Carboranyl-substituted polyphosphazenes are prepared by heat polymerizing a carboranyl halocyclophosphazene at 250 C for about 120 hours in the absence of oxygen and moisture. The cyclophosphazene is obtained by allowing a lithium carborane, e.g., the reaction product of methyl-o-carborane with n-butyllithium in ethyl ether, to react with e.g., hexachlorocyclotriphosphazene at ambient temperatures and in anhydrous conditions. For greater stability in the presence of moisture, the chlorine substituents of the polymer are then replaced by aryloxy or alkoxy groups, such as CF3CH2O. The new substantially inorganic polymers are thermally stable materials which produce a high char yield when exposed to extreme temperatures, and can thus serve to insulate less heat and fire resistant substances

Allcock, H. R.

Fewell, L. L.

Obrien, J. P.

Scopelianos, A. G.

English

NASA Technical Reports Server

United States Patent [191 
Allcock. et al. 
1111 4,288,585 
1451 Sep. 8,1981 
CARBORANY LCY CLOTRIPHOSPHAZENES 
AND THEIR POLYMERS 
Inventors: 
Appl. No.: 
Filed: 
Robert A. Frosch, Administrator 
of the National Aeronautics and 
Space Administration, with respect 
to an invention of; Harry R. Allcock, 
State College, Fa.; John P. O'Brien, 
Wilmington, Del.; Angelo 6. 
Scopelianos, University Park, Pa.; 
Larry L. Fewell, San Jose, Calif. 
129,799 
Mar. 12, 1980 
Int. C1.3 ....................... CO8G 73/00; C08G 79/02 
U.S. C1. ........................................ 528/4; 528/168; 
528/6; 528/7; 568/2; 568/4; 568/5; 528/399 
Field of Search ................... 528/4, 6, 7, 394, 399; 
568/2, 4, 5 
References Cited 
US. PATENT DOCUMENTS 
3,155,630 11/1964 Schroeder ............................... 528/6 
3,164,556 1/1965 Apley et al. ........................ 528/394 
3,320,185 5/1967 Alexander et ai. ..................... 528/6 
3,549,603 12/1970 Szmenuk et al. ....................... 528/4 
Primary Examiner-Wilbert J. Briggs, Sr. 
Attorney, Agent, or Firm-Darrell G. Brekke; John R 
Manning 
1571 ABSTRACT 
Carboranyl-substituted polyphosphazenes are prepared 
by heat polymerizing a carboranyl halocyclophospha- 
zene at 250" C. for about 120 hours in the absence of 
oxygen and moisture. The cyclophosphazene is ob- 
tained by allowing a lithium carborane, e.g. the reaction 
product of methyl-o-carborane with n-butyllithiurn in 
ethyl ether, to react with e.g. hexachlorocyclotriphos- 
phazene at ambient temperatures and in anhydrous con- 
ditions. For greater stability in the presence of moisture, 
the chlorine substituents of the polymer are then re- 
placed by aryloxy or alkoxy groups, such as 
CF3CH20-. 
The new substantially inorganic polymers are thermally 
stable materials which produce a high char yield when 
exposed to extreme temperatures, and can thus serve to  
insulate less heat and fire resistant substances. 
4 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19820010515 2020-03-21T16:21:22+00:00Z
1 
4,288,585 
CARBQRANYLCYCLOTRIPHQSPHAZENES AND 
THEIR POLYMERS 
2 
c /R  
CI CI 
CI N' \N C1 
/o\ 
\ /  
BioHio 
/c- P 
5 ORIGIN OF THE INVENTION 
P 
Ci N' \N C1 
R-C-C-Li 
\ O /  
BlOHlO \! II/ 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 42 U.S.C. 2457). 
\! II/ 
10 / \N/p\cl < CI / \N/p\cl 
CI 
I 
This invention TECHNICAL relates to carboranylcyclophospha- FIELD 
15 j N\ zene monomers and to heat resistant high char yield polymers made from such monomers. 
/R BACKGROUNDART C 
20 / o \  
Various polymerizable compounds can be prepared 
by reaction of lithium carborane with a bromocom- 
3,669,993, column 2, lines 1 to 15), or by a Grignard 
type reaction involving a bromoalkylcarborane and an 25 
alkenylbromide (U.S. Pat. No. 3,431,234). In the latter 
BIOHIO 
pound containing ethylenic unsaturation (U.S. Pat. No. R1O N' \N OR1 
\! !' $ . = ~ ~  
R'O' 'N' \OR' 
111 IV case, the resulting carborane is further converted to a 
carboranylsilane which can be polymerized to a heat 
resistant polysiloxane resin. 30 
Another type of polymer known to the art is made by 
polymerizing cyclic dihalophosphazenes and, for water 
resistance, substituting alkoxy or aryloxy groups for the 
halogens in the molecule (e.g., U.S. Pat. Nos. 3,370,020; 35 
NaORl 
R 
I 
1 
phosphazene 3,880,800; and compounds, 3,883,451). One N3P3F6, of these has cyclic given dihalo- good 
$N-rlx I p..- N=P- 
I 
yields of mixed fluorophenyl phosphazenes, N3P3F6 
general, however, organolithium reagents have 
showed, upon reaction with cyclic phosphazenes, a 
n&, when allowed to react with phenyl lithium, cbLi. In OR' OR1 
V 
40 Y 
tendency to yield ring-opened compounds instead ofthe 
expected alkylated or arylated derivatives. 
new carborane-substituted cyclophosphazenes and to 
polymerize these compounds to heat-resistant polymers 
that are mainly inorganic in character. 
In the above formulas, R represents a hydrogen atom, 
a lower alkyl radical having up to 6 carbon atoms, or an 
The principal object of this invention is to synthesize 45 aryl radical of up to 9 carbon atoms. The methyl and 
Phenyl groups, however, are Preferred- R1, On the Other 
hand, stands for an alkyl group, an aryl group, a haloge- 
nated homolog of said groups, or a mixture of any of 
these groups. The preferred groups are those of the 
50 formula F(CF2)aCHp- or H(CF&(CHz)- in which a 
and b are small integers not greater than 9. In polymeric 
The objects of this invention have been achieved by formulas IV and V, the ratio of x to y is 2:1, the number 
allowing a lithium carborane to react with a halocyclo- and type of polymeric units that it quantifies being de- 
phosphazene at about 25" C.  in diethyl ether to form a termined by the carboranylcyclotriphosphazene struc- 
carboranyl-substituted halocyclophosphazene. The lat- 55 ture 'I. 
The lithium carborane employed in the above scheme ter a car- is prepared from the alkyl or arylcarborane by reaction 
Omer and the Polymer so prepared, the halogen atoms these alkylcarboranes, methylcarborane, was prepared 
may be replaced by one or more alkoxy or aryloxy 60 from the bromomethyl homolog by reaction with mag- 
groups for greater stability in the presence of moisture. nesium metal and subsequent hydrolysis of the metal 
organic bromide obtained. 
DETAILED DESCRIPTION O F  THE Attempts to convert o-carborane to methylcarborane 
INVENTION via the organolithium route were unsuccessful. 
65 The reaction between the carborane and the or- 
The reactions and the ganolithium, preferable n-butyllithium, was carried out 
at ambient temperature in a solvent such as die- 
thylether. The resulting solution was combined with a 
DISCLOSURE OF INVENTION 
is then heat polymerized to 
boranyl-substituted PolYPhosPhazene. In both the man- with n-butyllithium in the conventions] manner. One of 
in the present invention can be more easily visualized by 
reference to the following scheme: 
3 
4,288s 85 
similar solution of a halocyclotriphosphazene to yield, 
after about 12 hours at ambient temperature, the desired 
carboranylhalocyclotriphosphazene. The preferred 
cyclic phosphazene for this purpose is the penta- 
chlorocyclotriphosphazene, although other homologs 
with fluorine or bromine can also be employed. 
'The carboranylpentahalotriphosphazene monomer 
may then be polymerized simply by heating at 250" C. in 
the absence of air and moisture during about 120 hours. 
These conditions will of course vary depending on the 
exact nature of the monomeric compound used and the 
desirability of optimizing the process. 
The carboranyl substituted polychlorophosphazenes 
that can be produced by the method just described, as 
well as the monomeric entities, can be converted to the 
penta-alkoxy or aryloxy homologs by reaction with a 
suitable sodium alcoholate or phenolate, NaORI. The 
reaction as well as the reactants that can be employed to 
carry it out, are fully described in the art, e.g. in U.S. 
Pat. Nos. 3,888,800 and 3,888,451. Unexpectedly, the 
relatively large carborane cage structure exerts only a 
minimal steric shielding effect on the geminal phos- 
phorus-chlorine bond both in the trimer and in the poly- 
mer. 
The carboranyl-substituted polychloro- and polyalk- 
oxyphosphazenes of this invention have a molecular 
weight within the range of about 1X105 to 1x106. 
They are thermally stable materials which, upon de- 
composition at extreme temperatures, produce a high 
char yield which serves to insulate other less resistant 
materials from the effects of heat and flame. 
The process of the invention will now be illustrated in 
operational detail by the following examples which are 
not intended to limit the scope of said invention as 
stated in the appended claims. 
EXAMPLE 1 
Phenyl-o-carborane, 4.95 g (2.25X 10-2 mol), and 
n-butyllithium, (2.25 X 10-2 mol), were dissolved in 
diethyl ether, 10 ml, at 25" C. To  this solution, there was 
then added a solution of hexachlorocyclotriphospha- 
zene (I), 7.85 g (2.25 X mol) in diethyl ether, 20 ml. 
The reaction was allowed to proceed for 12 hours at 25" 
C. in anhydrous conditions. The solvent was removed 
under reduced pressure and the residue was heated at 
80" C. and 0.05 mm Hg to remove unreacted starting 
material. A subsequent increase in temperature to 120" 
C. brought about the volatilization and condensation of 
11. Recrystallization of this compound from heptane 
yielded a substance melting at 133" C., which was iden- 
tified as phenylcarboranyl-pentachlorocyclotriphos- 
phazene (11) by elemental microanalysis, infrared, mass 
spectrometric, and NMR techniques. A single-crystal 
X-ray structure determination confirmed the structure. 
All features of the molecule were identified, including 
the hydrogen atoms attached to the boron atoms. 
EXAMPLE 2 
The preparation of Example 1 was repeated with 
methyl-o-carborane instead of phenyl-o-carborane, and 
yielded methylcarboranylpentachlorotriphosphazene 
(11), a compound with a melting point of 93" C. Again, 
the structure was deduced by elemental microanalysis, 
infrared, mass spectrometric, and NMR techniques. 
EXAMPLE 3 
Phenylcarboranylpentachlorotriphosphazene (11), 
1.00 g (1.87x lO-3mol), was dissolved in dry THF (15 
4 
ml), and treated with a solution of sodium trifluoroe- 
thoxide, 3.42 g (2.80x 10-2mol), in T H F  (20 ml) for 28 
hours at 66" C. The mixture was then neutralized to 
litmus with concentrated hydrochloric acid and the 
product was isolated by extraction with benzene and 
dried over MgS04. Upon filtration and removal of the 
solvent, the oily product I11 was obtained. Analysis of 
the oily material thus obtained by I.R., NMR and mass 
spectrometric techniques showed that all five chlorine 
atoms on the triphosphazene had been replaced by tri- 
fluoroethoxy groups (CF3CH20-) to yield phenylcar- 
boranylpentatrifluoroethoxycyclotriphosphazene (111). 
EXAMPLE 4 
10 
15 
The phenylcarboranylcyclopentachlorotriphospha- 
zene monomer (11) of Example 1 was polymerized by 
20 heating in an evacuated pyrex tube at 250" C. for 120 
hours. The polymeric product (IV), 1.00 g (1.87X 10-3 
mol), was subjected to chlorine replacement by reacticn 
with sodium trifluoroethoxide, 1.71 g (1.40x 10-2 mol), 
25 in boiling tetrahydrofuran, 40 ml, for a period of 120 
hours, to yield the fluoroethoxy-substituted polymer 
(V). The product was concentrated and neutralized to 
litmus with HCI. The precipitate was filtered off, 
washed with water and dried. The high polymers were 
30 obtained by fractional precipitation of a T H F  solution 
of the products into hexane and benzene to give V. 
Infrared, microanalytical, and NMR data obtained were 
compatible with the structure shown for V. Gel perme- 
35 ation chromatography gave a molecular weight of 
Thermographic analysis with a duPont Model 990 
thermoanalyzer was carried out on a sample of the 
40 polymer at a heating rate of 2" C. per minute to a tem- 
perature of 1000" C. in nitrogen. Some loss of weight 
was observed, principally between 250" and 550" C., but 
a char yield of 56.5% of the original sample weight 
45 remained at 1000" C. A parallel test of the material in air 
showed a substantially similar decomposition curve and 
produced a char yield of 53.0%. The polymer therefore 
appears to be resistant to oxidation at high tempera- 
tures. For comparison purposes, a conventional poly(- 
bis-trifluoroethoxy)phosphazene, i.e. the basic polymer 
without carboranyl substituents, underwent rapid 
weight loss commencing at about 280" C. and was com- 
pletely volatilized at 400" C. when tested under the 
1 x 105. 
50 
55 same conditions in nitrogen. 
EXAMPLE 5 
On repeating the polymerization procedure described 
60 in Example 4 with the methylcarboranylcyclopenta- 
chlorotriphosphazene of Example 2, there was obtained 
a polymer with a molecular weight of 1 X 106, as deter- 
mined by the gel permeation chromatographic tech- 
65 nique. 
We claim: 
I. A carboranylphosphazene polymer having the 
formula 
4,288,5 85 
5 
about 9 carbon atoms, chlorinated aryl radicals contain- 
ing up to about 9 carbon atoms, and mixtures thereof. 
2. The polymer of claim 1 wherein R1, R2 and R3 
stand for the CF3CH2- group and R is methyl or 
~ jRI ~ I k B , o H , o j  ~ 5 phenyl. 3. A process for the preparation of carboranylphos- 
phazene polymers, which comprises: 
(a) allowing to react at about ambient temperature for 
OR2 II OR3 b "  a period of up to about 12 hours, about equimolar 
quantities of a halocyclotriphosphazene and a lith- 
ium carborane dissolved in an anhydrous inert 
organic solvent, 
(b) insolating the resulting carboranylpentahalocy- 
clotriphosphazene, and 
about 250" C. for about 120 hours in the absence of 
oxygen and moisture. 
4. The process of claim 3 wherein the halocyclot& 
N=P N=P 
10 
wherein the ratio of a to b is about 2:l; n is an integer 
such that the molecular weight of the polymer is within 
the range of about 1 x lo5 to 1 X 106; R is selected from 
about 6 carbon atoms, and aryl radicals of up to about 9 
carbon atoms; R1, R2, and R3 are selected from the class 
consisting of alkyl radicals containing UP to about 6 
carbon atoms, fluorinated alkyl radicals containing up 
the consisti% of alkyl Of to 15 (c) polymerizing said triphosphazene by heating at 
phosphazene is the hexachloro homolog. 
to about 6 carbon atoms, aryl radicals containing up to 20 * * * * *  
25 
30 
35 
40 
45 
6 
50 
55 
60 
65 


Carboranylcyclotriphosphazenes and their polymers

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server