NASA CASE NO.

PRINT FIG.

tI .

NOTICE

The invention disclosed in this document resulted from

research in aeronautical and space activities performed under

programs of the National Aeronautics and Space Administration.

The invention is owned by NASA and is, therefore, available for

licensing in accordance with the NASA Patent Licensing

Regulation (14 Code of Federal Regulations 1245.2).

To encourage commercial utilization of NASA-owned inventions,

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Address inquiries and all applications for license for this

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available from the above address.

(bASA-Ca_e-L_-13S88-1}

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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 Me Hergenrother John W. Connell 

Address: 304 Old Dominion Road 827 Forrest Drive. #26 

Yor 92 

ss: 

Employer : NAS 

~nitial Evaluator: Terry L. St.Clair 

Serial No. : 250,661 

Filed: September 28, 1988 

ss: 
!

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LAR 13988-1 -IPOLYPHENYLQUINOXALINES 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 thermoplastics 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
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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, diphenylmethane, 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

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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

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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_ Nh N

H, there are no configurational
LAR 13988-1 -4- PATENT

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where X is selected from th_ group in Equations V and VI:

0 0 0 0

,,A, _L L l_ 80Z, _C C-- ,

' -Vand 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:

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z z

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LAR 13988-1 -5- PATENT

b.

solvent

alkali metal base

host

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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 2 20

where

and

X is: C=O, SO 2 ,

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o

0 o

30-.

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Where the di(hydroxyphenyl)quinoxaline monomers have

structural isomers, the resultant polyphenylquinoxaline is

not configurationally ordered, but the polyphenylquinoxalines 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 polyphenylquinoxalines are semi-crystalline.

The configurationally ordered polyphenylquinoxalines

are insoluble in polar aprotic solvents such as
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LAR 13988-1 -6- PATENT

N,N-dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide, and are insoluble in chlorinated hydrocarbons

such as methylene chloride, chloroform and tetrachloroethane. 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.

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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 "_, •

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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%.

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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-phenylquinoxaline] 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 polyphenylquinoxaline where Y is F, X is

and Ar is

o

and Z is H. See Equation V.

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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.

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Example 3

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The following Example illustrates the reaction sequence

for the synthesis of a semi-crystalline polyphenylquinoxaline where Y is F, X is SO 2 and Ar is
LAR 13988-1

See Equation V.

-9- PATENT

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Monomer S_nthesis - 1,3-bis[2-quinoxalyl-3-(4-hydroxyphenyl)]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.

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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.

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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.

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LAR 13988-1 -11- PATENT

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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"

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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.

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0 ,..

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