Aromatic crystalline polyimides are disclosed that are synthesized from polyamide-acid and when heated to 200 C to 300 C become cyclized to afford an opaque polymer. X-ray diffraction of the unoriented film exhibited 47 percent crystallinity. Differential scanning calorimetry reveals a melt at 425 C with no glass transition in these crystalline polyimides

St.clair, A. K.

St.clair, T. L.

English

NASA Technical Reports Server

United States Patent [191 
St. Clair et al. 
[54] CRYSTALLINE POLYIMIDES 
[75] Inventors: Terry L. St. Clair; Anne I(. St. Clair, 
1731 Assignee: The Ukted States of America as 
both of Poquoson, Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 906,299 
[22] Filed: May 15, 1978 
1511 Int. C1.z .............................................. CO8G 73/10 
[52] U.S. C1. ..................................... 528/207; 528/208 
[58] Field of Search ..................... 260/47 CD, 28 T F  
528/206, 208 
WI References Cited 
U.S. PATENT DOCUMENTS 
3,833,546 9/1974 Takekoshi et al. .............. 260/47 CP 
4,180,648 
[45] Dec. 25, 1979 
3,847,867 11/1974 Heath et al. ..................... 260/47 CP 
3,983,093 9/1976 Williams et al. ................ 260/47 CP 
3,850,885 1 1 ~ 9 7 4  Takekoshi et al. ............. 260/47 CZ 
3,989,670 11/1976 Takekoshi et al. .............. 260/47 CP 
3,991,004 11/1976 Takekoshi et al. ................ 260/37 N 
Primary Examiner-Lester L. Lee 
Attorney, Agent, or Firm-Wallace J. Nelson; John R. 
Manning; Howard J. Osborn 
[571 ABSTRACT 
Novel aromatic crystalline polimides are disclosed that 
are synthesized from polyamide-acid and when heated 
to 200" to 300" C. become cyclized to afford an opaque 
polymer which by X-ray diffraction of the unoriented 
film exhibited 47 percent crystallinity. Uifferential 
Scanning Calorimetry (DSC) indicates a melt at 425" C. 
with no glass transition in these crystalline polyimides. 
4 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19800007898 2020-03-21T02:41:10+00:00Z
1 
4,180,648 
2 
these matrix resins are polyimides, polyimide fibers 
should be more compatible and stronger bonds should 
be formed. 
CRYSTALLINE POLYIMIDES 
ORIGIN OF THE INVENTION 
The invention described herein was made by employ- 
ees of the United States Government and may be manu- 
factured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
BACKGROUND OF THE INVENTION 
Polyimides are high temperature, amorphous poly- 
BRIEF DESCRIPTION OF THE INVENTIC Y 
A highly crystalline polyimide has been discovered 
and prepared by reacting 4,4'-bis-(3,4-dicarboxy- 
phen0xy)diphenylsulfide dianhydride (BDSDA) with 
p-phenylenediamine (PDA) in dimethylacetamide 
(DMAc) and then thermally cyclizing the resulting 
polyamide-acid to the corresponding polyimide 
(BDSDA-PDA). 
BDSDA - PDA 
where n is > 10 
mers that are finding applications as adhesives and com- 
posite matrix resins. At present, no suitable polyimide 
exists for use as a composite reinforcement fiber or 
fabric because of the amorphous nature of this polymer 
class. In order to meet the high tensile strength (HTS) 
and high modulus (HM) requirements of a reinforce- 
ment the polymer must exhibit either crystallinity or a 
high degree of order which is usually induced by draw- 
ing or extruding. 
The polymerization of this polyimide was achieved at 
room temperature in freshly distilled DMAc at 15 per- 
cent solids using purified monomers. The resulting 
amide-acid solutions from several preparations had in- 
30 herent viscosities when run at 0.5 percent solids in 
DMAc (35" C.) of 1.3 to 1.7. 
Another crystalline polyimide, as observed by differ- 
ential scanning calorimetry melt, was synthesized from 
BDSDA and benzidine (BDSDA-benzidine). 
where n is > 10 BDSDA - BENZIDINE 
BDSDA + 
NHZ 
BDSDA 
4,180,648 
3 4 
-continued 
BDSDA + 
H2N 
BDSDA 
BDSDA 
BDSDA 
BDSDA 
+ 
+ 0 H2Nab NH2 
+ PDA OR BENZIDINE 
+ PDA OR BENZIDINE 
+ PDA OR BENZIDINE 
PDA OR BENZIDINE 
+ PDA OR BENZIDINE 
In the only two cases where crystalline polyimides 
were discovered, the polyamide-acids were evidently of 
a highly extended rod-like structure in solution, thus 65 the temperature region of 190" C. Differential scanning 
allowing crystallization upon loss of solvent and subse- calorimeter (DCS) traces of the crystalline films cured 
quent cyclization to the polyimide. The crystallization to 300" C. exhibited intense endothermic crystalline 
began to be noticable (as evidenced by opaqueness) in melts. The melting maximum by DSC for the BDSDA- 
5 
4,180,648 
PDA polyimide is 426" C. and for BDSDA-benzidine 
480° C. After melting, both materials become amor- 
phous with glass transition temperatures of 226" C. and 
285" C. respectively. 
The X-ray diffraction pattern of the BDSDA-PDA 5 
polyimide indicated that this polymer was 47 percent 
crystalline with peaks occurring at 27.60 d;, 5.09 A, 4.37 
A and 3.72 A. 
Torsional braid analysis (TBA) of BDSDA-PDA 
showed a glassy transition to be absent on the room 10 
temperature to 450" C. run, but the cool-down curve 
exhibited a sharp glass transition at 230" C. indicating 
the material was initially crystalline and became amor- 
phous upon melting. This same phenomenon occurred 
when a sample of the crystalline film was run in clamps 15 
on a Thermomechanical Analyzer (TMA). The initial 
film stretching occurred on melting at 425" C. and after 
cooling and reheating the stretching occurred at 238" C. 
( W .  
SPECIFIC EXAMPLES 
Example I. A solution of 5.1048 g of BDSDA and 
1.0815 g of PDA in 35.02 g of DMAc was prepared in 
a 75 ml serum bottle under a nitrogen atmosphere. This 
solution was stirred with a magnetic stirring bar and 25 
began to build up viscosity as the reactants dissolved. 
The solution was stirred overnight at room temperature 
and then a film of this mixture was cast at 0.020 in on 
plate glass. The cast film was placed in a dry box and 
heated to 40" C. to evaporate the solvent. It was then 30 
cured for one hour at 100" C., one hour at 200" C. and 
one hour at 300" C. After slow cooling to room temper- 
ature the film was removed from the glass. It was 
opaque and brittle, which is characteristic of crystalline 
polymers. The inherent viscosity of the solution was 35 
1.42 (0.5 percent solids at 35" C.) indicating a high mo- 
lecular weight for this polymer system. 
Example 11. A solution of 0.5105 g of BDSDA and 
0.1842 g of benzidine in 3.937 g of DMAc was prepared 
in a 15 ml serum bottle under nitrogen atmosphere. This 40 
solution was stirred with a magnetic stirring bar and a 
20 
6 
build up in viscosity was observed shortly after the 
monomers dissolved. The solution was stirred over- 
night and a fim of the mixture was cast at 0.015 in on 
plate glass. The solution viscosity for this formulation 
was 1.30 (0.5 percent solids at 35" C,). After the film 
was air dried at 40" C. for two hours, it was placed in an 
air oven and held for one hour each at 100" C., 200" C., 
and 300" C. The film was brittle but clear. 
It is thus seen that the present invention yields crys- 
talline polyimides that exhibit properties excellent for 
the production of high tensile strength, high modulus 
fibers that should prove useful as reinforcing fibers in 
high temperature composites and adhesives as well as 
useful in flame resistant applications. 
The above specific examples are considered illustra-. 
tive of the invention and there may be modifications and 
variations therein that will be apparent to those skilled 
in the art without departing from the spirit and scope of 
the invention as set forth herein. 
What is claimed as new and desired to be secured by 
Letters Patent of the United States is: 
1. A crystalline polyimide formed as the reaction 
product of 4,4'-bis-(3,4-dicarboxyphenoxy)diphenylsul- 
fide dianhydride and p-phenylenediamine. 
2. A crystalline polyimide formed as the reaction 
product of 4,4'-bis-(3,4-dicarboxyphenoxy)diphenylsul- 
fide dianhydride and benzidine. 
3. A method of making a crystalline polyimide by 
reacting 4,4'-bis(3,4-dicarboxyphenoxy)diphenylsulfide 
dianhydride with a diamine selected from the group 
consisting of p-phenylenediamine and benzidine. 
4. A method of making a crystalline polyimide as in 
claim 3 wherein the diamine is dissolved in the solvent 
dimethylacetamide prior to being combined with the 
dianhydride and the resulting mixture is heated to ap- 
proximately 40" C. to evaporate the solvent and cy- 
clized by heating to and maintaining the temperature 
thereof at 100" C. for one hour, at 200" C. for the next 
one hour, and at 300" C. for the third hour. * * * * *  
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Crystalline polyimides

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