Polyphenylquinoxalines are produced by an aromatic nucleophilic displacement reaction involving an activated aromatic dihalide with an appropriate quinoxaline monomer. Polyphenylquinoxalines are high temperature thermoplastics used as adhesives, coatings, films and composite matrices. The novelty of this invention is threefold: (1) some of the quinoxaline monomers are new compositions of matter; (2) the phenylquinoxaline polymers which are the end products of the invention are new compositions of matter; and (3) the method of forming the polymers is novel, replacing a more costly prior art process, which is also limited in the kinds of products prepared therefrom

Connell, John W.

Hergenrother, Paul M.

English

NASA Technical Reports Server

NASA CASE NO.
PRINT FIG.
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NOTICE
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https://ntrs.nasa.gov/search.jsp?R=19890002443 2020-03-20T05:56:55+00:00Z
POLYPHENYLQUINOXALINES VIA AROMATIC NUCLEOPHILIC 
DISPLACEMENT 
AWARDS ABSTRACT 
NASA Case NO. LAR 13988-1 
According to this invention, polyphenylquinoxalines are produced 
by an aromatic nucleophilic displacement reaction involving an 
activated aromatic dihalide with an appropriate quinoxaline 
monomer. Polyphenylquinoxalines are high temperature 
thermoplastics used as adhesives, coatings, films and composite 
matrices. 
The novelty of this invention is threefold: 
1, Some of the quinoxaline monomers are new compositions of 
matter. 
2. The phenylquinoxaline polymers which are the end 
products of the invention are new compositions of matter. 
3. The method of forming the polymers is novel, replacing a 
more costly prior art process, which is also limited in the kinds 
of products prepared therefrom. 
Inventors: Paul M e  Hergenrother John W. Connell 
Address: 304 Old Dominion Road 827 Forrest Drive. # 2 6  
Yor 92 
ss: 
Employer : NAS 
~nitial Evaluator: Terry L. St.Clair 
Serial No. : 250,661 
Filed: September 28, 1988 
ss: 
!5
10
15
2O
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LAR 13988-1 -I-
POLYPHENYLQUINOXALINES VIA AROmaTIC NUCLEOPHILIC
DISPLACEMENT
PATENT
Origin of Invention
The invention described herein was made by employees of
the United States Government and may be manufactured and
used by or for the Government for governmental purposes
without payment of any royalties thereon or therefor.
Background of Invention
Polyphenylquinoxalines are high temperature thermo-
plastics which exhibit excellent performance as adhesives,
coatings, films and composite matrices. These materials are
heterocyclic polymers synthesized by the condensation
reaction of a bis(phenyl-u-diketone) with an aromatic
bis(o-diamine).
Schematically, this may be represented in Equation I:
0 0 0 0
solvont
30
Polyphenylquinoxalines prepared from such condensations
are configurationally unordered with three possible isomers
distributed randomly along the polymer chain; see
Hergenrother, Encyclopedia of Polymer Science Technology,
Vol. 13, p. 55, (1988).
35 As a direct result of the use of the condensation
reaction to synthesize polyphenylquinoxalines, there are
several limitations.
First, because the polyphenylquinoxalines are not
configurationally ordered, their mechanical properties (as
40 evidenced for example by tensile modulus) and strength are
i0
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25
30
35
40
LAR 13988-1 -2- PATENT
limited, and the resultant lack of crystallinity renders
them subject to attack by chlorinated organic solvents.
Second, the bis(phenyl-u-diketones) required for
polyphenylquinoxaline formation are relatively difficult to
prepare and expensive.
Third, the structure of polyphenylquinoxaline is
difficult to vary.
Thus, it is an object of this invention to prepare
configurationally ordered polyphenylquinoxalines, in order
to improve strength and resistance to attack by organic
solvents.
It is a further object to devise a means of preparing
polyphenylquinoxaline, either configurationally ordered or
not, by a means other than the bis(phenyl-u-diketone)/
bis(_-diamine) condensation, so that the use of expensive
bis(phenyl-u-diketones} may be avoided and so that the
polyphenylquinoxaline structure can be more readily and
conveniently varied.
Summary of Invention
The objects of this invention are obtained by (i)
forming di(hydroxyphenyl)quinoxaline monomers (a) by the
condensation of 2 moles of a hydroxybenzil with an aromatic
bis(o-diamine) as represented in Equation If:
Isolvent
N/r_H ON
HO
H 2H _Ar,/N H !
4.
H2N / _NH I
Eq.X
where Ar is 1,2,4,5-tetrasubstituted benzene, 3,3',-
4,4'-tetrasubstituted; biphenyl, diphenylether, diphenyl-
methane, diphenylketone, diphenylsulfone, diphenylthioether
or any appropriate bis(_-diamine} and mixtures thereof. The
catenation of the hydroxy group may be meta-meta, para-para,
or para-meta.
LAR 13988-1 -3- PATENT
5
I0
15
Alternatively, the di(hydroxyphenyl) quinoxaline
monomers are formed (b) by the condensation of a
dihydroxybenzil with an aromatic _-diamine, which may be a
substituted o-diamine, as represented in Equation III:
HzN- V "Z
I solvent
heat
HO_ OH
2O
25
38
35
40
where Z = H, CI, Br, OCH 3, CH 3, CH2CH 3, or Ph. The
catenation of the hydroxy group may be meta-meta, para-para,
or para-meta.
More complex dihydroxybenzils may be used, producing
correspondingly more complex phenylquinoxaline monomers, as
represented in Equation IV:
o o II II oN
.o ___ c-c .'
H3N - _,_
l so|ven!
heal
In the case where Z is
isomers.
(2) Polyphenylquinoxalines are produced by the
aromatic nucleophilic displacement reaction of a phenyl
quinoxaline monomer (described above) with an activated
aromatic compound of the following structure:
_OH
.o_ hN N
H, there are no configurational
LAR 13988-1 -4- PATENT
5
i0
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20
where X is selected from th_ group in Equations V and VI:
0 0 0 0
,,A, _L Ll_ 80Z, _C C-- ,' -V-
and where Y is F, CI, or NO 2.
The polyphenylquinoxaline synthesis and product
structure may be represented below, in its two main
variants:
ae
alkali metal base
solvent
r_
heat
where Ar is:
25
30
z z
35
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LAR 13988-1 -5- PATENT
b.
solvent
alkali metal base
host
15
Y is F, Cl, or NO 2,
R is nil, SO 2, CO, O, S, C(CH 3)2, C(CF 3)2, or CH 220
where
and
X is: C=O, SO 2 ,
25
o0 o
30-.
35
40
Where the di(hydroxyphenyl)quinoxaline monomers have
structural isomers, the resultant polyphenylquinoxaline is
not configurationally ordered, but the polyphenyl-
quinoxalines are new and have excellent properties.
Where the di(hydroxyphenyl}quinoxaline monomers have no
structural isomers, the resultant polyphenylquinoxaline is
configurationally ordered; certain of these polyphenyl-
quinoxalines are semi-crystalline.
The configurationally ordered polyphenylquinoxalines
are insoluble in polar aprotic solvents such as
510
15
LAR 13988-1 -6- PATENT
N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl-
sulfoxide, and are insoluble in chlorinated hydrocarbons
such as methylene chloride, chloroform and tetra-
chloroethane. Thin films of representative
configurationally ordered polyphenylquinoxalines were
immersed in hydraulic fluid for 24 hours and chloroform for
one hour, after which no noticeable swelling or crazing was
observed.
Detailed Description of Invention
Having generally described the invention, a more
complete understanding thereof can be obtained by reference
to the following specific examples which are provided herein
for purposes of illustration only and do not limit the
invention.
20
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EXAMPLES
Example ,1
The following Example illustrates the reaction sequence
for the synthesis of the polyphenylquinoxaline where Y = F,
R = nil and X is:
see Equation VI.
0 "_, •
35
40
Monomer Synthesis -
6,6'-bis[2-(4-hydroxyphenyl}-3-phenylquinoxaline] and
isomers: Into a 250 ml round bottom flask equipped with a
magnetic stirrer and reflux condenser was placed
4-hydroxybenzil (6.23 g, 0.0274 mol), 3,3'-diaminobenzidine
(2.94 g, 0.0137 mol), absolute ethanol (30 ml) and benzene
(30 ml}. The mixture was stirred at room temperature for
one hour, then refluxed overnight. The solution was cooled
and the yellow solid was filtered, washed with water and
dried at 1000C for three hours. Yield 7.94 g (98%), m.p.
LAR 13988-1 -7- PATENT
• 360oc. Anal. Calcd. for C40H26N402: C, 80.79%; H, 4.41%;
N, 9.42%. Found: C, 80.56%; H, 4.22%; N, 9.48%.
I0
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30-
35
Polyphenylquinoxaline Synthesis - Into a 250 ml three neck
round bottom flask equipped with a mechanical stirrer,
thermometer, nitrogen inlet, moisture trap, and reflux
condenser was placed 1,3-bis(4-fluorobenzoyl}benzene (1.9339
g, 0.006 mol}, 6,6'-bis[2-(4-hydroxyphenyl)-3-phenyl-
quinoxaline] and isomers (3.5678 g, 0.006 mol) powdered
anhydrous potassium carbonate (1.90 g, 0.0138 mol),
N,N-dimethylacetamide (40 ml) and toluene (25 ml}. The
mixture was heated to 135°C for three to four hours to
remove water, toluene was removed from the system and the
temperature was increased to 155°C overnight. The polymer
was isolated by precipitation into water/acetic acid
mixture, washed successively with water and methanol and
dried. Yield 5.1g (97%} of off-white polymer with an
inherent viscosity of 1.09 dL/g and a glass transition
temperature of 240°C. Thin films cast from m-cresol
solution gave tensile strength, tensile modulus and
elongation at 25°C of 11,500 psi, 353,000 psi and 7.7% and
at 177°C of 6550 psi, 250,000 psi and 65 percent
respectively.
Example 2
The following Example illustrates the reaction sequence
for the synthesis of a semi-crystalline polyphenyl-
quinoxaline where Y is F, X is
and Ar is
o
and Z is H. See Equation V.
40
510
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LAR 13988-1 -8- PATENT
Monomer Synthesis - 2,3-bis(4-hydroxyphenyl)-
quinoxaline: Into a 250 ml round bottom flask equipped with
a magnetic stirrer and reflux condenser was placed 1,2-
diaminobenzene (2.3275 g, 0.0215 mol), 4,4'-dihydroxybenzil
(5.2135 g, 0.0215 mol) and absolute ethanol (30 ml). The
solution was stirred for one-half hour at room temperature,
and a yellow precipitate formed. The mixture was heated to
reflux overnight. The solvent was removed by vacuum
distillation and the solid dried at 100°C for two hours to
give 6.6 g (97%) of yellow powder. The material was
recrystallized from 1,4-dioxane/water mixture. Yield 6.0 g
(89%) m.p. 336°C-338°C. Anal. Calcd for C20H14N202 : C,
76.42%; H, 4.49%; N, 8.91%. Found: C, 76.54%; H, 4.44%;
N,8.96%.
Polyphenylquinoxaline Synthesis - Into a 100 ml three
neck round bottom flask equipped with a mechanical stirrer,
thermometer, nitrogen inlet, moisture trap and reflux
condenser was placed 1,4-bis (4-fluorobenzoyl) benzene (1. 4604
20
g, 0. 0045 tool), 2,3-bis (4-hydroxyphenyl) quinoxaline (1. 4243
g, 0.0045 mol), powdered anhydrous potassium carbonate (1.45
g, 0.0104 mol}, N,N-dimethylacetamide (19 ml} and toluene
(20 ml). The mixture was heated to 135°C for three hours to
remove water, then increased to 155"C overnight. The
polymer had precipitated from solution overnight during the
synthesis. The mixture was poured into acetic acid/water to
give a white powder which was subsequently washed with water
and then methanol and dried at 100"C. Yield 2.6 g (97%) of
white polymer with a glass transition temperature of 208°C
30 _
and a crystalline melt temperature of 365°C. The inherent
viscosity of a 0.5 percent solution in m-cresol measured at
25°C was 0.83 dL/g. A thin film cast from m--cresol was
determined to be semi-crystalline by wide angle X-ray
diffraction.
35
Example 3
40
The following Example illustrates the reaction sequence
for the synthesis of a semi-crystalline polyphenyl-
quinoxaline where Y is F, X is SO 2 and Ar is
LAR 13988-1
See Equation V.
-9- PATENT
10
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Monomer S_nthesis - 1,3-bis[2-quinoxalyl-3-(4-hydroxy-
phenyl)]benzene. Into a 250 ml round bottom flask equipped
with a magnetic stirrer and reflux condenser was placed
1,3-bis(4-hydroxyphenylglyoxylyl)benzene (5.1412 g, 0.0137
mol), 1,2-diaminobenzene (2.9705 g, 0.0274 mol) and absolute
ethanol (45 ml). The solids dissolved rapidly to give an
orange solution, and after 15 minutes a yellow precipitate
formed. The mixture was diluted with absolute ethanol (125
ml} and refluxed overnight. The mixture was poured into
water, collected and dried to give 7.0 g (98%) of yellow
solid. The solid was recrystallized from ethanol/water
(5:1) mixture to give yellow needles, m.p. 339"C-343°C.
25
30_
35
40
Pol_phenylquinoxaline Synthesis - Into a 100 ml three
neck round bottom flask equipped with a mechanical stirrer,
thermometer, nitrogen inlet, moisture trap and reflux
condenser was placed 4,4'-difluorodiphenyl sulfone (1.2712
g, 0.005 mol), 1,3-bis[2-quinoxalyl-3-(4-hydroxyphenyl)]
benzene (2.5927 g, 0.005 mol), powdered anhydrous potassium
carbonate (1.6 g, 0.0115 mol), N,N-dimethylacetamide (20 ml)
and toluene (35 ml}. The mixture was heated to 135°C for
three to four hours to remove water, then increased to 155°C
overnight. The polymer had precipitated from solution
overnight during the synthesis. The mixture was poured into
acetic acid/water to give an off-white powder which was
subsequently washed with water and then methanol and dried
at 100"C. Yield 3.55 g (99%} of polymer with a glass
transition temperature of 235°C and a crystalline melt
temperature of 388"C. The inherent viscosity of a 0.5
percent solution in m-cresol measured at 25"C was 0.24 dL/g.
LAR 13988-1 -10- PATENT
Polymer characterization is presented in Tables 1 and 2
below.
10
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TABLE 1
POLYMER CHARACTERIZATION
R x Zac '"
nil SO2 0.90 283
nil CO 0.80 252
nil isophthaloyl 1.09 240
CO S02 0.69 268
CO CO 1.30 253
CO terephthaloyl 1.01 255
CO isophthaloyl 0.61 235
0 S02 0.34 240
0 terephthaloyl 0.45 226
0 isophthaloyl 0.46 213
Q
Inherent viscositiesin IIPcresolat 0.5% concentration(w/v) at 25'C.
**Determined by differentialscanning¢alorimeWat 20'Clmin.
25
0...
35
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LAR 13988-1 -11- PATENT
5
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TABLE 2
POLYMER CHARACTERIZATION
]Ii.._ I0 "c'"
0.54 240
0.58 209
0.83 2os (Tin. 365)
0.50 179
CO 0.52 179 (Tm- ST/)
80_ 0.24 235 (Ten.3ee)
30"-. dsoos_sinm.o.solw 0.5%concontra_on(w/v)ad25"C.
.DeummimSW eMmnUlmmener.m'mwYmZ°'C'mm"
35
40
What is claimed as new and desired to be secured by
Letters Patent of the United States is:
LAR 13988-1 PATENT
5
POLYPHENYLQUINOXALINESVIA AROMATICNUCLEOPHILIC
DISPLACEMENT
Abstract of Disclosure
Polyphenylquinoxalines are prepared by the nucleophilic
displacement reaction of di (hydroxyphenyl} quinoxaline
monomers with activated aromatic dihalides or dinitro
i0
compounds. The reactions are carried out in polar aprotic
solvents using alkali metal bases at elevated temperatures
under nitrogen. The di(hydroxyphenyl)quinoxaline monomers
are prepared either by reacting stoichiometric quantities of
aromatic bis(o-diamines} with a hydroxybenzil or by reacting
15
o-phenylenediamine with a dihydroxybenzil or
bis (hydroxyphenylglyoxylyl) benzene.
20
25
0 ,..
35
40


Polyphenylquinoxalines via Aromatic Nucleophilic Displacement

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