Acrylate ester ether derivatives

A process for synthesizing ethers of alkyl alpha(hydroxymethyl)-acrylate by reacting alkyl acrylate and formaldehyde in the presence of a DABCO catalyst. The ethers may be used as cross-linking agents for thermoplastic polymers. Further, these ethers in turn enable synthesis of cyclopolymers that may show promising biological activity.

BACKGROUND OF THE INVENTION 
The present invention relates to acrylate ester ethers, processes for their 
production and isolation, and their use in bulk and solution 
polymerization. The invention has particular application as cross-linking 
agents for polymers. 
Reaction of methyl acrylates with various aldehydes in the presence of 
1,4-diazabicyclo-[2.2.2]-octane (DABCO) has been reported by H. M. R. 
Hoffmann and J. J. Rabe, 50 J. Org. Chem. 3849 (1985). Lower members of 
this series have been used previously as synthons in natural product 
synthesis. Hoffmann and Rabe did not describe, however, products produced 
when methylacrylate is reacted with formaldehyde. One such product, ethyl 
alpha(hydroxymethyl) acrylate was synthesized by a Wittig-Horner reaction 
of triethylphosphonoacetate by J. Villieras and M. Rambaud, Synthesis, p. 
924 (1982). Like the Hoffmann and Rabe publication, the Villieras and 
Rambaud article did not describe the preparation of the products of the 
present application. 
European application number EP 0,184,731 discloses the preparation of 
2-1-hydroxy-methyl-acrylonitrile or acrylic acid ester derivative by 
reacting acrylonitrile or acrylic acid ester with hydrated formaldehyde or 
formaldehyde semi-acetal using a tertiary amine catalyst such as 
1,4-diazabicyclo-[2.2.2]-octane, pyrrocholine or quinolidine. However, 
this application does not disclose the formation of any ethers. 
SUMMARY OF THE INVENTION 
When methylacrylate is reacted with formaldehyde under appropriate 
conditions a series of ether by-products are produced. These by-products 
are of the formulas: 
##STR1## 
Other reactive groups may be substituted for the carboxymethyl group in the 
acrylate ester reactant used to make these ether compounds. Consequently, 
the present invention as it is embodied and broadly described herein 
comprises a compound of the following formula: 
##STR2## 
Where n is an integer from 0 to 4 and R is a member selected from a group 
consisting of carboxy, carboxyalkyl, carbonylalkyl, cyano, carboxamide, 
and substituted carboxamide. 
A second aspect of the present invention is the inclusion of the 
above-described monomers in polymer compositions as cross-linking agents 
for those compositions. 
A third aspect of the present invention is the cyclopolymerization of the 
ether compounds of the type shown in formula 2 to form cyclopolymers 
having the following repeating units: 
##STR3## 
where R' is a member selected from the group consisting of carboxy, 
carboxyalkyl, carbonyalkyl, cyano, carboxamide, and substituted 
carboxamide. Generally m is greater than 5. 
One advantage of the present invention is that it provides a class of 
monomers that may act as cross-linking agents in polymer compositions. 
Another advantage is that the inclusion of the above-described monomers in 
polymer products produces clear, tough, hydrolytically stable cross-linked 
products. 
Additional advantages of the invention will be set forth in part in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention relates to products produced in the reaction of 
acrylate esters and other ethylenically unsaturated monomers with 
paraformaldehyde, formalin or gaseous formaldehyde in the presence of 
catalytic amounts of DABCO. The primary product of the reaction in which 
methyl acrylate is the ethylenically unsaturated monomer is a methyl 
alpha-hydroxymethyl acrylate of the formula: 
##STR4## 
This reaction also produces a number of by-products, primarily homologous 
ethers having the following formulas: 
##STR5## 
These by-product ethers can be separated from the distillation residue by 
column chromatography. 
The alpha-hydroxymethyl acrylate product 1 may be removed from the reaction 
mixture by water extraction, followed by fractional crystallization or 
column chromatography of the water insoluble fraction. These compounds can 
be employed in both addition and condensation polymerizations. 
The ether compounds 2, 3 and 4 are bis-unsaturated ethers which can 
function as cross-linking agents, while compound 2 has the additional 
ability of cyclopolymerization to tetrahydropyran or tetrahydrofuran 
containing polymers. 
In general, the methods of making and isolating the products of the present 
invention are as follows: 
When paraformaldehyde is the formaldehyde source, an alkylacrylate, 
preferably methyl or ethyl acrylate, and paraformaldehyde, preferably 
having a molecular weight between 5 and 20, are mixed in a molar ratio of 
preferably about 3:2 to about 8:2 alkylacrylate to paraformaldehyde. The 
components are then stirred at room temperature for a period of about 5 to 
about 10 days in the presence of about 5 to 10% by weight DABCO (based on 
the weight of paraformaldehyde in the mixture). 
After the paraformaldehyde is completely consumed, the excess alkylacrylate 
is removed by evaporation under a reduced pressure of about 10-20 mm Hg. 
and may be recycled if desired. The resulting product mixture will 
generally consist of about 45-60% by weight alkyl alpha-(hydroxymethyl) 
acrylate, about 30-45% of ether compounds 2, 3 and 4 and about 2-8% of a 
polymeric material consisting of higher ethers and/or vinyl polymers. 
The products made in this process may be isolated using either of two 
procedures. In the first procedure, the mixture is extracted with water, 
in which the alkyl alpha-(hydroxymethyl) acrylate is soluble. 
Re-extraction of the aqueous phase with about an equal volume of ether and 
evaporation of the ether generally yields a product in about 85% purity. 
This material may then be distilled in a fractional vacuum to yield about 
98% purity. The overall yield based on the limiting reagent is generally 
about 30-40%. 
The water insoluble phase may be dissolved in a minimum amount of methanol, 
acidified with an amount of about 1% by volume of 10% by weight aqueous 
solution of H.sub.2 SO.sub.4 and stirred at room temperature for about 
three hours. The ether compounds 3 and 4 may be hydrolyzed to provide more 
alkyl alpha-(hydroxymethyl) acrylate. Although compounds 3 and 4 are 
hydrolyzed, ether compound 2 remains unchanged. 
Evaporation of compound 1 followed by a water extraction and ether 
re-extraction provides more compound 1 and may bring the total yield of 
alkyl alpha-(hydroxymethyl) acrylate up to 60-70%. Re-crystallization of 
the water insoluble residue from methanol produces compound 2 in about 
10-20% yield. 
The second procedure that may be used to increase the total yield of the 
alpha-(hydroxymethyl) acrylate is to vacuum distill the reaction mixture, 
which converts ether compounds 3 and 4 to compound 1. The yield of 
compound 1 is generally 60-70% in about 93-95% purity. The distillation 
conditions lead to hydrolysis of compounds 3 and 4 to compound 1 and 
formaldehyde. The distillation residue can be fractionally recrystallized 
from methanol to give a yield of compound 2 of about 10-20%. 
The ethers of the present invention can also be formed directly from the 
alkyl alpha-(hydroxymethyl) acrylates by heating the acrylates in the 
presence of DABCO for a sufficient length of time to permit the reaction 
to occur. For example, bis[2-ethoxycarbonyl-2-propenyl]ether, compound 2, 
can be formed by heating purified ethyl alpha-(hydroxymethyl) acrylate and 
DABCO at about 74.degree. C. for about 23 hours. Over a 50% yield of the 
ether can be obtained. 
When formalin is the formaldehyde source, an alkyl acrylate and commercial 
formalin may be mixed in a molar ratio of about 1:1 to about 5:1 alkyl 
acrylate to formalin, preferably a 1.1:1 molar ratio is used. This mixing 
provides a two-phase mixture. An alkyl alcohol (equal volume to formalin) 
is also added. This mixture is stirred for about 2 to about 10 days, 
preferably 4 days, with incremental addition of 2% DABCO per day until 
about 5-8% DABCO by weight (based upon the amount of formalin) has been 
added. The acrylate and alcohol are then removed by evaporation and the 
remaining aqueous solution is extracted with ether to give essentially 
pure compound 1 in about 20-25% conversion. Longer reaction times will not 
generally improve this conversion. 
When gaseous formaldehyde is the formaldehyde source, gaseous formaldehyde, 
such as is produced by pyrolysis of paraformaldehyde or by 
de-polymerization of trioxane, is fed into a stirring mixture of alkyl 
acrylate and DABCO over the course of 3 days. There is generally 
considerable re-polymerization of formaldehyde both in the liquid acrylate 
and on the walls of the flask. However, the reaction proceeds as expected 
to give a product mixture which is essentially the same as that obtained 
when paraformaldehyde is used as the formaldehyde source. Purification of 
this product in the same manner as described above for the alkyl 
acrylate/paraformaldehyde mixture produces about 30-35% conversion and 
about 60% yield of compound 1. 
The polymers of the present invention can be prepared using any 
conventional polymerization technique. These polymers include as monomers 
20 to 99% by weight of at least one ethylenically unsaturated monomer and 
from 1 to 80% by weight of the methyl .alpha.-hydroxymethyl acrylate ether 
monomers of the present invention. 
The ethylenically unsaturated monomers useful to form the polymer of the 
present invention preferably includes monoalkenyl aromatic monomers, 
acrylic monomers and other vinylic monomers. The monoalkenyl aromatic 
monomers include, for example, .alpha.-methyl styrene, styrene, vinyl 
toluene, tertiary butyl styrene, ortho-chlorostyrene and mixtures thereof. 
The term "acrylic monomer" as employed herein includes acrylic or 
methacrylic acid, esters of acrylic or methacrylic acid and derivatives 
and mixtures thereof. Examples of suitable acrylic monomers include the 
following methacrylate esters: methyl methacrylate, ethyl methacrylate, 
n-propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, 
isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, isoamyl 
methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 
N, N-dimenthylaminoethyl methacrylate, N, N-diethylaminoethyl 
methacrylate, t-butylaminoethyl methacrylate, 2-sulfoethyl methacrylate, 
trifluoroethyl methacrylate, glycidyl methacrylate, benzyl methacrylate, 
allyl methacrylate, 2-n-butoxyethyl methacrylate, 2-chloroethyl 
methacrylate, sec-butyl-methacrylate, tertbutyl methacrylate, 2-ethylbutyl 
methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl 
methacrylate, cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, 
furfuryl methacrylate, hexafluoroisopropyl methacrylate, methallyl 
methacrylate, 3-methoxybutyl methacrylate, 2-methoxybutyl methacrylate, 
2-nitro-2-methylpropyl methacrylate, n-octylmethacrylate, 2-ethylhexyl 
methacrylate, 2-phenoxyethyl methacrylate, 2-phenylethyl methacrylate, 
phenyl methacrylate, propargyl methacrylate, tetrahydrofurfuryl 
methacrylate and tetrahydropyranyl methacrylate. 
Other suitable acrylic monomers include methacrylic acid derivatives such 
as: methacrylic acid and its salts, methacrylonitrile, methacrylamide, 
N-methylmethacrylamide, N-ethylmethacrylamide, N,N-diethylmethacrylamide, 
N,N-dimethylmethacrylamide, N-phenylmethacrylamide and methacrolein. 
Typical acrylate esters employed include: methyl acrylate, ethyl acrylate, 
n-propyl acrylate, isopropyl acrylate, n-butyl acrylate and n-decyl 
acrylate. 
Acrylic acid derivatives employed as the acrylic monomer include: acrylic 
acid and its salts, acrylonitrile, acrylamide, methyl 
.alpha.-chloroacrylate, methyl 2-cyanoacrylate, N-ethylacrylamide, 
N,N-diethylacrylamide and acrolein. 
The acrylic monomer can also include acrylates or methacrylates containing 
cross-linkable functional groups, such as hydroxy, carboxyl, amino, 
isocyanate, glycidyl, epoxy, allyl, and the like. The functional polymers 
are usually prepared by polymerization employing a functional monomer or 
by post-reaction of a polymer of the invention to introduce the desired 
functionality. 
Esters of methacrylic acid or acrylic acid containing a suitable 
condensable cross linkable functional group may be used as a monomer. 
Among such esters are t-butylaminoethyl methacrylate, isopropylidene 
glyceryl methacrylate and oxazolidinylethyl methacrylate. 
The following examples are representative of the methods of producing the 
products of the invention. In the following Examples all parts and 
percentages are by weight unless otherwise noted and all temperatures are 
in degrees Celsius.

EXAMPLE I 
Methylacrylate (1450g), paraformaldehyde (180g) and DABCO (20g) were mixed 
and stirred at room temperature for 10 days. At the end of this period 
excess paraformaldehyde was removed by filtration and excess methyl 
acrylate was removed on a rotary evaporator at 20 mm pressure and 
65.degree. C. temperature. The remaining mixture contained 49% of compound 
1, 22% of compound 2, 18% of compound 3 and 6% of compound 4. Fractional 
distillation of this mixture at 0.05 mm pressure and 60.degree.-65.degree. 
C. head temperature gave 275g of compound 1 (66%, based on 
paraformaldehyde consumed). Continued distillation at 0.05 mm pressure and 
85.degree.-105.degree. C. and recrystallization of the distillate from 
methanol gave 22g of compound 2 (3% based on paraformaldehyde consumed). 
EXAMPLE II 
n-Butyl acrylate (32g), paraformaldehyde (6g) and DABCO (1.5g) were mixed 
and stirred at room temperature for 10 days. At the end of this period the 
mixture was dissolved in 200 ml of ether, filtered to remove a small 
amount of insoluble material, washed twice with 5% aq. HCl and the ether 
evaporated to give 34g of product mixture. Part of this mixture was 
separated by preparative gas chromatography to give 23% untreated n-butyl 
acrylate, 20% alpha-(hydroxymethy)-n-butyl acrylate, the n-butyl homologue 
of compound 1; 19% of the n-butyl homologue of compound 2, 21% of the 
n-butyl homologue of compound 3 and 5% of the n-butyl homologue of 
compound 4. Product 1 can be separated from the mixture by fractional 
distillation at 0.08 mm and 82.degree. C. head temperature. 
EXAMPLE III 
Formalin (8g), methyl acrylate (103g) and DABCO (5g) were mixed and stirred 
for a total of 20 days at room temperature. Five more grams of DABCO were 
added in increments during this period. At the end of 20 days the reaction 
was stopped. Two phases separated. The aqueous phase was extracted with 
ether after acidification with HCl to give 13.5g of compound 1. The 
organic phase was evaporated under vacuum to give 8.0g of compound 1 with 
a combined yield of 21.5g. Recovered methyl acrylate was 76g giving a 26% 
conversion and 58% yield. 
The crude reaction mixtures from Examples I-III can be heated at about 
60.degree.-100.degree. C. to convert the hydroxymethyl compounds to the 
ether compounds before separation to increase the yield of the ethers. The 
reaction can be carried out for a period of several hours to several days 
with longer periods increasing the amount of ether formed. 
EXAMPLE IV 
Methyl acrylate (1600g), paraformaldehyde (200g) and DABCO (40g) were 
stirred at 65.degree. C. for 2-1/2 days. Workup as in Example I gave 33% 
product 1. There was considerable discoloration and polymerization at this 
higher reaction temperature. 
EXAMPLE V 
Ethyl alpha-(hydroxymethyl) acrylate (982mg, 96.3% pure) containing 0.4% of 
the corresponding ether, and 1, 4-diazabicyclo-[2.2.2]-octane (124mg, 
11.2% by weight) were heated at 74.degree. C. for 23 hours. Gas 
chromatography showed that the mixture contained 20% starting material, 
54% ether (bis[2-ethoxycarbonyl-2-propenyl]ether), and two unidentified 
compounds present in amounts of 6% and 3%. Overall conversion of the 
acrylate to the ether was greater than 65% 
The difunctional ether compounds 2, 3 and 4 are useful as cross-linking 
agents and are capable of cyclopolymerization. Compound 2, for example, 
readily undergoes polymerization in dimethylsulfoxide initiated with 
2,2'-azobisisobutyronitrile to give a clear, tough polymer that is 
insoluble and highly cross-linked. This material is surprising tenacious 
in retaining solvent which cannot be removed even with extended solvent 
exchange with water. 
Photopolymerization of a thin film of compound 2 in the presence of 
catalytic amounts of benzoin isopropyl ether gives a clear film with good 
physical properties. The IR spectrum of this film shows disappearance of 
the monomer with formation of the polymer. 
These difunctional acrylate ethers have the potential to replace existing 
diacrylate esters in a variety of applications such as photocurable 
coatings and photolithography. In addition, they yield products that are 
more hydrolytically stable since hydrolysis of the ester groups will not 
lead to a decrease in the polymer cross-link density. 
Radical and photoinitiated bulk polymerization, and radical solution 
polymerization of compound 2 in dimethylsulfoxide gives only highly 
cross-linked insoluble products. Another procedure, however, leads to the 
synthesis of polymers having the following repeating unit: 
##STR6## 
Partial hydrolysis of this structure leads to its water soluble derivative: 
##STR7## 
The following example describes a process for making the soluble polymer 
structure 6. 
EXAMPLE VI 
A 3% benzene solution of compound 2 was polymerized with 
2,2'-azobisisobutyronitrile at 60.degree. C. The polymer that precipitated 
was soluble in chloroform and methylene chloride. Reprecipitation into 
ether produced cyclopolymer 6 as a white powder having a 
melt/decomposition temperature of 270.degree.-275.degree. C. DSC confirmed 
the melting transition at 270.degree. C. and also showed a strong glass 
transition at 170.degree. C. The intrinsic viscosity of this polymer was 
found to be 0.43 dL/g in CHCl.sub.3 at 25.degree. C. Chloroform and 
acetone are also good solvents for this process. 
Homologues of ether compound 2 can also be polymerized to form 
cyclopolymers corresponding to cyclopolymer 6. 
The following example describes a process for hydrolyzing cyclopolymer 6 to 
produce cyclopolymer 7. 
EXAMPLE VII 
Cyclopolymer 6 was hydrolyzed overnight under heterogeneous conditions in a 
1:1 mixture of methanol and water containing 5% NaOH at 
65.degree.-70.degree. C. A viscous polymer solution resulted, which was 
acidified to precipitate the polycarboxylic acid cyclopolymer 6 which was 
soluble in aqueous base. 
The IR spectrum of this material showed strong, broad peaks at 3350 and 
1170 cm.sup.-1 attributed to the free acid groups. .sup.13 C NMR in dilute 
base showed a greatly reduced peak for the ester methyl carbon, and two 
peaks for the carbonyl groups corresponding to hydrolyzed and unhydrolyzed 
ester units. The ratio of these latter two peaks was approximately 3:1, 
indicating about 75% hydrolysis. 
EXAMPLE VIII 
A mixture of the ether compound 2 (500mg, 2.34 mmol) and 
azobisisobutyronitrile (AIBN, 15mg, 4 mole% of monomer) was dissolved in 
13 ml benzene. The solution was flushed with nitrogen for 5 minutes and 
sealed. The solution was then heated in a hot water bath at 
60.degree.-70.degree. for several hours, during which precipitate formed. 
The solution was cooled, and solvent removed by rotary evaporation. The 
white product thus obtained was extracted first with ether to remove any 
unreacted monomer. The residual powder was then mostly dissolved in 
chloroform, although a small amount remained insoluble and was removed by 
filtration. The chloroform solution was slowly added to rapidly stirring 
methanol to give a white powdery precipitate which was removed by 
filtration and dried under vacuum. 
The total yield of soluble and insoluble polymer increases with the 
initiator concentration and the length of polymerization, while the ratio 
of soluble to insoluble material increases with increasing initiator 
concentration. 
Polymer characterization involved infrared and nuclear magnetic 
spectroscopy, dilute solution viscosity and thermal analysis. Spectroscopy 
confirmed the absence of residual vinyl groups in the soluble polymer and 
is consistent with a cyclopolymerized structure. Intrinsic viscosity 
values were obtained for polymer synthesized in a number of different 
solvents including chloroform and acetone, and all values were in the 
range of 0.1-0.5 dL/g. Thermal analysis indicated a glass transition of 
approximately 145.degree.-170.degree. C. and a decomposition temperature 
of approximately 300.degree. C. 
Hydrolysis of the obtained cyclopolymer was accomplished in a heated 
mixture of sodium hydroxide, water and methanol. Gradual dissolution of 
the initially insoluble polymer gave a viscous solution. Acidification 
with dilute acid led to precipitation of the partially or completely 
hydrolyzed polymer. The degree of hydrolysis increased with reaction time. 
The hydrolyzed polymer can be redissolved in dilute aqueous base and 
analyzed by nuclear magnetic resonance spectroscopy to determine the 
extent of hydrolysis 
Pyran copolymers, obtained from the 2:1 copolymerization of divinyl ether 
and maleic anhydride, have been found to exhibit high activity as 
anti-tumor and anti-metastatic agents. See Butler, G. B., 22 J. 
Marcrolmol. Sci., Rev. Mac. Romol. Chem. Phys., p. 89 (1982); Shultz, R. 
M., Altom, M. G., 5 J. Immunocharmacol, p. 277 (1983); Zaharko, S. D., 
Covey, G. M., 68 Cancer Treat. Rep., p. 1255 (1984). Because of the 
structural similarity between cyclopolymers 6 and 7, it would be expected 
that these products would have similar biological utility as has been 
shown in the products described in the above-cited references. 
The utility of compound 2 as a cross-linking agent is shown in the 
following example. 
EXAMPLE IX 
A mixture of methyl methacrylate with 3.5% of ether 2 and 1% 
azobisisobutyronitrile was heated at 70.degree. C. for two hours, 
producing an insoluble sample of poly(methyl methacrylate) that contained 
no residual unsaturation. 
Photopolymerization of ether 2 and methyl methacrylate in the presence of 
benzoin isopropyl ether in bulk or in thin films also gave insoluble 
poly(methyl methacrylate). 
The IR and .sup.13 C NMR spectra of the insoluble polymers produced in 
Example IX were essentially identical to those of soluble poly(methyl 
methacrylate) prepared under the same reaction conditions. When 
cross-linked and uncross-linked samples were subjected to identical 
hydrolysis conditions, the former did not swell while the latter swelled 
and dissolved. 
Example IX therefore shows that ether compound 2 produces hydrolytically 
stable cross-links that possess real advantages over other available 
bis-acrylate esters now used for cross-linking. 
The following example shows a process for synthesizing a rubbery polymer 
with an amount of the diacid analog of ether compound 2 shown in the 
following formula: 
##STR8## 
EXAMPLE X 
Ether compound 2 was hydrolyzed in aqueous methanol under basic catalysis. 
This hydrolysis produced the salt of the bisacrylic acid ether compound 8. 
Upon acidification, ether compound 8 precipitated in quantitative yield as 
a white powder melting with concurrent polymerization at 
118.degree.-120.degree. C. 
An aqueous solution of acrylic acid containing 3.2 mol% of ether compound 8 
was heated with V-50 azo initiator (a water-soluble azo initiator produced 
by Wako Chemical U.S.A., Inc., Warrington, PA) producing a rubbery 
polymer. This polymer, unlike poly(acrylic acid), could not be dissolved 
by addition of more water or aqueous base. 
Examples IX and X show that both the di-ester compound 2 and the di-acid 
compound 8 are highly reactive cross-linking agents for vinyl polymers. 
They are superior to commercially available bis-acrylate esters because 
the cross-links formed in ether compounds 2 and 8 consist of carbon and 
ether linkages. Unlike the ester linkages contained in currently available 
analogs, these ether linkages are not readily susceptible to hydrolysis. 
The following example shows the use of the ether compounds of the present 
invention to form additional polymers. 
EXAMPLE XI 
Bis(.beta.,.beta.'-mercaptoethyl)ether (325mg, 2.4mmol) and bis 
(2-ethoxycarbonyl-2-propenyl) ether (580mg, 2.4 mmol) were mixed together. 
Triethylamine (16mg, 1.7 wt-%) was added and an exothermic reaction 
occurred along with a rapid increase in the viscosity of the mixture. 
After 30 minutes of reaction, chloroform was added to dissolve the 
mixture. Further increase in solution viscosity occurred over a several 
day period. Polymer was isolated by pouring the viscous solution into 
ether. The solvent was then decanted and the residual material dried under 
vacuum. The polymer was a very viscous oil. 
A variety of bisthiols were reacted with the ether compound 2 to give 
polymers. These included alkyl and aryl compounds. Polymerizations usually 
took place at ambient temperature, although heating the reaction mixture 
increased the rate of polymer formation. Spectroscopic characterization of 
the polymers confirmed polymer structures resulting from addition of the 
thiol units to the unsaturated groups in the ether, thus leading to new 
thioether units in the polymer. 
In addition to the bisthiols, amines can be reacted with the ether 
compounds of the present invention to give polyamines. 
Additional advantages and modifications will readily occur to those skilled 
in the art. The invention in its broader aspects is therefore not limited 
to the specific examples shown and described. Accordingly, departures may 
be made from the detail shown in the examples without departing from the 
spirit or scope of the disclosed general inventive concept.