The preparation of crosslinked 1,2,4-oxadiazole elastomers is described. The technique involves thermally condensing (1) a monomer having the formula H2N(HON)C-R-Q, wherein Q is a triazine ring-forming groups such as nitrile or amidine or a mixture of such group with amidoxime, or (2) a mixture of the same monomer with R(C(NOH)NH2)2, with R in these formulas standing for a bivalent organic radical. In the monomer charge, the overall proportions of amidoxime groups to triazine ring-forming groups varies depending on the extent of crosslinking desired in the final polymer

Kwongs, H.

Rosser, R. W.

Shalhoub, I. M.

English

NASA Technical Reports Server

United States Patent 1191 [111 4,269,787 
Rosser et al. [45] May 26, 1981 
[54] BIFUNCTIONAL MONOMERS HAVING 
TERMINAL OXIME AND CYANO OR 
AMIDINE GROUPS 
[76] Inventors: 
1211 Appl. No.: 
[22] Filed: 
Robert A. Frosch, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of Robert W. Rosser; 
Ibrahim M. Shalhoub, both of San 
Jose, Calif.; Hartoi Kwong, 
Sacramento, Calif. 
145,283 
Apr. 30, 1980 
Related U.S. Application bata 
[62] Division of Ser. No. 28,301, Apr. 9, 1979. 
[51] Int. Cl.3 ................... C07C 121/43; C07C 123/00 
[52] U.S. C1. ............................. 2fW465.5 R; 564/229; 
[58] Field of Search .................... 260/465.5 R, 564 G; 
528/310 
564/229 
1561 References Cited 
U.S. PATENT DOCUMENTS 
2,902,514 9/1959 de Benneville et al. ........ 260/564 G 
3,621,049 11/1971 Addor et al. ............. 2W465.5 R X 
3,707,555 12/1972 Wright et al. ............... 260/564 G X 
4,085,137 4/1978 Mitsch et al. ............. 260/465.5 R X 
4,145,524 3/1979 Frosch ............................. 548/131 X 
OTHER PUBLICATIONS 
Encyclopedia of Polymer Science and Technology, 
Plastics, Resins, Rubbers, Fibers, vol. 2, John Wiley & 
Sons, (1969), pp. 184-187. 
Primary Examiner-Joseph P. Brust 
Attorney, Agent, or Firm-Darrell G. Brekke; John R. 
Manning 
[571 ABSTRACT 
New crosslinked 1,2,4-oxadiazole elastomers have been 
prepared by thermally condensing (a) monomer having 
the formula HzN(HON)C-R-Q, wherein Q is a tri- 
azine rig-forming group such as nitrile or amidine or a 
mixture of such group with amidoxime, or (b) a mixture 
of said monomer with R[C(NOH)NH2]2, with R in 
these formulas standing for a bivalent organic radical 
having the formula 
--(CXZ)~-, or 
-CFY(OCF2CFY)mO(CX2)pO(CFYCF20),,. 
CFY- 
wherein X is fluorine or hydrogen, Y is fluorine or 
trifluoromethyl, p ranges from 1 to 18, and m + n ranges 
from 2 to 7. In the monomer charge, the overall propor- 
tions of amidoxime groups to triazine ring-forming 
groups varies depending on the extent of crmslinking 
desired in the final polymer. 
1 Claim, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19810015721 2020-03-21T09:48:32+00:00Z
4,269,787 
1 2 
radical, or a mixture of bivalent organic radicals, having 
BIFUNCTIONAL MONOMERS HAVING the formula 
TERMINAL OXIME AND CYANO OR AMIDINE 
GROUPS -(CXz)p-, or 
-CFY(OCF2CFY)mO(CX2)pO(CFYCF20),l- 
CFY--, 
5 
ORIGIN OF THE INVENTION 
The invention Qcribed herein was made in the per- in which x is fluorine or hydrogen, y is fluorine or 
formance of work under a NASA contract and is Sub- trifluoromethyl, p ranges from 1 to about 18, and m+n 
ject to the provisions Of Section 305 Of the National 1o ranges from 2 to about 7; and (2) Q is an amidoxime, 
Aeronautics and Space Act of 1958, Public Law 85-568 nitrile, or 
The triazine-crosslinked oxadiazole polymers of the (72 Stat. 435; 42 U.S.C. 2457). 
This is a division, of application Ser. No. 028,304 invention can be obtained by heating together at tem- 
peratures within the range of 50" C. to 210" C., any filed Apr. 9, 1979. 
15 suitable mixture of said monomers or any of said mono- 
group. 
BACKGROUND OF THE INVENTION 
mers containing the overall concentration of triazine- 
forming groups sufficient to achieve the particular de- 
gree Of crosslinking and curing desired. 
1. Field of the Invention 
The present invention relates to polymers that are 
derived from diamioxime monomers and contain 1,2,4- 
oxadiazole rings which serve as linking groups in the 2o 
polymer chain. More particularly, the invention relates 
to such polymers crosslinked by triazine rings. 
DETAILED DESCRIPTION O F  THE 
INVENTION 
2. Description of the Prior Art The polymers of the invention are prepared by the 
Viscous polymers have been prepared by the conden- heat induced condensation reaction Of amidoxime 
sation of diamidoxime monomers to form linear mole- 25 groups to form 1,2,4-oxadiazole linkages and of nitrile 
tules in which the 1,2,4-oxadiazole ring acts as linkages. or amidine groups to form triazine linkages. The follow- 
The chain segments between said linkages can be alkvl- ing reactions illustrate the various processes involved in 
Y Y 
ene radicals, arylene radicals, perfluorinated alkylether 
radicals, or perfluorinated alkylether radicals. The per- 
fluorinated linear poly( 1,2,4-oxadiazoles) have been 30 (A) HON 
843,090, now U.S. Pat. No. 4,145,524, while various 
the invention: 
described in copending patent application Ser. No. \\ JNOHh&+ 
\ 
NH2 
/C-R-c 
methods of synthesizing polymers of this type have 
been discussed in Encyclopedia of Polymer Science and 
Technology, Plastics, Resins, Rubbers, Fibers, Volume 35 
H2N 
diamidoxime (I) 
11, John Wiley & Sons, Inc., 1969, pp. 184-7. (B) HON 
SUMMARY OF THE INVENTION 'C-R-CN 
/ 
An object of this invention is to prepare poly(1,2,4- 
oxadiazoles) crosslinked by triazine rings. Another ob- 40 
ject is to prepare new monomers with which to carry 
out said polymerizations. Still another object is to pro- 
H2N 
(11) 
vide tough, heat and chemical resistant elastomeric \\ JNH - (c) HON 
NH2 
polymers. /C-R-c \ 
These and other objects of the present invention 45 H2N 
(111) 
which shall hereinafter become apparent, can be at- 
tained by the thermal reaction of certain monomers or 
mixtures of monomers containing various proportions 
of amidoxime, nitrile, and amidine groups. The resulting 
polymers are basically constituted by structures of the 50 (E) I + 111 
(D) I + 11 - 
following type: 
in which the number (x 
oxadiazole and triazine 
mined and are functions 
1,2,Coxadiazole polymer 
triazine crosslinked 
1,2,4-oxadiazole polymer 
The first reaction (A) has already been described in 
copending application Ser. No. 843,090, filed on Oct. 
17, 1977 and now U.S. Pat. No. 4,145,524. The other 
55 four reactions (B to E) show the various monomers and 
combination of monomers that will yield the cross- 
linked elastomers herein disclosed. In these formulas, R 
represents identical bivalent organic radicals or any 
combination of bivalent organic radicals selected from 
60 the group consisting of: -(CXZ)~-, wherein p ranges 
from 2 to about 18 and X is hydrogen or fluorine; and 
R- 
oligomeric or polymeric radicals prepared by reaction 
of a dicarboxylic acid halide with a perfluoroepoxide 
and having the formula 
and Y) and the Order Of the 
linkages are randomly deter- 
of the nature and the propor- 65 
tions of monomers present in the reaction mixture. The 
usable monomers can be represented by the formula 
-CFY(OCF2CFY)mO(CX2)pO(CFYCF20)n- 
CFY- 
HzN(HON)-R-Q in which: (1) R is a bivalent organic 
4,269,787 
3 4 
wherein Y is fluorine or trifluoromethyl, X is fluorine or 
hydrogen, p ranges from 1 to about 18 and m+n ranges 
from 2 to about 7. 
The polymers formed from these monomers will vary 
in structure according to the type and proportion of 5 
monomer end groups present. Thus, when an amidox- 
ime-amidine (111) monomer is used, the resulting poly- 
mer has a theoretically equal number of oxadiazole 
rings and crosslinking triazine rings. using any or a 
diamidoxime (I) will, of course, increase the proportion 
tion of triazine rings. Whatever propor- 
lected for the preparation of a given crosslinked poly- 
mer will depend ultimately on the properties that said 
polymer must have. In this respect, the preferred ratio 
of oxadiazole ring-forming groups to triazine ring-form- 
ing groups for obtaining the most adequate level of 2o 
elasticity in the polymer, when elasticity is desired, 
should be about 9 or 1O:l. Higher contents of triazine 
render them useful for other applications. 
Le., the amidoxime-nitrile (11) and the amidoxime-ami- 
dine, will now be described. 
EXAMPLE 1 
An amidoxime-nitrile compound (see formula 11) in 
which the value o f m + n  in the R group (See formula 
1") is equal to 6, was Prepared by Placing hYdroxYlam- 
0.355 g (10.78 mmoles) in a 100 ml round-bottomed 
flask and adding the corresponding dinitrile, 9.0154 g 
of the two mOnOmerS (11 and 111) with a 10 (5.89 mmmoles, 11.78 molar equivalents), and trichloro- 
trifluoroethane (Freon 13)9 2o ml. The flask was 
night. The solution was removed from the flask and the 
15 the amidoxime-nitrile, an 85% yield. Infrared analysis of 
the product showed absorption at 2.86 pm; 2.96 pm 
(NH2); 2.98 to 3.32 pm (OH); 4.43 pm (C=N); 5.96 pm 
(C=N); 6.33 pm (C=N); and 7 to 9 pm (C-F). The 
ratio of nitrile to amidoxime was 1:10.8. 
EXAMPLE 2 
ofoxadiazole linkages formed and decrease the propor- 
tions of reactive end groups are actually se- 
purged with nitrogen gas and the contents stirred Over- 
evaporated with nitrogen gas to give 8.07 g Of 
In a preparation similar to Example 1, the quantities 
moler equivalents) of the dinitrile, 0.60 g (18.17 mmoles) 
The condensation reactions undergone by the mono- 25 of hydroxylamine, and 30 ml Freon 113. After stirring 
for 16 hours, filtering, evaporating, and degassing for 2 
hours, 13.52 (93.1% yield) of the amidoxime-nitrile 
compound were obtained showing I R  absorption bands 
for NH2, OH, C=N, C=N, and CF. The nitrile to 
linkages increase the rigidity of the polymer and of materials used were 14.51 g (9.48 mmoles, 18.96 
to form the linear oxadiazole linkages and the 
tridimensional triazine linkages are carried out by heat- 
ing the monomer charge at temperatures of UP to about 
200" c. for a period sufficient to obtain the degree Of 
cure desired. The following table provides an idea of 30 amidoxime group ratio was 1~23 .  
what may be expected from various heating regimes for 
a particular monomer charge: EXAMPLE 3 
Another method of preparing the amidoxime-nitrile 
cross-linking reagent involves the use of absolute meth- 
35 anol as a solvent for the hydroxylamine. According to 
this method, hydroxylamine, 0.773 1 g (23.41 mmoles), 
150" c. 1 to 1.75 days 10,000 to 35,000 was dissolved in absolute methanol, 0.08 ml. This was 
150" C. 3.5 days - 35,oOO+ added to a round-bottomed flask containing the dinitrile 
of Example 1, 20.7759 g (13.58 mmoles, 27.16 molar 
- 
Temperature Time MW 
80-130" C .  3 days -3,ooO (3ooO-10,oOO) 
- 
Although heating at 150" c. has produced polymers of 40 equivalents), dissolved in Freon 113,30 ml. The homog- 
enous solution was stirred for 17 hours under a blanket weight average molecular weights of 35,000, as mea- of argon gas. After filtration and evaporation, 19.4878 g sured by viscosimetry, an elastomeric network ordinar- (93.8% yield) of the amidoxime-nitrile compound were ily begins to form during the 150" heating cycle and is obtained, having a 1:6.24 ratio of nitrile to amidoxime. completed during the 200" C. post-cure heating period. 45 
The heat and chemical resistant polymeric materials EXAMPLE 4 
of this invention can be compounded with a great vari- 
ety of fillers, extenders, and modifiers for use in numer- 
ous applications in which high stability, impermeability 
to liquids and gases, good plasticity and elasticity, or 50 the dinitrile used in ~~~~~l~ 1, with 0.28 
rigidity are advantageous. Keeping in mind that some of 
these desirable properties can be altered in any direction 
by selection of the mix and polymerization 
conditions, the resulting polymers may be employed, 
for example, as adhesives, caulking 
sealants, fuel tank liners, and the like. 
The invention having thus been generally described, 
a few specific embodiments will now be provided to 
illustrate the processes and products involved. These 
examples are not intended to be limiting of the invention 60 EXAMPLE 5 
scope. In a preparation similar to that of Example 4, an ami- 
The diamidoximes (I) that can be used in the prepara- doxime-amidine crosslinking agent was obtained by 
tion of the polymers of the present invention can be stirring together in a nitrogen atmosphere for 16 hours, 
synthesized by methods described in detail in U.S. Pat. 15.4413 g (10.09 mmoles, 20.18 molar equivalents) of the 
No. 4,455,244, methods which involve, for example, the 65 dinitrile of Example 1, with 0.5713 g (17.30 mmoles) 
successive conversion of the corresponding diacylfluo- hydroxylamine diluted with 35 ml Freon 1 13. Ammonia 
ride to the diamide, the dinitrile, and finally the diami- was then bubbled through the solution for 1 hour at 
doxime. The preparation of the other monomers used, room temperature. This gave 14.5303 g (94.1% yield) of 
An amidoxime-amidine compound (111) was prepared 
by stirring together in a nitrogen atmosphere for 16 
hours 1,02 (7.2 mmoles, 1 4 . ~  molar equivalents) of 
(8.48 
mmoles) hydroxylamine diluted with 30 ml F~~~~ 113. 
~~~~~i~ was then bubbled into the solution for 1 hour 
at room temperature. This gave 10.55 g (93.5% yield) of 
crosslinking agent having a 1:1.43 ratio of amidine to 
55 amidoxime groups. I R  absorption was measured at 2.84 
to 3.02 pm (NH2); 2.97 to 3.32 pm (OH); 5.77, 5.95, and 
6.33 pm (C=N amidoxime); 6.06, 6.25 pm (C=N ami- 
dine); and 7 to 9 pm (CF). 
c 
4,269,78 7 
J 
the crosslinking agent, having a 1:6.0 amidine to ami- 
doxime group ratio. 
EXAMPLE 6 
amidoxime (11) and amidine-amidoxime (111) monomers 
prepared as in Examples 1 and 2, containing various 
ratios of nitrile or amidine groups of amidoxime groups. 
Polymerization and crosslinking were accomplished 
simply by heating a monomer with a given triazine 10 
ring-forming group to amidoxime ratio in the following 
manner: 80"-130" C. for 2 days at 50 cm Hg; 150" C. for 
3 to 4 days in full vacuum; and 200" C. for 2 to 3 days in 
full vacuum. During this heating schedule, elastomers 
were formed at 150" C. after 3 days when the proper 15 
ratio of groups was present, and the molecular weight 
was increased by the further heating at 200" C. A selec- 
tion of monomers identified by their nitrile or amidine 
to amidoxime content ratio is listed in Table 1 along 
with some of the properties possessed by the polymers 20 
obtained by the heat treatment just described. All the 
polymers showed IR absorption at 6.29 pm (oxadiazole) 
and 6.45 pm (triazine). 
TABLE 1 
Various polymers were prepared from nitrile- 95 
7 5  "-. 
Crosslinked Oxadiazoles Obtained From Single Monomers 
Single Monomers Polymer Properties 
Ratio of ring- Modulus Glass Transition 
forming groups (dynes/cm2) temperature 
Nitrile to 
Amidoxime 
1:2.33 2.0 x 106 -46' C. 
30 
1:0.54 3.5 x I06 -47" c. 
1:4.5 4.3 x 105 -47" c. 
1:6.3 2.5 x 105 -47" c. 
35 trace nitrile viscous - no nitrile viscous - 
Amidine to 
Amidoxime 
1:l.O 2.6 X IO6 -46" c. 
1:3.0 1.5 X IO6 -48' c. 
1:4.1 1.0 x 106 -47' c. 
1:6.3 3.0 x 105 -41" C. 
1:10.7 elastic ' - 
trace amidine viscous - 
40 
Most of the polymers in the above table had a JP-4 jet 45 
fuel extractible content of about 1%, on a weight basis. 
Those with the 1:6.3 ratios, i.e., the most useful from the 
elastomeric point of view, had extractibles of about 
1.5%. 
50 
EXAMPLE 7 
Crosslinked polymers were prepared by heat treating 
various mixtures of nitrile or amidine (I1 and 111) hybrid 
monomers, as used in the earlier examples, with the 
corresponding diamidoxime compound (I) of said hy- 
brid monomers. The concentration of hybrid monomer 
in each mixture was adjusted to provide the ratio of 
triazine-forming groups to oxadiazole-forming groups 
desired and the resulting mixture was subjected to the 
following heat regime. 
Barometric 
Temperature Time Condition 
80-130' C. 2 days -50 cm Hg 
150' C. 6 days -50 cm Hg 
200" c. 2 to 3 days full vacuum 
During this curing schedule, elastomers were formed at 
150" C. after about 5 days and further heating at 200" C. 
served to increase the crosslinking. The nature and 
proportions of monomers used, as well as some of the 
properties of the crosslinked polymers produced, are 
recorded in Table 2. 
EXAMPLE 8 
In these preparations using the same monomers as in 
Example 7, the triazine ring-forming material and the 
diamidoxime were heated separately under reduced 
pressure before blending. The heat regime applied is 
shown below, with steps a to d being conducted in 
sequence : 
Barometric 
Temperature Time Condition 
Individual monomers: 
(a) 80-130' C. 2 days -50 cm Hg 
Blend of pre-heated monomers: ' 
(b) 80-130' C. 1 day - 5 0 c m H g  
(c) 150' c. 4 days -50 cm Hg 
Id) 200" C. ' 2 davs full vacuum 
It has been found that the blending methods just 
described which involve direct mixing or pre-treating 
the monomers with heat separately before they are 
blended, significantly improves the reproducibility of 
the polymer properties when relatively large quantities 
of monomers are mixed and then heated as in Examples 
7 and 8. 
The results of several amidine-amidoxime blends 
treated in the manner just described are reported in 
Table 2, along with the data from Example 7. 
TABLE 2 
Crosslinked Oxadiazoles Obtained From Monomer Mixtures Containing a Diamidoxime 
Monomer Mixture Extractibles (24 hrs) TGA Analysis 
Crosslinking Agent Diamidoxime Final Monomer Modulus** Boiling Boiling 275O C. in air 
Ratio* Weight(g) Weight(g) Ratio' Preheating (dynes/cm*) Water JP4 Fuel for 24 hours 
EXAMPLE 4: 
l:2.1 0.5242 0.5600 15.53 no 2.4 X IO6 1.0% 1.0% 2.0% 
1:2.1 2.0314 1.9835 13.13 no 3.5 x 106 .- - - 
1:4.1 0.4340 0.1637 1:6.02 no 1.0 x 105 1.0% 0.5% 2.1% 
1 :4. I 0.5925 0.1981 1:5.8 no 3.0 X lo5 1.0% 0.5% - 
1 :4.1 0.6670 0.2599 1:6.1 no 2.0 X lo5 0.5% 0.7% 2.2% 
EXAMPLE 5: 
1 :4.1 0.227 0.082 15.93 yes 2.0 x 105 1.45% 3.3% 4.2% 
1:4.1 0.261 0.137 1:6.8 yes 1.0 x 105 2.0% 1.34% 3.2% 
1 :4.1 2.692 2.512 1:8.86 yes - 1.2% high - 
7 
4,269,787 
8 
TABLE 2-continued 
Crosslinked Oxadiazoles Obtained From Monomer Mixtures Containing a Diamidoxime 
Monomer Mixture Extractibles (24 hrs) TGA Analysis 
Crosslinking Agent Diamidoxime Final Monomer Modulus** Boiling Boiling 275' C. in air 
Ratio' Weight(g) Weight(g) Ratio' Preheating (dynes/cm*) Water JP4 Fuel for 24 hours 
1:4.1 0.661 0.282 1:6.7 yes 1.0 x 105 0.5% 2.0% - 
'Ratio of nifrile to amidoxime (first run) and of amidoxime (last 9 runs). 
**Modulus values were determined by Duponf thermomechanical analyzer. 
What is claimed is: 
1. A bifunctional monomeric compound having the 
formula Q-R-C(NOH)NH~, wherein: (a) R is a bivalent 
organic radical selected from the class consisting of 
alkylene radicals of the formula -(CX&- and al- 
It is evident from the results in the above table that 
heat resistant Polymers can be Prepared with a broad 
range of Properties, depending on the nature and Pro- 
portions of monomers used. It has further been found l5 kylether radicals of the formula 
that the use of a diamidoxime (I) along with a hybrid 
monomer (I1 and 111) is quite desirable in achieving -CFY(OCF2CFY)mO(CX2)pO(CFYCF2O)n. 
reproducible polymer results, especially when such 
properties as elasticity are desired in optimum degree, 
e.g., at an overall triazine ring-forming group to ami- 20 or mixtures thereof, wherein X is fluorine of hydrogen, 
doxime group ratio of about 1:6. Y is fluorine or trifluoromethyl, p ranges from 1 to 
In any event, the presently disclosed and newly dis- about 18, and m+n ranges from 2 to about 7; and (b) Q 
covered possibility of crosslinking to any desired degree is a group selected from the triazine ring-forming class 
the conventional heat and chemical resistant 1,2,4- consisting of - c E N  and 
oxadiazole perfluorinated polymers of the art, greatly 25 
increases their utility in various applications which 
include those already mentioned as well as others for 
tions and variations of material and process that the man 
skilled in the art will surely accomplish without depart- 30 
CFY--, 
HNH2 
-c . 
NH2 
which they may become suited through the modifica- 
ing from the scope of the appended claims. 
\ 
* * * * *  
35 
40 
45 
50 
55 
65 


Bifunctional monomers having terminal oxime and cyano or amidine groups

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