Synthesis of wholly alicyclic polyimides from N-silylated alicyclic diamines and alicyclic dianhydrides

Article abstract of DOI:10.1021/ma011627k

A new synthetic method to give wholly alicyclic polyimides with high molecular weights has been developed. The polymerization of cyclobutanetetracarboxylic dianhydride (1a) or bicyclo [2.2.1]-heptane-2-methanecarboxylic-3,5,6-tricarboxylic-2,3:5,6-dianhydride (1b) with various N-silylated alicyclic diamines (2) was carried out in N,N-dimethylacetamide (DMAc) at room temperature, giving poly(amic acid trialkylsilylester)s (3) as precursor polymers that were hydrolyzed to poly(amic acid)s (4) with inherent viscosities up to 0.99 dL/g. Both polyimide precursors were readily converted to corresponding polyimides (5) by thermal treatment. These polyimides are readily soluble in polar aprotic solvents such as 1-methyl-2-pyrrolidone, N,N-dimethylacetamide and dimethyl sulfoxide at room temperature, and showed high thermal stability (T_d10 = 420-445 °C in N₂) and excellent transparency at wavelengths above 250 nm. The average refractive index of the polyimide 5aa was 1.498, and the dielectric constant estimated from the refractive index was 2.47.

Full text of DOI:10.1021/ma011627k

Macromolecules 2002, 35, 2277-2281
2277
Synthesis of Wholly Alicyclic Polyimides from N-Silylated Alicyclic
Diamines and Alicyclic Dianhydrides
Ya su fu m i Wa ta n a be, Yosh im a sa Sa k a i, Yu ji Sh iba sa k i, Sh in ji An d o, a n d
Mitsu r u Ued a *
Department of Organic & Polymeric Materials, Tokyo Institute of Technology, Ookayama 2-12-1,
Meguro-ku, Tokyo 152-8552, J apan
Yosh iyu k i Oish i a n d Ku n io Mor i
Department of Applied Chemistry and Molecular Science, Faculty of Engineering, Iwate University,
Morioka, Iwate 020-8551, J apan
Received September 13, 2001; Revised Manuscript Received December 11, 2001
ABSTRACT: A new synthetic method to give wholly alicyclic polyimides with high molecular weights
has been developed. The polymerization of cyclobutanetetracarboxylic dianhydride (1a ) or bicyclo[2.2.1]-
heptane-2-methanecarboxylic-3,5,6-tricarboxylic-2,3:5,6-dianhydride (1b) with various N-silylated alicyclic
diamines (2) was carried out in N,N-dimethylacetamide (DMAc) at room temperature, giving poly(amic
acid trialkylsilylester)s (3) as precursor polymers that were hydrolyzed to poly(amic acid)s (4) with inherent
viscosities up to 0.99 dL/g. Both polyimide precursors were readily converted to corresponding polyimides
(5) by thermal treatment. These polyimides are readily soluble in polar aprotic solvents such as 1-methyl-
2-pyrrolidone, N,N-dimethylacetamide and dimethyl sulfoxide at room temperature, and showed high
thermal stability (Td10 ) 420-445 °C in N2) and excellent transparency at wavelengths above 250 nm.
The average refractive index of the polyimide 5a a was 1.498, and the dielectric constant estimated from
the refractive index was 2.47.
In tr od u ction
molecular weights (ηinh ) 0.74 dL/g) by the polymeri-
zation of cyclobutanetetracarboxylic dianhydride (1a )
with N-trimethylsilylated alicyclic diamines (2).21 The
reaction of carboxylic anhydrides with N-silylated amines
produces amide-silylesters which do not form salts with
amines.
In this paper, we report the detailed preparation and
properties of various wholly alicyclic P Is from several
alicyclic dianhydrides (1) and N-silylated alicyclic di-
amines (2).
Polyimides (P Is) are a class of polymers used exten-
sively in microelectronics because of their outstanding
key properties such as thermoxidative stability, high
mechanical strength, and excellent electrical proper-
ties.1 They are used as interlayer dielectrics in inte-
grated circuit fabrication. Recently, semiaromatic P Is
have been used in the applications as optoelectronics
and interlayer dielectric materials thanks to the better
colorless transparency and the lower dielectric constant
compared with conventional fully aromatic polyim-
ides.2-13 They hardly form inter- or intramolecular
charge-transfer complexes, which increase the dielectric
constant and lower the transparency. Moreover, alicyclic
structures are effective to decrease a molecular density
because of their bulkiness, giving P Is with a low di-
electric constant.
The synthesis of wholly aliphatic or alicyclic P Is is
rather difficult.14-17 The polymerization of dianhydrides
with aliphatic or alicyclic diamines gives poly(amic
acid)s (P AAs), which make salts of P AAs with the free
diamines having a high basicity. This salt formation
prevents the formation of high molecular weight P AAs.
To remedy this problem, solution imidization and acid
chloride methods were reported.18,19
Exp er im en ta l Section
Ma ter ia ls. 1-Methyl-2-pyrrolidinone (NMP), N,N-dimethyl-
acetamide (DMAc), dimethyl sulfoxide (DMSO), triethylamine
(TEA), and toluene were purified by the usual manner, and
stored under an atmosphere of N2. 1,2,3,4-Cyclobutanetetra-
carboxylic dianhydride (1a ) was purified by recrystallization
from acetic anhydride and dried at 150 °C before use. Bicyclo-
[2.2.1]heptane-2-methanecarboxylic-3,5,6-tricarboxylic-2,3:5,6-
dianhydride (1b) was heated to 90 °C in acetic anhydride and
toluene, stirred for 1 h, filtered, and then dried at 90 °C for 1
h prior to use. 5-Amino-1,3,3-trimethyl-cyclohexane- methyl-
amine and 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane were
purified by distillation. Other reagents and solvents were used
as received.
5-Tr im eth ylsilyla m in o-N-tr im eth ylsilyl-1,3,3-tr im eth -
ylcycloh exa n em eth yla m in e (2a ). A 300-mL three-necked
round-bottomed flask equipped with a magnetic stirrer, a
nitrogen inlet, a 10 mL pressure-equalizing dropping funnel,
and a no-air stopper was charged with 5-amino-1,3,3-trimeth-
ylcyclohexanemethylamine (10.6 g, 60.0 mmol) and toluene
(150 mL) under an N2 stream. To this solution was added
trimethylchlorosilane (13.5 g, 120 mmol) at 5 °C, and the
solution was stirred for 30 min. Then, TEA (12.1 g, 120 mmol)
was added dropwise to this solution through the funnel. White
In a previous paper,20 we reported the synthesis of
aromatic polyimides from N,N′-bissilylated aromatic
diamines and aromatic tetracarboxylic dianhydrides.
Quite recently, we have reported briefly the successful
synthesis of wholly alicyclic P Is with relatively high
* To whom correspondence should be addressed. E-mail:
mueda@polymer.titech.ac.jp.
10.1021/ma011627k CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/16/2002

2278 Watanabe et al.
Macromolecules, Vol. 35, No. 6, 2002
HCl‚TEA salt precipitated immediately. The reaction was kept
for another 2 h at 5 °C and then 24 h at 60 °C. The reaction
mixture was filtered and concentrated at reduced pressure.
The crude product was distilled under reduced pressure to give
2a as a clear oil. The yield was 10.1 g (52%): bp 88-94 °C
(0.75 Torr). IR (NaCl): ν ) 3409 (N-H), 1249 (Si-CH3), 836
(Si-CH3) cm-1. Anal. Calcd for (C16H38N2Si2): C, 61.07; H,
12.17; N, 8.90. Found: C, 60.99; H, 12.32; N, 9.12.
2,5(2,6)-Bis(N-tr im eth ylsilylam in om eth yl)bicyclo[2.2.1]-
h ep ta n e (2b). This compound was prepared as described
above using 2,5(2,6)-bis(aminomethyl)- bicyclo[2.2.1]heptane
in place of 5-amino-1,3,3-trimethylcyclohexanemethylamine.
The yield of 2b was 48% as a clear oil: bp 106-110 °C (0.75
Torr). IR (NaCl): ν ) 3405 (N-H), 1249 (Si-CH3), 836 (Si-
CH3) cm-1. Anal. Calcd for (C15H34N2Si2): C, 60.33; H, 11.48;
N, 9.38. Found: C, 59.95; H, 11.14; N, 9.66.
5-ter t-Bu tyld im eth ylsilyla m in o-N-ter t-bu tyld im eth yl-
silyl-1,3,3-tr im eth ylcycloh exa n em eth yla m in e (2c). This
compound was prepared as described above using tert-butyl-
dimethylchlorosilane in place of trimethylchlorosilane. The yield
of 2c was 82% as a clear oil: bp 120-123 °C (0.15 Torr). IR
(NaCl): ν ) 3405 (N-H), 1253 (Si-tert-Butyl), 829 (Si-tert-
Butyl) cm-1. Anal. Calcd for (C22H50N2Si2): C, 66.26; H, 12.64;
N, 7.02. Found: C, 66.07; H, 12.32; N, 7.26.
4,4′-Met h ylen eb is(N,N′-ter t-b u t yld im et h ylsilylcyclo-
h exyla m in e) (2d ). This compound was prepared as described
above using 4,4′-methylenebis(cyclohexylamine) in place of
5-amino-1,3,3-trimethylcyclohexanemethylamine. The yield of
2d was 50% as a clear oil: bp 144 °C (0.02 Torr). IR (NaCl):
ν ) 3397 (N-H), 1249 (Si-tert-Butyl), 829 (Si-tert-Butyl)
cm-1. Anal. Calcd for (C25H54N2Si2): C, 68.42; H, 12.40; N, 6.38.
Found: C, 68.13; H, 12.11; N, 6.37.
(d,p)), which is implemented in the “Gaussian-98” (Revision
A.7) program, was used to calculate molecular orbital energies
of dianhydrides. The geometric structures of computed com-
pounds were fully optimized under no constraints prior to the
calculations of molecular orbital energies.
Resu lts a n d Discu ssion
Syn th esis of P oly(a m ic a cid tr ia lk ylsilyl ester s)
(3). As alicyclic dianhydrides (1), 1,2,3,4-cyclobutane-
tetracarboxylic dianhydride (1a ) and bicyclo[2.2.1]-
heptane-2-methanecarboxylic-3,5,6-tricarboxylic-2,3:5,6-
dianhydride (1b) were employed. On the other hand,
N-trimethylsilylated alicyclic diamines (2), 5-trimethyl-
silylamino-N-trimethylsilyl-1,3,3-trimethylcyclohexane-
methylamine (2a) and 2,5(2,6)-bis(N-trimethylsilylamino-
methyl)bicyclo[2.2.1]heptane (2b) were prepared by the
reactions of corresponding diamines with trimethyl-
chlorosilane in the presence of TEA.
To determine optimal conditions for polymerization,
the polymerization of 1a with N-silylated diamines 2a
or 2b was studied in detail. The ring-opening poly-
addition was performed with 1 mmol of monomers in a
solvent at room temperature for 1 h [eqs 1 and 2]
P oly(a m ic a cid tr ia lk ylsilylester )s (3). A flame-dried 25
mL flask was charged with 2a (0.899 g, 2.86 mmol) and DMAc
(3.41 g) under nitrogen. 1,2,3,4-Cyclobutanetetracarboxylic
dianhydride 1a (0.560 g, 2.86 mmol) was added to this solution
at 25 °C in one portion. The solution was stirred at this
temperature for 1 h under nitrogen. The inherent viscosity of
the resulting polymer solution was 0.99 dL/g, measured at a
concentration of 0.5 g/dL in DMAc at 30 °C. IR (KBr): ν ) 1708
(CdO, silylester), 1654 (CdO, amide) cm-1
.
P oly(a m ic a cid )s (4). The solution of polymer 3 was poured
into a 0.2 wt % aqueous HCl solution. The precipitate was
filtered off, washed with water, and dried under vacuum.
IR (KBr): ν) 1727 (CdO, carboxylic acid), 1646 (CdO,
amide) cm-1. Anal. Calcd for (C18H26N2O6‚0.8H2O)n: C, 56.77;
H, 6.88; N, 7.36. Found: C, 56.76; H, 6.51; N, 7.36.
P oly(im id e)s (5). The polyimide film was prepared by
casting the solution of polymer 3 on a silicon wafer at room
temperature and then by heating at 100, 150, 200, and 250
°C for 0.5 h and 300 °C for 1 h under nitrogen atmosphere.
IR (KBr): ν ) 1770 and 1708 (imide CdO), 1361 (C-N) cm-1
.
Anal. Calcd for (C18H22N2O4‚0.1H2O)n: C, 65.08; H, 6.74; N,
8.43. Found: C, 64.54; H, 6.58; N, 8.40.
Mea su r em en ts. The infrared spectra were recorded on a
Horiba FT-720 spectrophotometer. 1H NMR spectra were
obtained using a Bruker DPX300 (300 MHz) spectrometer. The
UV-visible spectra of polyimide films were recorded on a J asco
V-560 spectrophotometer. Thermogravimetry (TG) and dif-
ferential scanning calorimetry (DSC) were performed with a
Seiko TG/DTA 6300 and DSC 6200, respectively. Molecular
weights were determined by a gel permeation chromatograph
(GPC) with polystyrene calibration using TOSO HPLC (HLC-
8120GPC) equipped with a TOSO TSK gel column (TSKgel
GMHHR-M, TSKgel GMHHR-L) at 40 °C in DMF with LiBr.
Refractive indices of polyimide films formed on quartz sub-
strates were measured at a wavelength of 1.320 µm at room
temperature with a Metricon model PC-2000 prism coupler.
Using linearly-polarized laser light with parallel (TE: trans-
verse electric) and perpendicular (TM: transverse magnetic)
polarization to the film plane, the in-plane (nTE) and out-of-
plane (nTM) refractive indices and the film thickness of the
samples were determined.
Table 1 summarizes the effects of solvent on the
inherent viscosity of polymer 3. Polymerizations of 2a
or 2b with 1a proceeded rapidly in a homogeneous
solution without salt formation and were completed in
1 h, giving colorless and viscous polymer solutions. The
polymers with inherent viscosities ranging between 0.71
and 0.99 dL/g were obtained in DMAc.
On the basis of these results, the polymerization of
2a or 2b with 1b was performed in DMAc at room
temperature. Polymers 3ba or 3bb obtained after 24 h
showed very low inherent viscosities of 0.09 and 0.12
dL/g. The polymerization was carried out at 60 °C again,
but no discernible effect on the inherent viscosity was
observed (Table 2). This result would be explained by a
low reactivity of 1b compared to that of 1a . Ando et al.22
have reported that the acylation rate constants of
Ca lcu la tion s. A density functional level of theory (B3LYP)
with an extended basis set with polarization functions (6-31G-

Macromolecules, Vol. 35, No. 6, 2002
Synthesis of Wholly Alicyclic Polyimides 2279
F igu r e 1. Structures and numbers of wholly alicyclic polyimides synthesized in this study.
Ta ble 1. Syn th esis of Wh olly Alicyclic P oly(a m ic
a cid silyl ester s)a
Ta ble 3. Syn th esis of P oly(a m ic a cid silyl ester s)a
b
dianhydride
diamines
polymer
ηinh
inherent
1b
1b
2c
2d
3bc
3bd
0.35
0.29
dianhydride diamine solvent
polymer
viscosity (dL/g)b
1a
1a
1a
1a
1a
1a
1a
1a
2a
2b
2c
2d
2a
2b
2a
2b
DMAc
DMAc
DMAc
DMAc
NMP
NMP
DMSO
DMSO
3a a
3a b
3a c
3a d
3a a
3a b
3a a
3a b
0.99 (0.74)c
0.71
0.51
0.64
0.60
0.59
0.72
0.53
a
Polymerization was carried out with 1.0 mmol of each mono-
mer in the solvent at room temperature for 3 h under nitrogen.
Measured at a concentration of 0.5 g/dL in DMAc at 30 °C.
b
viscosities ranging between 0.29 and 0.35 dL/g were
produced (eq 3). Trimethylsilylated diamines show
higher reactivity than tert-butyldimethylsilylated di-
amines as can be seen in the synthesis of 3a a and 3a c
in Table 1. The inherent viscosity of 3a a increased
rapidly compared to that of 3a c.
a
Polymerization was carried out with 1.0 mmol of each mono-
mer in the solvent at room temperature for 1 h under nitrogen.
b
Measured at a concentration of 0.5 g/dL in each solvent at 30
°C. c Inherent viscosity of poly(amic acid).
Ta ble 2. Syn th esis of P oly(a m ic a cid silyl ester s)a
reaction
temp, °C
reaction
time, h
b
monomers
polymer
ηinh
1b + 2a
1b + 2b
1b + 2a
room temp
room temp
60
24
24
24
3ba
3bb
3ba
0.09
0.12
0.10
a
Polymerization was carried out with 1.0 mmol of each mono-
mer in the solvent at each temperature for 24 h under nitrogen.
b
Measured at a concentration of 0.5 g/dL in DMAc at 30 °C.
dianhydrides can be inferred from the molecular orbital
energies of the lowest unoccupied molecular orbital
(ꢀLUMO), electron affinities, and 13C chemical shifts of
carbonyl carbons. The calculated value of ꢀLUMO for 1a
(-1.87 eV) is considerably lower than that for 1b (-1.37
eV), which indicates that the former has higher acyla-
tion reactivity than the latter. The calculated value of
ꢀLUMO for bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic
2,3:5,6-dianhydrides that has the same skeletal struc-
ture as that of 1b but contains two five-membered
anhydride ring is -1.53 eV. This value is closer to ꢀLUMO
of 1b rather than that of 1a . Hence, the lower reactivity
of 1b is mainly ascribed to the skeletal norbornane
structure, though the introduction of six-membered
anhydride ring further reduces the acylation reactivity.
Polymers 3 were readily converted to poly(amic acid)s
(4) by pouring the solution of polymers 3 into a 0.2 wt
% aqueous HCl solution at room temperature.
P olym er Ch a r a cter iza tion . Polymers 3 were iden-
tified as the expected poly(amic acid trialkylsilyl ester)s
by IR spectroscopy. The IR spectra showed charac-
teristic amide and silyl ester absorptions at 1658 and
1708 cm-1. On the other hand, three characteristic
absorptions for amide, carboxyl, and hydroxyl groups
were observed at 1650, 1720, and 3000-3700 cm-1 for
polymers 4. Furthermore, elemental analyses also
supported the formation of the expected polymers 4.
Polymers 3 were soluble in THF, chloroform, and
polar aprotic solvents such as NMP, DMAc, and DMSO
at room temperature. The solubility of polymers 4 is
lower compared to that of polymers 3, but polymers 4
were still soluble in polar aprotic solvents at room
temperature.
N-Trimethylsilylated alicyclic diamines, which are
labile in polar aprotic solvents, might be hydrolyzed
to original diamines. Thus, more stable N-tert-butyl-
dimethylsilylated alicyclic diamines, 5-tert-butyldimeth-
ylsilylamino-N-tert-butyldimethylsilyl-1,3,3-trimethyl-
cyclohexanemethylamine (2c), 4,4′-methylenebis(N,N′-
tert-butyldimethylsilylcyclohexylamine) (2d ) were pre-
pared. The polymerization was carried out in DMAc at
room temperature for 3 h. The results are summarized
in Table 3. The polymers 3bc and 3bd with inherent
The molecular weight of 3bc having an inherent
viscosity of 0.35 dL/g was determined by means of GPC.
The chromatogram indicated that the Mn and Mw values
were 29 000 and 64 000, respectively, with respect to
polystyrene standards, and the ratio Mw/Mn was 2.2.

2280 Watanabe et al.
Macromolecules, Vol. 35, No. 6, 2002
Ta ble 4. Th er m a l P r op er ties of P olyim id esa
polymer
Tg (°C)b
Ts (°C)c
Td(5%) (°C)d
Td(10%) (°C)e
5a a
5a b
5a c
5a d
5bc
5bd
f
361
380
368
378
364
367
415
435
410
430
409
415
425
445
421
440
421
428
300
f
f
f
f
a
Determined by TG at heating rate of 10 °C/min under N2.
b
Glass transition temperature (Tg) measured by DSC at heating
rate of 20 °C/min under N2. c Starting temperature of decomposi-
tion. Temperature at 5% weight loss. e Temperature at 10%
d
weight loss. f Not detected.
Ta ble 5. Refr a ctive In d ices a n d Bir efr in gen ce of Wh olly
Alicyclic P olyim id es F ilm s
F igu r e 2. TGA curves of 3bc and 5bc.
b
c
d
polyimide d (µm)a
nTE
nTM
nAV
∆ne
ꢀf
These polyimide precursors 3 and 4 were converted
to the corresponding polyimides (5) by thermal treat-
ment. The structures and the abbreviations of the
polyimides are illustrated in Figure 1 (eq 4).
5bc
5a a
5.3
6.5
1.5174 1.5170 1.5173 0.0004 2.53
1.4977 1.4977 1.4977 0.0000 2.47
Film thickness. The in-plane refractive indices. c The out-
a
b
d
of plane refractive indices. Average refractive index; nAV
)
(2nTE + nTM)/3. e Birefringence; ∆n ) nTE - nTM
.
f Optically
2
estimated dielectric constant; ꢀ ) 1.10nAV
.
Thermal properties of the polyimides evaluated by
the TG technique have been listed in Table 4. The
10% weight loss temperatures (Td10) in nitrogen were
observed at 420-445 °C, respectively. These results
show that the thermal stability is lower than that of
aromatic polyimides, whereas it is enough for micro-
electronics applications.
The transmission UV-vis spectrum of the 5a a and
5bc film is shown in Figure 4. The wholly alicyclic
polyimide films exhibit cutoffs at 230 and 235 nm,
respectively. These values are close to those of other
alicyclic polyimides (234 nm). Although a small absorp-
tion due to the carbonyl n-π* is observed around
260 nm, these films are entirely colorless. A cutoff
wavelength is defined here as the point where the
transmittance becomes below 1% in the spectrum.
Dielectr ic Con sta n t of P olyim id e 5. As listed in
Table 5, the average refractive indices (nAV) of the
polyimides 5bc and 5a a were determined as 1.5173 and
1.4977, respectively. A dielectric constant (ꢀ) of material
at optical frequencies can be estimated from the refrac-
The traces of thermogravimetry for polymer 3bc and
the corresponding polyimide 5bc are shown in Figure
2. A rapid weight loss for 3bc was observed at 200-
350 °C. In this range, the weight loss was 37%, which
is in good agreement with the value of weight loss
calculated from the elimination of tert-butyldimethyl-
silanol due to the imidization.
The IR spectrum of thermally treated polymer 5bc
film (100 °C for 30 min, 150 °C for 30 min, 250 °C for
30 min, and 300 °C for 1 h) is shown in Figure 3, where
characteristic imide absorptions at 1778 and 1704 cm-1
are visible and the absorption due to the carboxylic acid
silyl esters at 1708 cm-1 had completely disappeared.
Furthermore, the structure of polymer 5bc was also
confirmed by elemental analysis.
tive index n according to Maxwell’s equation, ꢀ Z n2.
2
The ꢀ around 1 MHz has been evaluated as ꢀ Z 1.10nAV
,
including an additional contribution of approximately
F igu r e 3. IR spectrum of 5bc.

Macromolecules, Vol. 35, No. 6, 2002
Synthesis of Wholly Alicyclic Polyimides 2281
loss temperature around 430 °C. The wholly alicyclic
polyimides synthesized in this study exhibit low refrac-
tive indices, and the estimated dielectric constant is as
low as 2.47. Thus, the N-silylated diamine method is
considered to be a versatile and promising route for
synthesis of a variety of high molecular weight wholly
alicyclic polyimides.
Ack n ow led gm en t. This study was financially sup-
ported by Kawasaki Steel 21st Century Foundation.
Refer en ces a n d Notes
F igu r e 4. UV-vis spectra of wholly alicyclic polyimide
films: (a) polyimide 5bc; (b) polyimide 5a a .
(1) Ghosh, M. K., Mittal, K. L., Eds. Polyimides Fundamentals
and Applications; Marcel Decker: New York, 1996.
(2) Itamura, S.; Yamada, M.; Tamamura, S.; Matsumoto, T.;
Kurosaki, T. Macromolecules 1993, 26, 3490.
(3) J in, Q.; Yamashita, T.; Horie, K.; Yokota, R.; Mita, I. J . Polym.
Sci., Part A: Polym. Chem. 1993, 31, 2345.
(4) J in, Q.; Yamashita, T.; Horie, K. J . Polym. Sci., Part A:
Polym. Chem. 1993, 32, 503.
(5) Yamada, M.; Kusama, M.; Matsumoto, T.; Kurosaki, T.
Macromolecules 1993, 26, 4961.
(6) Matsumoto, T.; Kurosaki, T. Macromolecules 1995, 28, 5684.
(7) Matsumoto, T.; Kurosaki, T. Macromolecules 1997, 30, 993.
(8) Matsumoto, T.; Feger, C. J . Photopolym. Sci. Technol. 1998,
11, 231.
(9) Matsumoto, T. High Perform. Polym. 1999, 11, 367.
(10) Matsumoto, T.; Maeda, Y.; Takeshima, N. J . Photopolym. Sci.
Technol. 2000, 13, 327.
(11) Moore, J . A.; Dasheff, A. N. Chem. Mater. 1989, 1, 163.
(12) Moore, J . A.; Gamble, D. R. Polym. Eng. Sci. 1992, 32, 1642.
(13) Okita, H.; Tsuchida, A.; Yamamoto, M.; Moore, J . A.; Gamble,
D. R. Macromol. Chem. Phys. 1996, 197, 2493.
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Funct. Polym. 1996, 30, 61.
10% from the infrared absorption.14,23 The nAV of 1.5173
and 1.4977 can be translated into dielectric constants
of 2.53 and 2.47, respectively. These values are slightly
lower than the optically estimated ꢀ of an alicyclic poly-
imide (2.55)16 and a fluorinated semiaromatic polyimide
(2.6)14 and significantly lower than that of a semi-
aromatic polyimide (2.83).16 In addition, the in-plane/
out-of-plane birefringences (∆n) of the two polyimides
were estimated as 0.0004 and 0.0000, respectively.
These negligibly small birefringence implies that these
polymers have low polarizability anisotropy and the
polymer chains are randomly oriented in the film. The
absence of birefringence was also reported for an ali-
cyclic polyimide.16
Con clu sion s
The ring-opening polyaddition of N-trialkylsilylated
alicyclic diamines 2 with alicyclic tetracarboxylic dian-
hydrides 1 in DMAc at room temperature afforded poly-
(amic acid trialkylsilyl esters) 3 with high molecular
weights (ηinh ) 0.99 dL/g), because polymers 3 have good
solubility in organic solvents and do not undergo any
side reactions such as salt formation with N-silylated
diamine. Polymers 3 were easily hydrolyzed to corre-
sponding poly(amic acid)s 4. The films of polymers 3 and
4 were converted to transparent films of the wholly
alicyclic polyimides 5 with the elimination of tert-
butyldimethylsilanol and H2O by thermal treatment,
respectively. Polyimides 5 are transparent over 250 nm
and have good thermal stability with the 10% weight
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