Aryl ethynyl terminated imide oligomers and their cured polymers

Article abstract of DOI:10.1021/ma0205358

As part of a program to develop resins for high-performance/high-temperature aerospace structural applications, preliminary neat resin properties of naphthylethynyl terminated imide oligomers were determined and compared with the corresponding phenylethyn

Full text of DOI:10.1021/ma0205358

Macromolecules 2002, 35, 5835-5839
5835
Aryl Ethynyl Terminated Imide Oligomers and Their Cured Polymers
Cr a ig M. Th om p son † a n d P a u l M. Her gen r oth er *
NASA Langley Research Center, Hampton, Virginia 23681-2199
Received April 3, 2002
ABSTRACT: As part of a program to develop resins for high-performance/high-temperature aerospace
structural applications, preliminary neat resin properties of naphthylethynyl terminated imide oligomers
were determined and compared with the corresponding phenylethynyl terminated imide oligomers. Prior
to oligomer work, four naphthylethynyl and phenylethynyl phthalimide and four naphthylethynyl and
phenylethynyl naphthalimide model compounds were prepared and their thermal properties compared.
The naphthylethynyl end-caps in N-phenyl- or N-naphthylphthalimide model compounds reacted at a
lower temperature than the phenylethynyl end-cap in the same compounds, as previously reported. In
contrast to these results, replacement of the phthalimide groups with naphthalimide groups showed that
the phenylethynyl end-cap reacted at a lower temperature than the naphthylethynyl end-cap. Four aryl
ethynyl terminated imide oligomers having the same imide backbone and molecular weight but different
terminal units were prepared and the properties of the cured polymers compared. Phenylethynyl end-
capped or naphthylethynyl end-capped oligomers, cured at 340 or 371 °C, exhibited similar tensile
properties in thin films. The chemistry and properties of these materials are presented.
In tr od u ction
fabricated without any major problems.17 In addition,
PETI-5 adhesive and composite structures demon-
strated outstanding durability at 177 °C. Unfortunately,
the HSCT program was canceled in 1999. Work on
PETIs has continued at a lower effort with the emphasis
on the development of low melt viscosity resins for use
in high-temperature composite fabrication via resin
transfer molding18 and vacuum-assisted resin transfer
molding.19
Recent work at Virginia Commonwealth University
has involved terminating imide oligomers with naph-
thylethynyl and anthracenylethynyl groups.20-22 Using
the same imide segment as in PETI-5, these researchers
made the corresponding naphthyl- and anthracenyl-
terminated derivatives and claimed that these oligomers
cured 30 and 80 °C lower, respectively, than PETI-5 (the
phenyl analogue). The work reported herein was per-
formed primarily to determine whether substituting a
bulkier group (e.g., naphthyl) for the phenyl group
offered any distinct advantages in the physical and/or
mechanical properties and also to determine the proper-
ties of oligomers end-capped with aryl ethynyl naph-
thalic anhydride and their cured polymers.
In the development of polymers for high-performance/
high-temperature applications, a major effort has fo-
cused over the past 25 years on oligomers and polymers
containing phenylethynyl groups.1 Phenylethynyl groups
have been placed terminal on the ends of molecules,
pendent along the backbone, and both pendent and
terminal on the same molecules. More work has con-
centrated on imide oligomers and polymers than any
other system with the emphasis on imide oligomers
terminated with phenylethynyl groups. The initial work
on phenylethynyl terminated imide oligomers (PETIs)
and their cured polymers was performed in the early
1980s at The University of Akron.2,3 This work was
directed primarily toward the development of high-
performance polymers for microelectronic applications.
Since this early work, several organizations such as
National Starch and Chemical Corporation,4,5 NASA
Langley Research Center,6-8 Virginia Polytechnic In-
stitute and State University,9-11 General Electric Co.,12
Dow Chemical Co.,13 E. I. Du Pont de Nemours & Co.,
Inc.,14 Mitsui Toatsu Chemicals, Inc.,15 and Ube Indus-
tries, Ltd.16 have been involved in the development of
PETIs primarily as high-temperature structural resins
(composite matrices and adhesives).
Exp er im en ta l Section 24
Ma ter ia ls. The following chemicals were obtained from the
indicated sources and used without further purification: 3,4′-
oxydianiline (3,4′-ODA, Mitsui Petrochemical Ind., Ltd., mp
84 °C), 1,3-bis(3-aminophenoxy)benzene (APB, Mitsui Petro-
chemical Ind., Ltd., mp 108 °C), 3,3′,4,4′-biphenyltetracar-
boxylic dianhydride (BPDA, Chriskev Co., Inc., mp 305 °C),
4-phenylethynylphthalic anhydride (PEPA, Daychem Labora-
tories, Inc., mp 152 °C), and N-methyl-2-pyrrolidinone (NMP,
Aldrich Chemical Co.). 4-Bromo-1,8-naphthalic anhydride
(Aldrich Chemical Co.) was recrystallized from xylenes to yield
yellow crystals, mp 219 °C. m-Cresol (Fluka Chemical Co.) and
phenylacetylene (Aldrich Chemical Co.) were distilled under
reduced pressure before use. Other chemicals were used as-
received.
At NASA Langley, more than 100 different PETIs
were prepared and evaluated. From this effort, a ma-
terial designated PETI-5 from the reaction of 3,3′,4,4′-
biphenyltetracarboxylic dianhydride, 85 mol % of 3,4′-
oxydianiline, and 15 mol % of 1,3-bis(3-aminophenoxy)-
benzene and end-capped with 4-phenylethynylphthalic
anhydride at a calculated molecular weight of 5000
g/mol evolved. After significant development, PETI-5
was selected as the adhesive and composite matrix for
the United States Mach 2.4 high-speed civil transport
(HSCT) technology development program. Large PETI-
5, high-quality sandwich and skin stringer composite
structures with excellent mechanical properties were
Syn th esis of Ar yl Eth yn yl An h yd r id es. 4-(1-Naphthyl-
ethynyl)phthalic anhydride (NEPA) [mp 226 °C, lit.21 mp 220-
222 °C] was prepared following the literature procedure.21
Syn th esis of 4-(1-P h en yleth yn yl)-1,8-n a p h th a lic An -
h yd r id e. A 250 mL three-neck round-bottom flask containing
† National Research Council Research Associate.
* Corresponding author. E-mail: p.m.hergenrother@larc.nasa.gov.
10.1021/ma0205358 This article not subject to U.S. Copyright. Published 2002 by the American Chemical Society
Published on Web 06/18/2002

5836 Thompson and Hergenrother
Macromolecules, Vol. 35, No. 15, 2002
Ta ble 1. Ar yl Eth yn yl An h yd r id es
a magnetic stir bar, nitrogen inlet, and condenser was charged
with 4-bromo-1,8-naphthalic anhydride (10.0 g, 0.0360 mol),
phenylacetylene (6 mL, 5.5 g, 0.0540 mol), triphenylphosphine
(0.1956 g, 0.75 mmol), copper(I) iodide (0.0657 g, 0.35 mmol),
bis(triphenylphosphine)palladium dichloride (0.0322 g, 0.046
mmol), 50 mL of triethylamine, and 100 mL of toluene. The
mixture was heated to reflux for 6.5 h. The reaction was cooled
and filtered. The yellow solid was washed with water and dried
for 1.5 h at 120 °C (8.6 g, 80% crude yield). The solid was
recrystallized from toluene to give 7.5 g (69%) of yellow
needles, which displayed a sharp crystalline melting peak at
225 °C by differential scanning calorimetry (DSC). Anal. Calcd
for C20H10O3: C, 80.53%; H, 3.38%. Found: C, 80.71%; H,
3.18%.
Syn th esis of 4-(1-Na p h th yleth yn yl)-1,8-n a p h th a lic An -
h yd r id e. A 250 mL round-bottom flask containing a magnetic
stir bar was charged with 4-bromo-1,8-naphthalic anhydride
(2.5541 g, 0.0092 mol), triphenylphosphine (0.2860 g, 0.0011
mol), copper(I) iodide (0.0854 g, 0.45 mmol), bis(triphenylphos-
phine)palladium dichloride (0.0922 g, 0.13 mmol), and 50 mL
of triethylamine. 1-Ethynylnaphthalene (2.5 mL, 2.6 g, 0.97
mol) was added to the flask with 100 mL of toluene. A
condenser containing a nitrogen inlet was placed on the flask,
and the reaction mixture was heated to reflux for 14 h. The
reaction was cooled and filtered. The filtercake was washed
with toluene and dried for 1.5 h at ∼120 °C. The solid was
stirred in 150 mL of water, collected, and dried for 1.5 h to
give 2.93 g (92%) of yellow powder. The solid was recrystallized
from xylenes to give yellow needles which had a crystalline
melting peak at 224 °C by DSC. Anal. Calcd for C24H12O3: C,
82.75%; H, 3.47%. Found: C, 82.53%; H, 3.36%.
On e-Step Syn th esis of Ar yl Eth yn yl Ter m in a ted Im id e
Oligom er . The following procedure was used to prepare an
imide oligomer because the naphthylethynyl naphthalic an-
hydride failed to react at ambient temperature completely in
NMP to form an amide acid. A 50 mL three-neck round-bottom
flask fitted with a nitrogen gas inlet, mechanical stirrer, and
reflux condenser was charged with 3,4′-ODA (5.4293 g, 0.0271
mol), 1,3,3-APB (1.3994 g, 0.0048 mol), and 15 mL of m-cresol.
A slurry of BPDA (8.5398 g, 0.0290 mol) and 4-(1-naphthyl-
ethynyl)-1,8-naphthalic anhydride (2.0004 g, 0.0057 mol) in
15 mL of m-cresol was added to the flask. The solids were
washed into the flask with an additional 19 mL of m-cresol
(25% solids w/w). The mixture was stirred at room temperature
under nitrogen for 12 h. Isoquinoline (15 drops) was added to
the flask, and the reaction mixture was heated to ∼200 °C for
8 h. The reaction was cooled, and a thin film was cast onto
plate glass from a portion of the imide oligomer solution.
Details on film curing is given below.
F ilm s. Thin films (0.025-0.076 mm) were cast from either
amide acid oligomer solutions in NMP or imide oligomer
solutions in m-cresol generally at 25 or 30% solids (w/w)
content. The solutions were generally centrifuged, and the
decantate doctored onto clean, dry plate-glass and dried to a
tack-free form in a low-humidity air chamber overnight at
room temperature. The films were stage-cured in forced air
ovens by heating for 1 h each at 100, 150, 200, 250, and 371
°C. In most cases, the thin films were removed from the glass
by immersion in water. Specimens (15.2 cm long, 0.51 cm wide,
0.038-0.056 mm thick) were cut with a J DC precision sample
cutter, Thwing-Albert Instrument Co. The tensile properties
were determined following the general procedure in ASTM
D882 using five specimens per test condition. The test speci-
men gauge length was 5.1 cm, and the crosshead speed for
film testing was 0.51 cm/minute using a SinTech 2 instrument
with an Eaton model 3397-139 11.4 kg load cell.
Syn th esis of Mod el Com p ou n d s. Phthalimide and naph-
thalimide model compounds were prepared by the reaction of
the aryl ethynyl anhydrides with either aniline or 1-amino-
naphthalene. The reactions were carried out in either acetic
acid or m-cresol as warranted by reactivities of the anhydrides.
A standard procedure follows for the preparation of model
compounds in acetic acid: A 50 mL round-bottom flask
containing a magnetic stir bar was charged with 4-(1-phenyl-
ethynyl)-1,8-naphthalic anhydride (1.0080 g, 0.0034 mol),
1-aminonaphthalene (0.4886 g, 0.0034 mol), and 25 mL of
glacial acetic acid. A condenser was placed on the flask, and
the reaction mixture was heated to reflux for 12 h under
nitrogen. The reaction was cooled, and a yellow crystalline
material precipitated. The solid was collected, washed with
water, and dried at ∼120 °C for 4 h (1.0559 g, 73% crude).
The yellow solid was recrystallized from toluene to give yellow
needles having a crystalline melting peak at 249 °C. Anal.
Calcd for C30H17NO2: C, 85.09%; H, 4.05%; N, 3.31%. Found:
C, 84.81%; H, 3.89%; N, 3.33%.
Preparation of Model Compounds in m-Cresol. A 50 mL
round-bottom flask fitted with a reflux condenser and contain-
ing a magnetic stirbar was charged with 4-(1-phenylethynyl)-
1,8-naphthalic anhydride (0.4778 g, 0.0016 mol), aniline (1 mL,
1.022 g, 0.011 mol), and 10 mL of m-cresol. The reaction
mixture was heated to reflux under nitrogen for 6 h. The
reaction was cooled, and the dark solution was poured into
stirred methanol. The resulting yellow precipitate was col-
lected and dried in an oven overnight. The solid was recrystal-
lized from ethyl acetate/hexanes and dried for 4 h at 150 °C
in a vacuum oven to give 0.4432 g (74% yield) of yellow needles
having a crystalline melting peak at 228 °C. Anal. Calcd for
Oth er Ch a r a cter iza tion . Differential scanning calorim-
etry (DSC) was conducted on a Shimadzu DSC-50 thermal
analyzer with the sample sealed in an aluminum pan. Glass
transition temperatures (Tg’s) were determined by DSC at a
heating rate of 20 °C/min with the Tg taken at the inflection
point of the ∆T vs temperature curve. The crystalline melting
points (Tm’s) of the various compounds were taken at the
endothermic peak in the DSC curve (heating rate of 10 °C/
min). Dynamic thermogravimetric analyses (TGA) were de-
termined on films using a TA Instruments Auto TGA 2950 at
a heating rate of 2.5 °C/min in nitrogen and air atmospheres.
Elemental analyses were performed by Desert Analytics,
Tucson, AZ.
C
26H155NO2: C, 83.63%; H, 4.05%; N, 3.75%. Found: C,
83.70%; H, 4.00%; N, 3.72%.
Syn th esis of Ar yl Eth yn yl Ter m in a ted Am id e Acid
a n d Im id e Oligom er s. Amide acid oligomers were prepared
following a known procedure7 where the BPDA and PEPA were
added to the stirred diamine solution in NMP under nitrogen.
After stirring overnight, a portion of the amide acid solution
was removed and converted to the imide by heating in a
nitrogen atmosphere with toluene to azeotrope the water from
cyclodehydration. The cooled precipitated imide oligomer
slurry was poured into water; the isolated solid washed in hot
water and dried at 240 °C under vacuum for 4 h.
Resu lts a n d Discu ssion
En d Gr ou p s. Four aryl ethynyl anhydrides as shown
in Table 1 were used in this study. 4-Phenylethynyl
phthalic anhydride was obtained from a commercial
source. 4-Naphthylethynyl-1,8-naphthalic anhydride
was synthesized following a known procedure.21 The

Macromolecules, Vol. 35, No. 15, 2002
Oligomers and Their Cured Polymers 5837
Ta ble 2. Mod el Com p ou n d Ch a r a cter iza tion
F igu r e 1. DSC traces of model compounds 1a and 2a .
F igu r e 2. DSC traces of model compounds 3b and 4b.
Ta ble 3. Mod el Com p ou n d Elem en ta l An a lysis
made in m-cresol because reasonably pure crude prod-
ucts in near-quantitative yield could not be obtained in
acetic acid. The theoretical and found elemental analy-
ses of the new model compounds agreed well as pre-
sented in Table 3.
Representative DSC curves are shown in Figure 1 for
compounds 1a and 2a and in Figure 2 for compounds
3b and 4b. In comparing the DSC data in Table 2, the
amine portion of the molecule, the phenyl or naphthyl
group, had virtually no effect upon the exothermic
reaction of the phthalimide model compounds 1a , 1b,
2a , and 2b. However, this trend did not continue with
the naphthalimide model compounds 3a , 3b, 4a , and
4b. Compound 3b, the naphthyl derivative, had higher
onset, peak, and end temperatures than that of com-
pound 3a , the phenyl derivative. With compounds 4a
and 4b, the naphthyl derivative again had higher onset,
peak, and end temperatures than that of the phenyl
derivative.
In comparing the effect from the other side of the
compound, the phenylethynyl or naphthylethynyl group,
the latter had lower onset, peak, and end temperatures
than the corresponding phenylethynyl group for phthal-
imide model compound pairs 1a and 2a and 1b and 2b.
This effect has been previously reported.20-22 However,
the reverse trend was observed for the other four model
compounds derived from 4-aryl ethynyl-1,8-naphthalic
anhydride. The naphthylethynyl compounds, 4a and 4b,
had higher onset, peak, and end temperatures than the
corresponding phenylethynyl compounds, 3a and 3b.
The naphthalimide ring had a more pronounced effect
on the reaction of the naphthyl ethynyl groups than the
phenyl ethynyl groups. Besides electronic effects, the
naphthalimide ring may have provided some steric
hindrance to retard the reaction of the naphthylethynyl
group more than that of the phenylethynyl group. In
comparing the reaction exotherm data for groups of com-
other two compounds, 4-(1-phenylethynyl)-1,8-naph-
thalic anhydride and 4-(1-naphthylethynyl)-1,8-naph-
thalic anhydride, were synthesized in good yields from
the palladium-catalyzed reaction of phenylacetylene or
1-ethynylnaphthalene with 4-bromo-1,8-naphthalic an-
hydride.
Mod el Com p ou n d s. Prior to oligomer and polymer
work, a series of model compounds as shown in Table 2
were synthesized and characterized. Model compound
work was performed primarily to obtain information on
the curing reaction of these compounds as a function of
chemical composition. A total of eight model compounds
were made from the reaction of four aryl ethynyl
anhydrides with aniline or 1-aminonaphthalene in
boiling acetic acid or m-cresol (containing a catalytic
amount of isoquinoline). Two model compounds were

5838 Thompson and Hergenrother
Macromolecules, Vol. 35, No. 15, 2002
Ta ble 4. Oligom er a n d F ilm P r op er ties
thin film properties
23 °C tensile properties
TGA, temp (°C)
5 wt % loss
oligomer
designation
initial Tg
(Tm), °C
cure
temp, °C
strength, MPa
modulus, GPa
(COV, %)
elong, %
(COV, %)
Tg (Tm), °C
N2
air
(COV, %)
PEPTI-5
NEPTI-5
220 (290)
220 (317)
340
371
340
371
371
371
269 (366)
285
266 (365)
288
279
287
125.5 (5.5)
135.8 (0.7)
115.8 (5.9)
124.1 (4.6)
129.6 (2.8)
130.3 (2.4)
3.45 (2.3)
3.54 (1.7)
3.27 (4.5)
3.41 (4.4)
3.37 (2.7)
3.37 (2.9)
21.4 (86.0)
19.7 (68.4)
15.5 (26.6)
12.0 (32.2)
34.4 (27.5)
9.9 (14.9)
493
488
519
532
531
493
499
513
PENTI-5
NENTI-5
225 (320)
211
amide acid were semicrystalline. The Tm’s were found
to differ significantly and ranged from 290 to 320 °C.
The Tm’s are easily influenced by thermal history. The
Tm of PEPTI-5 (same as PETI-5) as well as other
phenylethynyl terminated imide oligomers (PETIs) has
varied widely as a function of thermal history. For
example, a crystalline melt temperature of 286 °C7 and
two crystalline melt temperatures of 251 and 352 °C and
290 and 353 °C23 have been reported for PETI-5 that
was exposed to different temperatures. No Tm was
detected for the oligomer made in m-cresol (NENTI-5).
In past work, PETIs made in m-cresol were amorphous.
By TGA at a heating rate of 2.5 °C/min, the temper-
ature of 5% weight loss in nitrogen and air for films
cured at 371 °C ranged from 493 to 532 °C and 488 to
513 °C, respectively. The NENTI-5 had the highest
temperature of 5% weight loss in both nitrogen and air
whereas PEPTI-5 has the lowest temperature of 5%
weight loss. No definite trend was observed as a function
of the reactive end group.
The NMP amide acid solutions and the m-cresol imide
solution were doctored onto clean plate glass and stage-
cured in air to 340 or 371 °C. Since the naphthylethynyl
terminated oligomer has been reported to cure 30 °C
lower than the corresponding phenylethynyl terminated
oligomer,21 the PEPTI-5 and the NEPTI-5 films were
cured at 340 and 371 °C to determine whether the lower
cure temperature offered any advantages. Past work
however with PEPTI-5 films cured at 350 °C has
provided good mechanical properties and a Tg of 270 °C.7
Composites and adhesives of PETI-5 (same as PEPTI-
5) are normally cured at 371 °C.17 The curing of PETIs
was proposed as a free radical process where curing in
air is preferred over curing in an inert atmosphere or
vacuum.1 Films of PEPTI-5 and NEPTI-5 cured for 1 h
at 340 °C in air were fingernail creaseable and opaque.
The films showed Tg’s by DSC at 269 and 266 °C and
Tm’s at 366 and 365 °C, respectively, for PEPTI-5 and
NEPTI-5. Films cured at 371 °C were fingernail
creaseable and transparent dark orange to dark red.
The films cured at 371 °C had undergone further
reaction as evidenced by the significant increase in Tg’s
to 285 and 288 °C for PEPTI-5 and NEPTI-5, respec-
tively. The unoriented thin film average tensile proper-
ties are presented in Table 4 with the coefficient of
variation (COV) for each set of films reported in
parentheses. The tensile strengths and moduli are very
similar, regardless of cure temperature or end unit. The
noticeable difference is the elongation where films from
the phenylethynyl terminated oligomers showed higher
elongations than those from the naphthylethynyl ter-
minated oligomers. This may be due more to film quality
than to the difference in end group chemistry. Film
elongation is more sensitive to flaws within the test
specimens caused by foreign particles (e.g., gel particles
F igu r e 3. Oligomer chemistry.
pounds derived from aryl phenyl substituted phthalic
and naphthalic anhydride, the naphthalimide com-
pounds (3a , 3b, 4a , and 4b) have lower onset, peak, and
end temperature than those of the corresponding
phthalimide compounds (1a , 1b, 2a , and 2b).
Oligom er s a n d P olym er s. Four oligomers with the
same imide backbone and similar calculated number-
average molecular weights (∼5000 g/mol) but different
end units were prepared according to the synthetic
scheme in Figure 3. Designations for the four oligomers
are given in Figure 3. Three of the oligomers were made
via the amide acid in NMP and subsequently cyclo-
dehydrated to the imide by heating the NMP amide acid
solutions containing toluene to azeotrope the water. The
fourth oligomer (NENTI-5) was prepared in m-cresol
since the naphthylethynyl naphthalic anhydride failed
to react at ambient temperature completely in NMP to
form an amide acid. Insoluble solid was isolated from
the NMP solution and identified as unreacted naph-
thylethynyl naphthalic anhydride. The Tg’s of the imide
oligomers by DSC ranged from 211 to 225 °C as shown
in Table 4. All of the imide oligomers made via the

Macromolecules, Vol. 35, No. 15, 2002
Oligomers and Their Cured Polymers 5839
(4) Paul, C. W.; Schultz, R. A.; Fennelli, S. P. In Advances in
Polyimide Science and Technology; Feger, C., Khoyasteh, M.
M., Htoo, M. S., Eds.; Technomic: Lancaster, PA, 1993; p 220.
(5) Paul, C. W.; Schultz, R. A.; Fennelli, S. P. U.S. Pat. 5,138,28,
1992 (to National Starch and Chemical Corp.).
(6) Bryant, R. B.; J ensen, B. J .; Hergenrother, P. M. Polym.
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and dust), wrinkles, and minor specimen misalignment
during the test than strength or modulus. The five
PEPTI-5 film specimens cured at 371 °C had an elonga-
tion at break that varied from 9 to 48%. The elongations
of 19.7 and 34.4% for the films from the phenylethynyl
terminated oligomers (PEPTI-5 and PENTI-5) cured at
371 °C suggest that these films have very low cross-
link density.
Con clu sion s
(9) Meyer, G. W.; J ayaraman, S.; McGrath, J . E. Polym. Prepr.
1993, 34 (2), 540.
Two new aryl substituted anhydrides, 4-(2-phenyl-
ethynyl)-1,8-naphthalic anhydride and 4-(1-naphthyl-
ethynyl)-1,8-naphthalic anhydride, were used to prepare
model compounds and aryl ethynyl terminated imide
oligomers. Other model compounds and oligomers were
made using phenylethynyl and naphthylethynyl phthal-
ic anhydride. Of the eight model compounds, naphthyl-
ethynyl phthalimide model compounds cured at lower
temperature than the corresponding phenylethynyl
phthalimide model compounds. However, the opposite
was found for the naphthalimide model compounds. The
phenylethynyl naphthalimide model compounds cured
at lower temperature than the corresponding naph-
thylethynyl naphthalimide model compounds. Four
imide oligomers with the same imide backbone and
molecular weight end-capped with phenylethynyl and
naphthylethynyl phthalimide units and phenylethynyl
and naphthylethynyl naphthalimide units gave similar
Tg’s and thin film tensile properties after curing at 371
°C. Two of the oligomers terminated with phenylethynyl
and naphthylethynyl phthalimide units gave very simi-
lar Tg’s and thin film tensile properties after curing at
340 °C. The naphthylethynyl group did not afford any
advantage over the phenylethynyl group.
(10) (a) Meyer, G. W.; Glass, T. E.; Grubbs, H. J .; McGrath, J . E.
Polym. Prepr. 1994, 35 (1), 549. (b) Meyer, G. W.; Glass, T.
E.; Grubbs, H. J .; McGrath, J . E. J . Polym. Sci., Part A:
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(11) McGrath, J . E.; Meyer, G. W. U.S. Pat. 5,493,002, 1996 (to
Virginia Polytechnic Institute and State University).
(12) J ohnston, J . A.; Li, F. M.; Harris, F. W.; Takekoshi, T.
Polymer 1994, 35 (22), 4865.
(13) Earls, J . D.; Burton, B. L.; Colegrove, B. T. U.S. Patent
6,136,949, 1998 (to Dow Chemical Company).
(14) Boyce, R. J .; Gannett, T. P.; Sonnett, J . M.; Tanikella, M. S.;
Auman, B. C. U.S. Pat. 5,478,913, 1995 (to E. I. Du Pont de
Nemours and Company).
(15) Okawa, H.; Tamai, S.; Ohta, M.; Yamaguchi, A. U.S. Patent
5,708,128, 1998 (to Mitsui Toatsu Chemicals, Inc.).
(16) Yokota, R.; Hasegawa, M.; Yamaguchi, H. European Patent
1,018,507 A1, 2000 (to Ube Industries, Ltd.); U.S. Patent
6,281,323 B1, 2001 (to Ube Industries, Ltd.).
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