High performance, thermooxidatively stable polyimides are prepared by reacting aromatic diamines with pendant trifluoromethyl groups and dianhydrides in an amide solvent to form a poly(amic acid), followed by cyclizing the poly(amic acid) to form the corresponding polyimide

Gerber, Margaret K.

Pratt, J. Richard

St.clair, Anne K.

St.clair, Terry L.

English

NASA Technical Reports Server

111111 llllllll 111111111 Il11 11111 11111 11111 lll 11111ll Il 11111 Il1 
United States Patent 
USOO52 18083A 
[ i i ]  Patent Number: 5,218,083 
Gerber et al. [45] Date of Patent: Jun. 8, 1993 
[54] POLYIMIDES PREPARED FROM 
1751 Inventors: Margaret K. Gerber, Newport News; 
Terry L. St. Clair, Poquoson; J. 
Richard Pratt, Poquoson; Anne K. St. 
Clair, Poquoson, all of Va. 
[73] Assignee: The United States of America as 
represented by the United States 
National Aeronautics and Space 
Administration, Washington, D.C. 
3,5-DIAhfINOBENZOTRIFLUORIDE ’ 
[21] Appl. No.: 429,574 
[22] Filed: Oct. 31, 1989 
[51] Int. C l . 5  ...................... C08G 69/26; C08G 73/10; 
C08G 77/04 
[52] U.S. Cl. ...................................... 528/353; 528/26; 
528/28; 528/125; 528/128; 528/170; 528/172; 
528/173; 528/179; 528/183; 528/188; 528/220; 
528/229; 528/350; 528/351 
[58] Field of Search ................... 528/353, 26, 28, 229, 
528/170, 172, 125, 173, 128, 179, 183,220,351, 
350, 188, 351 
~561 References Cited 
U.S. PATENT DOCUMENTS 
4,588,804 5/1986 Fryd .................................... 528/125 
4,876,329 10/1989 Chiang et al. ....................... 528/353 
4,876,330 10/1989 Higashi et al. ...................... 528/353 
4,996,278 2/1991 Lee ........................................ 528/26 
4,997,908 3/1991 Lee ........................................ 528/26 
5,021,540 6/1991 Leone-Bay et al. ................ 528/183 
5,061,781 10/1991 Leone-Bay et al. ................ 528/351 
5,093,453 3/1992 St. Clair .............................. 528/188 
OTHER PUBLICATIONS 
Synthesis and Characterization of Essentially Colorless 
Polyimide Films, Ann K. St. Clair, Terry L. St. Clair 
and Keziban R. Shevet. 
“Approaches to Organic Dielectrics with Reduced 
Moisture Absorption & Improved Electrical Proper- 
ties”, David L. Goff et al., E. I. Du Pont De Nemours 
& Co., Electrical Dept. pp. 186-189. 
CA 101 : 152884h “Regular Aromatic Fluorine Contain- 
ing Polyamides for Heat Resistant Films”, B. F. Mali- 
chenko, et al. 
“Synthesis of Characterization of a Series of Polyimides 
Derived from 4,4‘[2,2,2-Trifluoro-l-(trifluoromethyl- 
)ethylidenel-bis [ 1,3,-isobenzofurandione”], G. R. 
Husk et al., Macromolecules, 1988 vol. 21, 1234-1238. 
“5-Trifluoromethyl-1,7-phenanthroline”, J. Heterocy- 
clic Chem., 13, 375 (1976), pp. 375-376. 
PTimaTy Exuminer-John Kight, 111 
Assisrunr Examiner-P. Hampton-Hightower 
Attorney, Agent, or Firm-George F. Helfrich 
P I  ABSTRACT 
High performance, thermooxidativel y stable pol yimides 
are prepared by reacting aromatic diamines with pen- 
dant trifluoromethyl groups and dianhydrides in an 
amide solvent to form a poly(amic acid), followed by 
cyclizing the poly(amic acid) to form the corresponding 
polyimide, which has the following general structure: 
r o  0 1 
Where R is any aromatic or substituted aromatic group, 
Ar is any aromatic or substituted aromatic group and 
n 10-100. 
4 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19930019894 2020-03-24T07:31:39+00:00Z
1 
5,2 18,083 
2 
POLYIMIDES PREPARED FROM 
3,5-DIAMINOBENZOTRI~UORIDE 
NH2 
ORIGIN O F  THE INVENTION 5 
The invention described herein was made in the per- H2N NH2 H2N 
formance of work under a NASA contract and is sub- 
Aeronautics and Space Act of 1958, as amended, Public 
Law 85-568 (72 Stat. 435; 42 USC 2457). 
BACKGROUND OF THE INVENTION 
ject to the provisions of Section 305 of the National m-PDA DABTF 
10 An object of the present invention is to provide a 
polyimide based on DABTF that provides high molec- 
ular weight poly(amic acid) solutions that yield creasa- 
1. Field of the Invention ble free-standing films and coatings in the fully cured 
The present invention relates generally to polymeric form. 
materials which are suitable for high temperature appli- 15 Another object of the present invention is to provide 
cations as a result of this high themooxidative stability. based On DABTF with 
It relates particularly to a series of polyimides based on enhanced solubility in common organic solvents such as 
aromatic diamines with a. pendant trifluoromethyl methylene chloride, N,N-dimethylacetamide @MAC) 
grouping. and m-cresol. 
2. Description of Related Art Another object is to provide a polyimide composition 
Polyimides are an important class of polymers for based on DABTF which exhibits a lowered dielectric 
high temperature applications due to their high therm consant, compared to state-of-the-art polyimides, in the 
mooxidative stability. One monomer of major impor- range Of 2.5 to 3*0 at lo GHz. 
tance in preparing these high temperature polyimides is Another object is to provide a high temperature are- 
1J-phenyIenediamine (m-PDA), 3 , 5 - ~ i ~ ~ i ~ ~ b ~ ~ ~ ~ t ~ i -  25 matic polyimide prepared from DABTF which exhibits 
fluoride (DABTF), a reported diamine (R. A. Henry, improved optica1 transparency, compared to s@te-of- 
D. W. Moore and R. L. Atkins, J.  Heterocyclic Chem., the-art polyimides* 
13, 375 (1976).), is an analog ofm-PDA and contains a A further object is to provide pob'imides based on 
symmetrically, substituted polar CF3 group. Diamines DABTF that form well-consolidated 
and dianhydrides containing two or more ofthese triflu- 3O Another object is to provide a polyimide based on 
oride groups such as 2,2-bis(3,4-dicarboxypheny])hexa- 4-trifluoromethyl-2,6-diarninopyridine and 6FDA that 
fluoropropane dianhydride (6FDA), 2,2-bis(3-amino- 
phenyl)hexa-fluoropropane, (6F) 2,2-bis[4-(4-amino- Another object is to provide a polyimide with pen- 
phenoxy)phenyl]hexafluoropropane (4-BDAF), and dant trifluoromethyl groups that contains a n o n & ~  
2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropro- 35 zenoid aromatic moiety. 
pane dianhydride (BFDA) are known in the polyimide 
literature. (D. L. Goff and E. L. Yuan, Polymeric Mate- 
rials Science and Eng., Preprints 59, 186 (1988). G. R. BY the Present invention, a series of thermooxida- 
Husk, P. E. Cassidy and K. L. Gebert, Macromolecules 
21, 1234-1238 (1988). T. L. St. Clair, A. K. St. clair and 40 greater solubility in polar solvents, less color and lower 
E. N. Smith, Structure-Solubility Relationships in poly- dielectric constants than state-of-the-art polyimides. 
mers, Academic Press, Inc. New York, N.Y. 199-214 These polyimides form free-standing films, coatings and 
(1977).) moldings. It is anticipated that these polyimides will 
provide useful materials for aerospace and electronic 
The polyimides of the present invention are advanta- 
geously prepared by reacting 3,5-diaminobenzotrifluo- 
ride (DABTF) with one or more of the following dian- 
hydrides: 
cured polyimide 
20 
has a high level of fluorine atoms per repeat unit. 
SUMMARY O F  THE INVENTION 
tively polyimides are produced which have 
45 applications. 
3 
0 
5,2 18,083 
-continued 
BPDA 0 ob!aze 0 0 0 0 
0 
II IDPA 11 
0 0 
0 0 CH3 0 
0 
11 
0 SIDA 0 SOzDPA 0 0 
0 0 
II BDSDA II 
0 0 
4 
-continued 
Poly(amic acid) 40 
in N,N-dimethylacetamide (DMAc) and then thermally 45 
0 0  
cyclizing the resulting poly(amic acid) to the corre- 
sponding polyimide. 
DESCRIPTION O F  THE PREFERRED 
EMBODIMENTS 50 
Polyimide film 
According to the present invention, polymerizations 
were conducted at room temperature in amide solvents 
such as DMAc at 20 percent solids using purified mono- 
55 
mers consistent with-the following react'on scheme: 
0 0  
II 11 
/c\R/c\o 
\/ \/ 
II II H2N NH2 
0 0  
Room temperature in 
amide solvent, 20% 
w/w solids 
35 
Where n = 10-100 
Where R is: 
60 
5,218,083 
C 
J 
-continued 
CF3 0 
0 0 
II II 
10 
15 
Or 
25 
6 
ric analysis (TGA) indicated a five percent weight loss 
at 520" C. and ten percent weight loss at 551" C. The 
film had a Tg of 294" C. by differential scanning calo- 
rimetry (DSC). The dielectric constant of this poly- 
imide film was 2.90 at 10 GHz. 
Example I1 
A solution of DMAc (2.8 176 g) and DABTF (0.2000 
g, 0.001 135 mol) was prepared. 2,2-Bis(3,4-dicarboxy- 
pheny1)hexafluoropropane dianhydride (6FDA) 
(0.5044 g, 0.001 135 mol) was added as a solid in a single 
portion and the solution was stirred at room tempera- 
ture overnight. The inherent viscosity of the resulting 
poly(amic acid) solution was 0.70 dl/g at 35" C. in 
DMAc. A film of 20 mil nominal wet thickness was cast 
on a soda lime glass plate and allowed to dry 24 hours 
in a low humidity chamber purged with dry air. The 
film was cured in a flowing air oven for one hour each 
at loo", 200' and 350" C. The resulting thermally imi- 
dized, pale gold colored film was creasable and insolu- 
ble in one percent refluxing methylene chloride. How- 
ever, the film was soluble in refluxing DMAc and m- 
cresol. Dynamic TGA indicated a five percent weight 
loss at 492" C. and ten percent weight loss at 511" C. 
The film had a Tg of 297" C. by DSC. The dielectric 
constant of this polyimide film was 2.58 at 10 GHz. 
Example I11 
Example I11 A solution of DMAc (4.4178 g) and 
A diamine solution was prepared in an amide solvent 30 DABTF (0.4oOo g, 0.002271 mol) was prepared. 44'- 
such as DMAc. The dianhydride was then added as a Oxydiphthalic anhydride (ODPA) (0.7044 g, 0.002271 
solid in one single portion at room temperature to form mol) was added as a solid in a single portion, and the 
a poly(amic acid). This solution was then poured onto a solution was stirred at room temperature overnight. 
glass plate and spread with a doctor blade set at a speci- 35 The inherent viscosity of the resulting poly(amic acid) 
fied blade gap to form a film or coating. The poly(amic solution was 0.34 dl/g at 35' C. in DMAc. A film of 20 
acid) film was then thermally converted to the poly- mil nominal wet thickness was cast on a soda lime glass 
imide by heating to 300" C. plate and allowed to dry in air overnight in a low hu- 
Although the dianhydrides shown above were used midity chamber purged with dry air. The film was 
in the examples set forth below, other dianhydrides cured in a flowing air Oven for one hour each at loo", 
could be used to prepare thermooxidatively stable poly- 200" and 300" c. The resulting thermally imidized ye]- 
mers with the DABTF diamine. low colored film was creasable and insoluble in 1 per- 
Although DMAc was used as the solvent n-~edium to cent refluxing methylene chloride. The film was soluble 
prepare the pOly(amiC acids) in the examples set forth in refluxing DMAc and m-cresol. Dynamic TGA indi- 
below, other solvents could be used such as N,N-dime- 45 cated a five percent weight loss at 524" C. and a ten 
thylforrnamide (DMF), tetrahydrofuran (THF) and percent weight loss at 558" C. The film had a Tg of 274' 
l-methYl-2-PYrrolidinone WMP). These would also C. The dielectric constant of this polyimide film was 
produce high quality polyimides. 2.91 at 10 GHz. 
SPECIFIC EXAMPLES Example IV 
50 
Example I Example IV A solution of DMAc (4.2725 g) and 
A solution of N,N-dimethylacetamide (DMAc) DABTF (0.4oOo g, 0.002271 mol) and 3,3',4,4- 
(10.96 g) and 3,5-diaminobenzotrifluoride (DABTF) biphenyltetracarboxylic dianhydride (BPDA) (0.668 1 
(0.9688 g, 0.0055 mol) was prepared. 3,3',4,4'-Benzo- g, 0.002271 mol) was prepared, and a film cast and 
phenonetetracarboxylic dianhydride (BTDA) (1.7723 55 cured as .in Example 111 The inherent viscosity of the 
g, 0.0055 mol) was added as a solid in a single portion, resulting p o l y ( d c  acid) solution was 0.89 dl/g at 35' 
and the solution was stirred at room temperature over- C. in DMAc. The resulting thermally imidized very 
night. The inherent viscosity of the resulting poly(amic pale-gold colored frlm was creasable and insoluble in 
acid) solution was 0.53 dl/g at 35' C. in DMAc. A film refluxing methylene chloride, DMAc and m-cresol. 
of 15 mil nominal wet thickness was cast on a soda lime 60 Dynamic TGA indicated a five percent weight loss at 
glass plate and allowed to dry for 24 hour in a low 550" C. and a ten percent weight loss at 572' C. The Tg 
humidity chamber purged with dry air. The film was of the polymer film was 329' C. 
cured for one hour each at loo", 200" , and 300" C. in a Example V flowing air oven. The resulting imidized pale yellow 
colored film was creasable and insoluble in approxi- 65 A solution of DMAc (4.1045 g) and DABTF (0.3000 
mately one percent refluxing methylene chloride. How- g, 0.001703 mol) and isophthaloyldiphthalic anhydride 
ever, the film was soluble in refluxing DMAc and m- (IDPA) (0.7261 g, 0.001703 mol) was prepared, and a 
cresol at this concentration. Dynamic therrnogravimet- film cast and cured as in Example 111. The inherent 
5,218,083 
7 8 
viscosity of the resulting poiy(amic acid) solution was hours at room temperature before phthalic anhydride 
0.53 dl/g at 35" C. in DMAc. The resulting thermally (0.0420 g, 0.0002838 mol) was added in one solid por- 
imidized gold colored film was creasable and insoluble tion ta end cap the polymer. This was stirred at room 
in refluxing methylene chloride, DMAc and m-cresol. temperature overnight. The inherent viscosity of the 
Dynamic TGA indicated a five percent weight loss at 5 resulting poly(amic acid) solution was 0.23 dl/g at 35' 
510" c. and a ten percent weight loss at 540" C. The Tg c. in DMAC. The solid was precipitated in toluene, 
of the polymer film was 253" C. filtered, dried and cured one hour at 100', 200" and 300' 
Example VI C. in flowing air. The imidized material was placed in a 
mold under lo00 psi pressure at 300" C. for one-half 
g, 0.002271 mol) and pyromellitic dianhydride (PMDA) o.087 inches in thickness. (0.4953 g, 0.002271 mol) was prepared, and a fim cast 
and cured as in Example 111. The inherent viscosity of 
the resulting poly(amic acid) solution was 0.93 dl/g at 
was brittle, gold colored and insoluble in refluxing 
A Of DMAc (3*5812 g) and DABTF (o.4000 lo hour to produce a one-inch in diameter disc molding, 
Example XI 
2,6-diaminopyridine (0.1500 g, 0.0008468 mol) was pre- 350 c. in D M A ~ .  ne resulting thermally imidized film 
methylene chloride and m-cresol. The film was soluble 
in refluxing DMAc. Dynamic TGA indicated a five 
A SOh.ltiOn Of DMAc (2.9818 g) and CtrifluoromethYl 
pared. 2,2-Bis(3,4-dicarboxypheny1)hexafluoropropane 
dianhydride ( 6 m A )  (0.3762 g, 0*0008468 
percent weight loss at 548' c. and ten percent weight added in a single solid portion, and the solution was 
loss at 570" C. A Tg for this polymer was not observed 20 stirred at room temperature overnight. The inherent 
by DSC or torsional braid analysis (TBA) up to 400" C. viscosity Of the reSUlthg poly(aRlk acid) Solution was 
0.14 dl/g at 35' C. in DMAc. The polyimide had the 
Example VI1 following specific structure: 
A solution of DMAc (3.6006) and DABTF (0.3000 g, 
0.001703 mol) and bis(3,4-dicarboxyphenyl)dimethylsi- 25 
lane dianhydride (SiDA) (0.6001 g, 0.001703 mol) was 
prepared, and a film cast and cured as in Example 111. 
The inherent viscosity of the resulting poiy(amic acid) 
solution was 0.64 dl/g at 35" C. in DMAc. The resulting 
thermally imidized film was pale gold colored and 30 
snapped on creasing. The film was soluble in room 
temperature methylene chloride and refluxing DMAc 
weight loss at 440' C. and ten percent weight loss at 
II and m-cresol. Dynamic TGA indicated five percent 0 
Example VI11 
A solution of DMAc (2.9833 g) and DABTF (0.2458 
g, 0.001395 mol) and sulfonyldiphthalic anhydride 40 
(S02DPA) (0.5000 g, 0.001395 mol) was prepared, and 
a film cast as in Example 111. The inherent viscosity of 
the resulting poly(amic acid) solution was 0.51 dl/g 35" 
ored film snapped on creasing. The film was soluble in 45 
room temperature DMAc and refluxing m-cresol. Dy- 
namic TGA indicated five percent weight loss at 492" 
polymer was 310" C. by DSC. 
C. in DMAc. The thermally imidized pale yellow col- N 
0 0  
c. and ten percent weight loss at 525" c. The Tg Of the ne present invention has h e n  described in detail 
with respect to certain preferred embodiments thereof. 
As is understood by those of skill in the art, variations 
and modifications in this detail may be effected without 
Example IX 
A of DMAc (4.6776 g) and DABTF (0.3000, 
and 4,4'-bis(3,edicarboxyphenoxy)- 
any departure from the spirit and scope of the present 
invention, as defined in the hereto-appended O*Ool 703 diphenylsulfide dianhydride (BDSDA) (0.8694 g, 
0.001703 mol) was prepared, and a film cast as in Exam- 55 
ple 111. The inherent viscosity of the poly(amic acid) 
mally imidized film was pale gold colored, creasable, 
and soluble in room temperature methylene chloride 
and refluxing DMAc and m-cresol. Dynamic TGA 60 
indicated five percent weight loss at 498' C. and ten 
percent weight loss at 528' C. The Tg of the polymer 
was 218" C. by DSC. 
Example X 
A solution of DMAc (13.7976 g) and DABTF (1.2500 
g, 0.007069 mol) was prepared, and ODPA (2.1574 g, 
What is claimed is: 
A high thermooxidately stable poly- 
was 0.37 dl/g at 35' C. in DMAc. The resulting ther- imide having the general structure: 
65 
0.006954 mol) added. The solution was stirred for 0.5 Where R is any aromatic or substituted aromatic group 
5,218,083 
9 
-continued 
and n 10-100. 
0 
2. A high performance, thermooxidately stable poly- 
imide prepared by reacting 4-trifluoromethyl-2,6- 5 
diaminopyridine and a dianhydride in an amide solvent 
to form a poly(amic acid), followed by cyclizing the 
poly(amic acid) to the corresponding pol yimide. 
3. A polyimide according to claim 1, having the fol- 
II 
C 
0 0 
It II  lowing specific structure: 10 
10 
4. A high performance, thermooxidatively stable 
polyimide having the following general structure: 
15 
20 
0 0  
25 where R is any aromatic or substituted aromatic group 
and n= 10-100, and having a specific structure selected 
from the group consisting of 
r 1 
L Jn 
* * * * *  
65 


Polyimides prepared from 3,5-diamino benzo trifluoride

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