Polyimides with enhanced electrical conductivity are produced by adding a silver ion-containing additive to the polyamic acid resin formed by the condensation of an aromatic dianhydride with an aromatic diamine. After thermal treatment the resulting polyimides had surface conductivities in the range of 1.7.times.10.sup.-3 4.5 .OMEGA..sup.-1 making them useful in low the electronics industry as flexible, electrically conductive polymeric films and coatings

Caplan, Maggie L.

Rancourt, James D.

St. Clair, Anne K.

Stoakley, Diane M.

Taylor, Larry T.

NASA Technical Reports Server

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US005520960A 
5,520,960 United States Patent 1191 [ i l l  Patent Number: 
Rancourt et al. 1451 Date of Patent: May 28, 1996 
ELECTRICALLY CONDUCTIVE 
POLYIMIDES CONTAINING SILVER 
TRIFLUOROACETYLACETONATE 
Inventors: James D. Rancourt, Blacksburg; Diane 
M. Stoakley, Poquoson, both of Va.; 
Maggie L. Caplan, Sun City West, 
Ariz.; Anne K. St. Clair, Poquoson; 
Larry T. Taylor, Blacksburg, both of 
Va. 
Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Appl. No.: 286,032 
Filed: Aug. 3, 1994 
Int. C1.6 ................................. B05D 3/02; B05D 5/12 
U.S. C1. ....................... 4271385.5; 427/58; 427/126.1 
Field of Search .............................. 427/385.5, 419.8, 
4271.58, 126.1 
~561 References Cited 
U.S. PATENT DOCUMENTS 
3,356,527 12/1967 Moshier et al. . 
3,474,464 10/1969 Matthews et al. ...................... 4271253 
4,387,115 6/1983 Kitamura et al. ......................... 427/96 
4,543,295 9/1985 St. Clair et al. ..................... 427/385.5 
5,230,965 7/1993 Cole, Jr. et al. ........................ 428/610 
5,395,642 3/1995 Hamerich et al. .......................... 42718 
3,966,595 6/1976 Gosser ................................ 260/429 R 
Primary Examiner-Diana Dudash 
Attorney, Agent, o r  F i r n 4 e o r g e  E Helfrich 
ABSTRACT 
Polyimides with enhanced electrical conductivity are pro- 
duced by adding a silver ion-containing additive to the 
polyarnic acid resin formed by the condensation of an 
aromatic dianhydride with an aromatic diamine. After ther- 
mal treatment the resulting polyimides had surface conduc- 
tivities in the range of 1 . 7 ~ 1 0 - ~  4.5 Q-' making them useful 
in low the electronics industry as flexible, electrically con- 
ductive polymeric films and coatings. 
14 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=20080005965 2019-08-30T03:02:32+00:00Z
5,520,960 
1 2 
ELECTRICALLY CONDUCTIVE 
TRIFLUOROACETYLACETONATE 
ORIGIN OF THE INVENTION 
a polyamic acid resin containing silver trifluoroacetylaceto- 
By the present invention, aromatic condensation polyim- 
ide films and coatings are produced which have surface 
5 conductivities that have been increased by the incorporation 
of silver trifluoroacetylacetonate. Provided are materials that 
are electrically conducting in the range that is useful for 
films and coatings for the electronics industry, where the 
combination of conductivity, mechanical strength and ther- 
mal stability are required. 
The novel conducting polyimide compositions of the 
present invention are a significant Improvement over the 
prior art. Conducting films according to the present inven- 
tion are achieved by using a lower cure temperature. In 
l5 addition, the method of the present invention eliminates 
altogether the need for a cumbersome blanket of carbon 
powder used in prior art methods to effect conductivity. The 
1. Field of the Invention method of the present invention is also superior to the prior 
This invention relates generally to conductive polymers. art method of counter-current diffusion, because of the 
It relates particularly to aromatic condensation polyimide 2o handicaps of the latter process which Include (1) a lack of 
films and coatings which have surface conductivities in the reproducibility in conductivity, (2) high cost, and (3) inabil- 
range of 1.7~10" to 4.5 !Z1, and to the process for their ity to produce large-scale quantities of material. 
preparation. 
POLYIMIDES CONTANING SILVER nate. 
The invention described herein was jointly made by an 
employee of the United States Government and contract 
employees during the performance of work under NASA 
Contract NAS1-19000 and is subject to the provisions of 
Section 305 of the National Aeronautics and Space Act of 
1958, as amended Public Law 85-568 (72 Stat. 435; 42 USC 
24571, during the performance of work under NASA 
Grant NAG-1-343, In accordance with 35 USC 202, the 
grantee elected not to retain title. 
BACKGROUND OF THE INVENTION 
2. Description of the Related Art 
The incorporation of metal salts and complexes has been 
used as a means of providing polyimides with increased bulk 
ties. Additives of metals including 
palladium, copper, cobalt, gold and silver have been inves- 3~ in a 
and L. T. Taylor, V. C. Carver, T. A. Furtsch, "Incorporation then as a and themally preferably at 
oFMetal Ions into Polyimides,~3 ACS Symposium Sen'es. No, 250"-300" c. to give a polyimide film. Examples of suitable 
121 ModiJicarion Polymers, C, E, carraher, Jr., and M, solvents are NN-dimethylacetamide, N-N-dimethylforma- 
Tsuda, Eds., pp 71-82, 1980.) mide, N-methyl-2-pyrrolidone, dimethylsulfoxide, and 
Polyimides with metallized silver surfaces have been 
with the addition of silver acetate and silver nitrate The polyamic acids of this invention involve the addition 
25 DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
conductivities and/or greatly enhanced surface conductivi- Preparation Of polyimide and according to 
the present invention involves the room temperature reaction 
Of an diamine with an 
Ligated. (L. T. Taylor, et al, U.S. Pat. No, 4,311,615(1982) dianhydride to yield a polyamic acid. This polymer resin is 
35 bis(2-methoxyethy1)ether. 
to the polyamic acid resin (A. L. Endrey and E. 1. DuPont De 
Nemours and Co,, U.S. Pat. No. 3,073,784 (1963) and A. 
Auerbach, J ,  Electrochem. So,-, p, 937, April 1984.). Con- 40 Or pyromellitic dianhydride (PMDA) to a 
Of an dianhydride such as 
3,3'94,4'-benzophenone tetracarboxylic dianhydride ( B m A )  
solution of 
quantity Of an 
ductive surfaces were achieved after extended cure times or an aromatic diamine such as 4,4'-oxydianiline (4,4'-ODA) or 
a high temperature (360" C.-370" C.) bake under a blanket 
of carbon powder. In addition to the incorporation of silver 
2,2[4-(4-aminophenoxy)pheny11 hexafluoropropane 
(CBDAF) in an amide-type solvent. Although BTDA and 
acetate or nitrate into p0ly-c acid resins as an approach to 
achieving conductive polyimides, counter-current diffusion 45 drides can be 
has also been successfully used to provide polyimide films 
PMDA were used for the 'pecific Other dianhy- 
such as 414'oxydiphthalic anhy- 
dride 4,4'-bis(3,4dicarboxyphenoxy) 
with conductive and reflective metallic interlayers (L. E. fide dia*ydride (BDSDA), 2,2'-bis(3,4- 
sion deposition of silver and compounds into films of 5o 3,4,3',4'-biphenyl tetracarboxylic dianhydride. The diamines 
polyphenylquinoxaline and several other high temperature that were in the 'pecific were 434'-0DA and 
polymers although polyimides were not among them (R, 4-BDAF; however other diamines also useful in the present 
Liepins et al, U.S. Pat. No. 4,876,032(1989.) invention include any isomer of oxydianiline, diaminoben- 
zophenone, diaminodiphenylmethane, phenylenediamine, 
aromatic condensation polyimide films and coatings that 55 hexafluoropropane. 
have surface conductivities in the range of 
1 . 7 ~  1 0-3%. 5Q-I. 
process for increasing the conductivity of an aromatic con- 
densation polyimide to a range useful for the electronics 6o phthalic h y d r i d e  
industry. 
M-ng, Polymer Communications, 28, 68, March 1987.) 
Conductive polymer films have also been repofled by infu- 
dicarbox~~henox~)hexafluoro~ro~ane dianhydride (6FDA), 
~4-bis(3~4-dicarboxyphenoxy) benzene dianhydride, and 
A primary Object Of the present invention is to provide diaminodiphenylsulfone and ~ ~ s ( ~ n o p ~ e n o x y ) p ~ e n y ~  
In addition to polyamic acid resins obtained by reacting 
equimolar amounts of aromatic diamine and dianhydride, 
invention. They are obtained by adding an of BTDA, 
or other hydride or dianhydride to 
the polyamic acid resin. 
According to the present invention, the incorporation of 
silver trifluoracetylacetonate into the polyamic acid resin 
The foregoing and additional objects and benefits are 65 was found to provide a means of increasing the surface 
conductivity of the thermally cured aromatic condensation 
polyimide. This silver complex can be added immediately 
Another Object Of the present invention is to provide a endcapped polyamic acid resins are also useful in the present 
SUMMARY OF THE INVENTION 
obtained by providing a surface conductive linear aromatic 
polyimide which is obtained from the thermal imidization of 
5,520,960 
3 
following the dianhydride, or after the polyamic acid poly- 
merization is complete. The solubility of the additive in the 
resin is enhanced by the addition of a small amount of 
solvent to the silver trifluroacetylacetonate before its addi- 
tion to the polyamic acid resin. 
Although, the most successful combination of film flex- 
ibility and conductivity hasbeen obtained using a 1:1,1:1.74 
or a 1:2 mole ratio of silver trifluoroacetylacetonate to 
polyimide repeat unit, higher and lower concentrations may 
be used with differing heating schedules to achieve highly 
satisfactory silver metallized films. 
SPECIFIC EXAMPLES 
Example 1 
3,3',4,4'-Benzophenone tetracarboxylic dianhydride 
(BTDA)/4,4'-oxydianiline (4,4'-ODA) resin endcapped with 
2% BTDA was prepared by reacting 4.005 g (0.0200 moles) 
4,4'-ODA with 6.572 g (0.0204 moles) BTDA in 56.2 g 
N,N-dimethylacetamide (DMAc). To 4.5424 g of this resin 
was added 0.2194 g (0.782 mmoles) silver trifluoroacety- 
lacetonate (Agtfa) in 2.0 ml of DMAc. After stirring for 1 Yi 
hours a film was cast onto a soda-lime glass plate to a wet 
thickness of 0.019". The silver ion-containing polyamic acid 
film was thermally converted to the corresponding surface 
conducting polyimide by successive one hour heatings in a 
forced air oven at loo", 200" and 300" C. The resulting 
flexible, reflective film had surface conductivity by four 
point probe. 
Example 2 
BTDN4,4'-ODA resin endcapped with 2% phthalic anhy- 
dride (PA) was prepared by reacting 4.005 g (0.0200 moles) 
4,4'-ODA with 6.381 g (0.0200 moles) BTDA and 
0.0593(0.0004 moles) PA in 42.2 g DMAc. To 34.522 g of 
this resin was added 1.9546 g (0.0200 moles) BTDA and 
0.0593 g Agtfa in 30 ml (28.1 g) DMAc. After stirring for 
2 hours a film was cast 0.019" thick on a glass plate. The 
silver ion-containing polyamic acid film was thermally 
converted to the corresponding surface conducting polyim- 
ide by heating in a preheated forced air oven for 20 min at 
80" C., 1 hour at loo", 1 hour at 200" and 2 hours at 300" 
C. The resulting flexible, reflective film had a conductivity 
of 1.5 Q-' by four point probe. 
Example 3 
BTDA/4,4'-ODA resin was prepared by reacting 10.012 g 
(0.050 moles) 4,4'-ODA with 16.081 g (0.050 moles) BTDA 
in 149.9 g DMAc. To 5.039 g of this resin was added 0.215 
g Agtfa in 1.182 g DMAc. After stirring for approximately 
2 hours a film was cast 0.018'' thick on a glass plate. The 
silver ion-containing polyamic acid film was thermally 
converted to the corresponding surface conducting polyim- 
ide by heating for 1 hour at loo", 1 hour at 200" and 4 hours 
at 300" C. The resulting flexible, reflective film had an 
average conductivity of <4.53Q-' by four point probe. 
Example 4 
PMDN4,4'-ODA resin was prepared by reacting 16.019 
g (0.080 moles) of 4,4'-ODA with 17.450 g (0.080 moles) of 
PMDA In 189.7 g DMAc. To 10.004 g of this resin was 
added 0.521 g Agtfa in 1.996 g DMAc. The mixture was 
stirred vigorously with a metal spatula and cast 0.018'' thick 
4 
film was thermally converted to the corresponding surface 
conducting polyimide by heating for 1 hour each at loo", 
200", and 300" C. and postcuring 2 hours at 300" C. The 
resulting flexible, reflective film had a conductivity of 1 . 7 ~  
10-3--6.2~10-3 Q-' by four point probe. 5 
Example 5 
A 15% solids solution of BTDN4-BDAF polyamic acid 
was prepared by dissolving 25.9445 g (0.05 moles) of 
lo 4-BDAF in 238.2 g of DMAc, and then adding 16.1085 g 
(0.05 moles) BTDA. To 40.0262 g of this polyamic acid 
resin was added 1.9374 g of Agtfa in 8.0108 g of DMAc. 
The solution was stirred vigorously with a metal spatula and 
Immediately cast on plate glass. The silver ion doped 
l5 polyamic acid resin was converted to the surface-conducting 
polyimide by curing in a forced air oven 1 hr each at 100" 
and 200" C. and 3 hr at 300" C. The average conductivity of 
the air side was 4.5 Q-' by four point probe. 
What is claimed as new and desired to be secured by 
Letters Patent of the United States is: 
1. A process for producing linear aromatic polyimide 
films and coatings having surface conductivity comprising: 
forming a polyamic acid solution by chemically reacting 
equimolar quantities of an aromatic diamine and an 
aromatic dianhydride in a solvent medium; 
adding silver trifluoroacetylacetonate in a solvent medium 
to the polyamic acid solution; 
applying a film layer of the polyamic acid solution 
containing the silver trifluoroacetylacetonate onto a 
surface; and 
thermally curing the applied film layer to yield a metal- 
lized surface conductive polyimide film. 
2. The process of claim 1, wherein endcapping of the 
35 polyamic acid is effected before the film layer is applied onto 
the surface. 
3. A process for producing linear aromatic polyimide 
films and coatings having surface conductivity comprising: 
preparing a solution of an aromatic diamine in a solvent 
medium and adding thereto an equimolar quantity of an 
aromatic dianhydride followed by silver trifluoroacety- 
lacetonate in a solvent medium to provide a reaction 
mixture; 
chemically reacting the aromatic diamine and the aro- 
matic dianhydride in the reaction mixture to form a 
solution of a polyamic acid containing silver trifluoro- 
acetylacetonate; 
applying a film layer of the solution of the polyamic acid 
containing silver trifluoroacetylacetonate onto a sur- 
face; and 
thermally curing the applied film layer to yield a metal- 
lized surface conductive polyimide film. 
4. The process of claim 3, wherein encapping of the 
55 polyamic acid is effected before the film layer is applied onto 
the surface. 
5. The process of claim 1, wherein silver trifluoroacety- 
lacetonate is added in an amount sufficient to provide a 
molar concentration of silver trifluoroacetylacetonate to 
60 polyimide repeat unit of from about 1:l to about 1:2. 
6.  The process of claim 3, wherein silver trifluoroacety- 
lacetonate is added in an amount sufficient to provide a 
molar concentration of silver trifluoroacetylacetonate to 
polyimide repeat unit of from about 1:l to about 1:2. 
7. The process of claim 1, wherein the aromatic diamine 
2o 
25 
30 
40 
45 
50 
65 
is selected from the group consisting of 4,4'-oxydianiline 
and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. on a glass plate. The silver ion-containing polyamic acid 
5,520,960 
5 6 
8. The process of claim 3, wherein the aromatic diamine 
is selected from the group consisting of 4,4'-oxydianiline 
and 2,2-bis[4-(4-aminophenoxy) phenyl] hexafluoropropane. 
9. The process of claim 1, wherein the aromatic dianhy- 
dride is selected from the group consisting of 3,3',4,4'- 5 
benzophenone tetracarboxylic dianhydride and pyromellitic 
dianhydride. N,-methyl-2-pyrrolidone, 
10. The process of claim 3, wherein the aromatic dian- 
hydride is selected from the group consisting of 3,3',4,4'- 
benzophenone tetracarboxylic dianhydride and pyromellitic IO 
dianhydride. 
11. The process of claim 2, wherein encapping is effected 
by means of an encapper selected from the group consisting 
of 3,3'-4,4'-benzophenone tetracarboxylic dianhydride and 
12. The process of claim 4, wherein encapping is effected 
by means of an encapper selected from the group consisting 
of 3,3'-4,4'-benzophenone tetracarboxylic dianhydride and 
phthalic anhydride. 
13. The process of claim 1, wherein the solvent medium 
is selected from the group consisting of: 
N, N-dimethylacetamide, 
N, N-dimethylformamide, 
phthalic anhydride. 15 
dimethylsulfoxide and bis(2-methoxyethyl) ether. 
14. The process of claim 3, wherein the solvent is selected 
from the group consisting of 
N, N-dimethylacetamide, 
N, N-dimethylformamide, 
N,-methyl- 2-pyrrolidone, 
dimethylsulfoxide and bis(2-methoxyethyl) ether. 
* * * * *  


Electrically conductive polyimides containing silver trifluoroacetylacetonate

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