Fluorine and phosphine oxide containing homo and copolyimides

Article abstract of DOI:10.1016/j.jfluchem.2016.03.016

In recent years the synthesis of fluorinated polyimides has become an active area of research. In this study perfluoroalkyl and phosphine oxide containing diamine monomer, bis(3,3′-aminophenyl)-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) phosphine oxid

Full text of DOI:10.1016/j.jfluchem.2016.03.016

Accepted Manuscript
Title: Fluorine and phosphine oxide containing homo and
copolyimides
¨
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Author: Emrah C¸ akmakc¸ı Atilla Gungor Ahmet Ceyhan
¨
Goren
PII:
S0022-1139(16)30077-X
DOI:
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http://dx.doi.org/doi:10.1016/j.jfluchem.2016.03.016
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Please cite this article as: Emrah C¸ akmakc¸i, Atilla Gungor, Ahmet Ceyhan Goren,
Fluorine and phosphine oxide containing homo and copolyimides, Journal of Fluorine
Chemistry http://dx.doi.org/10.1016/j.jfluchem.2016.03.016
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FLUORINE AND PHOSPHINE OXIDE
CONTAINING HOMO AND COPOLYIMIDES
Emrah Çakmakçı1, Atilla Güngör1*, Ahmet Ceyhan Gören2
1Marmara University, Department of Chemistry 34722 Istanbul/Turkey
2 TUBITAK-UME, Chemistry Group Laboratories, P.O. Box 54, 41470, Gebze/Turkey
* Corresponding Author
E-mail: atillag@marmara.edu.tr
Tel: +90 216 3487759 Fax: +90 216 3478783
1

Graphical Abstract
Phosphorous containing novel perfluorinated diamine monomer, mDA13FAPO was synthesized and used in the
preparation of homo and copolyimides. Due to the fluorous tail of mDA13FAPO polyimides exhibited
hydrophobicity with a water contact angle value of 102º and surface energy value of 30 mN/m.
Highlights
 Fluorine and phosphorous containing diamine monomer was synthesized.
 The new diamine monomer was used to prepare homo- and copolyimides.
 All homopolyimides displayed moderate Tg values but poor film forming properties.
 Copolymerization improved the film forming properties.
 Surface energy of the copolyimides were found to be between 30 and 37.5 mN/m.
2

ABSTRACT
In recent years the synthesis of fluorinated polyimides has become an active area of research.
In this study perfluoroalkyl and phosphine oxide containing diamine monomer, bis(3,3ˈ-
aminophenyl)- (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) phosphine oxide (mDA13FAPO),
was successfully prepared. mDA13FAPO was reacted with four different commercial
dianhydrides (BTDA, PMDA, ODPA and 6FDA) and corresponding homopolyimides were
prepared by thermal and solution imidization techniques. However, homopolyimides of
mDA13FAPO exhibited poor film forming properties. In order to overcome this problem
different amounts of mDA13FAPO containing copolyimides with BTDA and ODA were
prepared. The flame retardancy of the copolyimides was examined by limiting oxygen index
measurements. The surface energies of the copolyimides were determined by contact angle
measurements. mDA13FPO containing homopolyimides exhibited moderate Tg values (194-
233°C), good thermal stability and excellent solubility. The presence of ODA greatly
improved the film forming properties and crack-free, creasable copolyimide films were
obtained. As the amount of mDA13FAPO was increased, the flame retardancy and the water
contact angles of the copolyimides increased while the surface energies and the glass
transition temperatures decreased
.
Keywords: fluorine; phosphine oxide; polyimides; surface energy
3

1. Introduction
Aromatic polyimides which are known as high performance engineering polymers, have a wide
range of uses, from gas separation membranes to fuel cell applications, from electric-electronic
industry to optic materials, from aerospace industry to military applications due to their outstanding
thermal, mechanical, electrical and chemical properties [1-3].
Although polyimides have a wide range of uses they suffer from the lack of processability and
solubility which arise from their rigid polymer backbones. In order to increase the processability of
polyimides, several efforts such as the use of bulky side groups, flexible side groups, asymmetric
monomers, flexible linkages, fluorine containing monomer etc., have been made [4-6]. Among these
strategies to improve the solubility/processability of polyimides, the introduction of fluorine
containing species as main chain components or as pendant groups has several advantages such as low
dielectric constants, low refractive index, low water absorption, optical clarity, high permeability and
high selectivity for gas separation, hydrophobicity and oleophobicity, besides the increased solubility
[7-9]. On the other hand one of the main drawbacks of fluorine containing polyimides is their low
adhesion properties [9].
Generally fluorine is incorporated into polyimides as trifluoromethyl groups. Bulky
trifluoromethyl groups reduce the chain packing which results in high free volume and thus
trifluoromethyl group containing polyimides exhibit high solubility and processability [10].
Hexafluoroisopropylidene bisphthalic dianhydride, known as 6FDA, is one of the most widely used
fluorinated monomer which contains two trifluoromethyl groups (a hexafluoroisopropylidene group)
[11]. Up to now, several different monomers were designed with trifluoromethyl or
hexafluoroisopropylidene units which are generally attached to the aromatic backbone of polyimides
[12-16]. In addition to these fluorinated polyimides, pendant fluoroalkyl containing polyimides were
also prepared [17-19]. Introduction of a fluoroalkyl side chain allows to prepare polyimides with
high fluorine content and interesting properties [19]. For instance Bes et al. prepared
fluorinated alkoxy side group containing polyimides by using Mitsunobu reaction. The
resulting polyimides exhibited good thermal properties and enhanced solubility [19]. In
4

another study, gas separation properties of polyimides prepared from 2-(perfluorohexyl)ethyl-
3,5-diamino benzoate, were investigated and it was found that the fluorinated side groups
improve the permeability of these polyimides [20]. Recently a nice review has been published
on the synthesis of fluorinated monomers used in the preparation of polyimides [21].
Phosphorus containing polymers are considered as highly efficient halogen-free flame
retardant alternatives [22, 23]. Besides, polymers with phosphorus moieties have several
advantages such as good adhesion to various substrates, excellent solubility in organic
solvents, high thermal oxidative stability and radiation resistance [24-26]. Moreover it was
shown that polymers with phosphine oxide groups are resistant to atomic oxygen exposure
[27, 28]. To date, several phosphorus containing polyimides have been synthesized by using
either phosphorus containing diamines/dianhydrides or by using different phosphorylating
methods [29, 30].
Today, studies concerning fluorinated polyimides mainly focus on the synthesis of
polyimides by using new type of monomers. In the last decade to overcome the low adhesion
problems associated with fluorinated polyimides, Yoon and his group prepared several
polyimides from both fluorine and phosphine oxide containing diamine monomers [31-35].
These polyimides displayed excellent adhesion, good thermal properties and low dielectric
constants. Similarly different researchers have also designed novel monomers having both
fluorine and phosphorus and utilized them in the synthesis of polyimides [36, 37].
Previously synthesized both fluorine and phosphine oxide groups containing diamine
monomers are presented in Table SI.
Although, in literature several synthetic methods have been proposed for the
preparation of fluoroalkyl phosphines and phosphine oxides, to authors’ best knowledge there
is no published work on the preparation of the dinitro and diamine derivatives of these long
5

fluoroalkyl phosphine oxides and to our best knowledge no attempt was done to prepare
polyimides from both long-chain perfluoroalkyl and phosphine oxide containing monomers.
In this study perfluoroalkyl and phosphine oxide containing diamine monomer,
bis(3,3ˈ-aminophenyl)- (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) phosphine oxide
(mDA13FAPO) which contains 13 moles of fluorine per mole of the compound was
synthesized. Then four different homopolyimides were prepared from commercial
dianhydrides (BTDA, PMDA, ODPA and 6FDA) and mDA13FAPO. The monomers were
characterized by FT-IR, 1H-NMR, 19F-NMR and 31P-NMR measurements. However,
homopolyimides of mDA13FAPO were highly brittle and these materials exhibited poor film
forming properties. Therefore in this study a series of mDA13FAPO containing BTDA/ODA
based copolyimides were prepared in order to overcome this problem. Thermal properties of
novel polyimides were investigated by TGA and DSC measurements. The mechanical
properties of the copolyimides were investigated by tensile measurements. The flame
retardancy of these materials was examined by limiting oxygen index (LOI) measurements.
Moreover hydrophobicity and the surface energy of the coatings were determined by contact
angle measurements. The surface topology of the films was observed by a scanning electron
microscope (SEM).
2. Experimental
2.1. Materials
3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 2,2'-Bis-(3,4-
Dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), Pyromellitic Anhydride (PMDA),
4,4'-Oxydiphthalic anhydride (ODPA), Triphenyl phosphine (TPP), dimethyl formamide
(DMF), dimethyl acetamide (DMAc), dimethyl sulfoxide (DMSO), N-methyl pyrrolidone
(NMP), meta-cresol, (m-Cresol), tetrahydrofuran (THF) and toluene were all purchased from
Sigma Aldrich. All dianhydrides were dried under vacuum prior to use. 2- Perfluorohexyl
6

ethyl iodide was obtained from Alfaeaser. Sulfuric acid, nitric acid, sodium hydroxide,
ethanol, chloroform, benzene, isopropyl alcohol and 10% palladium on an activated carbon
(Pd/C) were purchased from Merck and used as received. Sodium bicarbonate and anhydrous
magnesium carbonate were obtained from AcrosOrganics. Celite was purchased from Fluka.
2.2. Characterization Methods
FT-IR spectra were recorded on Perkin Elmer Spectrum100 ATR-FTIR
spectrophotometer.
1H-NMR, 31P-NMR, 19F-NMR and 2-D NMR spectra were recorded using a Varian
Model T-60 NMR spectrometer at room temperature. All samples were dissolved in solvents
like CDCl3, acetone-d6 and tetramethylsilane was used as an internal reference for proton
shifts.
Thermogravimetric analyses (TGA) of polyimide films were performed using a
Perkin-Elmer Thermogravimetric analyzer Pyris 1 TGA model. Samples were run from 30 to
750 C with heating rate of 10 C / min under air atmosphere and nitrogen atmosphere.
DSC measurements were performed using Pyris Diamond DSC. Samples were run
from 30 to 300 C with a heating rate of 10 C / min. Glass transition temperatures were
obtained from the second heating scan.
The flammability characteristics of copolyimides were determined by LOI test. The
LOI values of the polyimide materials were measured by using a FTT (Fire Testing
Technology) type instrument.
Mechanical properties of polyimide films were determined by standard tensile stress-
strain tests to measure modules, ultimate tensile strength and elongation at break. Standard
tensile stress-strain experiments were performed at room temperature on a Materials Testing
Machine Z010 / TN2S, using a crosshead speed of 2 mm/min.
7

The wettability characteristics of polyimide surfaces were performed on a Kruss (Easy
Drop DSA-2) tensiometer. The contact angles (θ) were measured by means of sessile drop test
method in which drops were created by using a syringe. Measurements were made using 3-5
µl drops of distilled water. For each sample, at least five measurements were made, and the
average was taken. The surface energy of the coatings was calculated using Owens-Wendt-
Rabel & Kaelble approach. For the calculation of the surface energy three test solutions were
considered, water and ethylene glycol as polar solvents and diiodomethane as an apolar
solvent.
The transmission spectra of the novel polyimides were recorded in the wavelength
range of 300-800 nm using a Shimadzu 3100 UV–vis–NIR spectrometer.
SEM imaging of the films and mapping technique were performed on Philips XL30
ESEM-FEG/EDAX. The specimens were prepared for SEM by freeze-fracturing in liquid
nitrogen and applying a gold coating.
Solubility of the polyimides was determined by dissolving 10 mg of polymer samples
in 1 ml of solvent.
2.3. Synthesis of (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) diphenyl phosphine oxide
(13FADPPO)
The synthesis of the diamine monomer, bis(3,3ˈ-aminophenyl)
(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) phosphine oxide (mDA13FAPO), involves four
synthetic steps: 1) Synthesis of the phosphonium salt, 2) Hydrolysis (dephenylation) of the
phosphonium salt in step1, 3) Nitration and 4) Reduction. The synthetic route to
mDA13FAPO is depicted in Scheme 1.
In the first step, a fluorinated phosphonium salt was synthesized by reacting TPP and
2-perfluorohexyl ethyl iodide according to literature procedures [38, 39]. Briefly, the
fluorinated phosphonium salt was prepared by reacting TPP and fluoroalkyl iodide at 95 ˚C in
8

the absence of solvent. The reaction was continued for 24 hours until all of the mixture was
solidified. After cooling the resulting solid was washed several times with toluene and ether
respectively. Then the white solid was dried at 50 ˚C under vacuum.
Next, this phosphonium salt was dephenylated to give (3,3,4,4,5,5,6,6,7,7,8,8,8-
tridecafluorooctyl) diphenyl phosphine oxide (13FADPPO). The procedure of selectively
removal of one of the phenyl groups of the phosphonium salt was carried out similar to
literature [40]. Briefly, phosphonium salt was placed into a 1 liter round-bottomed flask and
treated with 0,271 moles of NaOH (four times excess of phosphonium salt) and with a
mixture of isopropyl alcohol/ water (v/v 1:3). The suspension was refluxed for one day at 120
˚C. At the end of the reaction, two phases were observed (water (bottom phase) and benzene
(top phase) phases). Two phases were separated and water phase was extracted with benzene
two times. Then benzene extracts were collected and dried over anhydrous MgSO4. After
filtration, benzene was evaporated under vacuum. White crystalline 13FADPPO was dried at
50 ˚C under vacuum without further purification. 20.4 g of product was obtained (yield: 55%).
(m.p. 107ºC. 1H-NMR (600MHz, CDCl3) δ 7,78 (4H, m); 7.58 (2H, m); 7.52 (4H, m); 2.54 (2H, m); 2.4 (2H,
m). 19F-NMR (564 MHz, CDCl3) δ -81.00; -114.87; -112.07; -123.05; -123.26; -126.34. 31P-NMR (242 MHz,
CDCl3) δ 27.63.)
2.4. Synthesis of bis(3,3ˈ-nitrophenyl)- (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)
phosphine oxide (mDN13FAPO)
In the third step, mDN13FAPO was prepared via nitration of 13FADPPO. A three
necked 500 ml round bottom flask, equipped with magnetic stirring, nitrogen inlet and an
addition funnel was placed in an ice/salt bath at -5 ˚C. The flask was first charged with 15
grams of 13FADPPO (0.0273 mol) and dissolved in 150 ml of concentrated sulfuric acid to
make a 10 % (w/v) solution. Then a cooled mixture of approximately 3.9 ml (0.06 mol) nitric
acid (%69) and 21 ml sulfuric acid was added dropwise for 3 hours while maintaining the
temperature below 0 ˚C. After this period, the yellow colored mixture was further stirred at
9

room temperature for 24 hours. At the end of the reaction period, the mixture was poured into
1 kg of crushed ice. After the ice was melted, the organic material was extracted with
chloroform. Chloroform extracts were washed several times with aqueous sodium bicarbonate
(5 wt. %) solutions and distilled water, respectively. Acid free chloroform solution was dried
over anhydrous MgSO4 and yellow organic material was obtained after rotary evaporation.
Finally mDN13FAPO was purified by recrystallization from ethanol. 17.4 grams of a light-
yellow product was obtained (yield: 95%). The total mole value of the nitric acid used for the
reaction was 2.2 excess of the mole value of 13FADPPO. Sulfuric acid which was mixed with
nitric acid was used as catalyst and its amount was adjusted to be 10 folds of the weight of
nitric acid.
1
( m.p. 145 ºC. H-NMR (600 MHz, CDCl3) δ 8.64 (2H, d), 8.48 (2H, d), 8.18 (2H, t), 7.83 (2H, t), 2.7
(2H, m), 2.48 (2H, m). 19F-NMR (564 MHz, CDCl3) δ -80.799, -114.55, -121.89, -123.01, -123.03, -126.2. 31P-
NMR (243 MHz, CDCl3) δ 24.499.)
2.5. Synthesis of bis(3,3ˈ-aminophenyl) (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)
phosphine oxide (mDA13FAPO)
Bis(3,3ˈ-aminophenyl) (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) phosphine oxide
(mDA13FAPO) was obtained by hydrogenation of mDN13FAPO in a high pressure reactor
(Parr Instrument Co., USA). mDN13FAPO (15 g), methanol (500 mL), and Pd/C catalyst (0.5
g) were charged into the flame dried pressure reactor. First, the reactor was purged with
nitrogen gas for several minutes and then pressured with hydrogen gas to 100 psi. The
reaction mixture was heated at 50 ˚C and allowed to react for 48 h under constant stirring.
Next, the reaction mixture was filtered over Celite. The methanol was removed by rotary
evaporation and a brownish-white crystals were obtained with a yield of approximately 65%.
10

1
(m.p. 126ºC. H-NMR (600MHz, CDCl3) δ 7.28 (2H, m); 7.1 (2H, d); 7.00 (2H, m); 6.84(2H, d); 4.96 ppm
(4H, s). 19F-NMR (564 MHz, CDCl3) δ -80,8; -114,7; -121,91; -122,9; -123,12; -126,17.31P-NMR (242 MHz,
CDCl3) δ 31,48.)
2.6. Synthesis of polyimides by thermal imidization
Thermally imidized polyimides were prepared similar to our previous publications
[41, 42]. To synthesize poly(amic acid) (PAA) solutions, calculated amount of mDA13FAPO
was first put into a flame dried three-neck flask. The monomer was then dissolved in DMF
under a nitrogen purge. The flask was then immersed in an ice/salt bath (-5-0˚C). After the
diamine was completely dissolved in DMF, an equimolar amount of dianhydride (PMDA,
ODPA, BTDA or 6FDA) was added to the flask batch by batch. The mixture was stirred at
this temperature for 3 hours than stirred overnight at room temperature to obtain a PAA
solution. The solid concentration was afforded as 20 (wt/wt) %. Polyimide membranes were
prepared by casting PAA solutions on clean dust-free glass plates. Then thermal imidization
was performed stepwise at 100, 150, 200, and 300˚C for 1h at each temperature. The
procedures for preparing poly(amic acid) and polyimide films are shown in Scheme 2. The
yields of these thermally polyimides were found to be between 75-80%.
2.7. Synthesis of polyimides by solution imidization
mDA13FAPO containing aromatic polyimides were also synthesized by a thermal
solution imidization method. Polyamic acid solutions were prepared as described above in a
three necked flask equipped with a nitrogen inlet, drying tube and a condenser. The poly(amic
acid) solution was then heated at 160 ˚C for 24 h in order to synthesize the desired polyimides
The water formed during condensation was removed by nitrogen gas. The polyimide solution
was cooled to room temperature and was precipitated into acetone. The polyimide was filtered
off and dried under vacuum at 120 ˚C. Dried polyimide powders were dissolved in solvents
like DMF or CHCl3 and their 5 wt. % solutions were prepared. Then these polyimide
solutions were cast on glass slides and polyimide membranes were obtained after removal of
11

the solvent by heating to 200 ˚C or below depending on the solvent used. The yields were
over 90% for the each of these solution imidized polyimides.
2.8. Preparation of copolyimides by thermal imidization
In this study different amounts of (0 %, 25 %, 50%, 75% and 100%) mDA13FAPO
containing copolyimides were prepared with the aid of ODA and BTDA. Polyimides were
prepared by the classical thermal imidization method. First calculated amount of
mDA13FAPO and ODA diamines were charged into a flame dried three-neck flask. The
diamine monomers were then dissolved in DMF under a nitrogen purge. The flask was then
immersed in an ice/salt bath (-5-0˚C). After complete dissolution of diamines in DMF, an
equimolar amount of BTDA was added to the flask batch by batch. The mixture was stirred at
this temperature for 3 hours than stirred overnight at room temperature to obtain a PAA
solution. The solid concentration was afforded as 20 (wt/wt) %. Polyimide membranes were
prepared by casting PAA solutions on clean dust-free glass plates. Then thermal imidization
was performed stepwise at 100, 150, 200, and 300˚C for 1h at each temperature. The
procedures for preparing poly(amic acid) and polyimide films are shown in Scheme 3. The
yields were in the range of 80-90%.
3. Results and discussion
In this study it was aimed to prepare polyimides from a new diamine monomer,
mDA13FAPO which possesses both fluorine and phosphine oxide groups. Different than the
previous studies, in this study fluorine is incorporated into this original monomer as a
perfluoroalkyl group and it is separated from the phosphine oxide group via an ethyl spacer
group.
12

3.1. Synthesis and characterization of monomers: 13FADPPO, mDN13FAPO and
mDA13FAPO
13FADPPO was synthesized by dephenylation of the phosphonium salt obtained from
the reaction of TPP and perfluorohexyl ethyl iodide. The melting temperature of the
phosphonium salt was found as 170 ˚C which is in good agreement with literature [38] and
the yield was about 90%. After dephenylation, 13FADPPO was obtained with a yield of 55%.
From the nitration and subsequent reduction of this compound, mDN13FAPO and
mDA13FAPO were synthesized with yields of 95% and 65% respectively. Thus the total
reaction yield is 34 % which is comparable to the yield of mDAPPO (bis(3-aminophenyl)-
phenyl phosphine oxide) [43].
Structural characterization of 13FADPPO, mDN13FAPO and mDA13FAPO were
performed by FTIR, 1H-NMR, 31P-NMR and 19F-NMR analysis. In the FTIR spectrum
(Figure 1) of 13FADPPO, the P=O stretching absorption was appeared at 1179 cm-1 while it
slightly shifted to 1184 cm-1 due to the electron withdrawing effect of nitro groups [32]. The
absorption band of the same group for mDA13FAPO was found at 1184 cm-1. In all FTIR
spectra, C-F bond vibrations were detected at 1300-1100 cm-1. Characteristic infra-red
absorption frequencies of the nitro groups were observed at 1345 cm-1 (symmetric) and 1532
cm-1 (asymmetric) for mDN13FAPO. After reduction of the nitro groups to amino groups,
these peaks were disappeared and in the spectrum of mDA13FAPO, new peaks were appeared
at 3454, 3329 and 1594 cm-1 which are related to amino groups. Moreover in all FTIR spectra,
aliphatic –CH groups’ stretching vibrations appeared at around 2980-2840 cm-1.
In the 1H-NMR spectrum of 13FADPPO three peaks were resonated at 7.78 (4H, m),
7.58 (2H, m) and 7.52 (4H, m) ppm in the aromatic region (Figure 2). Also in this spectrum
peaks at 2.54 (2H, m) and 2.4 (2H, m) ppm are due to the spacer –CH2CH2- group between
the fluorus tail and the P=O group. These two peaks are both multiplets and it shows that –
13

CH2 protons also split into neighbour fluorines. It can be seen from the proton spectrum of
mDN13FAPO that the peaks in the aromatic region were downfield shifted due to the electron
withdrawing effect (deshielding effect). Four aromatic proton peaks were observed at
8.64 (2H, d), 8.48 (2H, d), 8.18 (2H, t) and 7.83 (2H, t) ppm, respectively. Aliphatic –CH2
peaks were also observed as multiplets at 2.7 (2H, m) and 2.48 (m) ppm. Similarly
mDA13FAPO has four different aromatic protons which resonate at 7.28 (2H, m), 7.1 (2H, d),
7.00 (2H, m) and 6.84(2H, d). As expected these peaks appeared at lower chemical shift
values (shifted upfield) due to the electron donating effect of amino groups. Moreover the
peak at 4.96 ppm (4H, s) is due to amino groups.
31P-NMR spectra are important that they display the purity of the synthesized
compounds (Figure 3). In all phosphorous NMR spectra, only one single sharp peak was
observed and this indicates high purity of the monomers. Phosphorous NMR peaks were
observed at 27.63 ppm, 24.49 ppm and 31.48 ppm for 13FADPPO, mDN13FAPO and
mDA13FAPO, respectively. Contrast to proton NMR results, phosphorous NMR peaks were
upfield shifted upon nitration and downfield upon reduction [32-34].
19F-NMR spectra of the compounds are given in Figure 4. In all 19F-NMR spectra six
different sharp peaks were observed at almost same chemical shifts for 13FADPPO,
mDN13FAPO and mDA13FAPO, respectively. Furthermore these peaks are also in good
agreement with the 19F-NMR spectrum of 1H,1H,2H,2H-Perfluorooctyl)diphenylphosphine
[44].
Melting points of the newly synthesized monomers were determined by DSC
measurements. The melting points were found as 107 ˚C, 145 ˚C and 126 ˚C for 13FADPPO,
mDN13FAPO and mDA13FAPO, respectively. These compounds exhibited narrow melting
points which indicate high degree of purity.
14

Finally the percent amine content of mDA13FAPO was determined by titration and
found as 5.35 wt. % which is very close to the theoretical value, 5.54 wt. %.
3.2. Structural characterization of homo and copolyimides
In this study four different homopolyimides were synthesized via thermal and solution
imidization techniques. Moreover three copolyimides were synthesized via thermal
imidization technique. Also BTDA/ODA homopolyimide was prepared for comparison.
Figure S1 shows the FTIR spectra of the polyamic acids (PAA) of the corresponding
homopolyimides. All PAAs exhibited similar spectra. –P=O absorptions were detected at
around 1180 cm-1. The characteristic carbonyl stretchings due to –NHCO- bonds were
observed at 1660 cm-1. Also the peaks at 1548 cm-1 corresponds to –NH bending vibrations.
The FTIR spectra of synthesized homopolyimides and the copolyimides can be seen in Figure
5 and Figure S2 respectively. For all homo and copolyimides, characteristic imide peaks were
observed at 1780-1785 cm-1 (asymmetric stretching of imide carbonyls), 1720 cm-1
(symmetric stretching of imide carbonyls) and at 1360 cm-1 (C-N stretchings). These results
confirm that all polyimides were successfully synthesized. Different than the other
polyimides, BTDA- mDA13FAPO homopolyimide exhibited an additional carbonyl peaks at
1675 cm-1 due to the carbonyl group of BTDA. Finally after imidization –P=O absorptions
shifted to wavenumbers at around 1190 cm-1.
3.3. Solubility and film forming properties of polyimides
Generally polyimides obtained from solution imidization are much more soluble and
processable than the thermally imidized ones. This situation is related to crosslinking
reactions occur at high temperatures and thermal imidization favors chain packaging which
provides higher molecular order [44]. In this study homopolyimides prepared via the thermal
imidization technique were not soluble. But mDA13FAPO containing solution imidized
15

polyimides exhibited excellent solubility (Table 1) in several organic solvents owing to the
asymmetric phosphine oxide moiety and the flexible fluorous tail which increase the free
volume of the homopolyimides. Also phosphine oxide groups’ polarity and their ability to
form strong interactions with solvents enhanced the solubility properties of these polyimides
[32].
However, both the solution and the thermally imidized homopolyimides exhibited
poor film forming properties. It is known that a sufficient level of molecular weight should be
reached in order to prepare polymeric films with good filming properties thus monomers with
high purity are needed for the polycondensation reactions according to well-known Carother’s
equation. Although in our case NMR and other techniques indicate that monomers were in
high purity but the relatively small amounts of impurities and monofunctional species found
in mDA13FAPO monomer could have adversely affected the film forming properties of these
polyimides by preventing to reach high molecular weights. The relatively low viscosities for
mDA13FAPO containing polyimides support this view that the synthesized polyimides had
low molecular weights. The viscosity of both the polyamic acid and the polyimide solutions
were generally low (results are not given). On the other hand low viscosities can also be due
to the fluorous pendant groups which decrease the interactions between chains and decrease
the intrinsic viscosity of the polyimides.
It was previously reported that fluorine containing diamines have low reactivity due to
the electron withdrawing effect of fluorine [17, 45]. The reason for the poor filming properties
of the mDA13FAPO containing polyimides could also be related to the decreased reactivity of
this monomer bearing both electron withdrawing fluorine and phosphine oxide moieties.
Different than the previously synthesized mDA3FPPO, mDA6FPPO, and mDA7FPPO
monomers, mDA13FAPO monomer has higher amounts of fluorine and these fluorine atoms
16

are not attached to an aromatic ring. The long flexible fluorinated pendant alkyl group could
have caused steric hindrance and thus have decreased the reactivity of mDA13FAPO.
Although in literature there are several studies that report successfully preparation of
fluorine containing polyimide films, there are also several examples where polyimide films
were produced with poor filming properties. For instance G. Hougham at al., tried to prepare
several perfluorinated polyimide films and some of these polyimide films were found to be
highly brittle [17]. They then utilized a new method, which they referred as “cyclic process”
in order to increase molecular weight of the polyimides by redissolving the cured cracked
polyimide materials and redrying. This procedure was repeated until obtaining a crack free
polyimide films. Also Auman et al., prepared perfluorinated polyimides and found that most
of the films cracked during imidization [19]. In this study films prepared from BTDA and
6FPA had better film forming properties than ODPA and PMDA based polyimides.
Since both the solution and thermally imidized homopolyimides of mDA13FAPO
exhibited low mechanical strength and poor film forming properties we prepared its
copolymers with ODA in order obtain continuous films. 25 wt.% and 50 wt.% mDA13FAPO
containing films were found to be crack free and creasable. %75 mDA13FAPO containing
films were fair, but rather brittle.
3.5. Thermal properties
Generally long perfluoroalkyl groups adjacent to hydrogen bearing carbon atoms (i.e.:
-CH groups) cause a reduction in the thermal properties of polymers due to their relatively
low thermo-oxidative stability when compared to fluorine containing aromatic analogues [9,
18]. In this study the synthesized monomer mDA13FAPO, also addresses this problem by
combining a perfluoralkyl group with highly thermo-oxidative phosphine oxide groups.
Thermal properties of homopolyimides are given in Table 2. Figure S3 and Figure S4
show the thermal degradation behavior of mDA13FAPO containing homopolyimides under
17

air and nitrogen atmospheres. It can be seen from the results that all homopolyimides
exhibited high thermo-oxidative stability and high char yields. Parallel to the studies of Yoon,
ODPA-mDA13FAPO polyimides exhibited the highest thermal stability under air atmosphere
among other polyimides [32]. The higher thermal stability of these polyimides was attributed
to both fluorine and phosphine oxide groups. The obtained char yields were not as much as
expected due to the high inorganic content of the polyimides. This situation can be attributed
to early decomposition of the fluorous pendant group or rapid HF elimination at elevated
temperatures. On the other hand, owing to the presence of phosphine oxide groups, this
situation did not result a dramatic decrease in the thermal properties of these polyimides.
Thermal properties of copolyimides are given in Table 3. Thermograms of the
copolyimides under air and nitrogen atmospheres are given in Figure S5 and Figure S6
respectively. It can be seen from the results that all copolyimides exhibited high thermo-
oxidative stability and high char yields.
When compared to the BTDA/ODA homopolyimide films, a decrease was observed in
the initial decomposition and the maximum weight loss temperatures which can be attributed
to the early decomposition of these copolyimides which in turn exhibited high char yields
than BTDA/ODA homopolyimides.
Glass transition temperatures (Tg) of the polyimides and copolyimides are given in
Table 2 and Table 3 respectively. It can be clearly seen from these results that the fluorinated
pendant alkyl groups containing homopolyimides exhibit low Tg values. Pendant fluoro alkyl
groups decreased the chain packing and thus increased the free volume of the polyimides. The
highest Tg value was found as 233 ˚C for PMDA containing polyimides and it is attributed to
the rigid backbone of this polyimides.
For the copolyimides it was found that the glass transition temperatures were
decreased as the amount of mDA13FAPO increased in the copolymer composition. The glass
18

transition temperature for BTDA/ODA was found as 297 °C while the Tg of BTDA/
mDA13FAPO homopolyimide was 203 °C. All copolyimides exhibited single Tg values and
thus we compared the experimental Tg values with the calculated Tg values obtained from the
well-known Fox equation:
W1 W2
1


.
Tg Tg1 Tg2
where W1 and W2 are the weight fractions and Tg1 and Tg2 are the glass transition
temperatures of homopolyimides.
Weight fractions were calculated according to the following equation:
miMi
Wi 
miMi

where mi and Mi are the molar fraction and the molecular weight of the repeating unit [46].
Calculated and experimental results were found to be very close for 50 and 75 percent
mDA13FAPO containing copolymers. However, the calculated Tg value for 25 percent
mDA13FAPO containing copolymers was highly deviated from the experimental value. The
positive deviation from the Fox equation indicates additional interactions in the polymer
matrix. Thus, this deviation for 25 percent mDA13FAPO containing copolymers can be
attributed to the interactions between phosphine oxide groups and it can be said that the
fluorous tail was not as efficient as expected to increase the free volume particularly for these
copolyimides. When the amount of mDA13FAPO increases, the experimental and calculated
Tg values start to get closer. Therefore it can be said that at higher amounts of mDA13FAPO,
the flexibilizing effect of the perfluorinated alkyl chain is much more dominant than the
interactions caused by the phosphine oxide groups.
19

3.6. Flame retardancy properties
LOI test is a common method for the determination of the flame retardancy of
polymeric materials. Due to the poor film forming properties of mDA13FAPO containing
polyimides, we could not be able to determine the flammability characteristics of these
homopolyimides. But the flame retardancy of these homopolyimides were calculated
theoretically according to the following equation by van Krevelen [47] :
1/3
1/3
H
C
F
Cl
 
 
CP  o.65
1.1
 
 
C
 
C
 
where H/C, F/C and Cl/C are the atomic ratios of the respective elements in the polymer
composition and “cp” is composition parameter. And the LOI value can be derived from the
following correlations:
For CP ≤ 1: LOI ≈ 0.175 or 17.5 %
For CP ≥ 1: LOI ≈ 0.60 – 0.425 CP
Calculated LOI values are given in Table 2. The calculated LOI values were found to
change between 54 and 62. LOI values of the copolyimides are given in Table 3. All
copolyimides exhibited high flame retardancy and exhibited LOI values between 32 and 44.
The LOI values of copolyimide films were found to increase as the amount of mDA13FAPO
was increased due to the increase in the inorganic content and due to presence of both fluorine
and phosphine oxide groups. When previous studies on the flame retardant polyimides are
taken into consideration, it can be seen that the LOI values of several different neat
polyimides and their composites range from 28 to 60 [41, 48-53]. There are only few papers
that report the LOI values for the phosphorous containing polyimides [51, 52] or fluorinated
polyimides [41, 53]. For instance bis(3-aminophenyl) phenylphosphine oxide (BAPPO or
DAPPO) and bis(4-(3-aminophenoxy)phenyl) phenylphosphine oxide (m-BAPPO) containing
fluorinated copolyimides displayed high LOI values of 46 and 48, respectively [51]. In
20

another work the LOI value of the only 7 mole percent (DAPPO) containing copolyimide
fibers were found as 43 [52].
3.7. Mechanical properties of the copolyimides
Since the homopolyimides in this work were brittle and exhibited poor film forming
properties only the mechanical properties of the copolyimides were determined. Tensile
strength, elongation at break and tensile modulus of copolyimides are displayed in Table 4.
As can be seen from the results due to the presence of flexible perfluoroalkyl group, modulus
of the copolyimides decreased while elongation at break values increased. Thus it can be said
that 25 and 50 percent mDA13FAPO containing copolyimides exhibited tough and flexible
character with better film forming properties. 75 % mDA13FAPO containing copolyimide
films were rather brittle and results showed that the modulus of this copolyimide was slightly
higher than 50 percent mDA13FAPO containing films. On the other hand its elongation at
break values dramatically decreased which reflects its brittle character. Overall it can be
concluded that we successfully prepared copolyimide films with good mechanical properties
in line with our goal to improve the film quality of mDA13FAPO containing polyimides.
3.8. Optical properties of copolyimide films
Generally fluorine containing polyimides are characterized by their high optical
transparencies and they are suitable for optical devices. The optical transparencies of
mDA13FAPO containing copolyimide films were characterized by UV-vis. spectroscopy.
Fig. 6 shows the transmission spectra of novel copolyimide films in the range between 300
and 800 nm. It was found that the optical transmittance of copolyimides increased with
increasing amount of mDA13FAPO. However, even at 100% mDA13FAPO containing
polyimide films, the optical transparency was found to be lower than the transparency of
21

BTDA/ODA homopolyimides. This situation could be related to contribution of the
phosphine oxide group to the total UV absorption.
3.9. Surface energy and contact angle values of mDA13FAPO containing copolymers
The hydrophobicity and the oleophobicity of the hybrid coating materials were
investigated by water and diiodomethane contact angle measurements. The results are shown
in Table 5. All contact angle measurements were obtained from the air side of the polyimides
and the reported values are at least the average of five different measurements. The results
showed that the addition of fluorine significantly increases both the water and the
diiodomethane contact angles. This behavior of fluorine containing materials is related with
the segregation of the fluorinated segment on the surface of the coatings and as a result the
surface energy of the coatings decreases [54]. Thus the fluorine enriched surface of the
polyimides showed increased hydrophobicity. Water contact angle images of the
copolyimides are presented in Figure 7. The increase in both the water and diiodomethane
contact angles may not seem as high as expected. Although mDA13FAPO contains high
amounts of fluorine, it also possesses a phosphine oxide unit which is a polar group.
Moreover the obtained results are in accordance with the results reported in literature [19].
The monomer designed by Laurence et al., contains the same molar amount of fluorine with
mDA13FAPO and the highest water and diiodomethane contact angles reported by them are
90.1˚ and 65.5˚, respectively.
Furthermore the surface energy values of the copolyimides can be seen in Table 5. As
can be seen from the table the surface energy of the polyimides decrease with increasing
amount of mDA13FAPO. The surface energy of the BTDA/mDA13FAPO was found as 30
mN/m. This result is also in accordance with the results given by Laurence et. al. [19] and
ref. [20].
22

3.7. Morphology
Figure 8 shows the surface morphology of BTDA-mDA13FAPO homopolyimides. It
can be seen from the SEM images that several crater like structures were formed on the
surface of the BTDA- mDA13FAPO homopolyimides. At higher magnifications several
bulges were detected on the surface of these mDA13FAPO containing polyimides. These
structures were attributed to phase separation between the polymer main chain and the
fluorous pendant groups. Thus the poor filming properties of these homopolyimides can also
be attributed to this incompatible system. Moreover the elemental composition of the polymer
surface was determined by energy dispersive X-ray spectroscopy (EDS). According to the
EDS results the weight percentages of C, O, F and P were found as 57%, 9%, 22% and 10%
respectively.
Fluorine and phosphor mapping images of BTDA-mDA13FAPO homopolyimides are
given in Figure 9. As can be seen from this figure the surface of these polyimide films were
completely covered with fluorine and phosphorous.
4. Conclusions
In this study a novel diamine monomer; mDA13FAPO was prepared. First, an
Arbuzov type of reaction was performed between triphenyl phosphine and 2-perfluorohexyl
ethyl iodide and the resulting phosphonium salt was then dephenylated to give
(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) diphenyl phosphine oxide (13FADPPO).
mDA13FAPO was obtained after nitration and subsequent reduction of 13FADPPO. Then
mDA13FAPO containing homo and copolyimides were synthesized. These polyimides
exhibited moderate Tg values (194-233 °C), good thermal stability and excellent solubility.
On the other hand, homopolyimides displayed poor film forming properties.
Copolymerization improved the film forming properties of homopolyimides obtained from
23

mDA13FAPO and various dianhydrides. Moreover results showed that these copolyimides
have low surface energies and high contact angle values.
Fluorine and phosphorous containing mDA13FAPO has the potential to be used for
the synthesis of many other polymers like polyamides, polyureas and polyamide-imides, etc.
It can also be used a hardener for epoxy resins or as a chain extender for polyurethanes. This
new diamine compound can be functionalized with acrylic groups and can be used in
photocurable coatings.
We are currently working on the preparation mDA13FAPO containing sulfonated
polyimides for fuel cell applications. Our future work will focus on the investigation of the
effects of this diamine on the properties of epoxy resins and UV curable coatings.
Acknowledgement
This work was supported by Marmara University, Commission of Scientific Research Project
(M.Ü.BAPKO) under grant FEN-A-200611-0209.
24

References
[1] C.E. Sroog, Polyimides, Prog. Polym. Sci. 16 (1991) 561–594.
[2] C. Fegar, M.M. Khojasteh, J.E. McGrath, Polyimides: Materials, Chemistry, and
Characterization, Elsevier Science, Amsterdam, 1989.
[3] M.K. Ghosh, K.L. Mittal, Polyimides: fundamentals and applications, Marcel Dekker,
New York, 1996.
[4] S.H. Hsiao, K.H. Lin, Polyimides derived from novel asymmetric ether diamine, J. Polym.
Sci. Part A: Polym. Chem. 43 (2005) 331-341.
[5] H.R. Kricheldorf, S.C. Fna, L. Vakhtangishvili, G. Schwarz, D. Fritsch, Polyimides based
on new diamines having pendant imide groups, J. Polym. Sci. Part A: Polym. Chem. 43
(2005) 6272–6281.
[6] W.S. Choi, F.W. Harris, Synthesis and polymerization of trifluorovinylether-terminated
imide oligomers, Polymer 41 (2000) 6213-6221.
[7] G. Hougham, Fluorine-Containing Polyimides, in: G. Hougham, P.E. Cassidy, K. Johns,
T. Davidson (Eds.), Fluoropolymers 2: Properties, Kluwer Academic Publishers, New York,
2002.
[8] G. Hougham, G. Tesoro, A. Viehbeck, J.D. Chapple-Sokol, Polarization Effects of
Fluorine on the Relative Permittivity in Polyimides, Macromolecules 27 (1994) 5964-5971.
[9] S. Sasaki, S. Nishi, Synthesis of Fluorinated Polyimides, in: M.K. Ghosh, K.L. Mittal
(Eds.), Polyimides Fundamentals and Applications, Marcel Dekker, New York 1996.
[10] Y. Zhu, P. Zhao, X. Cai, W.D. Meng, F.L. Qing, Synthesis and characterization of novel
fluorinated polyimides derived from bis[4-(4′-aminophenoxy)phenyl]-3,5-bis(trifluoromethyl)
phenyl phosphine oxide, Polymer 48 (2007) 3116-3124.
[11] A.E. Feiring, B.C. Auman, E.R. Wonchoba, Synthesis and properties of fluorinated
polyimides from novel 2,2'-bis(fluoroalkoxy)benzidines, Macromolecules 26 (1993) 2779-
2784.
[12] S. H Hsiao, W.T. Chen, Syntheses and Properties of Aromatic Polyimides Based on 1,1-
Bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane and 1,1-Bis[4-(4-
aminophenoxy)phenyl]-1-phenylethane, J. Polym. Res. 10 (2003) 95–103.
[13] C.Y. Wang, H.P. Zhao, G. Li, J.M. Jiang, Novel fluorinated polyimides derived from an
unsymmetrical diamine containing trifluoromethyl and methyl pendant groups, Polym. Adv.
Technol. 22 (2011) 1816–1823
25

[14] F. Pithan, C. Staudt-Bickel, R.N. Lichtenthaler, Synthesis of highly fluorinated
copolyimide membranes for the removal of high boiling organics from process water and
wastewater by pervaporation, Desalination 148 (2002) 1–4.
[15] Z. Ge, L. Fan, S. Yang, Synthesis and characterization of novel fluorinated polyimides
derived from 1,1′-bis(4-aminophenyl)-1-(3-trifluoromethylphenyl)-2,2,2-trifluoroethane and
aromatic dianhydridesEur. Polym. J. 44 (2008) 1252–1260.
[16] G. Hougham, G. Tesoroj, J. Shaw, Synthesis and Properties of Highly Fluorinated
Polyimides, Macromolecules 27 (1994) 3642-3649.
[17] J.H. Kim, B.J. Chang, S.B. Lee, S.Y. Kim, Incorporation effect of fluorinated side groups
into polyimide membranes on their pervaporation properties, J. Membr. Sci. 169 (2000) 185–
196.
[18] B.C. Auman, D.P. Higley, K.V. Scherer Jr, E.F. McCord, W.H. Shaw Jr, Synthesis of a
new fluoroalkylated diamine, 5-[1H,1 H-2-bis(trifluoromethyl)- heptafluoropentyl]-1,3-
phenylenediamine, and polyimides prepared therefrom, Polymer 36 (1995) 651-656.
[19] L. Bes, A. Rousseau, B. Boutevin, R. Mercier, R. Kerboua, Synthesis and Properties of
Novel Polyimides Containing Fluorinated Alkoxy Side Groups, Macromol. Chem. Phys. 202
(2001) 2954-2961.
[20] J.H. Kim, S.B. Lee, S.Y. Kim, Incorporation effects of fluorinated side groups into
polyimide membranes on their physical and gas permeation properties, J. Appl. Polym. Sci.
77 (2000) 2756-2767.
[21] A.I. Wozniak, A.S. Yegorov, V.S. Ivanov, S.M. Igumnov, K.V. Tcarkova, Recent
progress in synthesis of fluorine containing monomers for polyimides, J. Fluorine Chem. 180
(2015) 45–54.
[22] B. Schartel, Phosphorus-based Flame Retardancy Mechanisms—Old Hat or a Starting
Point for Future Development?, Materials 3 (2010) 4710-4745.
[23] E. Çakmakçı, M.V. Kahraman, Boron/Phosphorus-Containing Flame-Retardant
Photocurable Coatings, in: A. Tiwari, A. Polykarpov (Eds.), Photocured Materials, Royal
Society of Chemistry, Cambridge (2015).
[24] K. Faghihi, K. Zamani, Synthesis and Properties of Novel Flame-Retardant Poly(Amide-
Imide)S Containing Phosphine Oxide Moieties In Main Chain By Microwave Irradiation, J.
Appl. Polym. Sci. 101 (2006) 4263–4269.
[25] B. Tan, C.N. Tchatchoua, L. Dong, J.E. McGrath, Synthesis and Characterization of
Arylene Ether Imide Reactive Oligomers And Polymers Containing Diaryl Alkyl Phosphine
Oxide Groups, Polym. Adv. Technol. 9 (1998) 84–93.
26

[26] J. Jin, D.W. Smith, C.M. Topping, S. Suresh, C. Shengrong, S.H. Foulger, N. Rice, J.
Nebo, B.H. Mojazza, Synthesis and Characterization of Phenylphosphine Oxide Containing
Perfluorocyclobutyl Aromatic Ether Polymers for Potential Space Applications,
Macromolecules 36 (2003) 9000-9004.
[27] K.A. Watson, F.L. Palmieri, J.W. Connell, Space Environmentally Stable Polyimides and
Copolyimides Derived from [2,4-Bis(3-aminophenoxy)phenyl]diphenylphosphine Oxide,
Macromolecules 35 (2002) 4968-4974.
[28] M.A. Alexander, T.T. Le, D.J.T Hill, J.W. Connell, K.A. Watson, The Behaviour of
Phenylphosphine Oxide Containing Polyimides In A Water Plasma Following γ-Radiolysis,
Radiat. Phys. Chem. 62 (2001) 171–177.
[29] T.C. Chang, K.H. Wu, Y.S. Chiu, Characterization and Degradation of Some
Phosphorus-Containing Polyimides, Polym. Degrad. Stab. 63 (1999) 103-109.
[30] Y.L. Liu, G.H. Hsiue, C.W. Lan, J.K. Kuo, R.J. Jeng, Y.S. Chiu, Thermal Properties, and
Flame Retardancy of Phosphorus Containing Polyimides, J. Appl. Polym. Sci. 63 (1997) 875-
882.
[31] K.U. Jeong, Y.J. Jo, T.H. Yoon, Synthesis and Characterization of Novel Polyimide
From Bis-(3-Aminophenyl)-4-(Trifluoromethyl)Phenyl Phosphine Oxide, J. Polym. Sci. Part
A: Polym. Chem. 39 (2001) 3335-3347.
[32] K.U. Jeong, J.J. Kim, T.H. Yoon, Synthesis and Characterization of Novel Polyimides
Containing Fluorine and Phosphine Oxide Moieties, Polymer 42 (2001) 6019-6030
[33] J.K. Choi, K.Y. Paek, T.H. Yoon, Adhesive and Dielectric Properties of Novel
Polyimides with Bis(3,3′-Aminophenyl)-2,3,5,6-Tetrafluoro-4-Trifluoromethyl Phenyl
Phosphine Oxide (mDA7FPPO), Eur. Polym. J. 45 (2009) 1652–1658.
[34] C.W. Lee, S.M. Kwak, T.H. Yoon, Synthesis and Characterization of Polyimides From
Bis(3-Aminophenyl)-2,3,5,6-Tetrafluoro-4-Trifluoromethylphenyl Phosphine Oxide
(mDA7FPPO), Polymer 47 (2006) 4140–4147.
[35] B.Y. Myung, C.J. Ahn, T.H. Yoon, Adhesion Property of Novel Polyimides with 1-[3′,5′-
Bis(Trifluoromethyl)Phenyl] Pyromellitic Dianhydride, J. Appl. Polym. Sci. 96 (2005) 1801–
1809.
[36] Z. Li, J. Liu, Z. Gao, Z. Yin, L. Fan, S. Yang, Organo-soluble and Transparent
Polyimides Containing Phenylphosphine Oxide and Trifluoromethyl Moiety: Synthesis and
Characterization, Eur. Polym. J. 45 (2009) 1139–1148.
[37] J.W. Connell, J.G. Smith Jr, P.M. Hergenrother, K.A. Watson, C.M. Thompson, Space
environmentally durable polyimides and copolyimides, US Patents 7109287, (2006).
27

[38] C. Cecutti, I. Rico, A. Lattes, A. Novelli, A. Rico, G. Marion, A. Graciaa, J. Lachaise,
New Formulation of Blood Substitutes: Optimization of Novel Fluorinated Microemulsions,
Eur. J. Med. Chem. 24 (1989) 485–492.
[39] B. Escoula, I. Rico, J.P. Laval, A. Lattes, A New Method of Fluoroalkylation by a Wittig
Reaction, Synth. Commun. 15 (1985) 35-38.
[40] G. Vla´d, F.U. Richter, I.T. Horva´th, Synthesis of Fluorous Trialkyl Phosphines with the
Complete Exclusion of PH3, Tetrahedron Lett. 46 (2005) 8605–8608.
[41] E. Çakmakçı, A. Güngör, Preparation and Characterization of Flame Retardant and
Proton Conducting Boron phosphate/Polyimide Composites, Polym. Degrad. Stab. 98 (2013)
927-933.
[42] A. Beyler-Çiğil, E. Çakmakçı, M.V. Kahraman, Thermal properties of phosphorylated
nanodiamond reinforced polyimides, Polym. Compos. DOI: 10.1002/pc.23406 (2015).
[43] M.F. Martinez-Nunez, V.N. Sekharipuram, J.E. McGrath, Synthesis and Characterization
of Polyimides Using a Novel Phosphorus-Containing Diamine, Polym. Prepr. 35 (1994) 709-
710.
[44] P. Bhattacharyya, D. Gudmunsen, E.G. Hope, R.D.W. Kemmitt, D.R. Paige, A.M.
Stuart, Phosphorus(III) Ligands with Fluorous Ponytails, J. Chem. Soc. Perkin Trans. 1, 1
(1997) 3609-3612.
[45] S. Ando, T. Matsuura, S. Sasaki, Perfluorinated Polyimide Synthesis, Macromolecules
25 (1992) 5858-5860.
[46] S.L. Liu, R. Wang, Y. Liu, M.L. Chng, T.S. Chung, The physical and gas permeation
properties of 6FDA-durene/2,6-diaminotoluene copolyimides, Polymer 42 (2001) 8847–8855.
[47] D. W. van Krevelen, K. Nijenhuis, Properties of polymers, Elsevier, Oxford, 2009.
[48] J. Liu, Y. Gao, F. Wang, M.Wu, Preparation and characteristics of nonflammable
polyimide materials, J. Appl. Polym. Sci. 75 (2000) 384-389.
[49] H. Fan, R. Yang, Flame-Retardant polyimide cross-linked with polyhedral oligomeric
octa(aminophenyl)silsesquioxanei Ind. Eng. Chem. Res. 52 (2013 ) 2493−2500.
[50] Z. Rafiee, S. Mallakpour, S. Khalili, Preparation and Characterization of
Polyimide/Titania Nanohybrid Films, 35 (2014) 1486–1493.
[51] C. Kızılkaya, M.Biçen, S. Karataş, Atilla Gungor, Structural effects of the monomer type
on the properties of copolyimides and copolyimide–silica hybrid materials, J. Serb. Chem.
Soc. 80 (2015) 1061–1071.
28

[52] D. Xiang, Q. Xuepeng, M. Xiaoye, G. Haiquan, G. Lianxun, Preparation，mechanical
properties and flame retardancy of phosphorus-containing polyimide fibers, Chinese Journal
of Applied Chemistry, 31 (2014) 667-671.
[53] B. Saritha and P. Thiruvasagam, Synthesis of diol monomers and organosoluble
fluorinated polyimides with low dielectric: study of structure– property relationship and
applications, High Perform. Polym. 27 (2015) 842-851.
[54] Y.C. Sheen, Y.C. Huang, C.S. Liao, H.Y. Chou, F.C. Chang, New approach to fabricate
an extremely super-amphiphobic surface based on fluorinated silica nanoparticles, J. Polym.
Sci. Part B: Polym. Phys. 46 (2008) 1984-1990.
29