It is the primary object of the present invention to prepare high temperature polymeric materials, especially linear aromatic polyimides, which maintain their integrity and toughness during long exposure times at elevated temperatures. According to the present invention, this object is achieved, and the attending benefits are obtained, by first providing the bis(exocyclodiene) bis(4-(3,4-dinethylene pyrrolidyl) phenyl) methane, which is formed from the monomer N-phenyl 3,4-dimethylene pyrrolidine. This bis-(exocyclodiene) undergoes Diels-Alder reaction with a bismaleimide without the evolution of gaseous by-products, to form the aromatic polyimide

Ottenbrite, Raphael M.

English

NASA Technical Reports Server

United States Patent [191 [11] Patent Number: 4,851,544 
Ottenbrite [45] Date of Patent: Jul. 25, 1989 
0.20 
F .- sc 0.15- 
0 
[54] BIS[4-(3,4-DIMETHYLENFYRROLIDYL)- 
PHENYLIMETHANE 
[75] Inventor: Raphael M. Ottenbrite, Midlothian, 
[73] Assignee: The United States of America as 
Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[2l] Appl. No.: 221,386 
[22] Filed: Jul. 19,1988 
[51] Int. Cl.4 ....................... C07C 87/50; C07C 87/62 
[52] U.S. Cl. .................................... 548/524; 526/262; 
528/322; 548/400 
[58] Field of Search ................. 548/400, 524; 528/322 
[561 References Cited 
U.S. PATENT DOCUMENTS 
4,000,135 12/1976 Kast .................................... 548/524 
4,036,977 7/1977 Lednicer ............................. 548/524 
Primaty Examiner-Harold D. Anderson 
Assistant Examiner-T. Mason 
Attorney. Agent, or Firm-George F. Helfrich; John R. 
Manning; Charles E. B. Glenn 
1571 ABSTRACT 
A polyimide composition consisting essentially of re- 
curring units having the following structural formula: 
- 
- ? 48 hr 
- ,O 24 hr 
I 
I 
I 
I 
- 
- 0,' I2 hr 
- / g  hr 
- /Os hr 
- o--- --0 
3 hr - I hr 
I I I I I I J 
0 
QN*N- II 
0 
I I 
is produced by the copolymerization of a bismaleimide 
and bis[4-(3,4-dimethylenepyrrolidyl)phenyl]methane. 
1 Claim, 1 Drawing Sheet 
https://ntrs.nasa.gov/search.jsp?R=19900011802 2020-03-24T03:13:54+00:00Z
US. Patent Jul. 25,1989 4,851,544 
0.20 - 
? 48 hr 
I 
I 
I 
I 0° 24 h r  
O0O 12 h r  
/ 9  h r  
E .- r 0.15- 
F 
o,----O / 0 5  h r  
3 h r  
I h r  
0- I I I I I I I 
0 I 2 3 4 5 6 7 
I I 
SIGNAL HEIGHT 
4,851,544 
1 2 
B I S [ 4 - ( 3 , 4 - D I O L ~ ~ ) -  SUMMARY OF THE INVENTION 
PHENYL]METHANE 
ORIGIN OF THE INVENTION 
formance of work under a NASA Grant. In accordance 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
ne present invention relates generally to high 
It is the primary object of the present invention to 
prepare high temperature polymeric materials, espe- 
5 cially linear aromatic polyimides, which maintain their 
The invention described herein was made in the per- 
with 35 USC 202, the grantee elected not to retain title. 
integrity and toughness long exposure times at 
According to the present invention, this object is 
temperatures* 
achieved, and the attending benefits are obtained, by 
10 first providing the bis(exocyc1odiene) bis[4-(3,4-dime- 
thylenepyrrolidy1)phenyll methane (identified as I in 
the general coPolY~~rization equation below), which is 
linear aromatic polyimides by copolymerizing 3,edimethylenepyrrolidine. This bis-(exocyclodiene) 
a bismaleimide with bis[4-(3,4-dimethylenepyrrolidyl)- 15 undergoes Diels-Alder reaction with a bismaleimide 
phenyl] methane. (identified as I1 in the general copolymerization equa- 
2. Description of Related Art tion below), without the evolution of gaseous by- 
A ma,or goal productsm, to form the aromatic polyimide (identified 
perawe polymeric materials. It relates particularly to a novel material formed from the mononler N - ~ h e n ~ l -  
the field of high temperature poly- 
mers has been to prepare aromatic p o l y i ~ d e s  that can as II1 in the generd copolymerization equation below), 
be easily fabricated with the required thermal and phys- 2o to the present invention. 
I 
0 
I1 
45 
50 
BRIEF DESCRIPTION OF THE DRAWING 
For a more complete understanding of the present 
invention, including its primary object and attending 
benefits, reference should be made to the Description of 
the Preferred embodiments, which is set forth below. 
This description should be read together with the ac- 
companying drawing, which is a plot of the relationship 
of viscosity to methylene proton NMR height during 
the copolymerization reaction according to the present 
invention. 
ical properties for aerospace applications. Recent re- 
search has been directed to achieve polyimides that are: 
(a) soluble in a common organic solvent; (b) melt-proc- 
essable; and (c) thermally curable without the evolution 
of volatile by-products. See, for example: Mittal, K. L., 
“Polyimides: Synthesis, Characterization, and Applica- 
tions”, New York: Plenum Press, 1984; Cassidy, P. E., 
“Thermally Stable Polymers: Synthesis and Proper- 
ties”, New York: Marcel Dekker, Inc., 1980; and Her- 
genrother, P. and T. L. St. Clair, “Proceedings of Sec- 
ond International Conference on Polyimides”, in Ellen- 
ville, N.Y., 1985. 
The melt processability of poiyimides can be en- 
hanced by lowering the flow temperature, using syn- 55 
thetic techniques such as the incorporation of aryl-ether 
A recent approach to obtain phenlylated polyimides 
involves the Diels-Alder polymerization of phenylated The synthesis of phenyl methane was carried out by 
biscyclopentadienones with bismaleimides (see Harris, 60 reacting 4,4’-methylenediamine arylenes with 2,3-bis(- 
H., “Polyimides: Synthesis, Characterization and Appli- bromomethyl)-1,3-butadiene. During the reaction, the 
cation”, ed., K. L. Mittal, p. 3., New York: Plenum flask was covered with foil to avoid light catalyzed 
Press, 1984). The problem with this process is that dur- polymerization of the diene group of the starting mate- 
ing the reaction, carbon monoxide is produced subse- rial and product. N2 sweep appeared to help retard the 
quent to the Diels-Alder addition. Furthermore, at tem- 65 oxidation of the product. The product, bis(3,4-dime- 
peratures greater than 300’ C., dehydrogenation, as thylenepyrrolidyl)arylene, is very reactive and readily 
well as other decomposition processes, occurs to yield a undergoes self-Diels-Alder addition. Since these dienes 
polymer with less solubility. have poor solubility in organic solvents and poor stabil- 
DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
methane 
and meta-phenylene linkages in the polymer backbone, synthesis of bis[4-(3,4-dimethy1enePY~olidyl)phenyll 
4,851.54 
3 
ity, attempts to purify these monomers were not suc- 
cessful. 
Self-Diels-Alder reaction of 
bis[4-(3,4-dimethylenepyrrolidyl)phenyl] methane 
Dimerization which can result from a Diels-Alder 
reaction between two exocyclic dienes was observed in 
the case of N-phenyl-3,4-dimethylenepyrrolidine. To 
evaluate the stability of these bisdiene compounds, 
bis[4-(3,4-dimethylenepyrrolidyl)phenyl] methane (5% 
monomer in CDC13) was heated at 50" C. and followed 
by 1H NMR spectroscopy. After heating at 50" C. for 
seven hours, new multiplet signals appeared at 6.2-3 
region with decreasing endo protons of the exocyclic 
diene at 6 5.5 region. It is estimated that the reaction 
ratio by self-Diels-Alder was 20-30% under model 
compound preparation conditions and 2-3% under con- 
ditions of polymerization based on the integration of the 
1H NMR spectra. 
Copolymerization of 
bis[4-(3,4-dmethylenepyrrolidyl)phenyl] methane with 
bis[4-(maleimidyl)phenyl] methane 
A polymer powder was prepared from the prepoly- 
mer solution which contained equimolar amounts of 
bis[4-(3,44imethylenepyrrolidyl)phenyl] methane I and 
bismaleimide I1 in solution. After standing overnight, 
the prepolymer solution became a gel. The polymer gel 
was washed with chloroform and acetone, and then 
dried in vacuo. 
Polymer film 
Polymer films were prepared by casting the prepoly- 
mer solution onto a clean glass surface. The glass plates 
were held at room temperature overnight to allow the 
solvent to evaporate. The films were then heated at 120" 
C. for 12 hours to give transparent flexible polymer 
films. These films were heated another 12 hours at 150" 
C. 
Observations 
It was observed that bis[4-(3,4-dimethylenepyr- 
rolidy1)phenyl'j methane reacts very rapidly with bis- 
maleimide by Diels-Alder addition. However, this reac- 
tion is slower in acidic solvents, such as tri-fluoroacetic 
acid, due to the protonation of the nitrogen in the pyr- 
rolidine ring. The polymerization of bis[4-(3,4-dime- 
thylenepyrrolidyl)phenyl] methane with bismaleimide 
was followed by 1H NMR spectroscopy. At 50' C. in 
trifluoroacetic acid, complete polymerization could be 
The Effect of Mole Ration of Monomer on Film 
Properties 
After determining the monomer concentration of 
bis[4-(3,4-dimethylenepyrrolidyl)phenyl] methane by 
1H NMR spectrum, the bismaleimide comonomer was 
added to the solution to make the prepolymer solution. 
Polymer films were then prepared from this prepolymer 
1o solution. Shown in Table 1 below are the film properties 
which were found to depend on the mole ratio of both 
monomers. The addition of 20-30% less bismaleimide I1 
than bisdiene I made good flexible films. This observa- 
tion might be explained by the fact that the 20-30% of 
15 the bisdiene may be undergoing a self-Diels-Alder pro- 
cess as described earlier. 
TABLE 1 
THE EFFECT OF MOLE RATIO 
OF MONOMERS ON FILM PROPERTIES 20 
Mole Ratio 
(0 (11) Solution Viscosity Film Property 
1.0 1.0 nonviscous brittle 
1.0 0.9 nonviscous brittle 
0.8 viscous - gel flexible 
0.7 viscous - gel flexible 
1.0 0.6 nonviscous brittle 
25 i:: 
Solubility 
The original polymer film was insoluble in organic 
solvents, hot, concentrated sulfuric acid was used as a 
solvent for five different polymer films which had dif- 
ferent curing temperatures after casting. See Table 2 
35 below. The polymer films were treated at temperatures 
above 120" C. were not soluble in hot This 
decreased solubility may be due to a crosslinking reac- 
tion taking place in the polymer film after heating at 
high temperatures and/or oxidation of the pyrrolidine 
TABLE 2 
SOLUBILITY OF POLYMER 
FILM IN CONCENTRATED H2SO4 
30 
4o ring to the aromatic pyrrole. 
Film Solubility 45 Film Curing Temperature (T.) 
25 partially soluble 
50 partially soluble 
120 insoluble 
160 insoluble 
200 insoluble 50 
achieved within 48 hours. The polymerization yield was 
estimated to be 92% based on the integration of the 1H 
NMR spectrum. 
Thermal Analysis 
The thermal stability and decomposition temperature 
The lH NMR peak height decreases for the bisdiene 55 ofthe polymer films were analyzed by thermogravimet- 
i c  analysis (TGA). The measurements were carried out protons md the PolYmer backbone proton area in- creases during the reaction. The new methylene pro- in Nz and in an air atmosphere, respectively. The poly- tons on the central ring due to the Diels-Alder addition mer film was thermally stable with weight is consistent with the decreasing exocyclic diene peak. 
loss at 357" C., and 20% weight loss occurred at 413" C. Consequently, it is considered that the Diels-Alder re- 60 
action is the process in this polymeriza- in nitrogen. The thermal data of the polymer film are 
tion. ne Merent viscosity determined during the poly- tabulated in Table 3 below. on the other hand, TGA 
merization was plotted against the 1~ NMR signal plots ak showed different behavior. There two pla- 
height due to the newly formed methylene protons. teau regions in the TGA curve were o b ~ r v e d -  The 
(See Drawing.) It appears that, after formation of oligo- 65 second rapid weight loss occurred above 400" C. and 
mer dimers and trimers within the first three hours, the was indicative of total decomposition of the polymer 
elongation of the polymer chain takes place as indicated backbone. The first moderate weight loss occurred at a 
by the increasing viscosity with time. much lower temperature (239" C.). 
4,851,544 
5 
The present invention has been described in detail 
with respect to certain preferred embodiments thereof. TABLE 3 
THERMAL PROPERTIES OF POLYMER FILM However, it is understood by those of skill in the art that 
variations in this detail may be made without any depar- BY THERMOGRAVIMETIC ANALYSIS 
5 ture from the spirit and scope of the present invention, 
as defined in the hereto appended claims. Atmosphere 10% Weight Loss 20% Weight Loss 
nitrogen 357 413 What is claimed is: 
air 239 385 1. Bis[4-(3,4-dmethylenepyrrolidyl)phenyl] methane. 
T CC.) T CC.) 
* * * * *  
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
6 
65 


Bis(4-(3,4-dimethylenepyrrolidyl)-phenyl) methane

The primary objective is to prepare high temperature polymeric materials, especially linear aromatic polyimides, which maintain their integrity and toughness during long exposure times at elevated temperatures. The attained benefits are obtained by first providing the bis (exocyclodiene) bis (4-(3,4-dimethylene-pyrrolidyl)-phenyl) methane, which is a novel material formed from the monomer N-phenyl-3,4-dimethylene-pyrrolidine. This compound undergoes Diels-Alder reaction with a bismaleimide, without the evolution of gaseous by-products, to form the aromatic polyimide bis (4-(3,4-dimethylene-pyrrolidyl)-phenyl) methane

United States Patent ti91 
Ottenbrite 
[i i]  Patent Number: 4,895,915 
[45] Date of Patent: Jan. 23, 1990 
[54] BIS[~-(~,~-DIMETH~ENE-PYRROLID~)- 
PHENYL] METHANE 
[75] Inventor: Raphael M. Ottenbrite, Midlothian, 
[73] Assignee: The United States of America as 
Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 311,551 
[22] Filed: Feb. 16, 1989 
Related U.S. Application Data 
[62] 
[51] Int. Cl.4 .............................................. COSG 73/10 
Division of Ser. No. 221,386, Jul. 19, 1988, Pat. No. 
4,851,544. 
[52] U.S. Cl. ..................................... 526/262; 528/322 
[58] Field of Search ......................... 526/262; 528/322 
1561 References Cited 
U.S. PATENT DOCUMENTS 
4,115,359 9/1978 Darms et al. ....................... 526/262 
4,839,440 6/1989 Barthelemy ......................... 528/322 
4,713,422 12/1987 Kaschig et al. ..................... 526/262 
Primary Examiner-Harold D. Anderson 
Assistant Examiner-". Mosley 
Attorney, Agent, or Firm-George F. Helfrich; Charles 
E. B. Glenn; John R. Manning 
, 
[57l ABSTRACT 
A polyimide composition consisting essentially of re- 
curring units having the following structural formula: 
cH2- 
It 
0 
0 
-Q-N=N- 
II 
0 
/x 
is produced by the copolymerization of a bismaleimide 
and bis[4-(3,4-dimethylenepyrrolidyl)phenyl] methane. 
2 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19910005105 2020-03-24T06:57:26+00:00Z
1 
4,895, 
BIS[4-(3,4-DIMETHYLENE-PYRROLIDYL)PHE- 
NYL] METHANE 
ORIGIN OF THE INVENTION 5 
The invention described herein was made in the per- 
formance of work under a NASA Grant. In accordance 
with 35 USC 202, the grantee elected not to retain title. 
This is a division of application Ser. No. 07/221,386, 
filed July 19, 1988. 10 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to high tem- 
perature polymeric materials. It relates particularly to 
linear aromatic polyimides prepared by copolymerizing 
a bismaleimide with bis[4-(3,4-dimethylenepyrrolidyl)- 
phenyllmethane. 
15 
2. Description of Related Art 
A major goal in the field of high temperature poly- 2o 
mers has been to prepare aromatic polyimides that can 
be easily fabricated with the required thermal and phys- 
915 
2 
well as other decomposition processes, occurs to yield a 
polymer with less solubility. 
SUMMARY OF THE INVENTION 
It is the primary object of the present invention to 
prepare high temperature polymeric materials, espe- 
cially linear aromatic polyimides, which maintain their 
integrity and toughness during long exposure times at 
elevated temperatures. 
According to the present invention, this object is 
achieved, and the attending benefits are obtained, by 
first providing the bis(exocyc1odiene) bis[4-(3,4-dime- 
thylenepyrrolidyl)phenyl]methane (identified as I in the 
general copolymerization equation below), which is a 
novel material formed from the monomer N-phenyl- 
3,4-dimethylenepyrrolidme. This bis-(exocyclodiene) 
undergoes Diels-Alder reaction with a bismaleimide 
(identified as I1 ixi the general copolymerization equa- 
tion below), without the evolution of gaseous by-pro- 
ducts, to form the aromatic polyimide (identified as I11 
in the general copolymerization equation below), ac- 
cording to the present invention. 
, 
0 0 
~ 
‘N*QcH2 0 0 II 0 
0 
I11 
ical properties for aerospace applications. Recent re- For a more complete understanding of the present 
search has been directed to achieve polyimides that are: 45 invention, including its p-rimary object and attending 
(a) soluble in a common organic solvent; (b) melt-proc- benefits, reference should be made to the Description of 
essable; and (c) thermally curable without the evolution the Preferred embodiments, which is set forth below. 
DESCRIPTION OF THE PREFERRED of volatile by-products. See, for example: Mittal, K. L., 
EMBODIMENTS “Polyimides: Synthesis, Characterization, and Applica- tions”, New York Plenum Press, 1984; Cassidy, P. E., 50 
“Thermally Stable Polymers: Synthesis and Proper- Synthesis of bis[4-(3,4-dimethylenepyrrolidyl)- 
ties”, New York Marcel Dekker, Inc., 1980; and Her- phenyllmethane. The synthesis of phenyl methane was 
genrother, P. and T. L. St. Clair, “Proceedings of Sec- carried out by reacting 4,4‘-methylenediamine arylenes 
ond International Conference on Polyimides”, in Ellen- with 2,3-bis(bromomethyl)-1,3-butadiene. During the 
ville, New York, 1985. 55 reaction, the flask was covered with foil to avoid light 
The melt processability of polyimides can be en- catalyzed polymerization of the diene group of the 
hanced by lowering the flow temperature, using syn- starting material and product. N2 sweep appeared to 
thetic techniques such as the incorporation of aryl-ether help retard the oxidation of the product. The product, 
and meta-phenylene linkages in the polymer backbone. bis(3,4-dimethylenepyrrolidyl)arylene, is very reactive 
A recent approach to obtain phenlylated polyimides 60 and readily undergoes self-Diels-Alder addition. Since 
involves the Diels-Alder polymerization of phenylated these dienes have poor solubility in organic solvents and 
biscyclopentadienones with bismaleimides (see Harris, poor stability, attempts to purify these monomers were 
H., “Polyimides: Synthesis, Characterization and Appli- not successful. 
cation”, ed., K. L. Mittal, p. 3., New York Plenum Self-Diels-Alder reaction of bis[4-(3,4-dime- 
Press, 1984). The problem with this process is that dur- 65 thylenepyrrolidyl)phenyl]methane. Dimerization 
ing the reaction, carbon monoxide is produced subse- which can result from a Diels-Alder reaction between 
quent to the Diels-Alder addition. Furthermore, at tem- two exocyclic dienes was observed in the case of N- 
peratures greater than 300” C., dehydrogenation, as phenyl-3,4-dmethylenepyrrolidine. To evaluate the 
3 
4,895.915 
stability of these bisdiene compounds, bis[4-(3,4-dime- 
thylenepyrrolidyl)phenyl]methane (5% monomer in 
CDCl3) was heated at 50" C. and followed by lH NMR 
spectroscopy. After heating at 50" C. for seven hours, 
new multiplet signals appeared at 62-3 region with 
decreasing endo protons of the exocyclic diene at 65.5 
region. It is estimated that the reaction ratio by self- 
Diels-Alder was 2@30% under model compound prep- 
aration conditions and 2-3% under conditions of poly- 
merization based on the integration of the 1H NMR 
spectra. 
Copolymerization of bis[4-(3&dimethylenepyr- 
rolidy1)phenyllmethane with bis[4-(maleimidyl)- 
phenyllmethane. A polymer powder was prepared from 
the prepolymer solution which contained equimolar 
amounts of bis[4-(3,4dimethylenepyrrolidyl)- 
phenyllmethane I and bismaleimide I1 in solution. After 
standing overnight, the prepolymer solution became a 
gel. The polymer gel was washed with chloroform and 
acetone, and then dried in vacuo. 
Polymer film. Polymer films were prepared by cast- 
ing the prepolymer solution onto a clean glass surface. 
The glass plates were held at room temperature over- 
night to allow the solvent to evaporate. The films were 
then heated at 120' C. for 12 hours to give transparent 
flexible polymer films. These films were heated another 
12 hours at 150" C. 
Observations. It was observed that bis[4-(3,4dirne- 
thylenepyrrolidyl)phenyl]methane reacts very rapidly 
with bismaleimide by Diels-Alder addition. However, 
this reaction is slower in acidic solvents, such as trifluo- 
roacetic acid, due to the protonation of the nitrogen in 
the pyrrolidine ring. The polymerization of bis[4-(3,4- 
dimethylenepyrrolidyl)phenyl]methane with bismalei- 
mide was followed by 1H NMR spectroscopy. At 50" C. 
in trifluoroacetic acid, complete polymerization could 
be achieved within 48 hours. The polymerization yield 
was estimated to be 92% based on the integration of the 
1H NMR spectrum. 
The 1H NMR peak height decreases from the bisdi- 
ene protons and the polymer backbone proton area 
increases during the reaction. The new methylene pro- 
tons on the central ring due to the Diels-Alder addition 
is consistent with the decreasing exocyclic diene peak. 
Consequently, it is considered that the Diels-Alder re- 
action is the predominant process in this polymeriza- 
tion. The inherent viscosity determined during the poly- 
merization was plotted against the 1H NMR signal 
height due to the newly formed methylene protons. 
(See Drawing.) It appears that, after formation of oligo- 
mer dimers and trimers within the first three hours, the 
elongation of the polymer chain takes place as indicated 
by the increasing viscosity with time. 
The Effect of Mole Ratio of Monomer on Film Prop- 
erties. After determining the monomer concentration of 
bis[4(3,4-dimethylenepyrrolidyl)phenyl]methane by 
'H NMR spectrum, the bismaleimide comonomer was 
TABLE 1 
T H F  EFFECT O F  MOLE RATIO OF MONOMERS ON 
FILM PROPERTIES 
Mole Ratio 
(I) (II) Solution Viscosity Film Property 
1.0 1.0 nonviscous brittle 
1.0 0.9 nonviscous brittle 
1.0 0.8 viscous - gel flex i b I e 
1.0 0.7 viscous - gel flexible 
1.0 0.6 nonviscous brittle 
5 
added to the solution to make the preopolymer solution. 60 
Polymer films were then prepared from this prepolymer 
solution. Shown in Table 1 below are the film properties 
which were found to depend on the mole ratio of both 
monomers. The addition of 20-30% less bismaleimide I1 
then bisdiene I made good flexible films. This observa- 65 
tion might be explained by the fact that the 20-30% of 
the bisdiene may be undergoing a self-Diels-Alder pro- 
cess as described earlier. 
Solubility. The original polymer film was insoluble in 
organic solvents, hot, concentrated sulfuric acid was 
15 used as a solvent for five different polymer films which 
had different curing temperatures after casting. See 
Table 2 below. The polymer films were treated at tem- 
peratures above 120" C. were not soluble in hot H2S04. 
This decreased solubility may be due to a crosslinking 
2o reaction taking place in the polymer film after heating at 
high temperatures and/or oxidation of the pyrrolidine 
ring to the aromatic pyrrole. 
TABLE 2 
SOLUBILITY OF POLYMER FILM IN CONCEN- 
TRATED H2SO4 
Film Solubility 
25 partially soluble 
50 partially soluble 
25 
Film Curing Temperature ("C.) 
120 insoluble 
160 insoluble 
200 insoluble 
30 
Thermal Analysis. The thermal stability and decom- 
position temperature of the polymer films were ana- 
lyzed by thermogravimetric analysis (TGA). The mea- 
surements were carried out in N2 and in an air atmo- 
sphere, respectively. The polymer film was thermally 
40 stable with only 10% weight loss at 357" C., and 20% 
weight loss occurred at 413" C. in nitrogen. The thermal 
data of the polymer film are tabulated in Table 3 below. 
On the other hand, TGA plots in air showed different 
behavior. These two plateau regions in the TGA curve 
45 were observed. The second rapid weight loss occurred 
above 400" C. and was indicative of total decomposition 
of the polymer backbone. The first moderate weight 
loss occurred at a much lower temperature (239" C.). 
35 
, 
50 TABLE 3 
THERMAL PROPERTIES O F  POLYMER FILM 
BY THERMOGRAVIMETIC ANALYSIS 
Atmosphere 10% Weight Loss 20% Weight Loss 
55 nitrogen 357 413 
air 239 385 
T ("C.) T ("C.) 
The present invention has been described in detail 
with respect to certain preferred embodiments thereof. 
However, it is understood by those of skill in the art that 
variations in this detail may be made without any depar- 
ture from the spirit and scope of the present invention, 
as defined in the hereto appended claims. 
What is claimed is: 
1. A polyimide composition consisting essentially of 
recurring units having the following structural formula: 
5 
4,895,9 15 
6 
-continued 
0 
2. The polyimide of claim 2, which is prepared by the 
copolymerization of bis[4-(3,4-dmethylenepyrrolidyl)- 
20 phenyllmethane and bis[4-(maleimidyl)phenyl]methane. * * * * *  
25 
30 
35 
40 
45 
50 
55 
60 
65 


Bis(4-(3,4-dimethylenepyrrolidyl)-phenyl) methane

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