A multiply-branched aliphatic-aromatic polyester and a method for producing that polymer. The method comprises condensing Z.sup.1 and Z.sup.2 groups of a branching reactant having the general formula Z.sup.1 --Ar--(Z.sup.2)j. In this formula, j is 2 or 3 and Ar is an aryl or heteroaryl group having from 1 to 3, solitary or linked or fused, substituted or unsubstituted, five or six membered rings. One of Z.sup.1 and Z.sup.2 is a group having the ##STR1## general formula in which R.sup.1 is selected from the group consisting of hydroxy, chloro, bromo, monovalent alkoxide having from 1 to about 6 carbons, and --O--(CH.sub.2).sub.d --OH, wherein d is an integer from 1 to 3; and the other is a group having the general formula ##STR2## in which R.sup.2 is a divalent alkyl group having from 1 to about 6 carbon atoms, and g is an integer from 0 to about 100.

BACKGROUND OF THE INVENTION 
The present invention pertains to processes for the preparation of highly 
branched polymers and aliphatic-aromatic polyesters. More particularly, 
the present invention pertains to multiply-branched polyesters and 
processes for the preparation of multiply-branched aliphatic-aromatic 
polyesters. 
Highly branched, non-crosslinked polymers have been prepared by "multiple 
generation" and "single generation" procedures. The multiple generation 
procedures are exemplified by Tomalia, D. A., et al., Angewandte Chemie, 
International Edition in English, 29, 138-175 (1990) and U.S. Pat, No. 
5,041,516 to Frechet, J. M. J. et al., which describe the preparation of 
highly branched, non-crosslinked polyamidoamines and polybenzyl ethers, 
respectively. Tomalia et al. identified the polymers produced as 
"starburst polymers" or "starburst dendrimers". Both publications describe 
preparations in which the macromolecules were prepared by repeatedly 
reacting, isolating and purifying a product through a series of growth 
steps. The product of each growth step is called a "generation". These 
procedures are highly laborious, but the product produced is highly 
uniform Newkome et al., Journal of the American Chemical Society, Vol. 
112, 8458, (1990) describes a similar step and repeat process used to 
build up various macromolecules described as tree-like and identified as 
"arborols". 
Single generation procedures are much less laborious than multiple 
generation procedures. The single generation procedures are exemplified by 
Flory, P. J., Journal of the American Chemical Society, 74, p. 2718 
(1952), which presents a theoretical analysis of the formation of highly 
branched, soluble polymers from monomers having the structure AB.sub.x, in 
which A and B are the reactive groups, by step-growth polymerization, with 
random branching and without cross-linking. Kim, Y. H. et al., Journal of 
the American Chemical Society, Vol. 112, p. 4592 (1990) and U.S. Pat. No. 
4,857,630 to Y. H. Kim, describe this kind of "single generation" approach 
in the preparation of hyperbranched polyphenylenes. U.S. Pat. No. 
3,669,939 to Baker, A. S. et al. teaches highly branched, non-crosslinked, 
aliphatic polyesters, prepared by a "single generation" melt condensation 
polymerization of monomers having a single carboxylic acid functionality 
and multiple alcohol functionalities. Hawker, C. J., Lee, R. and Frechet, 
M. J. M., Journal of the American Chemical Society, Vol. 113, No. 12, 
(1991) pp 4583-4588, teaches a single generation procedure for the 
preparation of all aromatic, highly-branched, non-cross-linked polyesters. 
In this procedure, 3,5-bis(trimethylsiloxy)benzoyl chloride is melt 
polymerized by the Kricheldorf method, described in H. R. Kricheldorf et 
al., Makromol. Chem. 184, 475 (1983), driving off trimethylsilylchloride. 
The product can be subjected to hydrolysis to provide phenolic terminated 
highly branched polyesters. This procedure has the shortcomings of 
requiring expensive, water-sensitive reactants and difficult monomer 
preparation steps. U.S. patent application No. 788,070, filed Nov. 11, 
1991, by S. Richard Turner et al., teaches the preparation of 
multiply-branched polyesters by reacting compounds having the general 
structure HOOC--Ar--(O--CO-alkyl)(2 or 3) or having the general structure 
alkyl-CO--O--Ar--(COOH)(2 or 3). The above-discussed all-aliphatic 
branched polyesters of Baker et al. and all-aromatic polymers of Hawker 
and Frechet et al. and Turner et al. have extremely divergent Tg's. The 
all-aliphatic polymers have very low Tg's, which limits use. temperatures. 
The all-aromatic polymers have very high Tg's, which makes melt 
condensation and various polymer processing procedures difficult. 
SUMMARY OF THE INVENTION 
The invention provides for highly-branched structures of high molecular 
weight having useful terminal groups and moderate Tg's in a useful range 
for melt condensation and polymer processing and has the advantages of not 
requiring multiple generations of reactions and purifications or the use 
of trimethylsilyl benzoic acid chlorides. 
The invention, in its broader aspects, provides a method for producing a 
multiply-branched polymer comprising condensing Z.sup.1 and Z.sup.2 groups 
of a branching reactant having the general formula Z.sup.1 
--Ar--(Z.sup.2)j. In this formula, j is 2 or 3 and Ar is an aryl or 
heteroaryl group having from 1 to 3, solitary or linked or fused, 
substituted or unsubstituted, five or six membered rings. One of Z.sup.1 
and Z.sup.2 is a group having 
##STR3## 
the general formula which R.sup.1 is selected from the group consisting of 
hydroxy, chloro, bromo, monovalent alkoxide having from 1 to about 6 
carbons, and --O--(CH.sub.2).sub.d --OH, wherein d is an integer from 1 to 
3; and the other is a group having the general formula 
##STR4## 
in which R.sup.2 is a divalent alkyl group having from 1 to about 6 carbon 
atoms, and g is an integer from 0 to about 100.

DESCRIPTION OF A SPECIFIC EMBODIMENT 
The method of producing multiply-branched aliphatic-aromatic polyesters of 
the invention utilizes a condensation of "AB.sub.x " monomer, in which "x" 
is 2 or 3. The AB.sub.x monomer, also referred to herein as "branching 
reactant", can be a single compound or mixture of two or more compounds. 
Each of the compounds in branching reactant has the general structure 
EQU Z.sup.1 --Ar--(Z.sup.2)j 
in which j=2 or 3, Z.sup.1 or Z.sup.2 is 
##STR5## 
and the other Z group has the general formula 
##STR6## 
In other words, the branching reactant is a compound or mixture of two or 
more compounds, all having the general structure R.sup.1 
--CO--Ar--((O--R.sup.2).sub.g --O--R.sup.2 OH)j or all having the general 
structure HOR.sup.2 --O--(R.sup.2 --O).sub.g --Ar--(COR.sup.1)j. 
R.sup.1 is selected from the group consisting of hydroxy, chloro, bromo, 
monovalent alkoxide having from 1 to about 6 carbons, and 
--O--(CH.sub.2).sub.d --OH, wherein d is an integer from 1 to 3. 
R.sup.2 is a divalent alkyl group having from 1 to about 6 carbon atoms, 
and g is an integer from 0 to about 100. 
Ar is an aryl or heteroaryl group having from 1 to 3, five or six membered 
rings. The rings are solitary or linked or fused. Ar can have additional 
substituents, so long as those substituents are unreactive, that is, 
substituents which do not have a deleterious effect, for example, 
condensation with Z.sup.1 or Z.sup.2 groups or steric hindrance or 
electronic deactivation of the condensation polymerization. For example, 
additional substituents cannot be hydroxyls, esters, aminos or sulfonic 
acids, since those groups would condense with Z.sup.1 or Z.sup.2. 
Acceptable substituents, which are not capable of reacting with Z.sup.1 or 
Z.sup.2 include: chloro; fluoro; cycloalkyl; and alkyl, alkoxy, and 
haloalkyl, all having from 1 to 4 carbons. The substituents on a ring, 
Z.sup.1 and Z.sup.2 groups and additional substituents, can be ortho or 
meta or para to each other. 
Linked rings can be joined by a linking group selected from the group 
consisting of --O--, --S--, 
##STR7## 
Each T.sup.1 is independently selected from the group consisting of alkyl 
and aryl, and d is an integer from 1 to about 6. Suitable --Ar-- groups 
include phenyl, naphthyl, anthracyl, phenanthryl, biphenyl, phenylether, 
diphenylsulfone, diphenylketone, diphenylsulfide, pyridine, quinoline, 
##STR8## 
T.sup.2 represents a group selected from aliphatic groups having from 1 to 
about 12 carbon atoms, and aryl groups having from 6 to about 24 carbon 
atoms. The total valence of each of these --Ar-- groups, that is, the 
number of bonds to Z.sup.1 and Z.sup.2 groups, indicated as unfulfilled 
bonds in the above aromatic residue structures, is 3 or 4, thus m.sup.1, 
m.sup.2 and m.sup.3 are each integers selected from 0 to 4 and m.sup.1 
+m.sup.2 +m.sup.3 (if any)=3 or 4. 
Repeating units for the embodiment of the invention disclosed herein, can 
be represented by the three structural formulas: 
##STR9## 
In these formulas, j, Ar and Z.sup.2 have the same meaning as above and Q 
is an ester linkage having the general formula: 
##STR10## 
For j=2, the latter two formulas are redundant and these j=2 repeating 
units bear either two ester linkages or a single ester linkage and an 
unreacted Z.sup.2 group. For j=3, these repeating units bear three ester 
linkages or two ester linkages and an unreacted Z.sup.2 group or one ester 
linkage and two unreacted Z.sup.2 groups. As the above repeating unit 
formulas indicate, condensation of Z.sup.2 groups of non-terminal 
repeating units is not complete and many non-branched Z.sup.2 groups 
remain unreacted after the condensation of the method of the invention. 
Termini or terminal repeating units have the general formula 
--Ar--(Z.sup.2). 
The terminal Z.sup.2 groups are thus either all 
##STR11## 
depending upon the embodiment of the invention. A single subunit in each 
macromolecule of the multiply-branched polyesters of the invention can 
bear an unreacted --Z.sup.1 group in place of an ester linkage. 
Repeating units in the polymers produced, except those at the ends, each 
have the --Ar-- residue bonded to an ester linkage, --Q--, which in turn 
is bonded to the next repeating unit. The order of the --O-- and carbonyl 
in each ester linkage, --Q--, depends upon Z.sup.1 and Z.sup.2. In an 
embodiment of the invention in which Z.sup.1 is --COR.sup.1 and Z.sup.2 is 
--(O--R.sup.2).sub.g --O--R.sup.2 OH, ester linkages have the order . . . 
--O--R.sup.2 --O--CO-- . . . --Ar--((O--R.sup.2).sub.g --O--R.sup.2 
OH).sub.j. This embodiment is represented by Example 1, which has the 
proposed reaction scheme: 
##STR12## 
in which represents the remainder of the macromolecule. 
In an embodiment of the invention in which Z.sup.1 is --(O--R.sup.2).sub.g 
--O--R.sup.2 OH and Z.sup.2 is --COR.sup.1, ester linkages have the order 
. . . --CO--(O--R.sup.2).sub.g --O--R.sup.2 --O-- . . . 
--Ar--(COR.sup.1).sub.j. This embodiment is represented by Example 2, 
which has the proposed reaction scheme: 
##STR13## 
in which represents the remainder of the macromolecule. 
For convenience, the branching reactant is generally discussed herein as an 
individual compound. Using an individual compound in the method of the 
invention produces a multiply-branched polymer which is analogous to a 
homopolymer, that is, although the repeating units in a macromolecule have 
the above-noted differences, each of those repeating units is derived from 
the same compound. The method of the invention is not limited to such 
"homopolymers". Mixtures of two or more compounds can be used as the 
branching reactant, to produce a multiply-branched polymer analogous to a 
copolymer. Relative percentages of the different compounds used can be 
varied. The compounds can differ in aromatic residues, in placement of 
Z.sup.1 and Z.sup.2 groups on aromatic residues, in R.sup.1 groups, in 
R.sup.2 groups, in values of m, in the number of Z.sup.2 groups or in a 
combination of these features. 
In a particular embodiment of the invention, the method of invention is 
limited to what can be referred to as a "self-condensation" of the 
branching reactant. The term "self-condensation" describes the 
condensation of subunits of the branching reactant with each other. Those 
subunits can be contributed by one compound or a mixture of compounds. In 
an alternative embodiment of the invention, the branching reactant is 
self-condensed and co-condensed with a non-branching reactant, which has 
the general structure Z.sup.1 --Ar--(Z.sup.2).sub.e, in which e is 0 or 1. 
If e is 0, the non-branching reactant provides "end-capping" repeating 
units which terminate branches of the multiply-branched polymer. If e is 
1, the non-branching reactant provides additional linear repeating units 
in the multiply-branched polymer. The end-capped termini and additional 
linear repeating units are, in effect, defects in that branching is 
reduced. Defects are desirably kept to a small percentage of repeating 
units. The polymers of the invention do not include a percentage of 
non-branching repeating units great enough to destroy multiple branching 
in the polymer and produce a polymer in which branches do not themselves 
also branch. 
It is necessary that a selected reactant polymerize under the reaction 
conditions employed. It is desirable that the reactants be sufficiently 
stable under the reaction conditions employed and that the reactants be 
free of groups which unduly retard the reaction by steric hindrance or 
other means. It is also desirable that the reactants not be subject to an 
unacceptable amount of undesirable side reactions, to prevent the 
formation of an unacceptable amount of by-product, for example, an 
unacceptable amount of linear repeating units. 
The exposed terminal groups of the multiply-branched aliphatic-aromatic 
polyesters can be reacted to modify the exposed terminal groups or attach 
other molecules to the termini or to cross-link the termini either within 
a polymer molecule or between polymer molecules. Suitable reactions are 
those of equivalent terminal groups of linear polyesters, such as: ester 
formation, amide formation, and urethane formation. Functional groups that 
can be thus provided as termini of the multiply-branched 
aliphatic-aromatic polyesters include: phenol; carboxylic acid; carboxylic 
acid chloride, perfluorinated aryl or alkyl; primary, secondary and 
tertiary amine groups; aryl halides such as --Cl, --Br, and --I; and 
benzyl chloride groups. Polymers can be joined to termini to provide star 
copolymers in which polymer arms are grafted to termini of the 
multiply-branched aromatic polyester core. Particularly convenient 
polymers for grafting are those having --OH, --NH.sub.2, --COOH, --Cl, 
--Br, and --I end groups, which can be joined to terminal acetoxy, phenol 
or carboxyl groups by reactions well known to those skilled in the art. 
The method of the invention can be conducted in the presence of a catalyst 
to enhance the rate of reaction. Catalysts useful in the method of the 
invention include condensation catalysts useful in the production of 
linear polyesters; for example: Mg, MgO, titanium compounds such as 
titanium(IV)butoxide and TiO.sub.2 and tin compounds having the general 
structure Sn(R).sub.4, such as dibutyl tin diacetate. A catalytic amount 
of catalyst is employed. By "catalytic amount" is meant an amount of 
catalyst which catalyzes the reaction to the desired extent. Generally, 
the amount of catalyst is at least about 0.005 mole percent based on the 
molar amount of reactant. There is no real upper or lower limit on the 
amount of catalyst, this being defined by secondary considerations such as 
cost and ease of separation of the catalyst from products and unreacted 
reactants. A preferred catalytic amount is from about 0.01 to about 1.0 
mole percent based upon the molar amount of reactant. The catalyst can be 
bound to a support or unsupported. 
The polymerization reaction is preferably carried out in the absence of 
solvent by merely heating the reactant. The polymerization reaction can be 
conducted in the presence of solvent, which appreciably dissolves 
reactants to provide a liquid reaction medium. The use of solvent slows 
the rate of reaction, in comparison to a melt polymerization. If solvent 
is used, it is desirable that the solvent be "inert" to the reaction, 
i.e., that the solvent not enter into the reaction in an undesired way. It 
is desirable that the solvent have a high boiling temperature so that 
elevated temperatures can be used in the reaction. The invention is not 
limited to a particular solvent or solvent system and a wide variety of 
solvents can be used. Examples of solvents are dimethylformamide and 
tetramethylenesulfone. The amount of solvent present is not critical, 
however, practical limits are imposed by the reduced reaction rate, the 
ease of separation of product from the reaction medium, cost and other 
factors. The reaction can also be carried out in the presence of a high 
boiling non-solvent or diluent such as biphenyl or Marlotherm-S. The 
purpose of this medium is to aid in heat transfer and processability of 
the polymerization monomer. 
During the polymerization reaction the small molecule elimination product 
acid of the --R.sup.1 group is produced and evolves from the reaction melt 
or solution or mixture. For example, if --R.sup.1 is --O--CH.sub.3, then 
methanol is produced. Removal of the H--R.sup.1 provides a driving force 
for completion of the polymerization reaction. The H--R.sup.1 can be 
removed by passing a stream of an inert gas such as nitrogen or argon over 
or through the reaction mass at atmospheric or superatmospheric pressure 
or alternatively by applying a vacuum to the reaction apparatus or by 
reacting H--R.sup.1 to produce a precipitate or the like. For example, if 
R.sup.1 is Cl, the H--R.sup.1 can be removed by reacting the H--R.sup.1 
with a macromolecular base such as polyvinylpyridine. The H--R.sup.1 may 
be collected for some other use. As a skilled practitioner will recognize, 
the specific means used to drive the polymerization reaction is not 
critical. 
A suitable reaction temperature for the method of the invention, affords a 
reasonable rate of reaction and does not give an undue amount of 
decomposition of products or reactants or solvent. The polymerization 
reaction is generally conducted at a temperature above about 130.degree. 
C. Although the reaction can be conducted at temperatures below 
130.degree. C., the polymerization reaction is much slower and molecular 
weight of product may be reduced. Non-reactive diluents can be used to 
conduct the polymerization at a reasonable rate at a lower temperature. 
The upper temperature limit on the polymerization reaction is determined 
by decomposition temperatures. A suitable temperature range is 
160.degree.-300.degree. C. The process of this invention is preferably 
conducted at a temperature within the range of from about 200.degree. C. 
to about 270.degree. C. for di- and tri- CO--R.sup.1 reactants and within 
the range of from about 160.degree. C. to about 240.degree. C. for di- and 
tri- 
##STR14## 
reactants. 
The reaction time is not a truly independent variable but is dependent at 
least to some extent on the other reaction parameters selected such as the 
reactivity of reactant, absence or presence of catalyst, reaction 
temperature, physical properties of the desired product and so forth. 
Generally, reaction times within the range of from about 0.5 to about 20 
hours are used. 
Agitation of the reaction mixture or solution is optional, however 
agitation assists in the production and yield of the polymer. Agitation of 
the reaction mixture can be accomplished by any known method, such as 
mechanical stirring. 
The polymerization reaction has been carried out in a batch reaction 
vessel. It is proposed that the polymerization reaction could be carried 
out as a continuous or semi-continuous process. It is further proposed 
that it might be preferred that the polymerization reaction would be 
conducted on a continuous basis as a melt in a continuous staged reactor. 
In that continuous process, an inert gas, such as nitrogen or argon could 
be passed though the melt, preferably in a countercurrent direction, 
thereby accomplishing agitation and mixing of the reaction melt and at the 
same time removing the alcohol evolved. Alternatively, in that continuous 
process, a vacuum could be applied to the reactor to remove the alcohol as 
it is generated. 
The multiply-branched aliphatic-aromatic polyesters of the invention can be 
used as coatings, additives, carriers and the like. Specific uses depend 
upon the nature of the terminal groups, which can be readily modified by a 
wide variety of reactions well known to those skilled in the art. For 
example, polymers of the invention having hydroxyl bearing terminal groups 
are soluble in various organic solvents and can be used as high solids 
industrial coatings. Other polymers of the invention have COOH terminal 
groups, which can be converted to COO.sup.- (Metal).sup.+ groups to 
provide ionomers that are soluble in aqueous media and can be used for 
coatings and additives. 
Reactants useful in the methods of the invention can be produced using 
procedures exemplified by the following preparations. 
Preparation 1 
##STR15## 
methyl(3.5-di(2-hydroxy)ethoxy)benzoate 
Methyl-(3,5-dihydroxy)benzoate (100 grams, 0.595 mole) was dissolved in 600 
milliliters of isopropanol in a pressure reactor. Ethylene oxide (70 
grams, 1.589 mole) and potassium carbonate (2.4 grams) were added at room 
temperature. The mixture was heated to 95.degree. C. and then charged with 
nitrogen to 75 psi, and maintained at that temperature and pressure for 
4.5 hours with stirring. The solvent was then distilled off and residue 
was purified by flash chromatography on silica using a solvent containing 
ethyl acetate (8 parts by volume), hexane (2 parts by volume), and acetic 
acid (0.025 parts by volume). The resulting white product showed a melting 
point of 91.degree.-93.degree. C. and a yield of 82.3 grams, 54 percent of 
theoretical yield. Melting point was determined, as in all of the 
preparations and examples using a Thomas-Hoover melting point apparatus. 
Proton nuclear magnetic resonance (NMR) was performed on a 300 MHz GE 
instrument using deuterated dimethylsulfoxide (DMSO-d.sub.6) gave the 
following peaks (in parts per million (ppm)): 3.65 (t,4H), 3.8 (s,3H), 
3.98 (t,4H), 4.85 (b,2H,OH), 6.7 (s,1H), 7.0 (m, 2H). 
Preparation 2 
##STR16## 
5-hydroxyethoxyisophthalic acid 
(a) Preparation of dimethyl(5-hydroxy)isophthalate 
Anhydrous HCl (13 grams, 0.356 mole) was bubbled into methanol (700 
milliliters) placed in a one liter round bottom three-necked flask 
equipped with stirrer and reflux condenser. 5-Hydroxyisophthalic acid (100 
grams, 0.55 mole) was added. The reaction mixture became clear after 10 
minutes. The reaction mixture was heated to reflux for 2 hours and then 
filtered hot. White solid product crystallized out of the solution 
overnight, was collected, washed carefully with water and dried to yield 
104 grams, 90 percent of theoretical yield. The product had a melting 
point of 158.degree.-159.degree. C. NMR performed as in Preparation 1 gave 
the following peaks (in ppm): 3.8 (s,6H), 7.48 (m,2H), 7.87 (s,1H), 10.3 
(b,1H,0H). 
(b) Preparation of dimethyl(5-hydroxyethoxy)isophthalate 
Dimethyl(5-hydroxy)isophthalate (100 grams, 0.476 mole), produced as 
above-described in (a), and ethylene oxide (56 grams, 1.27 mole) were 
heated in isopropanol (700 milliliters) to 95.degree. C. The pressure 
vessel was charged to 75 psi (metric) with nitrogen and the reaction was 
continued with stirring at 95.degree. C. for 4 hours. The pressure was 
released and the reaction mixture cooled to room temperature. Isopropanol 
was removed by rotary evaporation. The crude mixture was purified by 
column chromatography using a solvent containing ethyl acetate (3 parts by 
volume), hexane (6 parts by volume), and acetic acid (0.5 parts by 
volume). Yield of product was 64 percent of theoretical yield. NMR 
performed as in Preparation 1 gave the following peaks (in ppm): 3.7 (2H), 
3.84 (COOMe), 4.05 (2H), 5.1 (OH,1H), 7.6 (2H aromatic), 8.0 (1H 
aromatic). The integral due to the methyl ester was low, it is believed, 
as a result of partial hydrolysis of the ester during the reaction. 
(c) Preparation of 5-hydroxyethoxyisophthalic acid 
Crude dimethyl(5-hydroxyethoxy)isophthalate (20 grams), produced as 
above-described in (b), was dissolved in tetrahydrofuran (150 
milliliters). A solution of NaOH (7 grams) dissolved in water (100 
milliliters) was added. The mixture was refluxed for 72 hours and then 
cooled to room temperature. The pH was adjusted with hydrochloric acid to 
2-3 and then the solvent was partially removed by rotary evaporation. The 
product precipitated and was collected by filtration, washed with water 
and dried to yield 9.6 grams, 54 percent of theoretical yield. The product 
had a melting point of 200.degree.-203.degree. C. NMR performed as in 
Preparation 1 gave the following peaks (in ppm): 3.7 (2H), 4.05 (2H), 4.9 
(1H,OH), 7.65 (2H aromatic), 8.05 (1H aromatic), 13.2 (2H,COOH). 
The following examples are presented for a further understanding of the 
invention: 
EXAMPLE 1 
Polycondensation of methyl(3.5-di(2-hydroxy)ethoxy) benzoate 
Methyl(3,5-di(2-hydroxy)ethoxy)benzoate (6.0 grams) was placed in a 
condensation polymerization flask under argon. The flask was evacuated, 
flushed with argon twice to remove air and placed in an oil bath at 
175.degree. C. The monomer melted within 2 minutes. Three drops 
(approximately 0.15 milliliters) of tin dibutyldiacetate was added as 
catalyst. The melt was maintained at 175.degree. C. under a slow nitrogen 
stream for 1.5 hours. Vacuum was then applied (2.times.10.sup.-2 
torr)(metric) for 2 hours to remove methanol which was formed. The 
temperature was then increased to 185.degree. C. and a higher vacuum 
(7.times.10.sup.-4 torr) (metric) was pulled for an additional 1.5 hours. 
On cooling, a polymeric glass was obtained at a yield of 4.9 grams, 93 
percent of theoretical yield. T.sub.g was determined to be 70.degree. C. 
Decomposition onset temperature was determined to be 364.degree. C. The 
weight average molecular weight, M.sub.w, of 411,000 was obtained by size 
exclusion chromatography (SEC) in dimethylforamide using an SEC system 
having coupled low angle laser light scattering, differential viscometry 
and refractive index detection and having three 7.5 mmm. i.d..times.300 
mm. 10 micrometer particle diameter PLgel mixed-bed columns marketed by 
Polymer Laboratories of Amherst, Mass. coupled in series and calibrated 
against universal calibration standards. NMR performed as in Preparation 1 
gave the following peaks (in ppm): 3.66 (b,2H), 3.97 (b,2H), 4.32 (b,2H), 
4.54, 6.6-7.2 (3H). 
EXAMPLE 2 
Polycondensation of 5-hydroxyethoxyisophthalic acid 
5-hydroxyethoxyisophthalic acid (4 grams) was placed in a condensation 
polymerization flask under argon. The flask was evacuated, flushed with 
argon twice to remove air and placed in a preheated salt bath at 
228.degree. C. After the monomer melted, four drops (approximately 0.20 
milliliters) of tin dibutyldiacetate was added. The melt was maintained at 
228.degree. C. under a slow nitrogen stream for 50 minutes. Vacuum was 
then applied (2.times.10.sup.-2 torr)(metric) for 1 hour. On cooling, a 
polymer was obtained which was only partially soluble in hot 
dimethylforamide. T.sub.g was determined to be 153.degree. C. 
Decomposition onset temperature was determined to be 344.degree. C. NMR 
performed as in Preparation 1 gave the following peaks (in ppm): 4.35 
(2H), 4.55 (2H), 7.55 (2H aromatic), 7.9 (1H aromatic), 13.2 (1H,COOH). 
While specific embodiments of the invention have been shown and described 
herein for purposes of illustration, the protection afforded by any patent 
which may issue upon this application is not strictly limited to a 
disclosed embodiment; but rather extends to all modifications and 
arrangements which fall fairly within the scope of the claims which are 
appended hereto: