ARTICLE
SCHEME 1 Synthesis of the diamine 1,3-bis(3-aminophenoxy-40-benzoyl) benzene.
Its Tg was 222 ꢀC and melting temperature was 350 ꢀC.
However, this thermoplastic polyimide has high melt-proc-
essing temperature.
Vis 2501 spectrometer. Mechanical properties of the films
were measured with a SHIMADZU AG-I tensile apparatus at a
crossed speed of 8 mm/min on the strips of approximate 40–
60 lm thickness and 0.3 cm width with a 4 cm gauge length.
The equilibrium water uptake was determined by the weight
difference of vacuum-dried film specimens before and after
To prepare the thermoplastic polyimides with low melt pro-
cess temperatures remaining excellent thermal stability, a
more flexible isomer diamine 1,3-bis(3-aminophenoxy-40-
benzoyl) benzene was successfully synthesized. And a series
of polyimides were synthesized with this diamine and differ-
ent kinds of aromatic dianhydrides. The obtained polyimides
had lower Tgs and exhibited excellent thermoplasticity.
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immersion in deionized water at 25 C for 24 h. The crystalli-
zation of the films was characterized with a Rigaku Wide-
angle X-ray diffractometer (D/max rA, using Cu Ka radiation
at wavelength k ¼ 1.541E). The 2h scan data were collected at
0.05ꢀ intervals over ranges of 10–60ꢀ and scan speed was 0.5ꢀ
(2h)/min. SAXS was performed using the same instrument
over the ranges of 0.5–6ꢀ and scan speed was 0.2ꢀ (2h)/min.
All the properties of polymers were measured with films.
EXPERIMENTAL
Materials
3-Aminophenol (3-AP), potassium carbonate (K2CO3) and
1,3-Bis(4-fluorobenzoyl) benzene were commercially avail-
able and used as received. N,N-Dimethylformamide (DMF),
N,N-Dimethylacetamide (DMAc) and toluene were vacuum-
distilled after drying over calcium hydride. 3,30,4,40-Biphenyl-
tetracarboxylic acid dianhydride (s-BPDA, m.p.306 ꢀC) was
obtained from Chriskev Company, Benzophenonetetracarbox-
Synthesis of 1,3-Bis(3-aminophenoxy-40-benzoyl)
Benzene (BABB)
3-Aminophenol (24.01 g, 0.22 mol) was dissolved in a solu-
tion of N,N-dimethylformamide (226 mL) and toluene (45 mL)
in a 500 mL three-neck flask equipped with a magnetic stir,
thermometer, N2 gas inlet, Dean-Stark trap and condenser.
Powdered anhydrous potassium carbonate (34.55 g, 0.25 mol)
was added and water was removed by azeotropic distillation
with toluene. 1,3-Bis(4-fluorobenzoyl) benzene (32.23 g,
0.10 mol) was then added and the reaction mixture stirred
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ylic dianhydride (BTDA, m.p.221 C), 4,40-oxydiphthalic anhy-
dride (ODPA, m.p.228 ꢀC), pyromellitic dianhydride (PMDA,
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m.p.285 C), 2,2-Bis[4-(3,4-dicarboxypheoxy)phenyl] propane
dianhydride (BPADA, m.p.190 ꢀC) were purchased from Bei-
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jing Jiaohua company. These dianhydrides were dried in a
at 130–150 C for 8–15 h under a nitrogen atmosphere. The
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vacuum oven at 150 C for 4 h.
mixture was allowed to cool and precipitated in water as a
solid which was isolated by filtration and dried in a vacuum
oven at 40 ꢀC. Recrystallization from methanol afforded a
light yellow crystalloid 1,3-Bis(3-aminophenoxy-40-benzoyl)
benzene (BABB) (32.23 g, 64.4%). The Scheme 1 is the syn-
thetic route for the preparation of BABB.
Characterization
Fourier-transform infrared spectra were obtained on
a
Bruker Vector22 spectrometer. 1H NMR spectra were mea-
sured on a Bruker 500 spectrometer with tetramethylsilane
(TMS) as internal standard and DMSO-d6 as a solvent. Mass
spectra were performed on an AXIMA-CFR laser desorption
ionization flying time spectrometer (COMPACT). Glass transi-
tion temperatures (Tg) and melting points were determined
on a Mettler Toledo DSC 821e thermal analyzer under nitro-
gen atmosphere at a heating rate of 10 ꢀC/min. Elemental
analyses were performed with Perkin–Elmer 2400 CHN ana-
lyzer. Inherent viscosities (ginh) were obtained at a 0.5 g/dL
concentration of polyamide acid solutions with an Ubbelohde
Yield: 64.4%. m.p. (DSC): 148 ꢀC. IR (KBr, powder, cmꢂ1):
3467 and 3379 (NAH), 1641 (C¼¼O).
1H NMR (500MHz, DMSO-d6, ppm): 5.3 (s, 4H), 6.2 (d, 2H),
6.3 (s, 2H), 6.4 (d, 2H), 7.1 (m, 6H), 7.7 (t, 1H), 7.8 (d, 4H),
7.9 (s, 1H), 8.0 (d, 2H). Anal. Calcd. for C32H24N2O4: C,
76.78; H, 4.83; N, 5.60. Found: C, 76.77; H, 4.88; N, 5.62.
Synthesis of the Polymers
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viscometer at 25 C. Thermo gravimetric analysis (TGA) was
All the polymers were prepared via the two-step solution po-
lymerization and thermal imidization process as shown in
Scheme 2. The samples PI-a ꢃ PI-e were named according to
the sequence of dianhydrides. First of all, BABB and distilled
DMAc were charged into a dried conical flask equipped with
a magnetic stirrer. After the diamine was dissolved, stoichio-
metric amounts of dianhydride were added gradually, with
the solid content controlled to 20 wt %. The mixture was
stirred at room temperature for 5h to form a viscous solu-
tion of poly (amic acid) (PAA) precursor solution. Films were
cast from the PAA solution onto clean and dry glass plates.
The solvent was removed by drying in an oven with a
performed on a Perkin–Elmer (Pyris 1) thermogravimetric
analyzer with Pyris data collection and analysis software for
Windows. Measurements were carried out on 3–5 mg film
samples heated under nitrogen or air atmosphere at a heat-
ing rate of 5 ꢀC/min. Dynamic mechanical analysis (DMA)
was performed on thin film specimen (ca. 3 ꢁ 0.65 ꢁ 0.005
cm3) on a TA instrument DMA RSAP at a heating rate of
5
ꢀC/min and at a load frequency of 1 Hz under nitrogen
atmosphere. The peak on the tan d as a function of tempera-
ture curves was regarded as the Tg of the films. Ultraviolet-
Visible (UV-Vis) spectra of the films were recorded on a UV-
ETHER AND KETONE MOIETIES, YU ET AL.
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