Preparation of aryl compounds containing carboxyl and sulfonyl groups

Novel aryl ethers, containing both a carboxylic acid and a sulfonic acid functionality; and a process for making them are described. These difunctional aryl compounds comprise: PA0 i) a carboxylic acid group or its derivative, PA0 ii) a first aromatic group bonded to the carboxylic acid or its derivative, PA0 iii) a second aromatic group linked to the first aromatic group by a non-electron-withdrawing moiety, PA0 iv) a third aromatic group linked to the second aromatic group by a non-electron-withdrawing moiety, and PA0 v) a sulfonyl group or its derivative bonded to the third aromatic group.

BACKGROUND OF INVENTION 
This invention relates to the art of reactive difunctional acid compounds. 
Polybenzazole ("PBZ") polymers, such as polybenzoxazole ("PBO"), 
polybenzimidazole ("PBI") or polybenzothiazole ("PBT"), are a known class 
of polymers which are typically formed and fabricated in strongly 
dehydrating protic acid solvents. See e.g. Wolfe et al., Liquid 
Crystalline Polymer Compositions, Processes and Products, U.S. Pat. No. 
4,533,693 (Aug. 6, 1985) and 11 Ency. Poly. Sci. & Eng., 
Polybenzothiazoles and Polybenzoxazoles, 601 (J. Wiley & Sons 1988). 
In order to modify the properties of the PBZ polymers so that they will 
function adequately for various end use applications it is desirable to 
make copolymers of PBZ's and thermoplastic polymers. One such 
thermoplastic polymer is a polyarylethersulfone. See e.g. International 
Publication No. W090/03995 entitled Copolymers Containing Polybenzoxazole, 
Polybenzothiazole and Polybenzimidazole Moieties. 
A strongly protic acid solvent/initiator medium is usually required for any 
type of polymerization with PBZ monomers, because PBZ polymers and 
copolymers require such an environment in order to react and remain in 
solution once formed. Therefore, in order to make copolymers of PBZ it is 
required that all reagents must be able to function in a strong protic 
acid solvent system. 
Heretofore, such copolymers of PBZ's have been difficult, if not impossible 
to prepare, because of the lack of known reagents that were capable of 
reacting and remaining in solution in the strongly protic acid solvents 
required. 
SUMMARY OF THE INVENTION 
One aspect of the present invention is a difunctional aryl compound 
comprising: 
1. a carboxylic acid group or its derivative, 
2. a first aromatic group bonded to the carboxylic acid or its derivative, 
3. a second aromatic group linked to the first aromatic group by a 
non-electron-withdrawing moiety, 
4. a third aromatic group linked to the second aromatic group by a 
non-electron-withdrawing moiety, 
5. a sulfonyl group or its derivative bonded to the third aromatic group. 
A second aspect of the present invention is a process to prepare the above 
described difunctional aryl compound by reaction of methyl 
4-(4-phenoxyphenoxy) benzoate with a sulfonating agent under conditions 
such that the above described difunctional aryl compound is formed. 
A third aspect of the present invention is a process for synthesizing a 
polymer comprising the step of contacting the compound of the present 
invention or a dimer of that compound with at least one comonomer having a 
plurality of decoupled nucleophilic aromatic rings in a dehydrating protic 
acidic medium under conditions suitable to initiate Friedel-Crafts 
polymerization. 
The difunctional aryl compound which forms the first aspect of the present 
invention is synthesized by the process of the second aspect of the 
present invention. The difunctional aryl compounds are useful in forming 
copolymers such as those prepared by the third aspect of the present 
invention. The copolymers formed via the process of the third aspect of 
the present invention can be formed into useful shaped articles such as 
fibers and films. These fibers and films can then be used in items such as 
composites and laminates to impart desirable properties to those 
composites and laminates.

DETAILED DESCRIPTION OF THE INVENTION 
The difunctional aryl compounds of this invention contain aromatic groups. 
These aromatic groups include any aromatic group capable of being attached 
to either a carboxylic acid group or its derivative, a sulfonyl group or 
its derivative or a non-electron-withdrawing moiety. Each aromatic group 
may be polycyclic but each is preferably monocyclic. Each aromatic group 
is preferably carbocyclic and more preferably hydrocarbocyclic. Each 
aromatic group preferably contains no more than one substituent, in order 
to minimize steric hindrance about reactive sites. It is more preferably 
unsubstituted. However, when desired, aromatic groups with multiple 
substituents can be selected for inclusion in the compound in order to 
have substituents already present on locations on the individual aromatic 
group where aromatic electrophilic substitution is unwanted. Examples of 
preferred aromatic groups include divalent groups such as arylene, e.g., 
phenylene, naphthenylene and biphenylene. A phenylene group is the most 
preferred aromatic group in the present invention. 
Non-electron-withdrawing moieties connect the aromatic groups in the 
present invention. By "non-electron-withdrawing" it is meant an electron 
donating or a neutral group. The carboxylic acid group and the sulfonic 
acid group in the diacid compound deactivate each other with respect to 
Friedel-Crafts reactions in protic acid solutions. The 
non-electron-withdrawing moieties decouple the two acid groups and shields 
them from deactivation or minimizes their deactivation. Deactivation and 
decoupling are described in further detail in the two articles written or 
co-written by H. M. Colquhoun entitled, "Synthesis of Aromatic 
Polyetherketones in Trifluoromethanesulphonic Acid" as printed on pp. 
1902-1908 of Polymer, Vol. 29, October 1988 and "Synthesis of 
Polyetherketones in Trifluoromethanesulphonic Acid: Some Structure 
-Reactivity Relationships", as printed on pp. 17-18, of ACS Polymer 
Preprints, Vol. 25(2), 1984 which are incorporated herein by reference. 
These articles discuss in detail the considerations that must be given to 
selecting non-electron-withdrawing moieties with care, to enable desired 
reactions in compounds that contain aromatic groups linked together by 
linking groups. Suitable non-electron-withdrawing moieties comprise, for 
example, a bond or a sulfur atom (thioether) or an oxygen atom (ether 
linkage). The non-electron-withdrawing moiety may further comprise an 
aromatic group and a second ether or thio-ether linkage. A preferred 
non-electron-withdrawing moiety is an oxygen atom (an ether linkage). 
The non-electron-withdrawing moieties can be attached to the aromatic 
groups in any position. It is preferred that they are attached in a para 
position with respect to each other. The para isomers react better, 
leading to less side-reactions, than do the others. 
A carboxylic acid group or its derivative and a sulfonyl group or its 
derivative are attached to different aromatic groups in the difunctional 
aryl compound. The carboxylic acid group or its derivative and the 
sulfonyl group or its derivative are useful for reacting with other 
comonomers to form copolymers. The derivative of the carboxylic acid group 
or the sulfonyl group can be an acid halide, a lower alkyl (C.sub.1 
-C.sub.6) ester (preferably a methyl, ethyl, propyl or butyl ester), an 
amide, an aryl ester, or a corresponding thioester. The preferred 
derivative is the acid halide, such as an acid chloride, acid bromide or 
acid iodide, and the preferred acid halide is the acid chloride. The 
derivative of the carboxylic acid group and the derivative of the sulfonyl 
group may be, but do not have to be, identical in the same difunctional 
aryl compound. 
The carboxylic acid or its derivative and the sulfonyl group or its 
derivative are attached to different aromatic groups in any position 
relative to the non-electron-withdrawing moieties that connect the 
aromatic groups. It is preferred that they are attached in the para 
position relative to the non-electron-withdrawing moieties so that the 
structure of the difunctional aryl compound is primarily linear. The 
primarily linear structure of the difunctional aryl compound is important 
so that copolymers made with the difunctional aryl compound are also 
primarily linear. A linear structure in these copolymers is important so 
that it is possible to construct copolymers with long chains, leading to 
high molecular weight copolymers. A high molecular weight is a desired 
feature of these copolymers. 
The diacid compounds of the present invention are preferably represented by 
the formula: 
##STR1## 
wherein Each Ar is independently a divalent aromatic group, 
each D is independently a non-electron-withdrawing moiety, 
n is 2 or more, and 
each Y is independently --OH, --Cl, --Br, I, NH.sub.2 
or OR, where R=a lower alkyl group (C.sub.1 -C.sub.6) or an aryl group. 
A general method for manufacturing these difunctional aryl compounds is to 
add a sulfonating agent to a starting material such as methyl 
4-(4-phenoxyphenoxy) benzoate under conditions such that the sulfonyl 
group is attached to an aromatic group different from the aromatic group 
to which the methyl ester is attached. 
Sulfonyl groups can be added at any unsubstituted position on any aromatic 
group in the methyl phenoxyphenoxybenzoate ester compound. It is most 
preferred that the sulfonyl group is attached to the third aromatic group 
at the para position to the nearest non-electron-withdrawing moiety. 
Reactions at the 2,3,5 or 6 positions of the aromatic groups can be 
minimized by controlling the stoichiometry of the reactants in the 
sulfonating reaction as mentioned in the article by Ueda entitled, 
"Synthesis of Poly(phenylene ether sulfone) by Direct 
Self-polycondensation of Sodium 4-phenoxybenzenesulfonate Using Phosphorus 
Pentoxide/Methanesulfonic Acid as Condensing Agent and Solvent, " 
Makromol. Chem., Rapid Commun. 6, 271-274 (1985). 
Once it has been formed, the sulfonated methyl phenoxyphenoxybenzoate ester 
compound is then hydrolyzed using a mixture of base in alcohol and water 
followed by the addition of HCl which converts the base salts to the 
desired carboxylic acid and the sulfonic acid. The resulting 
(phenoxy-carboxylic-acid-phenoxy-sulfonic-acid-benzene) compound can be 
converted to the acid chloride derivative of the carboxylic acid group and 
the sulfonyl group by any of the standard methods known in the art to make 
an acid chloride. One such method is to react this material with thionyl 
chloride. 
The following formulae illustrate one example of the synthesis. 
1. Reaction of Starting Compound With Sulfonating Agent 
##STR2## 
2. Hydrolysis Reaction 
##STR3## 
3. Acid Chloride Reaction 
##STR4## 
4. Product 
##STR5## 
Even though chlorosulfonic acid is effective as the sulfonating agent in 
the first reaction of the preceding synthesis, it is anticipated that a 
wide variety of sulfonating agents, e.g., sulfur trioxide, or concentrated 
sulfuric acid, could be used to sulfonate the starting compound. 
Compounds of the present invention are useful for making polymers by a 
Friedel-Crafts type process. The compounds can be reacted with a comonomer 
that contains two aromatic groups linked by a suitable 
non-electron-withdrawing group. Exemplary comonomers include m- or 
p-diphenoxybenzene and 3- or 4-phenoxybiphenyl. This reaction may be 
carried out in an organic solvent in the presence of a Lewis Acid catalyst 
under known conditions. Preferably, however, the reaction is carried out 
in a dehydrating protic acid, such as polyphosphoric acid or a mixture of 
methanesulfonic acid and phosphorus pentoxide. The temperature is 
preferably at least about 25.degree. C. and more preferably at least about 
40.degree. C. It is preferably no more than about 100.degree. C. and more 
preferably no more than about 70.degree. C. Suitable comonomers and 
reaction conditions are described in the references of Colquhoun which are 
previously incorporated by reference. 
The compounds of the present invention may also be reacted to form a dimer 
before they are contacted with a comonomer in a polymerization reaction. 
For instance, two moles of the compound of the present invention may be 
reacted with one mole of: 4,6-diaminoresorcinol (hereinafter referred to 
as BB-PBZ monomer): 2,5-diaminohydroquinone: 
1,4-dithio-2,5-diaminobenzene: or an equivalent compound to form a dimer 
having two sulfonic acid groups or derivatives of sulfonic acid. 
Equivalent reagents are listed in U.S. Pat. No. 4,533,693 at Tables 1-3, 
which are incorporated herein by reference. 
Although all reactions of the difunctional acid compound described herein 
may take place in a mixture of methanesulfonic acid and phosphorus 
pentoxide, it is also possible for these reactions to take place in 
another mixture, e.g., AlCl.sub.3 in an appropriate Friedel Crafts solvent 
(nitrobenzene or ortho-dichlorobenzene) or other strong acids such as 
polyphosphoric acid or even trifluoromethane sulfonic acid. 
The step-by-step dimer reaction (first with BB-PBZ monomer, then with a 
comonomer) described above is depicted in the following reaction schemes. 
1. Reaction of diacid chlorode aryl compound with diaminoresorcinol 
dihydrochloride to form dimer 
##STR6## 
2. Polymerization Reaction 
##STR7## 
The following examples are given to illustrate the invention and should not 
be construed as limiting its scope. All parts and percentages are by 
weight unless otherwise indicated. 
EXAMPLE 1 Synthesis of the Diacid Aryl Compound 
A mixture of 9.00 g(28.1 mmol) of methyl 4-(4-phenoxyphenoxy) benzoate in 
150 mL of methylene chloride is cooled to 0.degree. C. under nitrogen 
atmosphere with stirring. A solution of 1.87 mL (3.27 g, 28.1 mmol) of 
chlorosulfonic acid in 50 mL of methylene chloride is added dropwise over 
a period of 15 minutes. The cooling bath is removed and the mixture is 
stirred for 14 hours. The precipitate is filtered, washed with 100 mL of 
methylene chloride and dried in air. It is mixed in a slurry with 120 mL 
of methanol, 60 mL of water, and 10.0 g of potassium hydroxide, and the 
slurry is refluxed for two hours. The cooled solution is quenched in 
aqueous HCl, filtered, washed with 100 mL of cold water, and dried in air. 
The product is recrystallized from 600 mL of a 5-1 by volume 
methanol-water solution and dried at 100.degree. C. under vacuum to yield 
10.84 g(91%) of 1-(phenoxy-4-carboxylic acid)-4-(phenoxy-4-sulfoniic acid) 
benzene which has the following structure. 
##STR8## 
EXAMPLE 2 Conversion of the Diacid Aryl Compound to the Diacidchloride of 
the Difunctional Aryl Compound 
A slurry of 10.00 g(25.9 mmol) of 1-(phenoxy-4-carboxylic 
acid)-4-(phenoxy-4-sulfonic acid) benzene in 250 mL of thionyl chloride 
and 0.50 mL of N,N-dimethylformamide is refluxed under nitrogen atmosphere 
for 16 hours with stirring. The slurry is cooled to 20.degree. C. and 
added to 3L of anhydrous n-hexane. The resulting precipitate is filtered, 
washed with n-hexane and dried under nitrogen atmosphere. It is stirred 
with 100 mL of anhydrous methylene chloride and filtered, and 900 mL of 
anhydrous n-hexane is added to the filtrate. The resulting solution is 
sealed and cooled to -15.degree. C. The product is filtered and dried 
under nitrogen atmosphere to yield 7.26 g (66 percent yield) of product. 
The product obtained can be converted to the dimethyl diester by refluxing 
with methanol under nitrogen atmosphere in anhydrous methylene chloride, 
if desired. 
EXAMPLE 3 Copolymerization of Difunctional Aryl Compound with Cis-PBO Dope 
A mixture of 0.30g(1.41 mmoles) of 4,6-diaminoresorcinol di(hydrogen 
chloride) and 1.84g(4.35 mmoles) of 
1-(4-chlorocarbonylphenoxy)-4-(4-chlorosulfonylphenoxy) benzene is stirred 
under nitrogen atmosphere. A 134.82-g solution containing a 10-1 mixture 
by weight of methanesulfonic acid and phosphorus pentoxide is added, and 
the mixture is warmed to 70.degree. C. for 2 hours. The temperature is 
raised to 90.degree. C. for 16 hours. A 25.00-g portion of dope was added 
containing polyphosphoric acid and about 14 weight percent cis-PBO 
polymer. The cis-PBO polymer dope is made according to the instructions 
contained in Example 1, pp. 135-137 of pending U.S. patent application 
Ser. No. 407,973, filed Sep. 15, 1989, Attorney Docket No. C-36,790C, and 
in Example 1, pp. 134-136 of International Publication No. W090/03995, 
Attorney Docket No. C-36,790C-F which are both incorporated by reference. 
The reaction of the PBO dope with the mixture of the title product and 
4,6-diaminoresorcinol di(hydrogen chloride) is continued for 48 hours at 
90.degree. C., and then cooled to 50.degree. C.. A 0.57-g(2.18 mmoles) 
portion of 1,4-diphenoxybenzene is added, followed by 88.60 grams of 10:1 
methanesulfonic acid:phosphorus pentoxide solution added in two portions 
30 minutes apart. The reaction is continued at 50.degree. C. for 72 hours. 
A small portion of the reaction product dope can be placed upon a 
microscope slide and quenched with water and dried in air to yield a film 
of good strength and integrity having no visible phase separation. 
A small quantity of the resulting block copolymer can be isolated as 
follows: it is coagulated in water, washed, dried, ground, rewashed and 
redried. This block copolymer has an inherent viscosity of 9.30 dL/g in 
methanesulfonic acid at 25.degree. C. and 0.05 g/dL concentration. 
EXAMPLE 4 Copolymerization of Difunctional Aryl Compound With 
p-Diphenoxybenzene 
In a N.sub.2 atmosphere 0.76g of 4,6-diaminoresorcinol dihydrochloride and 
3.00g of 1-(4-chlorocarbonylphenoxy)-4-(4-chlorosulfonylphenoxy) benzene 
are loaded into a 100 mL resin kettle which is sealed, transferred to a 
hood, and blanketed with N.sub.2. This mixture is mechanically stirred and 
warmed with thermoregulated oil bath. A 55.0g portion of methanesulfonic 
acid/phosphorus pentoxide (10/1) mixture is added to the reactor. The 
reactor is kept at 70.degree. C. for 2 hours under a N.sub.2 atmosphere, 
then the temperature is increased to 90.degree. C. and kept there for 16 
hours under a N.sub.2 atmosphere, then the reactor temperature is lowered 
to 50.degree. C. with a 0.93-gram portion of p-diphenoxybenzene then 
added, along with 25.1 grams of the 10/1 methanesulfonic acid/phosphorus 
pentoxide solution, and kept at 50.degree. C. for 48 hours under a N.sub.2 
atmosphere. At this point the reaction product becomes more viscous but it 
remains stirrable. 
The product, a polyetherbenzoxazole sulfone, is represented by the 
following formula: 
##STR9## 
The reaction product is then precipitated with water in a blender as a 
beige fibrous solid that powders. The product is collected, then 
re-slurried with a touch of aqueous NaOH, then recollected. The product is 
washed 3 times with deionized water and dried to a constant weight in a 
100.degree. C. vacuum oven. The single point intrinsic viscosity of the 
product was found to be 0.40 dL/gram in methanesulfonic acid at 
25.0.degree. C. 
EXAMPLE 5 Synthesis of Block Copolymer Containing Nonrigid Jointed PBO 
Sulfone Block and Poly (Aromatic Ether Sulfone) Thermoplastic Block 
Example 52 from pp. 180-183 of U.S. patent application Ser. No. 07/407,973 
entitled "Copolymers Containing Polybenzoxazole, Polybenzothiazole and 
Polybenzimidazole Moieties" assigned to The Dow Chemical Company is 
incorporated by reference.