U.S. patent number RE44,988 [Application Number 13/763,787] was granted by the patent office on 2014-07-01 for polymerizable sulfonate ionic liquids and liquid polymers therefrom.
This patent grant is currently assigned to The United States of America, as represented by the Secretary of the Navy. The grantee listed for this patent is The United States of America as represented by the Secretary of the Navy, The United States of America as represented by the Secretary of the Navy. Invention is credited to Holly L. Ricks-Laskoski, Arthur W. Snow.
United States Patent |
RE44,988 |
Ricks-Laskoski , et
al. |
July 1, 2014 |
**Please see images for:
( Certificate of Correction ) ** |
Polymerizable sulfonate ionic liquids and liquid polymers
therefrom
Abstract
Disclosed is a new ionic liquid monomer salt and methods of is
synthesis and polymerization. The ionic liquid monomer salt is
prepared by mixing equimolar amounts of an amine, such as
tris[2-(2-methoxyethoxy)-ethyl]amine and an acid functionalized
polymerizable monomer, such as
2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), which is
stirred at ambient temperature until salt formation is complete.
Also disclosed is a new ionic liquid polymer salts and method for
making the same. The synthesis of AMPS-ammonium salt polymer is
accomplished by adding 2,2'-azobisisobutyronitrile (AIBN) to the
ionic liquid monomer salt and heating the homogeneous melt at
70.degree. C. for 18 hr.
Inventors: |
Ricks-Laskoski; Holly L.
(Springfield, VA), Snow; Arthur W. (Alexandria, VA) |
Applicant: |
Name |
City |
State |
Country |
Type |
The United States of America as represented by the Secretary of the
Navy |
Washington |
DC |
US |
|
|
Assignee: |
The United States of America, as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
39082794 |
Appl.
No.: |
13/763,787 |
Filed: |
February 11, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
11894639 |
Aug 17, 2007 |
7807852 |
|
|
|
60822772 |
Aug 18, 2006 |
|
|
|
Reissue of: |
12862281 |
Aug 24, 2010 |
7858822 |
Dec 28, 2010 |
|
|
Current U.S.
Class: |
562/114 |
Current CPC
Class: |
C08F
2/02 (20130101); C07C 303/32 (20130101); C07C
309/21 (20130101); C07C 217/08 (20130101); C07C
309/15 (20130101) |
Current International
Class: |
C07C
309/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3236881 |
February 1966 |
Distler et al. |
4425455 |
January 1984 |
Turner et al. |
5708095 |
January 1998 |
Grezzo Page et al. |
8134024 |
March 2012 |
Ricks-Laskoski et al. |
|
Other References
Ise et al., "Mean Activity Coefficient of Polyelectrolytes, IX.
Activity Coefficients of Polyethylenesulfonates of Various
Gegenions" J. Phys. Chem. 72(4), 1366-1369 (1968). cited by
applicant .
Ricks-Laskoski et al., J. Am. Chem. Soc., 128, 12402-12403. cited
by examiner .
Zhao et al., J. Chem. Technol. Biotechnol. 2005, 80, 1089. cited by
applicant .
Welton, Chem. Rev. 1999, 99, 2071. cited by applicant .
Washiro, et al. Polymer, 2004, 45, 1577. cited by applicant .
Ding, et al., J. Poly. Sci. Part A, 2004, 42,5794. cited by
applicant .
Tang, et al. J. Poly. Sci. Part A, 2005, 43, 5477. cited by
applicant .
Nakajima, et al., Polymer, 2005, 46, 11499. cited by applicant
.
Ogihara, et al., Electrochim. Acta, 2004, 49, 1797. cited by
applicant .
Binnemans, Chem. Rev., 2005, 105, 4148. cited by applicant .
Anderson, et al., Anal. Chem. 2006, 78, 2893-2902. cited by
applicant .
Millefiorini,et al., J. Am. Chem. Soc. 2006, 128, 3098-3101. cited
by applicant .
Yoshizawa, et al., Poly. Adv. Technol. 2002, 13, 589-594. cited by
applicant .
Tang, et al., J. Poly. Sci.: Part A2005, 43, 1432-1443. cited by
applicant .
Quilliet, et a., Curr. Opin. Colloid Interface Sci. 2001, 6, 34-39.
cited by applicant .
Fisher, et al., Macromolecules, 1977, 10,949. cited by applicant
.
Bennett et al, Sensors and Actuators, 2004, 115, 79. cited by
applicant.
|
Primary Examiner: Puttlitz; Karl J
Attorney, Agent or Firm: US Naval Research Laboratory
Grunkemeyer; Joseph T.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This Application is a Divisional of application Ser. No. 11/894,639
filed on Aug. 17, 2007. Application Ser. No. 11/894,639 claims the
benefit of U.S. Provisional Application 60/822,772 filed on Aug.
18, 2006, both of which are incorporated herein by reference in
their entirety.
Claims
What is claimed as new and desired to be protected by Letters
Patent of the United States is:
1. An ionic liquid monomer salt having the formula: ##STR00017##
wherein R, R', and.[./or.]. R'' are each .[.independently selected
from H, or --(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or.].
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=.[.1 to 4, or
--(CH).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3 where n=1 to 6, or
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.]..
2. A method for making an ionic liquid monomer salt comprising:
.[.mixing.]. .Iadd.forming a solvent-free mixture of .Iaddend.an
equimolar amount of a sulfonic acid functionalized monomer having
the formula: ##STR00018## with the organic amine base having the
.[.general.]. formula: ##STR00019## wherein R, R', and.[./or.]. R''
are each .[.independently selected from H, or
--(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or.].
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=.[.1 to 4, or
--(CH).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3 where n=1 to 6, or
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.].; and .[.stiffing.]. .Iadd.stirring .Iaddend.said
.Iadd.solvent-free .Iaddend.mixture under an inert atmosphere until
said sulfonic acid functionalized monomer is dissolved, wherein the
dissolution completes formation of the ionic liquid monomer
salt.
3. A method for making an ionic liquid polymer salt comprising:
.Iadd.forming a solvent-free mixture by .Iaddend.providing the
ionic liquid monomer salt .Iadd.of .Iaddend.claim 1 .[.having the
general formula: ##STR00020## wherein R, R', and/or R'' are each
independently selected from H, or --(CH.sub.2).sub.nCH.sub.3 where
n=1 to 12, or --(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4,
or --(CH).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3 where n=1 to 6,
or --(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.].; adding a free radical polymerization catalyst to
said ionic liquid monomer salt; .Iadd.and .Iaddend. .[.stiffing.].
.Iadd.stirring .Iaddend.said .Iadd.solvent-free .Iaddend.mixture
under an inert atmosphere with application catalyst-specific
polymerization conditions.
Description
BACKGROUND OF THE INVENTION
Ionic liquids are salts composed of cationic and anionic components
whose structures impart a sub-room temperature melting point or
glass transition to the resulting material. A liquid character is
associated with ions that have very weak tendencies to coordinate
toward oppositely charged ions (e.g. charge delocalized or
sterically shielded), with substituents that have weak
intermolecular forces (e.g. fluorocarbons, alkanes, silicones) and
with a structural symmetry that is not conducive to efficient
molecular packing. Most ionic liquids are organic salts. The
cationic component is usually organic in nature (e.g.
alkyl-substituted ammonium, phosphonium, imidazolium and
pyridinium), and the anionic component is most often inorganic
(e.g. nitrate, sulfate, thiocyanate, halide, tetrafluoroborate,
hexafluorophosphate, etc.) but may also be organic (e.g. tosylate,
alkylsulfates, fluoroalkylsulfates, alkylcarboxylates,
fluoroalkylcarboxylates, etc.). These liquid materials have unique
properties (immeasurably low volatility, non-flammability, very
high polarity and solvating characteristics, high ionic
conductivity, and a wide electrochemical potential window). There
is currently much interest in their use as solvents for a large
variety of reactions and in sampling for chemical analysis. See
Zhao et al., J. Chem. Technol. Biotechnol. 2005, 80, 1089 and
Welton, Chem. Rev. 1999, 99, 2071.
A more unique form of ionic liquid is based on a system where one
of the two charged components is a polymer. As such, each repeat
unit incorporates the same ionic site. There are very few reports
in the literature of such systems. They are mostly based on the
imidazolium ion functionalized with a polymerizable vinyl, acrylic
or styryl moiety and have the physical form of a glass or sticky
rubber. Reports include imidazolium polymers. See Washiro, et al.
Polymer, 2004, 45, 1577; Ding, et al., J. Poly. Sci. Part A, 2004,
42, 5794; Tang, et al. J. Poly. Sci. Part A, 2005, 43, 5477; and
Nakajima, et al., Polymer, 2005, 46, 11499 and alkali metal
sulfonate polymers, see Ogihara, et al., Electrochim Acta, 2004,
49, 1797 and Binnemans, Chem. Rev., 2005, 105, 4148. These polymers
are prepared from monomers which themselves may or may not be ionic
liquids. In the case of cationic imidazolium polymers, certain
imidazolium monomer ionic liquids will yield the corresponding
polymer ionic liquid if appropriate substitution is made on the
imidazole ring; otherwise, a glassy solid is obtained. An
appropriate substitution relates to the addition of a sufficient
number and/or sufficient size of alkyl groups to the ring. In
contrast, the anionic-form of a polymer ionic liquid has yet to be
prepared directly from its analogous monomer ionic liquid. For
instance, the high melting sulfonate monomer solid (usually an
alkali metal salt) is first polymerized in solution followed by
substitution with an appropriate cationic counter ion. Solvent
removal is necessary to generate the anionic polymer liquid, still
retaining the alkali metal ion.
Polymerizable ionic liquids and their actuation in an electric
field are a combination of material and properties with unique
potential to display structural and fluid dynamics above that found
for small molecule ionic liquids. Small molecule ionic liquids are
generally monovalent organic salts with melting points or glass
transitions below room temperature. They derive their liquid
character from a selection of ionic structures which have very weak
tendencies to coordinate with oppositely charged ions, low
intermolecular forces and low symmetry. Their properties
(immeasurably low volatility, non-flammability, very high polarity
and solvating characteristics, high ionic conductivity, and a wide
electrochemical potential window) are of substantial interest
particularly with regard to applications as green solvents,
analytical extraction solvents, and electrochemical supporting
media. Very recently it has been reported that water immiscible
ionic liquids display significant electrowetting characteristics
with an interesting dependence on the size of the cationic and
anionic components. See Ralston, et al., J. Am. Chem. Soc., 2006,
126, 3098. Ionic liquids themselves provide an opportunity of
producing a more stable actuating medium, eliminating such issues
as solvent evaporation and degradation due to electrolysis,
typically found in aqueous based electric field induced
actuators.
In an ionic liquid polymer system the cationic or anionic centers
are constrained to repeat units in the polymer chain. As such, any
molecular flow or diffusion requires a concerted motion of as many
ionic centers as there are charged repeat units in the polymer
chain. When subjected to an electric field, a polymeric system may
respond in an enhanced or retarded manner relative to a small
molecule ionic liquid, depending on whether the covalent linkage of
cationic or anionic repeat units responds as a more highly charged
single molecule or whether its macromolecular size inhibits
molecular motion needed for a response.
BRIEF SUMMARY OF THE INVENTION
Disclosed is a new ionic liquid monomer salt and methods of is
synthesis and polymerization. The ionic liquid monomer salt is
prepared by mixing equimolar amounts of an amine, such as
tris[2-(2-methoxyethoxy)-ethyl]amine and an acid functionalized
polymerizable monomer, such as
2-acrylamido-2-methyl-1-propanesulfonic acid .[.(AMPS).].
.Iadd.1.Iaddend., which is stirred at ambient temperature until
salt formation is complete. Also disclosed is a new ionic liquid
polymer salts and method for making the same. The synthesis of
.[.AMPS.]. .Iadd.2-acrylamido-2-methyl-1-propanesulfonic
acid.Iaddend.-ammonium salt polymer is accomplished by adding
2,2'-azobisisobutyronitrile (AIBN) to the ionic liquid monomer salt
and heating the homogeneous melt at 70.degree. C. for 18 hr.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a differential scanning calorimetry comparison of
oxyethylene amine, .[.AMPS.].
.Iadd.2-acrylamido-2-methyl-1-propanesulfonic
acid-.Iaddend.oxyethylene ammonium salt monomer, and polymer
illustrating low Tg upon salt formation in the monomer and
polymer;
FIG. 2 is a depiction of an electrowetting actuation electrode
setup with (right) and without (left) an induced electric
field;
FIG. 3 shows electrowetting curves of monomer (left) and
polymer;
FIG. 4 shows electrowetting .[.AMPS.].
.Iadd.2-acrylamido-2-methyl-1-propanesulfonic
acid-.Iaddend.oxyethylene ammonium salt polymer as voltage increase
from 0 V (left) to 157 V (right).
DETAILED DESCRIPTION OF THE INVENTION
Ionic liquid polymers and their actuation in an electric field are
a combination of material and properties with unique potential to
display structural and fluid dynamics above that found in small
molecule ionic liquids. These structure and property dynamics are
directly dependent upon an incorporation of a large number of
positive or negative charges on the same polymer molecule while
maintaining a liquid character under ambient conditions and a large
temperature range where the polymer is a liquid or readily deformed
viscoelastic solid. The strategy used in this invention for
preparation of such polymers is to select acid functionalized
monomer and organic base components that form acid-base salts that
are liquids at room temperature and polymerize to form polymers
that are also liquids at room temperature or, if lightly
crosslinked, form very easily deformed viscoelastic solids. The
acid functionality is selected as one having a strong acidity and
one that is readily attached to polymerizable monomers. The
sulfonic acid is particularly attractive although phosphoryl or
carboxylic acids could also be made to serve this function.
Functionalization of an acid group onto a polymerizable monomer
such as a styrene, acrylate, olefin, vinyl ether, or acrylamide
results in a relatively high temperature melting monomer. The
2-acrylamido-2-methyl-1-propanesulfonic acid .[.(AMPS).]. monomer,
used in the example, has a 192.degree. C. melting point. Other
commercially available monomers appropriate for this invention
would include styrene sulfonic acid and vinyl sulfonic acid.
Sulfonic acid functionalized monomers are the preferred class acid
functionalized monomer with .[.the AMPS.]. monomer .Iadd.1
.Iaddend.being the most preferred.
An organic base which has a very low melting point or glass
temperature is selected so that it will depress the corresponding
melting point or glass transition of the salt it forms with the
acid monomer to an extent that its liquid range extends well below
room temperature. For example, the organic base
tris[2-(2-methoxyethoxy)-ethyl]amine, there are two oxyethylene
groups in each amine substituent. These substituents cause the
amine to have a very low glass transition, -104.degree. C., and it
is this low glass transition that causes the salt it forms with
.[.the AMPS.]. monomer .Iadd.1 .Iaddend.to also to have a low glass
transition, -57.degree. C. Other amines with similar
characteristics (e.g. different numbers or mixed numbers of
oxyethylene units) or with different substituents also correlating
with low glass transitions (e.g. dimethylsiloxane and
fluoromethylene) could work comparably. The amine base is the
preferred organic base with the oxyethylene functionalized tertiary
amine base being the most preferred. A physical mixing of the
sulfonic acid functionalized monomer with the amine base generates
the ionic liquid monomer salt which is then polymerized to form the
corresponding ionic liquid polymer salt. Although not required,
addition of a small amount of volatile solvent will promote a more
rapid dissolution of the sulfonic acid functionalized monomer in
the amine base; including, but not limited to methanol and
ethylacetate.
A small quantity of polymerization catalyst is added to ionic
liquid monomer salt to effect this transformation. The preferred
catalysts are those that initiate free radical polymerization, and
those that have high initiator efficiencies and solubility in the
ionic liquid monomer salt are the most preferred. In cases where
initiators need solubility, enhancement a small quantity of
volatile, readily removable solvent such as methanol or ethyl
acetate can be used to disperse the initiator in the monomer melt.
The quantity of catalyst and the polymerization conditions used
vary according to the specific characteristics of the catalyst and
polymer molecular weight desired. A preferred catalyst, such as
2,2'-azobisisobutyronitrile, will typically be used in a quantity
corresponding to a range of monomer:initiator ratio range of 50:1
to 1000:1 and under of temperature and reaction conditions of 50 to
110.degree. C. and 3 to 24 hours respectively. An important feature
of the monomer salt and of the ionic liquid polymer product is that
they be a homogeneous melt throughout all stages of polymerization
conversion. This feature results in the polymerization approaching
quantitative conversions without an added solvent which would have
to be subsequently separated. That the polymer product is also an
ionic liquid qualifies it for unique electric field driven
actuations such as physical shape changes, spreading on surfaces
and droplet movement.
Provided are a composition of matter identified as an ionic liquid
polymer salt, composed of an organic sulfonate repeat unit and a
cationic organic counter ion and a general synthetic procedures for
preparation of this class of compounds from ionic liquid monomers.
Interest in such compositions of matter is driven primarily by
electric field actuations in the form of electrowetting or Maxwell
stress deformation of such materials. More specifically, an ionic
liquid polymer system wherein a low molecular weight counter ion
promotes an ionic liquid character in both the monomer salts and
polymer salts and an observation of electrowetting where the
polymer salt displays a distinctive effect relative to that for the
monomer salt is disclosed. Disclosed is the preparation of a ionic
liquid monomer salt, its solvent-free or solvent-assisted
polymerization to the corresponding ionic liquid polymer salt, and
an electrowetting wetting property that exceeds that of low
molecular weight ionic liquids.
This new composition of matter is prepared utilizing a simple
process; yet, retains much versatility for property development. By
virtue of having a large number of ionic charges incorporated into
a single polymer molecule which has liquid-like characteristics,
this material has the capability of a unique response to an applied
electric field. Advantages and new features reside in the
accompanying properties and the applications they can support.
Compared with low molecular weight ionic liquids, this material is
capable of a large and polarity dependent response to an electric
field. Applications that can take advantage of this property are
actuators. In electronics it could find application as a dielectric
material in a capacitor or perhaps as an electromigrating
substance. Independent of the presence of an electric field, there
are surface application possibilities such as a primer to improve
surface wetting characteristics of low energy surface to accept
paints and coatings of low polarity, as a biocidal treatment for
surfaces, and as an adsorbent for opposite charged polyelectrolytes
and possibly simple ionic species in chromatography columns. In
solution this material could conceivably be used as a phase
transfer agent or as a sequestrate for ionic substances. As a
precursor to a polymer with different mechanical properties than a
liquid, it could be converted to an elastomer or a flexible plastic
and still retain its high ionic character.
In one embodiment, an ionic liquid monomer salt is provided, having
the general formula:
##STR00001##
wherein:
A represents H or CH.sub.3;
X represents --COY--, -p-C.sub.6H.sub.4--, -o-C.sub.6H.sub.4--,
-m-C.sub.6H.sub.4--, --O--, or --CH.sub.2--;
Y represents: --O(CH.sub.2).sub.n--, where n=1 to 4, or
--(OCH.sub.2CH.sub.2).sub.n where n=1 to 6, or --NHCH(CH.sub.3)--,
--NHC(CH.sub.3).sub.2--, --N(C.sub.12H.sub.25)
CH.sub.2CH.sub.2--,
--NHC(CH.sub.3)CH.sub.2--, or NHCH(C.sub.6H.sub.5)CH.sub.2--,
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the
following:
--H, or
--(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4, or
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, or
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.
Another embodiment of an ionic liquid monomer salt is presented,
having the formula:
##STR00002##
In another embodiment, an ionic liquid monomer salt is presented,
having the formula:
##STR00003##
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the
following:
--H, or
--(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4, or
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, or
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.
In another embodiment, an ionic liquid polymer salt is presented,
having the formula:
##STR00004##
wherein m>1;
A represents H or CH.sub.3;
X represents --COY--, -p-C.sub.6H.sub.4--, -o--C.sub.6H.sub.4--,
-m-C.sub.6H.sub.4--, --O--, or --CH.sub.2--;
Y represents:
--O(CH.sub.2).sub.n-- where n=1 to 4, or
--(OCH.sub.2CH.sub.2).sub.n where n=1 to 6, or
--NHCH(CH.sub.3)--, --NHC(CH.sub.3).sub.2--, --N(C.sub.12H.sub.25)
CH.sub.2CH.sub.2--.Iadd.,.Iaddend.
--NHC(CH.sub.3).Iadd..sub.2.Iaddend.CH.sub.2--, or
--NHCH(C.sub.6H.sub.5)CH.sub.2--,
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the
following:
--H, or
--(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4, or
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, or
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.
In another embodiment, an ionic liquid polymer salt is presented,
having the formula:
##STR00005##
In another embodiment, an ionic liquid polymer salt is presented,
having the formula:
##STR00006##
wherein m>1;
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the
following:
--H, or
--(CH.sub.2).sub.nCH.sub.3 where n=1 to 12,
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4,
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6,
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.
In another embodiment, a method for making an ionic liquid monomer
salt is presented. An equimolar amount of a sulfonic acid
functionalized monomer having the general formula:
##STR00007## wherein A represents H or CH.sub.3, X represents
--COY--, -p-C.sub.6H.sub.4--, -o-C.sub.6H.sub.4--,
-m-C.sub.6H.sub.4--, --O--, or --CH.sub.2--, Y represents
--O(CH.sub.2).sub.n-- where n=1 to 4, or
--(OCH.sub.2CH.sub.2).sub.n where n=1 to 6, or --NHCH(CH.sub.3)--,
--NHC(CH.sub.3).sub.2--, --N(C.sub.12H.sub.25) CH.sub.2CH.sub.2--,
--NHC(CH.sub.3).Iadd..sub.2.Iaddend.CH.sub.2--, or
--NHCH(C.sub.6H.sub.5)CH.sub.2--,
is mixed with an organic amine base having the general formula:
##STR00008##
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the
following:
--H, or
--(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4, or
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, or
--(CF.sub.2).sub.nCF.sub.3, --CH.sub.2(CF.sub.2).sub.nCF.sub.3
where n=1 to 8.
The mixture is stirred under an inert atmosphere until the sulfonic
acid functionalized monomer is dissolved, wherein the dissolution
completes formation of the ionic liquid monomer salt.
In another embodiment, a method for making an ionic liquid monomer
salt is presented. An equimolar amount of a sulfonic acid
functionalized monomer having the formula:
##STR00009##
is mixed with an organic amine base having the formula:
##STR00010##
The mixture is stirred under an inert atmosphere until the sulfonic
acid functionalized monomer is dissolved, wherein the dissolution
completes formation of the ionic liquid monomer salt. Optionally,
the ionic liquid monomer salt is in solvent methanol.
In another embodiment, a method for making an ionic liquid monomer
salt is presented. An equimolar amount of a sulfonic acid
functionalized monomer having the formula:
##STR00011##
is mixed with the organic amine base having the general
formula:
##STR00012##
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the following:
--H, or --(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4, or
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, or --(CF.sub.2).sub.nCF.sub.3,
--CH.sub.2(CF.sub.2).sub.nCF.sub.3 where n=1 to 8.
The mixture is stirred under an inert atmosphere until said
sulfonic acid functionalized monomer is dissolved, wherein the
dissolution completes formation of the ionic liquid monomer
salt.
In another embodiment, a method for making ionic liquid polymer
salts is presented. A free radical polymerization catalyst is added
to an ionic liquid monomer salt having the general formula:
##STR00013## wherein A represents H or CH.sub.3 X represents
--COY--, -p-C.sub.6H.sub.4--, -o-C.sub.6H.sub.4--,
-m-C.sub.6H.sub.4--, --O--, or --CH.sub.2-- Y represents
--O(CH.sub.2).sub.n-- where n=1 to 4, or
--(OCH.sub.2CH.sub.2).sub.n where n=1 to 6, --NHCH(CH.sub.3)--,
--NHC(CH.sub.3).sub.2--, --N(C.sub.12H.sub.25) CH.sub.2CH.sub.2--,
--NHC(CH.sub.3).Iadd..sub.2.Iaddend.CH.sub.2--, or
--NHCH(C.sub.6H.sub.5)CH.sub.2--,
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the following:
--H, or --(CH.sub.2).sub.nCH.sub.3 where n=1 to 12, or
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4,
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, --(CF.sub.2).sub.nCF.sub.3,
--CH.sub.2(CF.sub.2).sub.nCF.sub.3 where n=1 to 8
The mixture is stirred under an inert atmosphere with application
catalyst-specific polymerization conditions.
In another embodiment, a method for making ionic liquid polymer
salts is presented. A free radical polymerization catalyst is added
to an ionic liquid monomer salt having the formula:
##STR00014##
The mixture is stirred under an inert atmosphere with application
catalyst-specific polymerization conditions. Optionally, the free
radical polymerization can be conducted in solvent methanol.
Preferably, the free radical polymerization catalyst is
2,2'-azobisisobutyronitrile and the monomer to free radical
polymerization catalyst ratio is 100:1. The inert atmosphere is
preferably a nitrogen atmosphere. The catalyst-specific
polymerization conditions include heating the mixture to 70.degree.
C. and .[.stiffing.]. .Iadd.stirring .Iaddend.and heating steps are
conducted for about 18 hours.
In another embodiment, a method for making ionic liquid polymer
salts is presented. A free radical polymerization catalyst .Iadd.is
added .Iaddend.to said ionic liquid monomer salt .[.claim 3.].
having the general formula:
##STR00015##
wherein each R, R', and R'' can be the same group, or R can differ
from R', while R' is the same group as R'', or R, R', and R'' may
be all different groups; wherein
R, R', R'' each independently represented by one of the following:
--H, or --(CH.sub.2).sub.nCH.sub.3 where n=1 to 12,
--(CH.sub.2CH.sub.2O).sub.nCH.sub.3 where n=1 to 4,
--(CH.Iadd..sub.2.Iaddend.).sub.3(Si(CH.sub.3).sub.2O).sub.nCH.sub.3
where n=1 to 6, --(CF.sub.2).sub.nCF.sub.3,
--CH.sub.2(CF.sub.2).sub.nCF.sub.3 where n=1 to 8.
The mixture is stirred under an inert atmosphere with application
catalyst-specific polymerization conditions.
This invention converts 1:1 mixture of a monomer having a
polymerizable carbon-carbon double bond and a sulfonic acid or
sulfonate group (such as 2-Acrylamido-2-methyl-1-propanesulfonic
acid, .[.AMPS.]. .Iadd.1.Iaddend., mp 192.degree. C.) with an amine
base (such as tris[2-(2-methoxyethoxy)-ethyl]amine) to an ionic
liquid monomer salt that is polymerized to an ionic liquid polymer
salt in the absence or presence of solvent. To convert the sulfonic
acid monomer to a salt with a melting point or glass transition
below room temperature, it .Iadd.is .Iaddend.complexed with an
.[.an.]. amine .[.is added.].. This amine is functionalized with
large flexible substituent structures that depress a salt
solidification temperature and inhibit coordination between
oppositely charged species. Typical amine substituent structures
involve oxyethylene oligomers, silicone oligomers, and fluorocarbon
chains.
The synthesis is a two-step procedure as depicted below using
.[.the AMPS.]. monomer .Iadd.1 .Iaddend.and a tertiary amine with
oxyethylene appendages of seven atoms as an example. Both steps
proceed in remarkably good yields. The synthesis is detailed below
in Scheme 1:
##STR00016##
Scheme 1 shows the synthesis commencing with the formation of the
ammonium salt, 3. .[.AMPS-oxyethylene ammonium salt monomer.].
.Iadd.The monomer.Iaddend., 3, is synthesized by combining
2-acrylamido-2-methyl-1-propanesulfonic acid .[.(AMPS).]., 1, with
an equal molar quantity of freshly distilled
tris[2-(2-methoxyethoxy)-ethyl]amine, 2, under an inert atmosphere,
including but not limited to nitrogen or argon. The mixture is
stirred for 8 hours at ambient temperature until the .[.AMPS.].
crystals are completely dissolved and converted into the monomer
salt, 3, a slightly yellow viscous clear liquid. With no further
purification necessary, a radical initiator such as
2,2'-azobisisobutyronitrile (AIBN) is added to the reaction flask
utilizing air-free handling techniques under an inert atmosphere.
The reaction mixture is heated to 70.degree. C. and reacted for 18
hrs. The transparent amber ionic liquid polymer salt, 4, may be
used as is or further purified to remove a small percentage
(<5%) of unreacted monomer by dissolving in acetone and
reprecipitating in cold diethyl ether. This precipitate is
collected by cold suction filtration and upon warming, becomes a
tacky transparent yellow liquid. The glass transition temperatures
of the oxyethylene amine, 2, .[.AMPS.]. monomer salt, 3, and
polymer ionic liquid, 4, are -104, -57, and -49.degree. C.
respectively. Infrared, and NMR spectral analyses--are consistent
with the polymer repeat unit structure. The intrinsic viscosity
value of 0.3 is indicative of a low, but significant molecular
weight. Electrowetting characterization displays a reversible
contact angle change from 75.degree. to 30.degree. with an applied
voltage change from 0 to 157 volts. This change is larger than that
of the monomer salt or of commercial ionic liquids. Those skilled
in the art would understand that other radical initiators can be
used, and the time and temperature of the reaction would vary
depending upon the initiator chosen.
The properties of this ionic liquid polymer salt can be tuned by
varying the identity, size and symmetry of the substituents on the
amine counter ion or by varying the structure and function of the
sulfonated monomer; such that, the monomer itself could go from
being a repeat unit to a branch point to a crosslink.
These and other features and advantages of the present invention
will be presented in more detail in the following specification of
the invention and the accompanying figures, which illustrate, by
way of multiple examples, the principles of the invention.
Example
The formation of the ionic liquid monomer salt and its
polymerization is depicted in Scheme 1. The polymerizable component
is the 2-acrylamido-2-methyl-1 -propanesulfonic acid .[.(AMPS).].
monomer which is a crystalline compound with a 192.degree. C.
melting point. It is converted to a liquid ammonium salt by
addition of an equimolar quantity of
tris[2-(2-methoxyethoxy)-ethyl]amine. This tertiary amine was
selected as one that would solvate the .[.AMPS.]. monomer without
the need of a solvent and one whose oxyethylene substituents would
shield the protonated ionic center from coordinating with the
sulfonated anion, thereby depressing the melting point or glass
transition to a very low temperature.
The glass transitions of the free amine 2 (-104.degree. C.) and of
the .[.AMPS-ammonium.]. salt 3 (-57.degree. C.) presented in the
differential scanning calorimetry (DSC) thermogram in FIG. 1
demonstrate the remarkable capability of the oxyethylene
substituted amine to extend the liquid range of a salt to low
temperatures. After the liquid ammonium sulfonate monomer formation
is complete, a free radical initiator (2,2'-azobisisobutyronitrile,
AIBN) is added and reacted at 70.degree. C. The monomer conversion
is 95%, and the product is a clear acetone-soluble viscous liquid.
The spectroscopic characterization (IR, .sup.1H and .sup.13C NMR)
is consistent with polymer structure depicted in Scheme 1. The
molecular weight is low but significant as indicated by an
intrinsic viscosity measurement of 0.30 which is uncorrected for an
observed polyelectrolyte coil expansion effect. The glass
transition temperature of ionic liquid polymer 4 is -47.degree. C.
as depicted in the FIG. 1 thermogram. This is a remarkably modest
increase from that of the unpolymerized monomer salt.
Electrowetting is an electrostatically driven surface effect where
a liquid droplet's spreading on a hydrophobic surface is modulated
by application of a voltage to the droplet and an underlying
conducting substrate. A schematic of this effect is illustrated in
FIG. 2. The droplet rests on a very thin low-dielectric insulating
film (Teflon AF) which is supported on a conducting substrate and
is contacted at the top by a very fine wire contact. Application of
a voltage builds up a layer of charge on both sides of the
interface with the dielectric film and decreases the interfacial
energy.
The observed response is a spreading of the droplet and a changing
of its curvature. The dependence of the droplet's contact angle,
.theta., on the applied voltage, V, is described by the
Young-Lippmann equation as follows (Equation 1):
.times..times..theta..times..times..theta..times..times..gamma..times..ti-
mes..times..theta..times..times..times..times..times..gamma..times..times.-
.times. ##EQU00001##
where .theta..sub.O is the contact angle at zero voltage, C is the
capacitance per unit area, .gamma. is the surface tension of the
liquid, .di-elect cons. is the permittivity of the insulating
dielectric, .di-elect cons..sub.O is the electric constant and t is
the thickness of the dielectric layer. Surface tension measurements
of the monomer 3 and polymer 4 are 38.1 and 47.0 mJ/m.sup.2
respectively. The contact angle measurements of the
.[.AMPS-ammonium salt.]. monomer 3 and polymer 4 as a function of
applied DC voltage are shown in FIG. 3, and photographs of the
ionic liquid polymer droplet at zero and maximum applied voltages
in FIG. 4 show a substantial contact angle change.
A parabolic best fit of the experimental contact angles to the
voltage dependence of Equation 1 is represented by the continuous
line. A parabolic best fit of the experimental contact angles to
the voltage dependence of Equation 1 is represented by the
continuous line in FIG. 3. Separate best fits were made for the
negative and positive voltage regions of the curves. The
electrowetting curve for the .[.AMPS-ammonium sulfonate.]. monomer,
3, is similar to those reported for small molecule ionic liquids in
both magnitude and shape. No evolution of gas bubbles,
discoloration, or degradation was observed between 0 and 157 V.
A monomer vs. polymer comparison of contact angle data for
.[.AMPS.]. .Iadd.2-acrylamido-2-methyl-1-propanesulfonic
acid.Iaddend.-ammonium salt system presents an interesting
contrast. The polymer displays a larger contact angle at zero
voltage; a similar magnitude of contact angle change over the
voltage range; a departure from the Young-Lippmann equation at a
lower voltage; and a dissymmetry between the negative and the
positive voltage sections of the electrowetting curve.
These observed differences in electrowetting behavior correlate
with the higher surface tension of the polymer and with the
polyelectrolyte molecular structure. When no voltage is applied,
the greater surface tension of the polymer is clearly consistent
with the larger contact angle observed. When a voltage is applied,
an electric field is concentrated across the Teflon AF interface
and an ionic double layer of charge forms in the liquid at this
interface. This decreases the surface tension at the solid-liquid
interface and results in spreading of the liquid on the charged
surface. A depiction is illustrated in FIG. 2. The polymer differs
from the monomer in that one of the charged components is a small
cationic molecule and the other is a large anionic polyelectrolyte.
When the substrate is charged, an oppositely charged component of
the ionic liquid is adsorbed at the Teflon AF-ionic liquid
interface. On reversal of polarity, a grouping of small molecule
ions exchanges position with the polyelectrolyte. This disparity of
molecular size correlates with the dissymmetry observed between the
positive and negative sides of the electrowetting curve in FIG.
3.
All .sup.1H-HMR spectroscopy were obtained using a Bruker AC-300
spectrometer using d6-DMSO as solvent. FTIR spectra were obtained
using a Nicolet Magna-IR 750 spectrometer with sample supported on
a NaCl plate under a nitrogen purge of 40 cm.sup.3 min .sup.-1. All
differential scanning calorimetric (DSC) analysis were performed on
a TA Instruments DSC Q100 Modulated thermal analyzer at a heating
rate of 10.degree. C. min-1 and a nitrogen purge of 25
cm3min-1.
Synthesis of .[.AMPS.].
.Iadd.2-acrylamido-2-methyl-1-propanesulfonic
acid.Iaddend.-ammonium salt monomer. A nitrogen purged 50 ml
schlenk flask was charged with freshly distilled
tris[2-(2-methoxyethoxy)-ethyl]amine (1.69 g, 5.24 mmol) and
2-acrylamido-2-methyl-1-propanesulfonic acid .[.(AMPS).]. (1.09 g,
5.24 mmol) and stirred at ambient temperature for 8 hr or until
completely dissolved. Total dissolution completes formation of the
.[.AMPS-ammonium salt.]. monomer as a transparent light amber oil
in a 99% yield which was used immediately without further
purification.
Synthesis of .[.AMPS.].
.Iadd.2-acrylamido-2-methyl-1-propanesulfonic
acid.Iaddend.-ammonium salt polymer. To the prepared monomer was
added 2,2'-azobisisobutyronitrile (AIBN) (6.0 mg, 0.04 mmol) under
a nitrogen purge. The reaction flask was then sealed, allowed to
vent to a bubbler, and heated to 70.degree. C. for 18 hr. Upon
cooling to ambient temperature, the transparent dark amber mixture
was dissolved in acetone (10 ml) and precipitated as white
flocculants into cold diethyl ether (50 ml) (dry ice/acetone bath)
and quickly collected in a dry ice cooled Buchner funnel via
suction filtration. As the material warmed, the flocculants became
a transparent amber oil which was then dried under vacuum to remove
any residual solvents to yield polymer (95%).
Electrowetting actuation setup and experimentation. Actuation was
measured using the following setup as illustrated in FIG. 2: a VCA
OptimaXE commercial contact angle instrument fitted with a stage
was used to capture individual data points at various DC voltages.
An ITO coated slide, was spin-coated with Teflon AF (DuPont) at
2000 rpm for 30 seconds and heat treated in an oven at 80.degree.
C. for 18 hr which produced an insulating film with a thickness of
1.29 .mu.m (determined by a KLA Profilometer) with an intrinsic
roughness on the order of 0.5 .mu.m. The ITO slide was coupled to
an electrode in an area which was absent of Teflon AF and a Pt wire
with a diameter of 0.25 mm was used as the corresponding top
electrode. Small aliquots of ionic liquid monomer (3) or polymer
(4) (.about.50 .mu.l) were placed onto the ITO/Teflon AF coated
slide in droplet form. The Pt electrode was inserted into the
droplet and snapshots were taken at .about.8 V intervals from 0 to
157 V (DC) with polarities of the electrodes being reversed to
obtain measurements between -157 and 0 V (DC) with respect to the
ITO electrode. Contact angle software, from AST Products, Inc. VCA
Version 1.90.0.9 for Windows, calculated left and right advancing
angles for both the .[.AMPS oxyethylene ammonium salt.]. monomer 3
and polymer 4, which are plotted over a voltage range in FIG. 3.
The voltage polarity corresponds to the ITO electrode. No
discoloration, etching, or insoluble residue was resultant from
these experiments involving ionic liquid 3 and 4 nor was it
observed on the ITO surface itself. Once a voltage of 157 was
reached (for either polarity), receding contact angles were
recorded as the voltage was slowly decreased back to 0.
Surface Tension Measurements: Surface tensions for both the monomer
(3) and polymer (4) were measured at 23.degree. C. by the pendant
drop method using the VCA contact angle instrument and Pendant
Analysis Software (Version 2.22) and found to be 38.1 and 47.0
mJ/m2, respectively; higher than those previously reported for
other ionic liquids. To further address this issue, the surface
tensions of structurally relevant compounds are considered. The
surface tension of the free amine
(tris[2-(2-methoxyethoxy)-ethyl)amine, 2 was measured at 32.8 mJ/m2
(23.degree. C.). As a representative of a liquid organic sulfonic
acid, methane sulfonic acid has a surface tension of 50.2 mJ/m2
[Lange's Handbook of Chemistry, 15th Ed., J. A. Dean, 1999]. A
complex formed between these two components would probably have an
intermediate value assuming little contribution from the ammonium
sulfonate salt formation. As such this ammonium-hydrogen-sulfonate
ionic liquid is somewhat different from other ionic liquids
including those for which surface tensions have been reported in
that significant hydrogen bonding is incorporated into it. We would
speculate that the hydrogen bonding would elevate the surface
tension. We would further speculate that transformation of the
.[.AMPS-ammonium salt.]. monomer 3 to polymer 4 would enhance the
density of the hydrogen bonding and further elevate the surface
tension as observed. Hence, we speculate that a more dense
structure of the polymer and hydrogen bonding is consistent with an
increased surface tension.
This example represents synthesis and electrowetting of individual
members of new ionic liquid monomer and polymer systems. The
uniqueness of the oxyethylene amine formation of the ammonium
cationic species contributes to both the ionic and liquid nature of
the monomer and polymer. Even more remarkable is the ability of
this polymer to maintain its liquid nature after polymerization and
wet a substrate, showing preference for one polarity based upon the
makeup of the ionic backbone of the polymer formed.
Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that, within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described.
* * * * *