High thermal stability and rigid rod of novel organosoluble polyimides and polyamides based on bulky and noncoplanar naphthalene-biphenyldiamine

Article abstract of DOI:10.1021/ma048559x

The synthesis of a naphthalene-substituted monomer, 2,2′- dinaphthylbiphenyl-4,4′-diamine, and its use in the preparation of soluble polyimides and polyamides by reaction of the diamine with commercial dianhydrides and dicarboxylic acids, was analyzed. IR spectra of synthesized monomers and polymers were recorded in the range 4000-500 cm^-1 on a Jasco IR-700 spectrometer. The inherent viscosities of all polymers were measured using a Ubbelohde viscometer. The solubility, tensile properties, thermal properties, and dielectric constants of the obtained polyimides and polyamides were also investigated.

Full text of DOI:10.1021/ma048559x

4024
Macromolecules 2005, 38, 4024-4029
Notes
High Thermal Stability and Rigid Rod of
Novel Organosoluble Polyimides and
Polyamides Based on Bulky and Noncoplanar
Naphthalene-Biphenyldiamine
biphenylylene may disrupt the crystal packing, reducing
intermolecular interactions and enhancing solubility of
the polyimide and polyamide.
In the present paper, we will report the synthesis of
a new naphthalene-substituted monomer, 2,2′-dinaph-
thylbiphenyl-4,4′-diamine, and its use in the preparation
of soluble polyimides and polyamides by the reaction of
the diamine with commercial dianhydrides and dicar-
boxylic acids. The solubility, tensile properties, thermal
properties, electrochemical stability, and dielectric con-
stants of the obtained polyimides and polyamides are
also investigated.
D
e
r
-
J
a
n
g
L
i
a
w
,
*
,
†
F
e
n
g
-
C
h
y
u
a
n
C
h
a
n
g
,
†
‡
‡
Man-kit Leung, Meng-Yen Chou, and
Klaus Muellen§
Department of Chemical Engineering, National Taiwan
University of Science and Technology, Taipei, Taiwan, ROC;
Department of Chemistry, National Taiwan University,
Taipei, Taiwan, ROC; and Max-Planck-Institute for Polymer
Research, Ackermannweg 10, Mainz 55128, Germany
Experimental Section
Received July 15, 2004
Revised Manuscript Received January 18, 2005
Materials. Reagent-grade aromatic tetracarboxylic dian-
hydrides such as 4,4′-hexafluoroisopropylidenediphathalic an-
hydride (6FDA) (I-1), 4,4′-sulfonyldiphthalic anhydride (DSDA)
Introduction
(I-2), and 3,3′,4,4′-benzophenone-tetracarboxylic dianhydride
BTDA) (I-3) and aromatic dicarboxylic acids such as iso-
Rigid-rod aromatic polyimides and polyamides con-
stantly attract wider interest because of their unique
mechanical, thermal, and morphological properties.1-7
Synthesis and processing of these materials are gener-
ally more difficult due to their limited solubility and
infusibility. One of the successful approaches to increase
solubility and processability of polymers is by the
(
phthalic acid (II-1), 5-tert-butylisophthalic acid (II-2), 4,4′-
sulfonyldibenzoic acid (II-3), and 4,4′-hexafluoroisopropyli-
denedibenzoic acid (II-4) were used after purification by
crystallization. Reagent-grade calcium chloride was dried
under vacuum at 180 °C before use. N-Methyl-2-pyrrolidinone
(
NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylform-
8
-11
amide (DMF), pyridine, dimethyl sulfoxide (DMSO), triphenyl
phosphite (TPP), γ-butyrolactone, and cyclohexanone were
purified by distillation under reduced pressure over calcium
hydride and stored over 4 Å molecular sieves.
introduction of bulky lateral substituents,
flexible
1
2,13
14
15,16
alkyl side chains,
unsymmetric, alicyclic,
and
1
7-20
kinked structure.
To develop easily processable
high-performance materials, modifications that increase
the solubility while maintaining the rigid-rod character
and the thermal stability are of particular interest.
Another approach employed to increase the solubility
of rigid-rod polyimides and polyamides is by incorpora-
tion of the nonlinear moieties such as a bulky nonco-
planar group in the polymer backbone. In a previous
Measurements. IR spectra of synthesized monomers and
polymers (KBr disks) were recorded in the range 4000-500
-1
cm on a Jasco IR-700 spectrometer. Melting point was
recorded on a MEL-TEMP II. The inherent viscosities of all
polymers were measured using a Ubbelohde viscometer.
Nuclear magnetic resonance (NMR) spectra were recorded on
1
13
a Varian VXR400S ( H at 399.96 MHz and C at 100.58 MHz).
Mass spectra (MS) were recorded by a Joel JMS-HX 110.
Elemental analysis (EA) was recorded by a Heraeus CHN-O
Rapid. Thermogravimetric data were obtained on a TA 5100
thermal analysis system under nitrogen flowing conditions
2
1-28
study,
the solubility, thermal and thermooxidative
stability, optical properties, transition, and relaxation
behaviors of organosoluble aromatic polyimide could be
improved by addition of 2,2′-disubstituted groups like
methyl, cyano, trifluoromethyl groups, methyl-substi-
tuted phenyl groups, halogens, methacrylate, sulfonic
acid, trifluoromethylphenyl groups, and biphenyl groups
substituted at different positions to main-chain 4,4′-
diaminobiphenyls. The 2,2′-disubstituted biphenylylene
moiety could be considered as a rodlike structure and
adopts a noncoplanar conformation in the presence of
methyl substitution at the 2,2′-position. The substitution
at the 2- and 2′-positions of the biphenyl moiety forces
the rings out of the plane into adopting a noncoplanar
3
-1
-1
nitrogen (60 cm min ) at a heating rate of 10 °C min
.
Differential scanning calorimetric analysis was performed on
a differential scanning calorimeter (TA Instruments TA-2010)
-
1
at a heating rate of 10 °C min . Tensile properties were
determined from stress-strain curves obtained with a Orientec
Tensilon with a load cell of 10 kg. A gauge of 2 cm and a strain
-
1
rate of 2 cm min were used for this study. Measurements
were performed at room temperature with film specimens of
dimensions 0.4 cm wide, 5 cm long, and 0.1 mm thick.
Dielectric constants of polyimide thin film were measured by
the parallel-plate capacitor method using a dielectric analyzer
(
TA Instruments DEA 2970) at a frequency of 1 kHz. Gold
2
3,27,28
conformation.
Naphthalene structure is bulky and
electrodes were vacuum-deposited on both surfaces of dried
films, and measurements were made at 25 °C under a N2
atmosphere. Electrochemical stability was measured by a
cyclic voltammetry instrument BAS CV-27 voltammograph.
29,30
rigid which also has high heat resistance.
tion of the naphthalene group at the 2,2′-position of
Incorpora-
4 4
The method is (0-1.5 V, 100 mV/s) in DMF using Bu NClO
†
National Taiwan University of Science and Technology.
‡
(0.1 M) as the supporting electrolyte. The signals were
obtained on a platinum working electrode, with a Pt wire as
the counter electrode and a Ag/AgCl (saturated) electrode as
the reference electrode.
National Taiwan University.
§
Max-Planck-Institute for Polymer Research.
Corresponding author: Fax 886-2-23781441 or 886-2-27376644;
*
e-mail liaw@ch.ntust.edu.tw or liaw8484@yahoo.com.tw.
1
0.1021/ma048559x CCC: $30.25 © 2005 American Chemical Society
Published on Web 03/30/2005

Macromolecules, Vol. 38, No. 9, 2005
Notes 4025
Scheme 1. Synthesis of
,2′-Dinaphthylbiphenyl-4,4′-diamine (4)
restricted rotation around C-C bonds of the naphthylbiphenyl
groups leads to coalesced aromatic signals. We have success-
fully obtained structural evidence from X-ray crystallography
of 4,4′-dinitro-2,2′-dinaphthylbiphenyl. HRMS-FAB m/z calcd
2
for C32
sis: Calcd for C32
C, 77.36; H, 3.70; N, 5.44.
H
20
O
4
N
2
496.1423; found 496.1419. Elemental analy-
20 4 2
H O N
: C, 77.41; H, 4.06; N, 5.64; Found:
Synthesis of 2,2′-Dinaphthylbiphenyl-4,4′-diamine (4). A
solution of ammonia formate (0.83 g, 7.8 mmol), 10% Pd/C
(
(
0.18 g, 2.8 mmol), and 2,2′-dinaphthyl-4,4′-dinitrobiphenyl
0.65 g, 1.3 mmol) in DMF (2 mL) was heated at 80 °C for 3 h.
After then, water was added to quench the reaction. The crude
product was extracted with ethyl acetate several times. The
organic layer was collected, dried over anhydrous MgSO , and
4
concentrated under vacuum to give a glassy product which was
purified by column chromatography on silica gel (hexane:ethyl
acetate ) 1:3) and recrystallized from methanol to give 4 (0.45
1
g, 73%) as a light pink solid. H NMR (400 MHz, CD
3
COCD
3
):
1
3
δ 7.81-6.33 (m, 20H), 4.44 (s, 4H). C NMR (100 MHz,
CD COCD ): δ 146.72, 141.04, 140.40, 134.60, 133.70, 131.20,
28.56, 127.77, 127.36, 127.30, 125.91, 125.86, 125.33, 118.04,
17.87, 113.99. HRMS-FAB m/z calcd for C32 436.1940;
: C,
8.04; H, 5.54; N, 6.42. Found: C, 87.65; H, 5.56; N, 6.34.
3
3
1
1
24 2
H N
found 436.1935. Elemental analysis: Calcd for C32
24 2
H N
8
Polymerization. Preparation of Polyimide (PI-1 and PI-
). A three-necked flask was charged with 0.4366 g (1 mmol)
3
of naphthalenediamine (4) and 5 mL of DMAc. The solution
was stirred under a nitrogen atmosphere until the diamine
dissolved completely, and then 0.4442 g (1 mmol) of dianhy-
dride (I-1) was added to the reaction mixture slowly. The
mixture was stirred at ambient temperature for 2-4 h under
a nitrogen atmosphere to form poly(amic acid). The poly(amic
acid) was diluted with extra DMAc, and a mixture of equimolar
of acetic anhydride and pyridine was added to the poly(amic
acid) solution with stirring at ambient temperature for 1 h,
and then the mixture was heated to 100 °C and maintained
at 100 °C for 3 h. After cooling, the viscous polymer solution
was poured into methanol. The precipitate was filtered,
washed thoroughly with methanol and hot water, and dried
at 100 °C under vacuum. The inherent viscosity of the PI-1 in
Monomer Syntheses (Scheme 1). Synthesis of 4,4′-Di-
nitrobiphenyl (1). A concentrated HNO (70%, 4.4 mL) was
(98%, 5.2 mL) with stirring at 0
C for 5 min. Afterward, a solution of biphenyl [3 g, 19.5 mmol,
3
added to concentrated H
2
SO
4
°
2
2
M in nitromethane (MeNO )] was added dropwise with
stirring at 0 °C. After the addition was completed, the solution
was further stirred for 1 h at 0 °C and at for 2 h 35 °C. The
solution was poured into ice-water, and the solid precipitate
was collected, washed with water, and recrystallized from
-1
DMAc was 0.81 dL g , measured at a concentration of 0.5 g
methanol and toluene to give 1 (0.825 g, 17%) as light yellow
-1
dL at 30 °C. Elemental analysis: Calcd for (C51
26 4 2 6 n
H O N F ) :
1
solid. H NMR (400 MHz, CDCl
3
): δ 8.34 (d, J ) 8.6 Hz, 4H),
): δ 148.06,
C, 72.51%; H, 3.10%; N, 3. 32%. Found: C, 71.56%; H, 3.49%;
N, 2.96%. Since PI-3 synthesized by the chemical imidization
method was precipitated during imidization, PI-3 was obtained
by thermal imidization. The poly(amic acid) solution was also
carried out by an identical method. A poly(amic acid) film was
cast from the solution into a glass culture dish and heated (8
h at 80 °C, 2 h at 150 °C, 2 h at 200 °C, 2 h at 250 °C, and 2
h at 300 °C) under vacuum to convert the poly(amic acid) into
polyimide film. Elemental analysis: Calcd for (C H O N ) :
7
1
2
.77 (d, J ) 8.6 Hz, 4H). 13C NMR (100 MHz, CDCl
3
44.97, 128.32, 124.37. HRMS-FAB m/z calcd for C12
8 2 4
H N O
44.0484; found 244.0497.
Synthesis of 2,2′-Diiodo-4,4′-dinitrobiphenyl (2). A solution
of 4,4′-dinitrobiphenyl (10 g, 41 mmol), Ag SO (34.3 g, 110
mmol), and I (31.2 g, 123 mmol) in H SO (98%, 164 mL) was
SO
4
2
4
2
2
4
heated at 120 °C for 20-48 h. Since the reactivities of Ag
2
are different from batch of batch, the reaction was monitored
4
9
26
5
2 n
1
by using H NMR. When the conversion reached 75% or above,
C, 81.43%; H, 4.32%; N, 3.86%. Found: C, 79.84%; H, 3.97%;
N, 3.21%.
the solution was poured into 2000 mL of ice-water, and the
solid precipitate was collected, washed with water, and
recrystallized from ethyl acetate to give 2 (13.2 g, 65%) as a
Preparation of Polyamide (PA-1). A mixture of 0.2183 g (0.5
mmol) of diamine (4), 0.083 g (0.5 mmol) of isophthalic acid
1
light yellow solid; mp 148-149 °C. H NMR (400 MHz,
(
II-1), 0.5 mL of triphenyl phosphite (TPP), 0.5 mL of pyridine,
CDCl
3
): δ 8.75 (d, J ) 2.2 Hz, 2H), 8.30 (dd, J ) 8.4, 2.2 Hz,
3
.0 mL of N-methyl-2-pyrrolidone (NMP), and 0.30 g of calcium
1
3
2
H), 7.37 (d, J ) 2.2 Hz, 2H). C NMR (100 MHz, CDCl
52.96, 147.60, 133.91, 129.84, 123.27, 97.91. HRMS-FAB m/z
495.8417; found 495.8410.
3
): δ
chloride was heated with stirring at 100 °C for 3 h. After
cooling, the reaction mixture was poured into a large quantity
of methanol with constant stirring, and the polymer was
precipitated. The precipitate was filtered and washed thor-
oughly with methanol and hot water and dried at 100 °C under
vacuum. Various polyamides (PA-2-PA-4) were prepared by
using a similar procedure. The inherent viscosity of the
1
calcd for C12
6 4 2 2
H O N I
Synthesis of 2,2′-Dinaphthyl-4,4′-dinitrobiphenyl (3). A solu-
tion of 2,2′-diiodo-4,4′-dinitrobiphenyl (10.0 g, 20 mmol),
1
-naphthylboronic acid (20.8 g, 121 mmol), Pd(PPh
.4 mmol), and Na CO (6.6 g, 62 mmol) in benzene (30 mL),
O (15 mL), and ethanol (5 mL) was heated at 80 °C under
a N atmosphere for 4 h. When the reaction was completed,
the solution was quenched with H O and extracted with
CHCl . The organic layer was collected, dried over anhydrous
MgSO
3 4
) (0.46 g,
0
2
3
-
1
H
2
polyamide (PA-1) in DMAc was 0.73 dL g , measured at a
1
-
2
concentration 0.5 g dL at 30 °C. Elemental analysis: Calcd
for (C H O N ) : C, 84.78%; H, 4.62%; N, 4.94%. Found: C,
2
4
0
26
2
2 n
3
79.69%; H, 4.96%; N, 4.27%.
4
, and concentrated under vacuum to give a glassy
product which was purified by column chromatography on
Results and Discussion
silica gel (hexane:ethyl acetate ) 1:6) to give 3 (8.7 g, 87%) as
1
Monomer Synthesis. The 2,2′-dinaphthylbiphenyl-
4,4′-diamine (4) was prepared according to Scheme 1.
First, the biphenyl was nitrated to the 4,4′-dinitro-
biphenyl (1) compound with nitric acid and sulfuric acid
a yellow solid; mp 203-204 °C. H NMR (400 MHz, CDCl
3
):
): δ 146.87,
45.89, 140.38, 135.14, 133.61, 132.64, 128.67, 128.25, 126.85,
26.65, 126.15, 125.83, 125.03, 124.41, 121.77. Note that
1
3
δ 8.32-5.83 (m, 20H). C NMR (100 MHz, CDCl
3
1
1

4026 Notes
Macromolecules, Vol. 38, No. 9, 2005
Scheme 2. Synthesis of Various Polyimides
Scheme 3. Synthesis of Various Polyamides
(PI-1-PI-3)
(PA-1-PA-4)
removing solvent slowly. The polyimides obtained by
chemical method had inherent viscosities between 0.81
-
1
and 0.85 dL g in DMAc. The molecular weights of
polyimides were sufficient for casting tough and flexible
films. The IR spectra of polymers confirmed the forma-
tion of polyimides. The IR spectrum of polyimide, PI-1
obtained by the chemical imidization method showed
-
1
at 0 °C. The dinitro compound (1) was then iodinated
characteristic bands at 1788 and 1725 cm due to the
asymmetric and symmetric stretches of imide carbonyl
3
1
using Marvel’s reaction condition which is the elec-
trophilic aromatic substitution of iodine cation to give
the 2,2′-diiodo-4,4′-dinitrobiphenyl (2) compound. Fur-
ther, the diiodo-dinitro compound (2) treated with
-
1
groups, respectively, and a band at 1388 cm due to
C-N stretching which confirmed the formation of imide
structure.
1-naphthylboronic acid by the Susuki coupling reaction
Preparation of Polyamides. The novel polyamides
PA-1-PA-4 were prepared by direct polycondensation
of the diamine 4 with a series of aromatic dicarboxylic
acids in NMP using triphenyl phosphite (TPP) and
pyridine as condensing agents (Scheme 3). All the
polycondensations readily proceeded in homogeneous
solution. Tough and stringy precipitates formed when
the viscous polyamide solution were trickled into stir-
ring methanol. All the polymers were obtained in
quantitative yields with moderate to high inherent
afforded the 2,2′-dinaphthyl-4,4′-dinitrobiphenyl (3).
Finally, the nitrobiphenyl group was converted to an
amine group with ammonium formate, 10% Pd/C, and
DMF solution at 80 °C. All the structures of these
compounds were confirmed by NMR, MS, and EA. The
results of these compounds were in agreement with
their respective structure.
Preparation of Polyimides. Polyimides were pre-
pared by the conventional two-step polymerization
method, as outlined in Scheme 2, involving ring-opening
polyaddition forming poly(amic acid) and subsequent
chemical or thermal imidization. Reaction of dianhy-
dride with diamine at ambient temperature gave viscous
poly(amic acid) solution. The chemical imidization of
poly(amic acid)s proceeded with a dehydrating agent
such as a mixture of acetic anhydride and pyridine. The
dehydration was effective and afforded polyimides.
Before addition of dehydrating agents, extra DMAc was
added to the poly(amic acid) solutions to prevent gela-
tion. However, polyimide PI-3 synthesized by the chemi-
cal imidization method was precipitated during imid-
ization. The poly(amic acid) solution was cast into glass
plate and heated to 300 °C gradually under vacuum.
The polyimide was formed through cyclodehydration by
-
1
viscosities of 0.72-0.86 dL g in DMAc, as listed in
Table 1. The molecular weights of polyamides were
sufficient for casting tough and flexible films. The
formation of polyamides was confirmed by IR spectros-
copy. The IR spectra of polyamides exhibited charac-
-
1
teristic bands around 3300 cm due to amide N-H
-
1
stretching and around 1660 cm due to amide CdO
stretching confirmed the formation of amide structure.
Polymer Properties. Table 1 summarizes the solu-
bility and quality of the films of polyimides and poly-
amides. These polymers exhibited a good solubility in
a variety of solvents such as N-methyl-2-pyrrolidinone,
N,N-dimethylacetamide, N,N-dimethylformamide, pyri-
dine, tetrahydrofuran, dimethyl sulfoxide, γ-butyrolac-
tone, and cyclohexanone at ambient temperature or

Macromolecules, Vol. 38, No. 9, 2005
Table 1. Viscosity, Solubility and Film Quality of Various Polyimides and Polyamides
solubilityc
polymer code ηinh (dL g-1) NMP DMAc DMF DMSO pyridine THF γ-butyrolactone cyclohexanone film quality
Notes 4027
a
PI-1
0.81
0.85
b
N/A
0.73
0.86
0.72
0.76
N/A
++
++
+-
++
++
++
++
++
++
++
++
-
+-
++
++
++
++
++
++
++
-
+-
++
++
++
++
++
++
+-
-
+-
++
+
++
++
++
++
++
-
+-
++
++
++
++
+
++
+
++
+
++
+
flexible
flexible
flexible
PI-2
PI-3
-
-
-
d
Ref 1
PA-1
PA-2
PA-3
PA-4
Ref 2
+-
+-
+
-
-
++
++
++
+
+-
++
++
+
++
-
N/A
flexible
flexible
flexible
flexible
N/A
-
+
-
a
Measured in DMAc at a concentration of 0.5 g dL-1 at 30 °C. b Polymer was obtained by thermal imidization and insoluble in DMAc.
c
Solubility: ++, soluble at room temperature; +, soluble on heating at 70 °C; +-, partially soluble on heating at 70 °C; -, insoluble on
heating at 70 °C. Abbreviations: NMP, N-methyl-2-pyrrolidinone; DMAc, N,N- dimethylacetamide; DMF, N,N-dimethylformamide; DMSO,
dimethyl sulfoxide; THF, tetrahydrofuran. d N/A ) not available.
Figure 3. Structure of Ref 3.
Figure 1. Structure of Ref 1.
Table 3. Mechanical Properties of Various Polyimides
and Polyamides
polymer
code
tensile
strength (MPa)
elongation at
break (%)
tensile modulus
(GPa)
PI-1
PI-2
PI-3
PA-1
PA-2
PA-3
PA-4
99
105
128
84
108
97
94
8
6
2.2
2.2
2.6
2.2
2.0
2.3
2.1
8
6
Figure 2. Structure of Ref 2.
10
7
Table 2. Thermal Properties of Various Polyimides and
Polyamides
10
polymer
code
Td10 (°C)b
polymer
code
Td10 (°C)b
The temperature for 10% weight loss were in the range
of 533-583 and 505-520 °C for polyimides and poly-
amides, respectively. The Tg and Td10 of the polyimide
PI-1 and polyamide PA-3 were compared with the
corresponding reference polymers in Figure 3(Ref 3)
Tga (°C)
in N2
Tga (°C)
in N2
PI-1
PI-2
PI-3
PA-1
311
288
309
302
583
533
580
520
PA-2
PA-3
PA-4
298
318
303
511
512
505
(polyimide) and in Figure 2 (Ref 2) (polyamide), respec-
a
Glass transition temperature (Tg) was measured by DSC at a
tively. Polyimide PI-1 and polyamide PA-3 exhibited
-
1
b
10
heating rate of 10 °C min
loss occurred, as recorded on TGA at a heating rate of 10 °C min
.
Temperature at which 10% weight
lower Tg and higher Td than the reference polymers
-1
.
10
Ref 3 (Tg ) 325 °C and Td ) 523 °C) and Ref 2 (Tg )
3
20 °C and Td10 ) 439 °C), respectively. The incorpora-
upon heating at 70 °C. The good solubility was governed
by the structural modification through the incorporation
of the bulky and noncoplanar naphthalene groups in the
polymer backbone, which renders the polymer nonco-
planar and also decreases interchain interactions. Com-
paring PI-1 and PA-3 with Figure 1 (Ref 1) and Figure
tion with naphthalene group at the 2,2′-position on the
biphenyldiamine increase the size and sharp anisotropy
of the 2,2′-disubstituted group of the diamine and affect
the molecular packing. 2
1-23
This makes the motion
related to the â-relaxation evolvement from a non-
cooperative process to a cooperative one, and the
R-relaxation temperature which is the glass transition
temperature (Tg) is correspondingly decreased.2
Therefore, the incorporation of the bulky naphthalene
group could improve the processing characteristics of
these relatively intractable polymers. In addition, the
high Td10 of these novel polyimides and polyamides is
also due to the presence of a rigid naphthalene group
in the polymer backbone, which enhances the thermal
stability of these polymers.
2
(Ref 2), respectively, polymers Ref 1 and Ref 2
containing methyl substitution with smaller free volume
than naphthalene were prepared with the corresponding
dianhydride and dicarboxylic acid. It was observed that
polyimide Ref 1 and polyamide Ref 2 showed poorer
solubility than its analogous polymers PI-2 and PA-3.
It may be attributed to the presence of the naphthalene
group in the polymer backbone.
1-23
The thermal properties of the polyimides were evalu-
ated by differential scanning calorimetry (DSC) and
thermogravimetric analysis (TGA). The results are
summarized in Table 2.
The glass transition temperatures (Tg) of the polymers
were found to be in the range of 288-318 °C. The 10%
weight loss temperatures (Td ) of polymers in the
Table 3 lists the mechanical properties of the films of
polyimide and polyamide. The flexible films were ob-
tained by casting polymer solution in DMAc. They had
a tensile strength in the range of 84-128 MPa, an
elongation at break in the range of 6-10%, and a tensile
modulus in the range of 2.0-2.6 GPa. It was observed
that polymer PI-3 derived from thermal cyclodehydra-
1
0
-1
atmosphere of nitrogen at a heating rate of 10 °C min
were obtained by thermal gravimetric analysis (TGA).

4028 Notes
Macromolecules, Vol. 38, No. 9, 2005
Table 4. Dielectric Constant and Bulk Density of the Polyimides and Polyamides
a
The bulk density was measured by the method of Archimedes’ principle, Fbulk ) A/(A - B) × Fw, where A is the dry membrane weight
3
2
in air, B is the membrane weight in water, and Fw is the water density.
other hand, unlike the diamine precursor, PI-1 and
PA-2 are stable toward electrochemical oxidation. These
results indicated that all the diamine precursors had
been completely consumed in the reaction of condensa-
tion polymerization. No free amine was observed ac-
cording to the CV analysis.
Typical examples of the electrical insulating proper-
ties of polymers in comparison with the naphthalene
and methyl group on the 2,2′-position of biphenylene
moiety had been evaluated on the basis of dielectric
constant values (Table 4). In general, the π-conjugation
of benzene structure increased the polarizability of a
molecule.33 Interestingly, the dielectric constants of
polyimde or polyamide containing naphthalene group
are lower than methyl substitution. The bulky struc-
tures of the naphthalene group increase the free volume
of polymer and further decrease the number of polariz-
able groups per unit volume, resulting in lower values
for dielectric constant of atomic and dipolar.3
Figure 4. Cyclic voltammogram of polymer PI-1 in DMF with
Bu NClO (0.1 M) as the supporting electrolyte. Electrochemi-
cal oxidation and reduction behavior were measured by the
CV method (0-1.5 V, 100 mV/s) in DMF using Bu NClO (0.1
M) as the supporting electrolyte. The signals were obtained
on a platinum working electrode, with a Pt wire as the counter
electrode and a Ag/AgCl (saturated) electrode as the reference
electrode.
4
4
4
4
3,34
Conclusion
tion exhibited the highest tensile strength and tensile
modulus. The polymer films were strong and hard.
Cyclic voltammetry is a convenient method to deter-
mine the electrochemical stability of organic materials
A series of new noncoplanar polyimides and poly-
amides based on biphenyldiamine containing a naph-
thalene group were successfully prepared by the poly-
condensation method with various tetracarboxylic di-
anhydrides and aromatic dicarboxylic acids. The intro-
duction of a naphthalene group into the polymer back-
bone resulted in polyimides and polyamides with excel-
lent solubility and mechanical properties. These poly-
mers exhibited the characteristic of thermal stability
by the naphthalene group and reduce the glass transi-
tion temperature of the rigid-rod-like structure which
(
Figure 4.). Polymer solutions of PA-2 and PI-1 were
prepared in DMF using Bu4NClO4 (0.1 M) as the
supporting electrolyte. PA-2 was found to be stable
toward both electrochemical oxidation and reduction.
However, PI-1 shows a reversible reduction wave with
E1/2 at 1.12 V (Figure 4). We tentatively attributed this
to the electron-withdrawing of the imide groups. On the

Macromolecules, Vol. 38, No. 9, 2005
Notes 4029
could improve the processing characteristics. These
properties can make these polyimides and polyamides
attractive for practical applications such as processable
high-temperature engineering plastics because of the
bulky and noncoplanar naphthalene groups in the
polymer chain.
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