidity (r.h.) or dried
in vacuo (dry). The data obtained are presented in Table 5.
The PI films exhibit low water absorption, low relative
permittivity as well as low differences between dielectric
constants under dry and ambient conditions (humidity-induced
change in the dielectric constant). All these characteristics improve
as fluorine content increases in going from ODPA-based PI-2 to
6FDA-based PI-1. These facts agree with the known data that the
fluorine-containing PIs have lower dielectric constants and higher
hydrophobicity as compared with fluorine-free PIs [2].
The fluorine atoms and CF3 group affect the PIs relative
permittivity by several ways. The hydrophobic effect of fluorine
atoms and the increase of the fractional free volume, which reduce
the number of polarizable groups in a unit volume, decrease the
dielectric constant [10,30]. Accordingly, the insertion of the bulky
fluorine atoms and CF3 group instead of the hydrogen atoms, as
well as the 6F fragment instead of the oxygen linkage impedes a
close packing of the polymer chains, thus decreasing the relative
permittivity of PIs. In addition, the interchain electronic interaction
and, as a result, the efficiency of the chain packing diminish due to
the decrease in the donating effect of phenylenediamine fragment
under the action of the strong electron withdrawing fluorine atoms
and CF3 group. The last way is changing polarizability [31].
Fluorines and CF3 groups in the PI framework decrease the
electronic polarizability due to their electronegative nature. The
same effect can enlarge the dipole moment of the chain fragment,
thus increasing the orientation polarizability at low frequencies.
These factors act on the total polarizability in the opposite
directions, but the contribution of the second factor depends on the
important factor increasing Tg of PIs. Thereby, 6FTDA is
a
prospective monomer for the synthesis of highly fluorinated PIs
with high Tgs.
The short-term thermal stability of the PIs in inert and oxidative
atmospheres was studied using thermogravimetric analysis. The
decomposition temperatures are summarized in Table 4. The
polymers obtained show a high thermal stability intrinsic to
aromatic polyimides: there is no obvious weight loss before the
scanning temperature reaches to 500 8C. Temperatures of 5 and
10% weight losses of ODPA-based PI-2 exceed the same char-
acteristics of 6FDA-based PI-1 by 20–30 8E both in inert and
oxidative atmosphere. This tendency for Td changes is known to
realize for pair of ODPA/6FDA-based PIs prepared using various
diamines [25,27–29]; it is caused by a lower thermal stability of
the 6F linkage as compared with the oxygen linkage.
Incorporation of fluorine atoms and CF3 group in phenylene-
diamine fragment influences the PIs thermal stability ambiguously
[2]. According to the data [10] the complete replacement of
hydrogen atoms by fluorines slightly increases the thermal
stability of PIs, whereas incorporation of CF3 group slightly
decreases the thermal and thermooxidative characteristics. The
presence of the both structural factors evidently compensates for
these opposite tendencies. As a result, the thermal properties of
6FTDA-based PIs 1 and 2 are close to those of PIs containing non-
fluorinated diamine fragments, and exceed the characteristics of
PIs containing the long fluorinated side chain by 40–50 8E [2].
Table 4
Thermal degradation properties of 6FTDA-based polyimides and copolyimides.
Dianhydride
6FDA
Polyimide
In inert atmosphere
In oxidativeatmosphere
a
a
b
b
a
a
b
T5 (8C)
T10 (8C)
R700 (%)
R900 (%)
T5 (8C)
T10 (8C)
R600 (%)
PI-1
co-PI-1
co-PI-10
PI-2
528
523
511
549
524
554
550
538
574
562
55
55
47
52
52
42
44
40
44
43
515
506
492
534
474
526
522
513
555
495
17
15
5
ODPA
16
1
co-PI-2
a
T5, T10, temperature at 5% and 10% weight loss.
b
R600, R700, and R900, residual weight retention at 600, 700, and 900 8C.

214
I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
Table 5
Dielectric properties and water absorbtion of PI-1 and PI-2 films.
Polyimide (dianhydride)
e
a, 1 kHz
tg db, 1 kHz
Water absorption (%)
Fluorine content (%)
Dry
r.h.
dry
r.h.
PI-1 (6FDA)
PI-2 (ODPA)
2.68
2.87
2.92
3.27
0.0008
0.0009
0.0013
0.0016
0.35
0.54
35.5
22.1
a
e
, dielectric constant.
b
tg d, dissipation factor.
Table 6
Optical properties and color coordinates of PI-1 and PI-2 films.
a
Polyimide (dianhydride)
l0 (nm)
Film thickness (
mm)
Color coordinatesb
b* a*
1.2 0.2
Transmittance at 450 nm, films thickness 10 mm (%)
L*
PI-1 (6FDA)
PI-2 (ODPA)
CF3-containing PIc
Kapton
311
357
358
444
30
100
60
96.4
86.4
90.7
88.1
98
94
11.9
11.3
83.8
2.1
ꢂ3.1
5.0
40
a
l0, the cut-off wavelength.
b
The color parameters were calculated according to a CIE LAB equation. L* is lightness, 100 means white, and 0 means black. A positive a* indicates red color, a negative a*
indicates green color. A positive b* indicates yellow color, and a negative b* indicates blue color.
c
1,7-Bis(4-amino-2-trifluoromethylphenoxy)-naphthalene/6FDA polyimide, date on Ref. [26].
fragment symmetry. Due to the asymmetrical location of CF3 group
in meta-linked 6FTDA the orientation polarizability should
increase [31], however, the presence of fluorine atoms in the
aromatic ring compensates partially for the dipole of CF3 group.
Moreover, the contribution of the dipole orientation part into the
total polarizability is low for polyimides with a high Tg [2]. As a
result, fluorine-induced change of the polarizability and, conse-
quently, of the relative permittivity of PIs 1 and 2 appear to be
insignificant. This is confirmed by the low dissipation factors of the
PIs at 1 kHz (Table 5). Thereby, owing to the first two ways, the
6FTDA fragment provides a reduction of the PI dielectric constants.
The optical properties of the PI films were investigated using
UV–vis spectroscopy. The values of cut-off wavelength ( 0),
transmittance at 450 nm, and color intensity of the PI films are
summarized in Table 6 and Fig. 2. For comparison, Table 6 presents
the same characteristics of Kaptone and of the known PI containing
CF3 groups in amine and anhydride fragments [26].
l
The PI films exhibit low l0 values, high transparency, and have
color from pale fawny to colorless. The characteristics of the PIs,
especially the cut-off wavelength, depend on the anhydride
structure. The l0 value of 6FDA-based PI-1 is less than that of
ODPA-based PI-2 by 45 nm.
The PI optical properties are considered to depend on the intra-
and intermolecular charge-transfer complex (CTC) formation
[32]. Accordingly, structural features of macromolecules, which
reduce the CTC formation, improve the optical characteristics
[1,26,28,33]. The 6F fragment and meta-linked diamine fragment
disturb the conjugation within the PI chains, thereby preventing
the intrachain CTC formation. The electron-withdrawing fluorine
atoms and CF3 group reduce the donating effect of diamine
fragment to impede the interchain CTC formation. In addition,
the interaction between PI chains is hindered by the bulky CF3
groups. All these effects reduce the absorption at the UV–visible
wavelengths and the l0 values. As a result, the obtained highly
fluorinated PI films, especially 6FDA-based PI-1, exhibit the
excellent optical transparency.
4. Conclusions
New highly fluorinated aromatic polyimides based on hexa-
fluoro-2,4-toluenediamine (6FTDA) and 6FDA or ODPA were
synthesized and their properties were investigated. It was found
that presence of water in the reaction mixture causes partial
destruction of CF3 groups during the one-step high temperature
polycondensation. It results in the formation of co-PIs containing
trifluorophenylene fragments along with hexafluorotoluene frag-
ments. To prevent the undesirable process and prepare 6FTDA-
based PIs, special technique was developed for the one-step
polycondensation in benzoic acid melt.
Owing to CF3 group and fluorine atoms in the phenylenedia-
mine fragment the PIs obtained have a good solubility in organic
solvents including such a low boiling point solvent as chloroform,
high glass transition temperatures, thermal and thermooxidative
Fig. 2. UV–vis spectra of PI films: (a) transmittance and (b) absorbance.

I.K. Shundrina et al. / Journal of Fluorine Chemistry 132 (2011) 207–215
215
[12] I.K. Shundrina, T.A. Vaganova, S.Z. Kusov, V.I. Rodionov, E.V. Karpova, V.V. Koval,
Yu. V. Gerasimova, E.V. Malykhin, J. Fluorine Chem. 130 (2009) 733–741.
[13] T.A. Vaganova, S.Z. Kusov, V.I. Rodionov, I.K. Shundrina, E.V. Malykhin, Russ.
Chem. Bull. Int. Ed. 56 (2007) 2239–2246.
[14] (a) T.A. Vaganova, S.Z. Kusov, V.I. Rodionov, I.K. Shundrina, G.E. Sal’nikov, V.I.
Mamatyuk, E.V. Malykhin, J. Fluorine Chem. 129 (2008) 253–260;
(b) S.Z. Kusov, V.I. Rodionov, T.A. Vaganova, I.K. Shundrina, E.V. Malykhin, J.
Fluorine Chem. 130 (2009) 461–465.
[15] P. Sartori, A. Golloch, Chem. Ber. 101 (1968) 2004–2009.
[16] I.M. Moryakina, L.N. Diakur, Zh. Vses. Khim. Obshchest. im. D.I. Mendeleeva
(Russ.) 12 (1967) 698–699, C.A 68:119289.
[17] (a) S. Ando, T. Matsuura, Magn. Reson. Chem. 33 (1995) 639–645;
(b) C.D. Smith, R. Mercier, H. Waton, B. Sillion, in: G. Hougham (Ed.), Fluoropo-
lymers 2: Properties, Kluwer Academic/Plenum Publishers, New York, 1999, pp.
371–399.
stability. High fluorine content provides good dielectric properties
and low water absorption of 6FTDA-based PI films. Their excellent
optical transparency in the UV–vis region is achieved due to the
presence of meta-linked diamine moiety containing bulky
electron-withdrawing CF3 group and fluorine atoms.
Thereby, highly fluorinated 6FTDA-based PIs have a complex of
required properties. Owing to the low hydrogen content (H ꢀ 1%)
and the high hydrophobicity 6FTDA-based PIs are expected to
reveal low optical transmission losses in the near-infrared region
and to be promising materials for optical communications.
References
[18] (a) V.V. Korshak, S.V. Vinogradova, Ya.S. Vygodskii, Russ. Chem. Bull. Int. Ed 17
(1968) 1331–1332;
[1] S. Ando, T. Matsuura, S. Sasaki, in: G. Hougham (Ed.), Fluoropolymers 2: Proper-
ties, Kluwer Academic/Plenum Publishers, New York, 1999, pp. 277–303.
[2] G. Hougham, in: G. Hougham (Ed.), Fluoropolymers 2: Properties, Kluwer Aca-
demic/Plenum Publishers, New York, 1999, pp. 233–276.
[3] (a) Y.N. Sazanov, Russ. J. Appl. Chem. (Engl. Transl.) 74 (2001) 1253–1269;
(b) J. Abajo, J.G. Campa, Adv. Polym. Sci. 140 (1999) 23–59;
(c) M.G. Dhara, S. Banerjee, Prog. Polym. Sci. 35 (2010) 1022–1077.
[4] S. Sasaki, Nishi, in: M.K. Ghosh, K.L. Mittal (Eds.), Polyimides: Fundamental and
Applications, Marcel Dekker Inc., New York, 1996, pp. 71–120.
[5] (a) C.-P. Yang, Y.-Y. Su, K.-L. Wu, J. Polym. Sci. A: Polym. Chem. 42 (2004) 5424–
5437;
(b) Y. Shao, Y.F. Li, X. Zhao, T. Ma, C.L. Gong, F.C. Yang, J. Polym. Sci. A: Polym.
Chem. 44 (2006) 6836–6846;
(c) F. Yang, Y. Li, T. Ma, Q. Bu, S. Zhang, J. Fluorine Chem. 131 (2010) 767–775.
[6] (a) T. Ichino, S. Sasaki, T. Matsuura, S. Nishi, J. Polym. Sci. A: Polym. Chem. 28
(1990) 323–331;
(b) S.V. Vinogradova, Ya.S. Vigodskii, N.A. Churochkina, V.V. Korshak, Vysoko-
molekulyarnye Soedineniya B (USSR) 19 (1977) 93–94, C.A 86:140540;
(c) T. Kaneda, T. Katsura, K. Makagawa, H. Makino, J. Appl. Polym. Sci. 32 (1986)
3133–3149.
[19] S.V. Lavrov, A.A. Kusnetsov, V.I. Berendyaev, B.V. Kotov, N.B. Kotina, V.V. Yakush-
kina, A. Ya. Tsegelskay, SU Patent 1809612 (1996).
[20] A.A. Kuznetsov, High Perform. Polym. 12 (2000) 445–460.
[21] F. Hazanian, Z.-Y. Wang, Polymer 49 (2008) 831–835.
[22] S.S. Laev, L.Yu. Gurskaya, G.A. Selivanova, I.V. Beregovaya, L.N. Shchegoleva, N.V.
Vasil’eva, M.M. Shakirov, V.D. Shteingarts, Eur. J. Org. Chem. (2007) 306–316.
[23] H. Yamamoto, Y. Mi, S.A. Stern, J. Polym. Sci. B: Polym. Phys. 28 (1990) 2291–2304.
[24] Y. Li, M. Ding, J. Xu, Macromol. Chem. Phys. 198 (1997) 2769–2779.
[25] V. Kute, S. Banerjee, J. Appl. Polym. Sci. 103 (2007) 3025–3044.
[26] C.L. Chung, W.F. Lee, C.H. Lin, S.H. Hsiao, J. Polym. Sci. A: Polym. Chem. 47 (2009)
1756–1770.
[27] R. Hariharan, M. Sarojadevi, Polym. Int. 26 (2007) 22–31.
[28] K. Wang, L. Fan, J.G. Liu, M.S. Zhan, S.Y. Yang, J. Appl. Polym. Sci. 107 (2008) 2126–
2135.
(b) A.E. Feiring, B.C. Auman, R.R. Wonchoba, Macromolecules 26 (1993) 2779–
2784.
[7] B.C. Auman, D.P. Higley, K.V. Scherer, E.F. McCord, W.H. Shaw, Polymer 36 (1995)
651–656.
[29] S.H. Hsiao, W. Guo, C.L. Chung, W.T. Chen, Eur. Polym. J. 46 (2010) 1878–
1890.
[8] (a) A.L. Rusanov, L.G. Komarova, M.P. Prigozhina, A.A. Askadskii, S.A. Shevelev,
A.K. Shakhnes, M.D. Dutov, O.V. Serushkina, Polym. Sci. B 48 (2006) 209–212;
(b) J.K. Park, D.H. Lee, B.J. Song, J.B. Oh, H.K. Kim, J. Polym. Sci. A: Polym. Chem. 44
(2006) 1326–1342.
[9] (a) J.P. Critchley, V.C.R. McLoughlin, J. Thrower, I.M. White, Br. Polym. J. 2 (1970)
288–293;
[30] G. Hougham, G. Tesoro, A. Viehbeck, Macromolecules 29 (1996) 3453–3456.
[31] G. Hougham, G. Tesoro, A. Viehbeck, J.D. Chapple-Sokol, Macromolecules 27
(1994) 5964–5971.
[32] (a) R.A. Dine-Hart, W.W. Wright, Macromol. Chem. (1971) 189–206;
(b) B.V. Kotov, T.A. Gordina, V.S. Voishchev, O.V. Kolninov, A.N. Pravednikov,
Polym. Sci. USSR (Engl. Transl.) 19 (1977) 711–716.
(b) J.P. Critchley, M.A. White, J. Polym. Sci. A-1 10 (1972) 1809–1825;
(c) J.P. Critchley, P.A. Grattan, M.A. White, J.S. Pippett, J. Polym. Sci. A-1 10 (1972)
1789–1807.
[33] (a) C.P. Yang, R.S. Chen, K.H. Chen, J. Polym. Sci. A: Polym. Chem. 41 (2003) 922–
938;
(b) J.G. Liu, M.H. He, Z.X. Li, Z.G. Qian, F.S. Wang, S.Y. Yang, J. Polym. Sci. A: Polym.
Chem 40 (2002) 1572–1582;
(c) T. Matsuura, Y. Hasuda, S. Nishi, N. Yamada, Macromolecules 24 (1991) 5001–
5005;
[10] G. Hougham, G. Tesoro, J. Shaw, Macromolecules 27 (1994) 3642–3649.
[11] (a) S. Ando, T. Matsuura, S. Sasaki, Macromolecules 25 (1992) 5858–5860;
(b) G. Masuda, Y. Okumura, S. Nishimae, T. Naraya, US patent 2005/020839
(2005).
(d) S. Ando, T. Matsuura, S. Sasaki, Polym. J. 29 (1997) 69–76.