U.S. patent application number 10/771878 was filed with the patent office on 2004-08-12 for carbon dioxide-philic compounds and methods of synthesis thereof.
Invention is credited to Beckman, Eric J., Sarbu, Traian, Styranec, Thomas J..
Application Number | 20040158013 10/771878 |
Document ID | / |
Family ID | 30447955 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040158013 |
Kind Code |
A1 |
Beckman, Eric J. ; et
al. |
August 12, 2004 |
Carbon dioxide-philic compounds and methods of synthesis
thereof
Abstract
A method of synthesizing a CO.sub.2-philic analog of a
CO.sub.2-phobic compound, includes the step of: reacting the
CO.sub.2-phobic compound with a CO.sub.2-philic compound selected
from the group of a polyether substituted with at least one side
group including preferably a Lewis base, a polycarbonate, a
polycarbonate substituted with at least one side group including
preferably a Lewis base, a vinyl polymer substituted with at least
one side group including preferably a Lewis base a
poly(ether-ester) or a poly(ether-ester) substituted with at least
one side group including preferably a Lewis base, to create the
CO.sub.2-philic analog. A method of synthesizing a CO.sub.2-phile
includes the step of copolymerizing at least two monomers, wherein
a polymer formed from homopolymerization of one of the monomers has
a T.sub.g of less than approximately 250 K and a steric factor less
than approximately 1.8, at least one of the monomers contains a
group that results in a pendant group from the CO.sub.2-phile
backbone that contains a Lewis base group, and the resultant
CO.sub.2-phile does not contain both hydrogen bond donors and
acceptors.
Inventors: |
Beckman, Eric J.;
(Aspinwall, PA) ; Sarbu, Traian; (Pittsburgh,
PA) ; Styranec, Thomas J.; (Midland, MI) |
Correspondence
Address: |
Henry E. Bartony, Jr
Bartony & Hare, LLP
Law and Finance Building
429 Fourth Avenue, Suite 1801
Pittsburgh
PA
15219
US
|
Family ID: |
30447955 |
Appl. No.: |
10/771878 |
Filed: |
February 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10771878 |
Feb 3, 2004 |
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09668088 |
Sep 22, 2000 |
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6686438 |
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60155960 |
Sep 24, 1999 |
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Current U.S.
Class: |
526/232 ;
528/271; 528/370; 528/423 |
Current CPC
Class: |
C08L 71/03 20130101;
C08G 65/331 20130101; C08G 63/91 20130101; C08G 64/34 20130101;
C08G 63/914 20130101; C08G 63/672 20130101; C08G 64/0208 20130101;
C08G 64/183 20130101; C11D 1/008 20130101; C08G 65/3322 20130101;
C08G 64/02 20130101; C08L 2205/05 20130101; C08G 65/2654 20130101;
C08G 64/42 20130101; C08G 65/2603 20130101 |
Class at
Publication: |
526/232 ;
528/271; 528/370; 528/423 |
International
Class: |
C08G 064/00; C08F
004/32; C08G 063/00; C08G 067/00; C08G 069/00; C08G 073/06 |
Claims
What is claimed is:
1. A method of synthesizing a CO.sub.2-philic analog of a
CO.sub.2-phobic compound that is more CO.sub.2-philic than the
CO.sub.2-phobic compound, comprising the step of: reacting the
CO.sub.2-phobic compound with a CO.sub.2-philic compound, wherein
the CO.sub.2-philic compound is a polyether substituted with at
least one side group including a Lewis base, a
poly(ether-carbonate), a poly(ether-carbonate) substituted with at
least one side group including a Lewis base, a vinyl polymer
substituted with at least one side groups including a Lewis base, a
poly(ether-ester) or a poly(ether-ester) substituted with at least
one side groups including a Lewis base to create the
CO.sub.2-philic analog.
2. The method of claim 1 wherein the CO.sub.2-philic compound is a
polyether substituted with at least one side group including a
Lewis base, a poly (ether-carbonate), a poly(ether-carbonate)
substituted with at least one side group including a Lewis base, or
a vinyl polymer substituted with at least one side group including
a Lewis base.
3. The method of claim 1 wherein the CO.sub.2-philic contains no F
or Si atoms.
4. The method of claim 1 wherein the CO.sub.2-philic compound is a
polyether copolymer including the repeat units 5wherein R.sup.1,
R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8,
R.sup.9, R.sup.10, R.sup.11, and R.sup.12 are, independently, the
same or different, H, an alkyl group, --(R.sup.22')R.sup.22, or
R.sup.4 and R.sup.6 form of carbon cyclic chain of 3 to 8 carbon
atoms, wherein R.sup.22' is an alkylene group and z is 0 or 1, and
R.sup.22 is a Lewis base group, wherein at least one of R.sup.1, R
.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8,
R.sup.9, R.sup.10, R.sup.11, and R.sup.12 is
--(R.sup.22').sub.zR.sup.22, wherein, i, j, k, l, m, and n are
independently, the same or different, 0, 1 or 2, at least one of i,
j, and k being 1 or 2 and at least one of l, m, and being 1 or 2,
and x and y are integers.
5. The method of claim 4 wherein R.sup.22 is --O--C(O)--R.sup.23,
--C(O)--R.sup.23, --O--P(O)--(O--R.sup.23).sub.2, or
--NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23' are
independently, the same or different, an alkyl group.
6. The method of claim 4 wherein R.sup.22' is --(CH.sub.2).sub.a--
and a is an integer between 0 and 5.
7. The method of claim 6 wherein a is 1 or 2 and i is 0, j is 1, k
is 1, 1 is 0, m is 1 and n is 1
8. The method of claim 7 wherein R.sup.3, R.sup.4, R.sup.5,
R.sup.9, R.sup.10, and R.sup.11 are H, R.sup.6 is an alkyl group
and R.sup.12 is --(CH.sub.2).sub.a--R.sup.22.
9. The method of claim 8 wherein R.sup.22 is O--C(O)--R.sup.23,
--C(O)--R.sup.23, --O--P(O)--(O--R.sup.23).sub.2, or
--NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23' are
independently, the same or different, an alkyl group.
10. The method of claim 8 wherein R.sup.22 is
--O--C(O)--R.sup.23.
11. The method of claim 10 wherein R.sup.23 is a methyl group.
12. The method of claim 4 wherein the polyether copolymer contains
no F or Si atoms.
13. The method of claim 1 wherein the CO.sub.2-philic compound is a
poly(ether-carbonate) copolymer including the repeat units:
6wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6,
R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11, and R.sup.12, are,
independently, the same or different, H, an alkyl group,
--(R.sup.22').sub.zR.sup.22, or R.sup.4 and R.sup.6 form of carbon
cyclic chain of 3 to 8 carbon atoms, wherein R.sup.22' is an
alkylene group and z is 0 or 1, and R.sup.22 is a Lewis base group,
wherein, i, j, k, l, m, and n are independently, the same or
different, 0, 1 or 2, at least one of i, j, and k being 1 or 2 and
at least one of l, m, and being 1 or 2, and x' and y' are
integers.
14. The method of claim 13 wherein R.sup.22 is --O--C(O)--R.sup.23,
--C(O)--R.sup.23, --O--P(O)--(O--R.sup.23).sub.2, or
--NR.sup.23R.sup.23 ', wherein R.sup.23 and R.sup.23' are
independently, the same or different, an alkyl group.
15. The method of claim 14 wherein R.sup.22' is --(CH.sub.2).sub.a'
and a is an integer between 0 and 5.
16. The method of claim 15 wherein a is 1 or 2.
17. The method of claim 13 wherein i is 0, j is 1, k is 1, l is 0,
m is 1 and n is 1 and R.sup.3, R.sup.4, R.sup.5, R.sup.9, R.sup.10,
and R.sup.11 are H, R.sup.6 is an alkyl group and R.sup.12 is an
alkyl group.
18. The method of claim 13 wherein the poly(ether-carbonate)
copolymer contains no F or Si atoms.
19. The method of claim 1 wherein the vinyl polymer is a copolymer
including the repeat units: 7wherein R.sup.13, R.sup.14, R.sup.15,
R.sup.16, R.sup.17, R.sup.18, R.sup.19, and R.sup.20 are,
independently, the same or different, H, an alkyl group, an alkenyl
group, --O--R.sup.24, --(R.sup.22').sub.zR.sup.22, wherein,
R.sup.22' is an alkylene group, R.sup.22 is a Lewis base group and
z is 0 or 1, R.sup.24 is an alkyl group, wherein at least one of
R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18,
R.sup.19, and R.sup.20 is --(R.sup.22').sub.zR.sup.22, and x" and
y" are integers.
20. The method of claim 19 wherein R.sup.22' is
--(CH.sub.2).sub.a-- and a is an integer between 0 and 5.
21. The method of claim 20 wherein a is 1 or 2 and R.sup.22 is
--O--C(O)--R.sup.23, --C(O)--R.sup.23, --O--P(O)--(O--R ).sub.2, or
--NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23' are
independently, the same or different, an alkyl group.
22. The method of claim 21 wherein R.sup.22 is --O--C
(O)--R.sup.23.
23. The method of claim 19 wherein the vinyl copolymer contains no
F or Si atoms.
24. The method of claim 1 wherein the CO.sub.2-philic compound is a
poly(ether-ester) copolymer including the repeat units 8wherein
R.sup.1', R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are,
independently, the same or different, H, an alkyl group,
--(R.sup.22').sub.zR.sup.22, or R.sup.4 and R.sup.6 form of carbon
cyclic chain of 3 to 8 carbon atoms, wherein z is 0 or 1, R.sup.22'
is an alkylene group and R.sup.22 is a lewis base group, wherein,
i, j and k are independently, the same or different, 0, 1 or 2, at
least one of i, j, and k being 1 or 2, R.sup.21 is an alkylene
group, a cycloalkylene group, a difunctional ester group, or a
difunctional ether group, and x'" and y'" are integers.
25. The method of claim 24 wherein at least one of R.sup.1,
R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 is
--(R.sup.22').sub.zR.sup.22, and R.sup.22 is --O--C(O)--R.sup.23,
--C(O)--R.sup.23, O--P(O)--(O--R.sup.23).sub.2, or
--NR.sup.23R.sup.23, wherein R.sup.23 and R.sup.23' are
independently, the same or different, an alkyl group.
26. The method of claim 25 wherein R.sup.22' is
--(CH.sub.2).sub.a-- and a is an integer between 0 and 5.
27. The method of claim 26 wherein a is 1 or 2 and i is 0, j is 1,
and k is 1.
28. The method of claim 24 wherein R.sup.22 is --O--C(O)--R.sup.23,
--C(O)--R.sup.23, --O--P (O)--(O--R.sup.23).sub.2, or
--NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23' are
independently, the same or different, an alkyl group.
29. The method of claim 27 wherein R.sup.22 is
--O--C(O)--R.sup.23.
30. A surfactant for use in carbon dioxide, the surfactant
comprising a CO.sub.2-phobic group covalently linked to a
CO.sub.2-philic segment, wherein the CO.sub.2-philic segment
includes a polyether substituted with at least one side group
including a Lewis base, a poly(ether-carbonate), a
poly(ether-carbonate) substituted with at least one side group
including a Lewis base, a vinyl polymer substituted with at least
one side group including a Lewis base, a poly(ether-ester) or a
poly(ether-ester) substituted with at least one side group
including a Lewis base.
31. The surfactant of claim 30 wherein the polyether is a polyether
copolymer including the repeat units 9wherein R.sup.1, R.sup.2,
R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9,
R.sup.10, R.sup.11, and R.sup.12 are, independently, the same or
different, H, an alkyl group, --(R.sup.22').sub.zR.sup.22, or
R.sup.4 and R.sup.6 form of carbon cyclic chain of 3 to 8 carbon
atoms, wherein R.sup.22' is an alkylene group and z is 0 or 1, and
R.sup.22 is a Lewis base group, wherein at least one of R.sup.1,
R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8,
R.sup.9, R.sup.10, R.sup.11, and R.sup.12 is
--(R.sup.22').sub.zR.sup.22, wherein, i, j, k, l, m, and n are
independently, the same or different, 0, 1 or 2, at least one of i,
j, and k being 1 or 2 and at least one of 1, m, and being 1 or 2,
and x and y are integers.
32. The surfactant of claim 31 wherein R.sup.22 is
--O--C(O)--R.sup.23, --C(O)--R.sup.23,
--O--P(O)--(O--R.sup.23).sub.2, or --NR.sup.23R.sup.23', wherein
R.sup.23 and R.sup.23' are independently, the same or different, an
alkyl group.
33. The surfactant of claim 32 wherein R.sup.22' is
--(CH.sub.2).sub.a-- and a is an integer between 0 and 5.
34. The surfactant of claim 30 wherein the poly(ether-carbonate)
copolymer includes the repeat units: 10wherein R.sup.1, R.sup.2,
R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9,
R.sup.10, R.sup.11, and R.sup.12 are, independently, the same or
different, H, an alkyl group, --(R.sup.22').sub.zR.sup.22, or
R.sup.4 and R.sup.6 form of carbon cyclic chain of 3 to 8 carbon
atoms, wherein R.sup.22' is an alkylene group and z is 0 or 1, and
R.sup.22 is a Lewis base group, wherein, i, j, k, l, m, and n are
independently, the same or different, 0, 1 or 2, at least one of i,
j, and k being 1 or 2 and at least one of l, m, and being 1 or 2,
and x' and y' are integers.
35. The surfactant of claim 34 wherein R.sup.22 is
--O--C(O)--R.sup.23, --C(O)--R.sup.23,
--O--P(O)--(O--R.sup.23).sub.2, or --NR.sup.23R.sup.23', wherein
R.sup.23 and R.sup.23' are independently, the same or different, an
alkyl group.
36. The surfactant of claim 36 wherein R.sup.22' is
--(CH.sub.2).sub.a-- and a is an integer between 0 and 5.
37. The surfactant of claim 30 wherein the vinyl polymer is a
copolymer including the repeat units: 11wherein R.sup.13, R.sup.14,
R.sup.15, R.sup.16, R.sub.17, R.sup.18, R.sup.19, and R.sup.20 are,
independently, the same or different, H, an alkyl group, an alkenyl
group, --O--R.sup.24, --(R.sup.22').sub.zR.sup.22, wherein,
R.sup.22' is an alkylene group, R.sup.22 is a Lewis base group and
z is 0 or 1, R.sup.24 is an alkyl group, wherein at least one of
R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18,
R.sup.19, and R.sup.20 is --(R.sup.22').sub.zR.sup.22, and x" and
y" are integers.
38. The surfactant of claim 37 wherein R.sup.22' is
--(CH.sub.2).sub.a-- and a is an integer between 0 and 5.
39. The surfactant of claim 38 wherein a is 1 or 2 and R.sup.22 is
--O--C(O)--R.sup.23, --C(O)--R.sup.23,
--O--P(O)--(O--R.sup.23).sub.2, or --NR.sup.23R.sup.23', wherein
R.sup.23 and R.sup.23' are independently, the same or different, an
alkyl group.
40. The surfactant of claim 39 wherein R.sup.22 is
--O--C(O)--R.sup.23.
41. The surfactant of claim 30 wherein the CO.sub.2-philic compound
is a poly(ether-ester) copolymer including the repeat units
12wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6
are, independently, the same or different, H, an alkyl group,
--(R.sup.22').sub.zR.sup.22, or R.sup.4 and R.sup.6 form of carbon
cyclic chain of 3 to 8 carbon atoms, wherein z is 0 or 1, R.sup.22'
is an alkylene group and R.sup.22 is a lewis base group, wherein,
i, j and k are independently, the same or different, 0, 1 or 2, at
least one of i, j, and k being 1 or 2, R.sup.21 is an alkylene
group, a cycloalkylene group, a difunctional ester group, or a
difunctional ether group, and x'" and y'" are integers.
42. The surfactant of claim 41 wherein at least one of R.sup.1,
R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 is
--(R.sup.22').sub.zR.sup.22, the lewis base group is
O--C(O)--R.sup.23, --C(O)--R.sup.23, --O--P
(O)--(O--R.sup.23).sub.2, or --NR.sup.23R.sup.23', wherein R.sup.23
and R.sup.23' are independently, the same or different, an alkyl
group.
43. The surfactant of claim 42 wherein R.sup.22' is --(CH2).sub.a--
and a is an integer between 0 and 5.
44. The surfactant of claim 30 wherein the CO.sub.2-phobic group is
H, a carboxylic acid group, a hydroxy group, a phosphato group, a
phosphato ester group, a sulfonyl group, a sulfonate group, a
sulfate group, a branched or straight chained polyalkylene oxide
group, an amine oxide group, an alkenyl group, a nitryl group, a
glyceryl group, an ammonium, an alkyl ammonium, an aryl group
unsubstituted or substituted with an alkyl group or an alkenyl
group, or a carbohydrate unsubstituted with an alkyl group or an
alkenyl group.
45. The surfactant of claim 30 wherein the CO.sub.2-phobic group
includes at least one ion selected from the group of H.sup.+,
Na.sup.+2, Li.sup.+, K.sup.+, NH.sub.4.sup.+, Ca.sup.+2, Mg.sup.+2,
Cl.sup.-, Br.sup.-, I.sup.-, mesylate and tosylate.
46. A chelating agent for use in carbon dioxide, the chelating
agent comprising a CO.sub.2-phobic chelating group covalently
linked to a CO.sub.2-philic segment, wherein the CO.sub.2-philic
segment includes a polyether substituted with side groups including
a Lewis base, a poly(ether-carbonate), a poly(ether-carbonate)
substituted with side groups including a Lewis base, a vinyl
polymer substituted with side groups including a Lewis base, or a
poly(ether-ester).
47. The chelating agent of claim 46 wherein the chelating group is
a polyaminocarboxylic acid group, a thoicarbamate group, a
dithoicarbamate group, a thiol group, a dithiol group, a picolyl
amine group, a bis(picolyl amine) group or a phosphate group.
48. A method of synthesizing a CO.sub.2-philic copolymer comprising
the step of copolymerizing at least two monomers, wherein a polymer
formed from homopolymerization of one of the monomers has a T.sub.g
of less than approximately 250 K and a steric factor less than
approximately 1.8, at least one of the monomers results a Lewis
base group in the copolymer, and the resultant CO.sub.2-phile does
not contain both hydrogen bond donors and acceptors.
49. The method of claim 48 wherein a Lewis base group is within the
monomer backbone.
50. The method of claim 48 wherein the Lewis group is a pendant
group from the backbone of the at least one monomer.
51. The method of claim 50 wherein the Lewis base group is
separated from the CO.sub.2-phile backbone by 0 to 5 atoms.
52. The method of claim 51 wherein the Lewis base group is
separated from the CO.sub.2-phile backbone by 1 to 2 atoms.
53. The method of claim 48 wherein the CO.sub.2-phile includes no F
or Si atoms.
54. The method of claim 48 wherein the copolymer has less than 400
repeat units.
55. The method of claim 48 wherein the copolymer has less that 200
repeat units.
56. The method of claim 48 wherein the copolymer between 5 and 50
repeat units.
57. The method of claim 48 wherein repeat units of the copolymer
including the Lewis base are in the range of 1 to 50 percent of all
of the repeat units.
58. The method of claim 48 wherein repeat units of the copolymer
including the Lewis base are in the range of 5 to 35 percent of all
of the repeat units.
59. The method of claim 48 wherein repeat units of the copolymer
including the Lewis base are in the range of 10 to 25 percent of
all of the repeat units.
60. The method of claim 48 a first monomer is chosen such that a
polymer formed from homopolymerization of the first monomer has a
T.sub.g of less than approximately 250 K and a steric factor less
than approximately 1.8 and a second and different monomer results a
Lewis base group in the copolymer.
61. A method of synthesizing a CO.sub.2-phile comprising the step
of copolymerizing carbon dioxide and at least one oxirane.
62. The method of claim 61 wherein the oxirane is ethylene oxide,
propylene oxide cyclohexene oxide, or epichlorohydrin.
Description
RELATED APPLICATION
[0001] The present application is related to U.S. Provisional
Patent Application Serial No. 60/155,960, filed Sep. 24, 1999,
assigned to the assignee hereof, the disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to compounds that are soluble
in or miscible in carbon dioxide and to methods of synthesizing
such compounds.
BACKGROUND OF THE INVENTION
[0003] Various publications are referenced herein to, for example,
clarify the general state of the art. Reference to a publication
herein is not an admission that the publication is prior art or
relevant to the patentability of the present invention.
[0004] The feasibility of using carbon dioxide or CO.sub.2 as a
process solvent has been extensively investigated in both academic
and industrial circles because CO.sub.2 is considered to be an
environmentally benign solvent. Previous solubility parameter
calculations using equation of state information suggested that the
solvent power of CO.sub.2 was similar to that of short n-alkanes,
leading to hopes that CO.sub.2 could replace a wide variety of
non-polar organic solvents. King, J. W., Poly. Mat. Sci. Eng.
Prepr. (1984), 51, 707. Although such solubility parameter values
precluded the use of CO.sub.2 for processing of polar or
hydrophilic materials, it was believed that addition of
conventional alkyl-functional surfactants could effectively deal
with the problem. However, early attempts to employ conventional
surfactants in CO.sub.2 failed as a result of the poor solubility
of the amphiphiles, despite the fact that these same molecules
exhibited adequate solubility in ethane and propane. Consani, K.
A.; Smith, R. D.; J. Supercrit. Fl. (1990), 3, 51. It was later
discovered that the early solubility parameter calculations, while
mathematically correct, failed to note that the absolute value was
inflated by as much as 20% by the strong quadropole moment of
CO.sub.2 (which also inflates its critical pressure). Myers, A. L.;
Prausnitz, J. M., Ind. Eng. Chem. Fundam. (1965), 4, 209.
[0005] Johnston and colleagues suggested polarizability/volume as a
better quantity by which to judge solvent power. O'Shea, K.;
Kirmse, K.; Fox, M. A.; Johnston, K. P.; J. Phys. Chem. (1991), 95,
7863 (b) McFann, G. J.; Howdle, S. M.; Johnston, K. P.; AIChE J.
(1994), 40, 543 (c) Johnston, K. P.; Lemert, R. M.; in Encyclopedia
of Chemical Processing and Design, McKetta, J. J., Ed; Marcel
Dekker: New York (1996), 1. On the basis of polarizability/volume,
CO.sub.2 is a poor solvent compared to short n-alkanes. As the
1980's drew to a close, a number of research groups began to
explore the design of CO.sub.2-philic materials, (that is,
compounds which dissolve in or are miscible in CO.sub.2 at
significantly lower pressures than alkyl functional analogs). For
example, Harrison et al. generated a hybrid alkyl/fluoroalkyl
surfactant that both dissolved in CO.sub.2 and solubilized
significant amounts of water. Harrison, K.; Goveas, J.; Johnston,
K. P.; O'Rear, E. A.; Langmuir (1994), 10, 3536. DeSimone and
coworkers generated homo- and copolymers of fluorinated acrylates
which exhibit complete miscibility with CO.sub.2 at moderate
pressures. DeSimone, J. M.; Guan, Z.; Elsbernd, C. S.; Science
(1992), 257, 945. Block copolymers featuring fluorinated acrylate
monomers were used to support dispersion polymerization in
CO.sub.2, allowing generation of micron-size monodisperse spheres.
Hsiao, Y. L.; Maury, E. E.; DeSimone, J. M.; Mawson, S. M.;
Johnston, K. P.; Macromolecules (1995), 28, 8159.
Fluoroether-functional amphiphiles have been used to support
emulsion polymerization as described in Adamsky, F. A.; Beckman, E.
J.; Macromolecules (1994), 27, 312, solubilize proteins as
described in (a) Ghenciu, E.; Russell, A. J.; Beckman, E. J.;
Biotech. Bioeng (1998), 58, 572 (b) Ghenciu, E.; Beckman, E. J.;
Industr. Eng. Chem. Res. (1997), 36, 5366; and Johnston, K. P.;
Harrison, K. L.; Clarke, M. J.; Howdle, S.; Heitz, M. P.; Bright,
F. V.; Carlier, C. Randolph, T. W.; Science (1996), 271, 624, and
extract heavy metals from soil and water as described in (Yazdi, A.
V.; Beckman, E. J.; Ind. Eng. Chem. (1997), 36, 2368; and Li, J.;
Beckman, E. J.; Industr. Eng. Chem. Res. (1998), 37, 4768.
[0006] In general, compounds not soluble or miscible in CO.sub.2
(that is, CO.sub.2-phobic compounds) can be made soluble or
miscible in CO.sub.2 by synthesizing analogs of such compounds
incorporating one or more CO.sub.2-philic groups. Processes and
reactions that are normally not possible in CO.sub.2, are thereby
made possible. For example, surfactants, chelating agents and
reactants for use in carbon dioxide can be synthesized in this
manner. CO.sub.2-phobic compounds that can be modified with
CO.sub.2-philic groups to create CO.sub.2-philic analogs for
processing in CO.sub.2 are disclosed, for example, in U.S. patent
application Ser. No. 09/106,480, entitled Synthesis of Hydrogen
Peroxide and filed Jun. 29, 1998, the disclosure of which is
incorporated herein by reference, in which hydrogen peroxide is
synthesized in CO.sub.2 using a CO.sub.2-philic functionalized
anthraquinone reactant. Moreover, CO.sub.2-philic chelating agents
for extraction of metals in carbon dioxide are disclosed U.S. Pat.
No. 5,641,887 and U.S. Pat. No. 5,872,257, the disclosures of which
are incorporated herein by reference. Other CO.sub.2-philic
functionalized compounds are disclosed in U.S. Pat. No. 5,589.105,
U.S. Patent No. 5,789,505, U.S. Pat. No. 5,639,836, U.S. Pat. No.
5,679,737, U.S. Pat. No. 5,733,964, U.S. Pat. No. 5,780,553, U.S.
Pat. No. 5,858,022, U.S. Pat. No. 5,676,705, U.S. Pat. No.
5,683,977, and U.S. Pat. No. 5,683,473, the disclosures of which
are incorporated herein by reference.
[0007] It has been theorized that only molecules with very low
solubility parameters (that is, fluorine-containing and
silicon-containing molecules) are sufficiently CO.sub.2-philic to
synthesize CO.sub.2-philic analogs or amphiphiles suitable for
commercial processing in CO.sub.2. O'Neill, M. L., Cao, Q.; Fang,
M.; Johnston, K. P.; Wilkinson, S. P.; Smith, C. D.; Kerschner, J.
L.; Jureller, S. H.; Ind. Eng. Chem. Res. (1998), 37, 3067. Indeed,
it is the common belief in the art that only fluorine-containing
and silicon-containing molecules are viable solutions in
synthesizing commercially viable CO.sub.2-philic analogs. The most
successful CO.sub.2-philic modifiers or moieties to date are
fluorinated compounds. Despite success in development of
fluorinated and silicon-containing CO.sub.2-philic amphiphiles, the
cost (on a mass basis) of these materials (typically, on the order
of $1/gram) renders the economics of a process unfavorable unless
the amphiphile can be efficiently recycled. Whereas in-process
recycling of a "CO.sub.2-phile" may at times be straightforward,
this is not true in all cases where CO.sub.2 has been proposed as a
replacement for organic solvents.
[0008] It is very desirable to develop CO.sub.2-philic compounds or
CO.sub.2-philes that are effectively soluble in or miscible in
CO.sub.2 while being relatively inexpensive to synthesize and
use.
SUMMARY OF THE INVENTION
[0009] The present invention provides, generally, a method of
synthesizing a CO.sub.2-philic analog of a CO.sub.2-phobic
compound, comprising the step of: reacting the CO.sub.2-phobic
compound with a CO.sub.2-philic compound to create the
CO.sub.2-philic analog. Preferably, the CO.sub.2-philic compound
contains no F or Si.
[0010] Preferably, the CO.sub.2-philic compound is a polyether
substituted with at least one side group including a group that
interacts favorably with or has an affinity for CO.sub.2
(preferably a Lewis base group), a poly(ether-carbonate), a
poly(ether-carbonate) substituted with at least one side group
including preferably a Lewis base, a vinyl polymer substituted with
at least one side group including preferably a Lewis base, a
poly(ether-ester) or a poly(ether-ester) substituted with at least
one side group including preferably a Lewis base. Preferably, the
CO.sub.2-philic compound contains no F or Si atoms. The
CO.sub.2-philic analog of the CO.sub.2-phobic compound has
increased solubility or miscibility in CO.sub.2 (that is, increased
CO.sub.2-philic nature) compared to the CO.sub.2-phobic
compound.
[0011] In one embodiment, the CO.sub.2-philic compound is a
polyether copolymer including the repeat units 1
[0012] wherein R.sup.1, R.sup.2, R.sup.3 , R.sup.4, R.sup.5,
R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11 and R.sup.12
are, independently, the same or different, H, an alkyl group,
--(R.sup.22').sub.zR.sup.22, or R.sup.4 and R.sup.6 form of carbon
cyclic chain of 3 to 8 carbon atoms. R.sup.22' is a spacer or
connecting group, and preferably is an alkylene group, and z is 0
or 1. R.sup.22 is a group that interacts favorably with CO.sub.2
and is preferably a Lewis base group. Preferably, at least one of
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7,
R.sup.8, R.sup.9, R.sup.10, R.sup.11, and R.sup.12 is
--(R.sup.22').sub.zR.sup.22.
[0013] In the above equation, i, j, k, l, m, and n are
independently, the same or different, 0, 1 or 2. At least one of i,
j, and k is 1 or 2, and at least one of l, m, and is 1 or 2. x and
y are integers. Preferably, i, j, k, l, m, and n are 0 or 1. More
preferably, i is 0, j is l, k is 1, l is 0, m is 1 and n is 1. In
the case that one of i, j, k, l, m, or n is 2, each of the
substituents on the two carbon atoms can be different. In that
regard, for example, --(CR.sup.1R.sup.2).sub.2-- expands to
--(CR.sup.1R.sup.2--CR.sup.1'R.sup.2')-- wherein R.sup.1, R.sup.2,
R.sup.1', and R.sup.2' are, independently, the same or different,
H, an alkyl group, --(R.sup.22').sub.zR.sup.22. Likewise, pendant
R's on adjacent carbons can form a carbon chain of 3 to 8 carbon
atoms.
[0014] In several embodiments R.sup.22' is --(CH.sub.2).sub.a-- and
a is an integer between 0 and 5. Preferably, a is 1 or 2. Suitable
Lewis base groups R.sup.22, include, but are not limited to,
carbonyl-containing groups such as --O--C(O)--R.sup.23 or
--C(O)--R.sup.23, --O--P (O)--(O--R.sup.23).sub.2, or
--NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23' are preferably
independently, the same or different, an alkyl group.
[0015] In one embodiment in which i is 0, j is 1, k is 1, l is 0, m
is 1 and n is 1, R.sup.3, R.sup.4, R.sup.5, R.sup.9, R.sup.10, and
R.sup.11 are H, R.sup.6 is an alkyl group and R.sup.12 is a Lewis
base. For example, the lewis base group can be O--C(O)--R.sup.23.
In one such embodiment, R.sup.23 is a methyl group. In one
embodiment the methyl group is substituted with a Cl
(--CH.sub.2Cl).
[0016] Preferably, the polyether copolymer contains no F or Si
atoms.
[0017] In the repeat units of the polyether, x and y are integers.
Preferably x and y are each at least 1. Preferably, the total chain
length of the CO.sub.2-philic group (x+y) is less than
approximately 400 repeat units. More preferably, the total chain
length of the CO.sub.2-philic group (x+y) is less than
approximately 200 repeat units. For many application (for example,
surfactants) the total chain length is preferably between 5 and 50
repeat units. More preferably, the chain length in such
applications is between approximately 20 to 40 repeat units. The
percentage of repeat units including a Lewis base group is
preferably in the range of approximately 1 to approximately 50%.
More preferably, the percentage of repeat units including a Lewis
base group is in the range of approximately 5 to approximately 35%.
Even more preferably, the percentage of repeat units including a
Lewis base group is in the range of approximately 10 to
approximately 25%.
[0018] In another embodiment, the CO.sub.2-philic compound is a
poly(ether-carbonate) copolymer including the repeat units: 2
[0019] wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 R.sup.6,
R.sup.7, R.sup.8, R.sup.9, R.sup.10 , and R.sup.11, and R.sup.12
are, independently, the same or different, H, an alkyl group,
--(R.sup.22')R.sub.z.sup.22, or R.sup.4 and R.sup.6 form of carbon
cyclic chain of 3 to 8 carbon atoms as described above. Likewise,
i, j, k, l, m and n are as described above (0, 1 or 2). Preferably,
i, j, k, l, m and n are 0 or 1. In several embodiments, i and l are
0, and j, k, m and n are 1. In this copolymer a Lewis base group is
incorporated into the copolymer backbone. The copolymer can also
include one or more pendant groups that react favorably with
CO.sub.2 (preferably, Lewis base groups). Preferably, the
poly(ether-carbonate) copolymer contains no F or Si atoms.
[0020] In one embodiment i and l are 0, j, k, m and n are 1,
R.sup.3, R.sup.4, R.sup.5, R.sup.9, R.sup.10, and R.sup.11 are H,
R.sup.6 is an alkyl group (for example, a methyl group) and
R.sup.12 is an alkyl group (for example, a methyl group).
[0021] In the repeat units of the polycarbonate, x' and y' are
integers and, preferably, each is at least 1. Preferably, the total
chain length of the CO.sub.2-philic group (x'+y') is less than
approximately 400 repeat units. More preferably, the total chain
length of the CO.sub.2-philic group is less than approximately 200
repeat units. For many application (for example, surfactants) the
total chain length is preferably between 5 and 50 repeat units.
More preferably, the chain length in such applications is between
approximately 20 to 40 repeat units. The percentage of repeat units
including the carbonate linkage (that is, the Lewis base in the
copolymer backbone indicated by y') is preferably in the range of
approximately 1 to approximately 50%. More preferably, the
percentage of repeat units including the carbonate linkage is in
the range of approximately 5 to approximately 35%. Even more
preferably, the percentage of repeat units including the carbonate
linkage is in the range of approximately 10 to approximately
25%.
[0022] In one aspect, the vinyl polymer is a copolymer including
the repeat units: 3
[0023] wherein R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17,
R.sup.18, R.sup.19, and R.sup.20 are, independently, the same or
different, H, an alkyl group, an alkenyl group, --O--R.sup.24,
--(R.sup.22').sub.zR.sup.22- , wherein, z, R.sup.22' and R.sup.22
are as described above. Preferably, at least one of R.sup.13,
R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19, and
R.sup.20 is --(R.sup.22').sub.zR.sup.22. x" and y" are integers.
The vinyl copolymer preferably contains no F or Si atoms.
[0024] In several embodiment, R.sup.22' is --(CH.sub.2).sub.a --
and a is an integer between 0 and 5. In such embodiments, a is
preferably 1 or 2 and R.sup.22 is, for example,
--O--C(O)--R.sup.23, --C(O)--R.sup.23, --O--P(O)--(O--R.sup.23
).sub.2, or --NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23'
are independently, the same or different, an alkyl group.
[0025] In the polyvinyl copolymer, x" and y" are integers and
preferably each is at least 1. Preferably, the total chain length
of the CO.sub.2-philic group (x"+y") is less than approximately 400
repeat units. More preferably, the total chain length of the
CO.sub.2-philic group is less than approximately 200 repeat units.
For many application (for example, surfactants) the total chain
length is preferably between 5 and 50 repeat units. More
preferably, the chain length in such applications is between
approximately 20 to 40 repeat units. The percentage of repeat units
including a Lewis base is preferably in the range of approximately
1 to approximately 50%. More preferably, the percentage of repeat
units including a Lewis base is in the range of approximately 5 to
approximately 35%. Even more preferably, the percentage of repeat
units including a Lewis base is in the range of approximately 10 to
approximately 25%.
[0026] In another aspect, the CO.sub.2-philic compound is a
poly(ether-ester) copolymer including the repeat units 4
[0027] wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and
R.sup.6 are as defined above, and i, j and k are as defined
above(O, 1 or 2). Preferably, i, j, k, l, m and n are 0 or 1. In
several embodiments, i and 1 are 0, and j, k, m and n are 1.
R.sup.21 is a connecting group that can, for example, be an
alkylene group (a difunctional alkyl group), a cycloalkylene group
(a difunctional cycloalkyl group), a difunctional ester group, (for
example, --(CR.sup.25R.sup.26).sub.p'--C(O)--O--(CR.sup-
.27R.sup.28).sub.p"--), a difunctional ether group (for example,
--(CR.sup.25R.sup.26).sub.p'--O--(CR.sup.27R.sup.28).sub.p'.
R.sup.25, R.sup.26, R.sup.27 and R.sup.28 are preferably
independently H or an alkyl group. x'" and y'" are integers.
[0028] Such poly(ether ester) copolymers include a Lewis base group
in the copolymer backbone. The copolymer can also include one or
more pendant groups that interact favorably with CO.sub.2
(preferably, Lewis base groups). In that regard, at least one of
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 can be
--(R.sup.22').sub.zR.sup.22, wherein R.sup.22' and R.sup.22 are as
defined above. The group R.sup.22 can, for example, be
O--C(O)--R.sup.23, --C(O)--R.sup.23, --O--P(O)--(O--R.sup.23)-
.sub.2, or --NR.sup.23R.sup.23', wherein R.sup.23 and R.sup.23' are
as defined above.
[0029] In a number of embodiments, R.sup.22' is
--(CH.sub.2).sub.a-- and a is an integer between 0 and 5. In
several such embodiments, a is 1 or 2 and i is 0, j is 1, and k is
1.
[0030] In the polyvinyl copolymer, x'" and y'" are integers and
preferably each is at least 1. Preferably, the total chain length
of the CO.sub.2-philic group (x'" +y'") is less than approximately
400 repeat units. More preferably, the total chain length of the
CO.sub.2-philic group is less than approximately 200 repeat units.
For many application (for example, surfactants) the total chain
length is preferably between 5 and 50 repeat units. More
preferably, the chain length in such applications is between
approximately 20 to 40 repeat units. The percentage of repeat units
including the ester linkage (that is, the Lewis base in the
copolymer backbone indicated by y'") is preferably in the range of
approximately 1 to approximately 50%. More preferably, the
percentage of repeat units including the carbonate linkage is in
the range of approximately 5 to approximately 35%. Even more
preferably, the percentage of repeat units including the carbonate
linkage is in the range of approximately 10 to approximately
25%.
[0031] The polyether copolymers, poly(ether-carbonate) copolymers,
vinyl copolymers and poly(ether-ester copolymers) described above
are preferably not alternating copolymers. Moreover, other monomer
or repeat units can incorporated in the copolymers (for example,
between the repeat units set forth above).
[0032] The present invention also provides a surfactant for use in
carbon dioxide, the surfactant includes a CO.sub.2-phobic group
covalently linked to a CO.sub.2-philic segment, wherein the
CO.sub.2-philic segment includes a polyether substituted with at
least one side group including a group that interacts favorably
with CO.sub.2 (preferably a Lewis base group), a
poly(ether-carbonate), a poly(ether-carbonate) substituted with at
least one side group including preferably a Lewis base, a vinyl
polymer substituted with at least one side group including
preferably a Lewis base, a poly(ether-ester) or a poly(ether-ester)
substituted with at least one side group including preferably a
Lewis base. The polyether, polycarbonate, vinyl polymer and
poly(ether-ester) are preferably copolymers as described above.
[0033] The CO.sub.2-phobic group of the surfactants of the present
invention can be generally any head group usable in surfactants,
including, but not limited to, H, a carboxylic acid group, a
hydroxy group, a phosphato group, a phosphato ester group, a
sulfonyl group, a sulfonate group, a sulfate group, a branched or
straight chained polyalkylene oxide group, an amine oxide group, an
alkenyl group, a nitryl group, a glyceryl group, an aryl group
unsubstituted or substituted with an alkyl group or an alkenyl
group, a carbohydrate unsubstituted or substituted with an alkyl
group or an alkenyl group, an alkyl ammonium group, or an ammonium
group. Carbohydrates groups include, for example sugars such as
sorbitol, sucrose, or glucose. The CO.sub.2-phobic group may
likewise include an ion selected from the group of H.sup.+,
Na.sup.+2, Li.sup.+, K.sup.+, NH.sub.4.sup.+, Ca.sup.+2, Mg.sup.+2,
Cl.sup.-, Br.sup.-, I.sup.-, mesylate and tosylate.
[0034] The present invention also provides a chelating agent for
use in carbon dioxide. The chelating agent includes a
CO.sub.2-phobic chelating group covalently linked to a
CO.sub.2-philic segment, wherein the CO.sub.2-philic segment
includes a polyether substituted with at least one side group
including a group that interacts favorably with CO.sub.2
(preferably a Lewis base), a polycarbonate, a polycarbonate
substituted with at least one side group including preferably a
Lewis base, a vinyl polymer substituted with at least one side
group including preferably a Lewis base a poly(ether-ester) or a
poly(ether-ester) substituted with at least one side group
including preferably a Lewis base. The polyether, polycarbonate,
vinyl polymer and poly(ether-ester) are preferably copolymers as
described above. The chelating group may, for example, be a
polyaminocarboxillic acid group, a thoicarbamate group, a
dithoicarbamate group, a thiol group, a dithiol group, a picolyl
amine group, a bis(picolyl amine) group or a phosphate group.
[0035] The present invention also provides a method of synthesizing
a CO.sub.2-phile including the step of copolymerizing at least two
monomers, wherein a polymer formed from homopolymerization of one
of the monomers has a T.sub.g of less than approximately 250 K and
a steric factor less than approximately 1.8. At least one of the
monomers results in a group in the copolymer that interacts
favorably with CO.sub.2 (for example, a Lewis base group), and the
resultant CO.sub.2-phile does not contain both hydrogen bond donors
and acceptors. For example, a first monomer can be selected wherein
a polymer formed from homopolymerization of the first monomers has
a T.sub.g of less than approximately 250 K and a steric factor less
than approximately 1.8, while a second monomer results in a repeat
unit within the copolymer that includes a Lewis base group (either
in the copolymer backbone or pendant therefrom).
[0036] The CO.sub.2-phile is preferably a polyether, a
polycarbonate, a vinyl copolymer or a poly(ether-ester) as
described above. A Lewis base group, when pendant, is preferably
separated from the CO.sub.2-phile backbone by 0 to 5 atoms (more
preferably, 1 to 2 atoms).
[0037] The present invention also provides a method of synthesizing
a CO.sub.2-phile comprising the step of copolymerizing carbon
dioxide and at least one oxirane. The oxirane may, for example, be
epichlorohydrin, ethylene oxide, propylene oxide or cyclohexene
oxide.
[0038] Prior to the present invention, only fluorous and silicon
polymers were thought to be generally suitable for use in creating
CO.sub.2-philic analogs of CO.sub.2-phobic compounds. However, the
hydrocarbon CO.sub.2-philic compounds and groups of the present
invention exhibit phase boundaries in CO.sub.2 that occur at
pressures comparable to those of fluorinated polyethers of similar
chain length, and substantially lower than those of silicones.
Moreover, these hydrocarbon CO.sub.2-philic groups are
substantially less expensive to manufacture and use than
fluorinated or silicon compounds.
[0039] The CO.sub.2-philic compounds and groups of the present
invention can be used in a wide variety of applications including,
for example, the cleaning industry in which they can be
incorporated into surfactants, detergents, fabric softeners and
antistatic agents. As chelating agents, they can be used, for
example, in metal recovery. The CO.sub.2-philic compounds and
groups of the present invention can also be incorporated in
cleaners used in the electronics industry to, for example, remove
oils, greases and other residues from electronic components. The
CO.sub.2-philic compounds can further be used in dispersants for
polymers or inorganic particles (stabilizers), affinity ligands for
proteins, catalyst ligands and coatings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 illustrates a block diagram of an embodiment of
CO.sub.2-philic material design of the present invention.
[0041] FIG. 2 illustrates a method of synthesizing
poly(epichlorohydrin-gl- ycidyl acetate).
[0042] FIG. 2 illustrates the phase behavior of the acetate
functionalized poly(epichlorohydrin).
[0043] FIG. 3 illustrates phase behavior of acetate functionalized
epichlorohydrin N=25 repeat units (1-33% acetate; 2-40% acetate;
3--PO homopolymer (also 25 repeat units); 4-45% acetate).
[0044] FIG. 4 illustrates phase behavior of acetate functionalized
poly(epichlorohydrin) (1-Epichlorohydrin homopolymer; 2-28%
acetate; 3-100% acetate; 4-33% acetate; 5 38% acetate).
[0045] FIG. 5 illustrates phase behavior of functionalized
poly(epichlorohydrin) with 33% acetate (1-N=25 repeat units; 2-N=7
repeat units).
[0046] FIG. 6 illustrates several embodiment of sterically hindered
aluminum catalysts.
[0047] FIG. 7 illustrates synthesis of polycarbonate copolymers
from an oxirane such as propylene oxide and carbon dioxide.
[0048] FIG. 8 illustrates the phase behavior propylene oxide-carbon
dioxide (PO/CO.sub.2) polycarbonate copolymers with N=25 repeat
units (1--PO/CO.sub.2 copolymer with 56% carbonate; 2--PO
homomopolymer; 3--PO/CO.sub.2 copolymer with 40% carbonate).
[0049] FIG. 9 illustrates the phase behavior propylene oxide-carbon
dioxide polycarbonate copolymers compared to the phase behavior of
a fluororether (1--PO/CO.sub.2 copolymer with N=220 repeat units
and 15% carbonate; 2-Krytox (available from Dupont) with N=176
repeat units).
[0050] FIG. 10 illustrates the phase behavior or an ethylene
oxide-carbon dioxide (EO/CO.sub.2) polycarbonate copolymer compared
to polyethylene oxide homopolymer (PEO) (1--EO/CO.sub.2 copolymer
with N=103 repeat units and 33.7% carbonate; 2--PEO with N=16).
[0051] FIG. 11 illustrates the phase behavior cyclohexene
oxide-carbon dioxide (CHO/CO.sub.2) polycarbonate copolymers (1-47%
carbonate with N=27; 2-40% carbonate with N=20; 3-50% carbonate
with N=16).
[0052] FIG. 12 illustrates phase behavior cyclohexene oxide-carbon
dioxide polycarbonate copolymers with low content of carbonate
units (1-8.8% carbonate with N=124; 2-2.3% carbonate with
N=88).
[0053] FIG. 13 illustrates phase behavior of poly(propylene glycol)
diol (1), poly(propylene glycol) monobutyl ether (2) and
poly(propylene glycol) acteate (3) with 21 repeat units.
[0054] FIG. 14 illustrates phase behavior of
epichlorohydrin/CO.sub.2 copolymer compared to acetate modified
poly(epichlorohydrin) (1--ECH/CO.sub.2 copolymer with N=17 and 25%
carbonate; 2-Modified poly(epichlorohydrin) (PECH) with N=25 and
45% acetate).
[0055] FIG. 15 illustrates phase behavior of vinyl acetate and
ethyl vinyl ether homopolymers (1-poly(vinyl acetate) with 90
repeat units; 2-Poly(ethyl vinyl ether) with 20 repeat units;
3-poly(vinyl acetate) with 70 repeat units).
[0056] FIG. 16 illustrates phase behavior of vinyl acetate/ethyl
vinyl ether copolymers and vinyl acteate homopolymer with 90 repeat
units (1-39.8% vinyl acetate (VA); 2-22.4% VA; 3--VA
homopolymer).
[0057] FIG. 17 illustrates phase behavior of vinyl acetate/ethyl
vinyl ether copolymers and vinyl acetate homopolymer with 70 repeat
units (1-67% VA; 2-63% VA; 4--VA homopolymer; 4-18.47% VA.)
[0058] FIG. 18 illustrates phase behavior of vinyl acetate/ethyl
vinyl ether copolymers (1-135 repeat units and 46.6% VA; 2-90
repeat units and 39.8% VA).
[0059] FIG. 19 illustrates the general design of an analog of a
CO.sub.2-phobic compound that is made miscible or soluble in
CO.sub.2 by incorporation of one or more CO.sub.2-philic
groups.
DETAILED DESCRIPTION OF THE INVENTION
[0060] As used herein, the term "polymer" refers to a compound
having multiple repeat units (or monomer units) and includes the
term "oligomer," which is a polymer that has only a few repeat
units. The term "copolymer" refers to a polymer including two or
more dissimilar repeat units (including terpolymers--comprising
three dissimilar repeat units--etc.).
[0061] The terms "alkyl", "alkenyl", "aryl", "akylene" and other
groups refer generally to both unsubstituted and substituted groups
(that is, having one or more hydrogen atoms replaced with one or
more substituent groups) unless specified to the contrary. Unless
otherwise specified, alkyl groups are hydrocarbon groups and are
preferably C.sub.1-C.sub.10 (that is, having 1 to 10 carbon atoms)
alkyl groups, and more preferably C.sub.1-C.sub.6 alkyl groups, and
can be branched or unbranched, acyclic or cyclic. Unless otherwise
specified, the term "aryl group" refers generally to a phenyl group
or to a napthyl group. The term "alkylene group" refers generally
to bivalent forms of alkyl groups and can be linear (for example,
--(CH.sub.2).sub.a--), branched, acyclic or cyclic (for example, a
bivalent form of cyclohexane). Alkylene groups are preferably
C.sub.1-C.sub.10 alkylene groups and, more preferably,
C.sub.1-C.sub.5 alkylene groups.
[0062] The term "alkenyl" refers to a straight or branched chain
hydrocarbon groups with at least one double bond, preferably with
2-10 carbon atoms, and more preferably with 2-6 carbon atoms (for
example, --CH.dbd.CHR.sup.4 or --CH.sub.2CH.dbd.CHR.sup.4, wherein
R.sup.4 is an alkyl group).
[0063] Preferably, the groups of the present invention, if
substituted, are substituted with substituent groups that enhance
or at least do not substantially negatively effect the CO-philic
nature of the CO-philic compound or group. In addition to Lewis
base groups, such substituents, include, but are not limited to
alkyl groups, alkoxy groups, ether groups, Cl, and alkenyl
groups.
[0064] As used herein and understood in the art, the term
"CO.sub.2-philic" preferably refers generally to compounds and
groups that are appreciably soluble in or miscible in carbon
dioxide, preferably at pressures below approximately 300 atm. More
preferably, the compounds and groups are appreciably soluble in or
miscible in carbon dioxide at pressures below approximately 200
atm. Most preferably, the compounds and groups are appreciable
soluble in or miscible in carbon dioxide at pressures below
approximately 125 atm. Likewise, such solubility or miscibility is
preferably exhibited at temperatures in the range of approximately
0 to 100.degree. C. (more preferably, in the range of approximately
0 and 50.degree. C.; most preferably, between approximately 0 and
30.degree. C.) As used herein, the term "CO.sub.2-phobic" refers
generally to compounds and groups that exhibit little solubility or
miscibility in carbon dioxide over the pressure and temperature
ranges set forth above.
[0065] It is difficult to quantify a cutoff point as to whether a
particular type of compound is CO.sub.2-philic or CO.sub.2-phobic
as, for example, solubility or miscibility of a particular molecule
in CO.sub.2 depends (inversely) upon the chain length. In general,
under the conditions set forth above, a CO.sub.2-philic compound of
approximately 25 repeat units preferably has a solubility of at
least approximately 2% by weight. More preferably, the compound has
a solubility of at least approximately 2% by weight at
approximately 100 repeat units. Even more preferably, the compound
has a solubility of at least approximately 2% by weight at greater
than 200 repeat units.
Design Criteria for Hydrocarbon CO.sub.2-philes
[0066] In designing a hydrocarbon CO.sub.2-phile, the free energy
of mixing between the target compound and CO.sub.2 must be
favorable (that is, negative) at moderate pressures for the
material to be considered CO.sub.2-philic. Although the entropy and
enthalpy of mixing are coupled, one can at first treat the two
factors separately by considering only the configurational entropy
of mixing (entropic contributions owing to segment-segment
interactions can be considered later).
Heuristics to Maximize the Entropy of Mixing
[0067] One can choose structures that enhance the entropy of mixing
of the CO.sub.2-philes of the present invention and CO.sub.2 by
choosing moieties that permit relatively unfettered rotation, and
thus relatively larger number of potential configurations. Although
the exact mathematical description of .DELTA.S.sub.mix is still a
matter for discussion, previous research on the subject suggests
that the entropy of mixing of a chain molecule with a solvent will
increase as the flexibility (and hence the number of configurations
available) of the chain molecule increases. Decreasing molecular
weight is one way to increase the number of available
configurations (as a result of effects arising from segment
connectivity), but it is also possible to choose molecular
structures that exhibit greater inherent chain flexibility.
Choosing such structures in the design of the CO.sub.2-philes of
the present invention will enhance the entropy of mixing, and hence
the potential for forming a single-phase mixture with CO.sub.2.
[0068] A useful gauge of chain flexibility is the steric factor
(.sigma.), as defined in Young, R. J., Introduction to Polymers
(1981), Chapman and Hall, Ltd, London, Chapter 3:
<r.sup.2>.sub.0=.sigma.nl.sup.2{(1-cos .theta.)/(1+cos
.theta.)} (1)
[0069] where <r.sup.2>.sub.0 is the mean squared end-to-end
distance of the unperturbed chain, n is the number of segments, 1
is the segment length, and .theta. is the C--C bond angle in the
main chain. The steric factor provides the ratio of the actual size
of a polymer coil to that which would be measured in the absence of
hindrances to free rotation, and is thus a measure of the relative
flexibility of a given polymer type. Lower values of the steric
factor a suggest higher degrees of flexibility and thus potentially
higher entropy of mixing with any solvent. Values of a are
tabulated for a number of polymers in Polymer Handbook 3d ed.,
Brandrup and Immergut, Eds. (1975) Wiley, N.Y.
[0070] To optimize the configurational entropy of mixing (at
constant chain length) one preferably chooses to incorporate those
chemical structures or repeat units that provide for high free
volume and high chain flexibility. Increasing specific free volume
and chain flexibility decreases the glass transition temperatures
(T.sub.g). Therefore, low T.sub.g and low steric factor can be used
as "markers" to help guide the choice of chemical structure of the
CO.sub.2-philes of the present invention.
[0071] Chain topology (branched vs. linear) can also affect the
entropy of mixing in that higher degrees of branching increase the
entropy of mixing versus linear analogs of the same number of
repeat units. See Kleintjens, L. A.; Koningsveld, R.; Gordon, M.;
Macromolecules (1980), 13, 303.
[0072] Therefore, to promote high entropy of mixing in the
CO.sub.2-philes of the present invention, materials with high chain
flexibility and free volume (and thus relative low T.sub.g and
relatively low v as discussed above) that include branched
structures are preferably synthesized.
Effect of CO.sub.2-Phile Structure on the Enthalpy of Mixing
[0073] It is also desirable to choose structures for inclusion into
the CO.sub.2-philes of the present invention that will enhance
solute-solvent interactions while not increasing the strength of
solute-solute (or solvent-solvent) interactions to the point where
dissolution in CO.sub.2 is prevented.
[0074] Materials with relatively weak self-interaction will tend to
exhibit low cohesive energy density, and hence low values of both
the interfacial tension and solubility parameter. Favorable cross
interactions can also play a significant role in determining the
phase behavior of polymers in CO.sub.2. Specific interactions in
CO.sub.2-solute systems can, for example, be of the
dipole-quadropole variety, or also Lewis acid/Lewis base, given
that CO.sub.2 is a known Lewis acid. The importance of favorable
cross-interactions decreases as the temperature is raised.
[0075] In light of the above, to optimize the enthalpy of mixing,
one preferably begins with a base material having a low cohesive
energy density to minimize the impact of solute-solute interactions
(this base material should also exhibit a low T.sub.g and steric
factor, as indicated in the previous section). However, functional
groups that interact favorably with CO.sub.2 (preferably, Lewis
bases) are preferably added to enhance cross interactions.
[0076] Given the criteria developed above through entropic and
enthalpic considerations, the CO.sub.2-philic hydrocarbons of the
present invention are preferably synthesized as a copolymer
wherein:
[0077] 1. At least one of the monomers/repeat units preferably
provides high flexibility and high free volume, as evidenced by low
T.sub.g and low steric parameter, to enhance the entropy of mixing,
and also a low cohesive energy density, to minimize the impact of
solute-solute interactions. In that regard, a polymer formed from
polymerization of such a monomer preferably has a T.sub.g of less
than approximately 250 K. More preferably, the T.sub.g is less than
approximately 200 K. The steric factor of a polymer formed from
polymerization of such a monomer is preferably less than
approximately 1.8. More preferably, the steric factor is less than
approximately 1.5. Most preferably, the steric factor is less than
approximately 1.3.
[0078] 2. At least one of the monomers/repeat units preferably
contains a group or groups that are known to interact specifically
with CO.sub.2 (for example, Lewis bases), yet the resultant
CO.sub.2-phile preferably does not contain both hydrogen bond
donors and acceptors. The presence of both hydrogen bond donors and
acceptors will tend to lower flexibility, and inflate both T.sub.g
and the cohesive energy density.
[0079] 3. The functional groups described in (2) above are
preferably separated from the polymer backbone by 1 or 2 atom
spacer when present in a side chain.
[0080] Use of a flexible chain (1) with a branched architecture (3)
ensures that the entropy of mixing will be as high as possible.
Further, choosing a base material with a low cohesive energy
density reduces the strength of solute-solute interactions, and
thus favors mixing. Finally, inclusion of functional groups
(preferably, Lewis bases) that interact favorably (albeit weakly)
with CO.sub.2 produce favorable solute-CO.sub.2 interactions, and
thus enhance the enthalpy of mixing. However, adding such groups
will likely also raise the cohesive energy density, and thus the
optimal number of such groups is such that the two effects are
preferably balanced.
[0081] A copolymer including two monomers exhibiting the above
criteria is represented graphically in FIG. 1.
[0082] (A) In FIG. 1, Monomer 1 (M.sub.1), contributes to high
flexibility, high free volume, and weak solute/solute interactions
(low cohesive energy density or interfacial tension). As described
above, low Tg and steric parameter are generally used as evidence
for high flexibility and free volume in polymeric materials. These
factors combine to create a favorable entropy of mixing for the
copolymer in CO.sub.2, as well as weak solute-solute interactions,
easing dissolution into CO.sub.2.
[0083] (B) Monomer 2 (M.sub.2), produces specific solute/solvent
interactions between the polymer and CO.sub.2, through a group with
affinity for carbon dioxide such as a Lewis base group (for
example, a carbonyl group) in a side chain or in the backbone of
the polymer.
[0084] Ideally, interactions between M.sub.1 and M.sub.2 should be
enthalpically unfavorable, further helping to promote dissolution
in carbon dioxide. It is possible that this feature is a strong
contributor to the low miscibility pressures of fluoroacrylate
polymers in CO.sub.2, in that interactions between the fluorinated
side chains and acrylate backbone of this material are likely to be
unfavorable. Because use of a homopolymer of either M.sub.1 or
M.sub.2 only serves to optimize part of the free energy, if both
monomer 1 and monomer 2 are chosen in the proper proportions the
copolymer will be more soluble than either of the homopolymers.
[0085] In addition to the location of the phase boundaries in P-x
space, the effect of temperature on miscibility pressure is also of
importance. If increasing temperature raises the miscibility
pressure (LCST type behavior) for a particular CO.sub.2-phile,
increasing chain flexibility (through alterations to copolymer
composition) may favorably impact phase behavior. On the other
hand, if UCST behavior is observed (decreasing miscibility pressure
as temperature increases), then increasing the concentration of
functional groups that interact with CO.sub.2 is recommended.
[0086] The present inventors have discovered that adherence to the
criteria set forth above in designing CO.sub.2-philes, enables
synthesis of CO.sub.2-philes that are strongly CO.sub.2-philic
without the necessity of incorporating fluorine or silicon atoms.
Monomers that produce polymers (and that preferably do not contain
fluorine or silicon) with low cohesive energy density and low
T.sub.g include, for example, alpha olefins (for example, ethylene
and/or propylene), dienes (for example, butadiene and/or isoprene),
and various cyclic ethers. Functional groups that are likely to
interact favorably with CO.sub.2 include Lewis bases such as
carbonyls, tertiary amines, and phosphonyls.
[0087] Some of the above-identified monomeric base materials (for
example, polyethylene and polybutadiene) can readily crystallize in
certain forms in which chain packing is straightforward.
Crystallization is not desirable in the CO.sub.2-philes of the
present invention because the operating temperature (and thus the
pressure) required to form a single phase solution in CO.sub.2 will
be elevated (to melt the material), increasing the cost of a
potential processes. Fortunately, incorporation of a comonomer
(preferably in an atactic fashion) reduces order in the molecule
and thereby reduces the potential to pack and crystallize.
[0088] The entropy of mixing drops as the chain length of the
solute increases. Preferably, the total chain length of the
CO.sub.2-philic group is less than approximately 400 repeat units.
More preferably, the total chain length of the CO.sub.2-philic
group is less than approximately 200 repeat units. For many
application (for example, surfactants) the total chain length is
preferably between 5 and 50 repeat units. More preferably, the
chain length in such applications is between approximately 20 to 40
repeat units.
[0089] Although the entropy and enthalpy of mixing have been
treated separately in the present analysis, it is clear that they
are inextricably linked. As the number specific interactions
(CO.sub.2-solute) increases, the enthalpy of mixing may become more
favorable but the entropy of mixing will decrease. Increasing the
number of comonomers with Lewis base groups in the chain (either in
the backbone or pendant) can hinder rotation about the chain, also
reducing the entropy of mixing. Likewise, substitutions or side
groups other than Lewis base groups on the comonomers can also
hinder rotation.
[0090] Finally, as mentioned above, increasing the number of Lewis
base functional groups will also raise the cohesive energy density,
and thus a point may be reached where further incorporation of such
groups is an enthalpic detrement, rather than an advantage. In the
CO.sub.2-philes of the present invention, the preferred number of
functionalized comonomers (much like a "bound" co-solvent) per
chain is that which provides a suitable balance between enthalpy
gain through favorable cross-interactions, enthalpy loss from
increased solute cohesive energy density, and entropy loss and is
readily determined experimentally.
Model Studies With Carbonyl-Functional Poly(Dimethyl Siloxane)
[0091] The effect of side chain functionalization with Lewis bases
on the CO.sub.2 phase behavior of a model silicone CO.sub.2-phile
was studied. Silicones are considered CO.sub.2-philic, although not
as strongly CO.sub.2-philic as fluorinated ethers and fluorintated
acrylates. It was observed that silicones exhibit UCST type
behavior (as temperature increases, the pressure required to
solubilize a given amount of material drops), which suggested that
the enthalpy of mixing of these materials with CO.sub.2 might be
improved through the incorporation of Lewis bases in side chains.
Silicones exhibit amongst the lowest T.sub.g (150K) and steric
parameter (1.39) observed in synthetic polymers, and hence it would
appear that chain flexibility (and thus the entropy of mixing) is
not an area requiring extensive improvement.
[0092] Functionalized silicones were prepared via the hydrosilation
of model dimethyl siloxane-hydromethyl siloxane oligomers (25
repeat units total, with 1, 2, or 5 hydromethyl groups per chain,
received from Gelest, Inc.) over a platinum catalyst. Allyl acetate
or 1 hexene were used to generate the side chains, to allow
comparison of the efficacy of adding Lewis base groups to adding
simply methylene units. The carbonyl group was thus separated from
the main chain by a propyl spacer.
[0093] The phase behavior of the model CO.sub.2-philes was measured
as described previously in Hoefling, T. A.; Newman, D. A.; Enick,
R. M.; Beckman, E. J.; J. Supercrit. Fl. (1993), 6, 165, using a
variable volume high-pressure view cell. Phase behavior results
were quite dramatic, in that addition of five acetate functional
side chains to the silicone oligomer lowered the cloud point curve
by over 2500 psi at room temperature. Addition of simple alkyl side
chains raised the cloud point curves to higher pressures. Finally,
the magnitude of the change in the location of the cloud point
curve was found to be proportional to the number of side
chains.
[0094] This model study confirmed that addition of Lewis base
groups in side chains removed from the polymer backbone of a known
silicon-containing CO.sub.2-philic compound renders the material
"more CO.sub.2-philic." Subsequently, studies were performed upon
hydrocarbons that did not contain F or Si to determine whether
addition of Lewis base groups would improve or establish
CO.sub.2-philic nature in such compounds.
Functionalized Polyether Copolymers
[0095] Polyethers are known to exhibit low T.sub.g's (typically, in
the range of approximately 190 to approximately 230 K) and
relatively low cohesive energy densities. Previous studies have
shown that polyethers are more "CO.sub.2-philic" than many other
common polymers, yet significantly less so than fluorinated
polymers or silicones. The present studies explored the effect of
side chain functionalization with Lewis bases (for example, a
functional group comprising a carbonyl group) on the phase behavior
of model polyethers in CO.sub.2. Carbonyls have been shown to
interact favorably with carbon dioxide. The effect of C.dbd.O
placement in polyethers, as well as the effect of the extent of
functionalization with carbonyl groups were studied. The phase
behavior of a homopolymer of propylene oxide (PO) with the same
number of repeat units was used as a baseline for comparison.
[0096] Lewis base functionalized PO (and/or, for example ethylene
oxide (EO)) copolymers may, for example, be generated via
copolymerization of either of the two oxiranes with the
acetate-functional analog synthesized from glycidol and acryloyl
chloride. It has also been shown previously that tertiary amines
interact favorably with CO.sub.2 via an acid-base mechanism.
Reaction between an epichlorohydrin homo- or copolymer and a
dialkyl amine will produce a tertiary amine-functional polyether.
One can, for example, synthesize a compound with pendant phosphonyl
groups via reaction of glycidol with chloro (diethyl) phosphonate,
followed by copolymerization of the new monomer with, for example,
propylene oxide.
[0097] In one study, epichlorohydrin was polymerized using boron
trifluoride etherate at temperatures below 0.degree. C., and
characterized via GPC. Acetate-functional derivatives (see FIG. 2)
were then prepared via reaction of potassium acetate with the
epichlorohydrin polymer in the presence of a phase transfer
catalyst. Phase behavior presented in FIG. 3 shows that addition of
acetate groups lowers the cloud point pressures considerably.
The Effect of Side Chain Functionalization on Solubility
[0098] A homopolymer of epichlorohydrin (25 repeat units) exhibits
cloud point pressures above the limits of the instrument used (400
atmospheres, or 6000 psi) for concentrations greater than 0.5
weight %. As one can see from FIG. 3, although the homopolymer of
epichlorohydrin is insoluble at the operating conditions, the
acetate modified polymers are soluble in CO.sub.2, and their cloud
point pressures decrease as the amount of acetate is increased.
Thus, a polymer modified with 45% acetate exhibits lower cloud
point pressures than a homopolymer of propylene oxide of the same
chain length.
[0099] A lower molecular weight (seven repeat units)
poly(epichlorohydrin) was also modified with different amounts of
acetate groups, and their solubilities compared (FIG. 4). The cloud
points dropped by 100 atm as the percent acetate incorporated into
the polymer increased from 28 to 38%, yet the cloud point pressures
of a 100% acetate were higher. It is believed that the acetate
groups act like a bound cosolvent. However, as the amount of
acetate increased a point of diminishing returns was reached.
Although increasing the amount of acetate enhances CO.sub.2-polymer
interactions, it also stiffens the chain and likely enhances
polymer-polymer interactions as well. Comparing
poly(epichlorohydrin) with 7 and 25 repeat units (FIG. 5) with the
same amount of acetate (33%), it was seen that the cloud points of
the two differed by as much as 70 atm, as expected.
Polyether/Polycarbonates Copolymers
[0100] It was believed that incorporation of the Lewis bases such
as carbonyl groups into side chains would be the most productive
route to increase miscibility or solubility in CO.sub.2, as a
result of enhancement of both the enthalpy and entropy of mixing.
Nevertheless, the incorporation of carbonyls into the polymer
backbone via copolymerization of CO.sub.2 itself with propylene
oxide (PO), cyclohexene oxide (CHO) and ethylene oxide (EO).
Sterically hindered alkoxy aluminum catalysts (examples of which
are illustrated in FIG. 6) were identified that copolymerize
propylene oxide and other cyclic ethers with CO.sub.2 at much
higher efficiencies (greater than 200 grams of polymer per gram of
aluminum) than has previously been reported. These catalysts are
living in character (yields in the range of 200-1200 g polymer/g
catalyst) with one type of site available for polymerization, and
can be monofunctional or difunctional. The extent to which CO.sub.2
is incorporated into the polymer depends on the temperature and
pressure at which the polymerization is carried out, as well as on
the nature of sterically hindered substituents attached to the
aluminum atoms and on the oxirane type.
[0101] Using the sterically hindered alkoxy aluminum catalysts, a
series of PO/CO.sub.2 copolymers were synthesized as illustrated in
FIG. 7. In a typical experiment, aluminum chloride was reacted with
first, propylene glycol, then 2,6 di-isobutyl, 4-methyl phenol at
0.degree. C. under argon to generate the catalyst. The catalyst was
characterized via .sup.1H and .sup.27Al NMR. Other sterically
hindered aluminum catalysts were prepared similarly by changing the
nature of the alcohols. Copolymerizations were conducted between
CO.sub.2 and, for example, ethylene oxide (EO), propylene oxide
(PO), and cyclohexene oxide (CHO) at temperatures between 5.degree.
C. and 60.degree. C. (depending upon oxirane type) and pressure
between 800 and 2500 psi, for times up to 24 hours. The molecular
weight was controlled via the ratio of oxirane to catalyst.
Typically, catalyst was charged to a stainless steel 50 cc reactor
under argon, followed by CO.sub.2 at its vapor pressure. The
oxirane was then charged using a manual syringe pump, and the
pressure and temperature brought to their desired points. At a
pre-designated time, the polymerization was quenched with acidic
methanol, and the residual oxirane was removed under vacuum.
Furthermore, these types of copolymers can also be formed by the
reaction of phosgene and diols.
[0102] Phase behavior studies in CO.sub.2 indicated that
copolymerization of CO.sub.2 and oxiranes produce CO.sub.2-philic
hydrocarbons. Only a small percentage of carbonate repeat units was
needed to produce a CO.sub.2-philic material. Further, choice of
the correct percentage of carbonate repeat units lead to phase
behavior that is superior to either of the homopolymers.
[0103] Comparing PO/CO.sub.2 copolymers with 25 repeat units (FIG.
8) one can see that a copolymer with 56% carbonate is less
CO.sub.2-philic than a homopolymer of PO, but a polymer with 40%
carbonate exhibits miscibility pressures lower than those of the
homopolymer. A polycarbonate homopolymer (that is, a completely
alternating CO.sub.2/propylene copolymer) with 25 repeat displays
miscibility pressures beyond the limits (6000 psi) of the
instrument used. These results are consistent with the design
hypothesis of FIG. 1, that if the certain proportions of monomer 1
and monomer 2 as described in the above criteria are chosen, the
copolymer will be more soluble than either of the homopolymers.
[0104] Indeed, PO/CO.sub.2 copolymers are apparently more
CO.sub.2-philic than fluoroether polymers, in that the cloud points
of a 250 repeat unit PO/CO.sub.2 copolymer (15.4% carbonate) were
significantly lower than those for a poly(perfluoroether)
(Krytox.TM. available from DuPont) with 175 repeat units (FIG. 9).
This behavior is quite dramatic since poly(perfluoroethers) are one
of the most CO.sub.2-philic polymers known to date, and the
PO/CO.sub.2 copolymers are likely to be at least {fraction (1/100)}
the cost of the fluorinated materials.
[0105] The phase behavior of other oxirane/CO.sub.2 copolymers was
also examined. Ethylene oxide (EO) was copolymerized with carbon
dioxide. It was found that an EO/CO.sub.2 copolymer with 103 repeat
units had almost the same phase behavior (FIG. 10) as a homopolymer
of EO with only 16 repeat units (a EO homopolymer with 103 would be
essentially insoluble in this pressure range).
[0106] Copolymers of cyclohexene oxide and CO.sub.2 were also
synthesized. One might expect that the chain would be less flexible
as a result of the cyclohexane rings. Miscibility pressures for
these types of copolymers (as for others) are a function of
molecular weight and of incorporated carbon dioxide (as carbonate
units). For example, the data in FIG. 11 show that miscibility
pressures increase upon increasing chain length at (relatively)
constant % of carbonate, as expected. However, as shown in FIG. 12,
the amount of carbonate required to render these copolymers
"CO.sub.2-philic" was apparently much lower than the levels in the
materials in FIG. 11. FIG. 12 shows that copolymers with less than
10% carbonate repeats exhibited miscibility pressures below 150
atmospheres. The cloud point curves for CHO--CO.sub.2 copolymers
with N=124 repeat units (8.8% carbonate) and N=88 repeat units
(2.3% carbonate) showed almost the same behavior despite being
different by 36 repeat units. That the CHO/CO.sub.2 copolymers are
so CO.sub.2-philic is somewhat surprising. The data in FIG. 12 may
be a result of increased chain flexibility upon introduction of
carbonate repeats into a poly(CHO) or to unfavorable enthalpic
interactions between carbonate and cyclohexyl groups.
[0107] It should be also noted that the solubility of low molecular
weight polymers in carbon dioxide is affected by the nature of the
end groups. It was observed that mono hydroxy terminated polyethers
are more soluble than a difunctional homologue with the same number
of repeat units, but less soluble than an acetoxy terminated
polyether (FIGS. 13). Again, addition of an acetate group provides
a superior response to addition of an alkyl group.
[0108] The phase behavior of these materials illustrates that
hydrocarbons can indeed be strongly CO.sub.2-philic without F or Si
atoms incorporated therein. Furthermore, by incorporating the
carbonyl group in the main chain, these materials are biodegradable
as well as CO.sub.2-philic.
[0109] The above studies demonstrate that the solubility of
polyethers in CO.sub.2 is dramatically affected either by addition
of acetate groups in the side chain or carbonate groups in the
backbone of the polymer. Miscibility pressures of polyethers
modified with acetate groups decrease as the acetate contents
increases, yet a point is reached where additional acetate content
raises cloud point pressures. These observations are consistent
with the general criteria set forth above. The oxirane/CO.sub.2
copolymers were very soluble even to the point where a PO/CO.sub.2
copolymer was more soluble than a poly(perfluoroether). It remains
unclear, however, if it better to put carbonyl groups in the side
chain or the backbone. FIG. 14 shows that a copolymer of
epichlorohydrin and CO.sub.2 with 17 repeat units and 25% carbonate
was less soluble than a poly(epichlorohydrin) with 25 repeat units
modified with 45% acetate groups. However it is not known if 25% is
the optimum level of carbonate linkages in the ECH/CO.sub.2
copolymer for maximum solubility (or if 45% acetate is also
optimal). In general, there is preferably a balance between the
favorable entropic effects from chain flexibility and the enthalpic
effects created by solute/solvent interactions.
CO.sub.2-Philic Vinyl Polymers
[0110] The polyethers and polyether/polycarbonate copolymers
described above are synthesized from commodity raw materials (for
example, CO.sub.2 and oxiranes) and are hence far less expensive
than fluorinated CO.sub.2-philes. However, the polymerization mode
(coordinative ring opening) does not always lend itself to easy
generation of functionalized polymers. Hydrocarbons generated from
simple vinyl monomers may also be polymerized from inexpensive
reagents and generally are readily functionalized with a wide range
of functional groups.
[0111] The criteria established in the present invention for
CO.sub.2-philes indicates that copolymers based on either ethylene
or propylene will provide good candidates for CO.sub.2-philic
hydrocarbons as polymers formed from each of these monomers exhibit
very low T.sub.g and low cohesive energy density. Each of these
monomers may present some synthetic difficulties, however.
Free-radical copolymerization of ethylene with functional monomers
(such as vinyl acetate), wherein the functional monomer is in the
minority (40 mole % and below), can only occur at extreme
conditions (for example, 2000 bar, and above 200.degree. C.).
Burkhart, R. D.; Zutty, N. L.; J. Polym. Sci., Part A (1963), 1,
1137. Unfortunately, Ziegler-type catalysts that operate under mild
conditions do not copolymerize polar monomers with ethylene or
propylene (see, Odian, G.; Principles of Polymerization, 3.sup.rd
Edition (1991), John Wiley & Sons, New York, Section 8-4d.).
One can "mask" the polar group, however, allowing copolymerization.
Xie, H -Q.; Baker, W. E.; Arshady, R.; in Desk Reference of
Functional Polymers; Synthesis and Applications, Arshady, R.,
editor (1997), Amer. Chem. Soc., Washington, DC, 133. Propylene is
also somewhat problematic, in that it can only be copolymerized
(other than with Ziegler style catalysts, which will not function
with polar monomers) cationically, possibly limiting one to vinyl
ethers as potential comonomers in that reaction scheme.
[0112] Nickel di-imine catalysts as known in the art may be
suitable to copolymerize ethylene or propylene and vinyl acetate
(for example) under mild conditions and somewhat elevated
pressures.
[0113] Butadiene also presents a promising base material/monomer
for the vinyl CO.sub.2-philes of the present invention. In that
regard, polybutadiene exhibits a very low T.sub.g, and also a
cohesive energy density lower than that of polypropylene oxide.
Butadiene is inexpensive and can be copolymerized with a variety of
vinyl monomers using free-radical initiators, easing the synthesis
of CO.sub.2-philic oligomers. Free-radical polymerization of
butadiene also creates repeat units of both the 1,2 and 1,4 types,
which distribution desirably tends to eliminate the potential of
crystallization and raise free volume.
[0114] Copolymerizations of butadiene and comonomers may be
conducted free-radically in solvent using butyl mercaptan to limit
the molecular weight to the desired number of total repeat units
(GPC, Waters 150 CV may be used to ascertain molecular weight).
[0115] Side chains with the various functional groups of interest
(preferably, Lewis bases) may be generated using the strategy
outlined below. Generation of carbonyl-containing ester-functional
side chains with a 1 or 2 atom spacer, for example, is relatively
straightforward. Vinyl acetate may be copolymerized with butadiene
to generate the ester-functional side chain with a 1-atom spacer.
The mole % of the comonomer is relatively easy to manipulate and to
ascertain (via .sup.1H NMR). Generation of the analog with a 2-atom
spacer is readily accomplished via (a) free-radical
copolymerization of butadiene with acrolein, followed by (b)
reduction of the aldehyde side chains to CH.sub.2OH, and then (c)
reaction of the hydroxyl group with acetoyl chloride. Given the low
molecular weight of the precursor oligomers and the innate high
yield of the proposed reactions, near quantitative conversion of
the original aldehyde side groups to acetate may be accomplished.
Characterization may be performed using .sup.1H NMR (tracking the
signals resulting from the C(O)--H proton, the CH.sub.2--O protons,
and ultimately those of the ester group). FT-IR can be used to
qualitatively follow the change from aldehyde to alcohol to
ester.
[0116] Analogs with phosphonyl groups as side chains are readily
prepared via (a) base-catalyzed hydrolysis of the vinyl
acetate/butadiene copolymer described above, followed by (b)
reaction with chloro-diethyl phosphonate (Aldrich) with a base
catalyst to generate the analog with a 1-atom spacer. An analog
with a 2-atom spacer is prepared, for example, via a reduced
acrolein copolymer discussed above, followed again by reaction with
the chloro diethyl phosphonate. By employing common precursors for
both the carbonyl and phosphonyl analogs, one can eliminate
molecular weight and compositional distributions as variables in
the phase behavior analysis. As in the case of the carbonyl
variants, the proposed reactions can proceed to near quantitative
yield, and are easily followed using .sup.1H and .sup.31P NMR.
[0117] A number of viable routes are available for the preparation
of a tertiary amine-containing oligomer with, for example, a 1-atom
spacer. For example, the reduced acrolein copolymer described above
(with side chains of --CH.sub.2--OH) can be tresylated, then
reacted with dimethyl amine to form the required model
CO.sub.2-phile. As discussed above, this route is advantageous
because it eliminates effects arising from variances in molecular
weight and composition distribution (through use of common
precursors). A simpler method, however, involves (a)
copolymerization of butadiene with N,N dimethyl acrylamide,
followed by (b) reduction of the amide groups to, fro example,
CH.sub.2--N(CH.sub.3).sub.2 using lithium aluminum hydride. As
before, such a reaction on a low molecular weight, highly soluble
oligomer may be nearly quantitative. The extent of the reduction is
readily followed via .sup.1H NMR or FT-IR.
[0118] In several studies of the present invention, copolymers of
vinyl acetate (VA) and ethyl vinyl ether (EVE) with varying chain
length and vinyl acetate composition were prepared free radically.
These monomers were chosen, in part, for ease of synthesis. The
amount of vinyl acetate incorporated depended on the initial amount
of vinyl acetate that was used to charge the reactor, while chain
length was a function of the amounts of initiator and chain
transfer agent employed. Characterization was done using .sup.1H
NMR from the peaks at 5.03 (--CH from vinyl acetate) and 3.43
(--CH.sub.3 from ethyl vinyl ether). The solubility of the polymers
in liquid CO.sub.2 was studied at 22.degree. C.
[0119] Ethyl vinyl ether is a synthetically tractable yet non-ideal
choice for monomer 1, as it exhibits a higher Tg (.about.230K) and
cohesive energy density than optimally desired. This is shown
clearly in FIG. 15, wherein a homopolymer of ethyl vinyl ether of
only 20 repeat units exhibited miscibility pressures above 260 bar
for concentrations above 1 weight percent. By contrast, a 25
repeat-unit homopolymer of propylene oxide exhibited miscibility
pressures well below 200 bar, and homopolymers of vinyl acetate of
significantly longer chains lengths exhibited miscibility pressures
in the same general pressure range (FIG. 15). Nevertheless, the use
of EVE was instructive in the pursuit of the design of non-fluorous
CO.sub.2-philes via balancing the contributions of monomer 1 and
monomer 2.
[0120] FIG. 16 shows the phase behavior of copolymers of EVE and
vinyl acetate wherein the total chain length of the copolymers was
70 (.+-.5) repeats. As hypothesized, adjustment of vinyl acetate
(monomer 2 in the scheme of FIG. 1) content allowed for lower
miscibility pressures of the copolymer than either of the
homopolymers (note that cloud point pressures for a homopolymer of
EVE of 70 repeats are above the pressure limits of the equipment).
This trend was repeated for chains of 90 repeats (.+-.5), as shown
in FIG. 17. From the data in FIGS. 16 and 17, it can be estimated
that a vinyl acetate content of 25-30% will provide the lowest
miscibility pressures for this class of copolymer. Unfortunately,
it is difficult to a priori predict the optimal monomer 2 (in this
case vinyl acetate) content of the copolymer. The above studies of
ether-carbonate copolymers, illustrate that the ideal carbonate
content varied significantly as the type of oxirane varied from
ethylene oxide to propylene oxide to cyclohexene oxide. At
relatively constant vinyl acetate content, changing molecular
weight produces the expected effect (FIG. 18), wherein increasing
chain length increased miscibility pressures.
[0121] The results for vinyl copolymers can be greatly improved
(that is, lower miscibility pressures observed) in copolymers
wherein the T.sub.g and cohesive energy density of polymers of
monomer 1 were lower than that of poly(ethyl vinyl ether). For
example, either butadiene or isobutylene are effective choices for
monomer 1.
CO.sub.2-Philic (Ether-Esters)
[0122] Poly(ether-ester) copolymers of the present invention can be
synthesized by reacting, for example, a dihydroxy polyalkylene
oxide (a polyether with a hydroxy group at each end) with a
di-acid, a di-alkyl ester, or a di-acid halide at elevated
temperature (generally, above 65.degree. C., but below 200.degree.
C.), using vacuum to remove the byproduct (water or alcohol).
Alternatively, a base can be added in the case of the di-acid
halide (byproduct is HCl). These synthetic techniques and others
for synthesizing the poly(ether-ester) copolymers of the present
invention are well known to those skilled in the art. Like the
poly(ether-carbonate) groups discussed above, the poly(ether-ester)
copolymers of the present invention include a Lewis base (carbonyl
group) in the copolymer backbone.
Synthesis of CO.sub.2-Philic Analogs
[0123] In general, compounds not soluble or miscible in CO.sub.2
(that is, CO.sub.2-phobic compounds) can be made more soluble or
miscible in CO.sub.2 by synthesizing "CO.sub.2-philic analogs" of
such compounds incorporating one or more CO.sub.2-philic groups.
Processes and reactions that are normally not possible in CO.sub.2,
are thereby made possible. For example, surfactants, chelating
agents and reactants for use in carbon dioxide can be synthesized
in this manner. See, for example, U.S. patent application Ser. No.
09/106,480; U.S. Pat. No. 5,641,887; and U.S. Pat. No.
5,872,257.
[0124] FIG. 19 sets forth a general formula for such compounds. As
illustrated in FIG. 19, CO.sub.2-philic analogs of CO.sub.2-phobic
compounds include generally a CO.sub.2-phobic group corresponding
to the underlying CO.sub.2-phobic compound and a CO.sub.2-philic
segment including at least one CO.sub.2-philic group (g is an
integer of at least one in FIG. 19). The CO.sub.2-phobic group and
the CO.sub.2-philic group(s) are preferably covalently attached via
a spacer or connector group. As known from previous work with
fluorinated and silicon CO.sub.2-philes, the compounds of FIG. 19
can be prepared from the CO.sub.2-philes of the present invention
by preferably synthesizing such CO.sub.2-philes with a reactive
terminal functionality or reactive functional group such as a
hydroxyl group. This terminal functional group of the
CO.sub.2-phile is preferably reactive with a functional group on
the CO.sub.2-phobic compound. The reaction between the terminal
functional groups of the CO.sub.2-phobic compound and the
CO.sub.2-phile results in the spacer or connector group. Many such
functional groups are know to those skilled in the art. The
functional groups of the CO.sub.2-phobic compound and the
CO.sub.2-phile(s) preferably results in a spacer group that
enhances or does not substantially reduce the CO.sub.2-philic
nature of the compound of FIG. 19. Spacer groups may, for example,
include divalent forms of an ester, a keto, an ether, a thio, an
amido, an amino, a polyalkylene oxide, a phosphate, a sulfonyl, a
sulfate, an ammonium, an alkylene or combinations thereof.
[0125] An end group (typically not a reactive functionality unless
difunctionality is desired) at the other terminus of the
CO.sub.2-philic compounds of the present invention can be almost
any group. However, such end groups preferably enhance or do not
substantially reduce the CO.sub.2-philic nature of the
CO.sub.2-philic analog of FIG. 19. Preferred end groups include,
but are not limited to H, alkyl, alkenyl or ether groups.
[0126] Surfactants may, for example, be synthesized using these
materials. Copolymerizations of oxiranes and CO.sub.2 using
sterically hindered alkoxy aluminum catalysts are "living" in
character, and thus block copolymer synthesis is relatively
straightforward. For example, one can generate a water-soluble
surfactant by copolymerizing EO and CO.sub.2, then removing the
CO.sub.2 before all of the EO is polymerized (via flashing).
Conversely, one can begin a homopolymerization of EO, then added
CO.sub.2 (via simply opening a valve) part way through the
polymerization. These techniques produce a carbonate-ether diblock
material that does lowers interfacial tension of water. Generating
an optimized CO.sub.2-philic surfactant with a
poly(ether-carbonate) CO.sub.2-philic group simply requires, for
example, (a) identifying the most appropriate carbonate (for
example, CHO, EO- or PO-based), then determining the correct ratio
of carbonate/ether block length to produce a CO.sub.2-soluble
surfactant. All the optimizing determinations are readily made
experimentally.
[0127] Previous work on design of CO.sub.2-philic surfactants has
also identified both linear ammonium carboxylates and branched
sodium sulfonates (for example, AOT) as useful structures. See
Johnston, K. P.; Harrison, K. L.; Clarke, M. J.; Howdle, S.; Heitz,
M. P.; Bright, F. V.; Carlier, C.; Randolph, T. W.; Science (1996),
271, 624; and Hoefling, T. A.; Enick, R. M.; Beckman, E. J.; J.
Phys. Chem. (1991), 95, 7127.
[0128] To synthesize CO.sub.2-philic analogs from the vinyl
CO.sub.2-philic compositions of the present invention,
hydroxy-terminal oligomers may, for example, generated by replacing
the conventional initiator (AIBN) with a hydroxy-functional analog,
and by replacing the butyl mercaptan chain transfer agent with a
hydroxy-thiol analog (Aldrich). See Okaya, T.; Sato, T.; in
Polyvinyl Alcohol--Developments, Finch, C. A., editor (1992), John
Wiley & Sons, New York, Chapter 5. This technique could also be
used to generate surfactants directly by employing an inifer
surfactant as described by Guyot and Vidal. See Guyot, A.; Vidal,
F.; Polym. Bull. (1995), 34, 569 (c) Vidal, F.; and Hamaide, T.;
Poym. Bull. (1995), 35, 1.
[0129] Ammonium carboxylate surfactants may, for example, be
synthesized by reaction of the hydroxy-terminated oligomers with
maleic anhydride, followed by neutralization with ammonium
hydroxide. AOT analogs may generated via reaction of two
equivalents of the hydroxy-oligomer with fumaryl chloride, followed
by sulfonation with sodium hydrogen sulfite.
Experimental
Materials
[0130] All synthesis were carried out in purified argon atmosphere.
Monomers and solvents were purified as described previously.
Ethylene oxide was used as received. Epichlorohydrin (Aldrich
Chemicals, Milwaukee, Wis.) was distilled under reduced pressure.
Carbon dioxide and argon (both 99.99% purity from Praxair,
Pittsburgh, Pa.) were passed through high pressure purifiers before
use.
[0131] Vinyl acetate (VA) and ethyl vinyl ether (EVE) were obtained
from Aldrich Chemical Company. Vinyl acetate was purified by
passage through an inhibitor-sorbing column (Aldrich) to remove
hydroquinone. Ethyl vinyl ether was distilled under an argon
atmosphere. The initiator, 2,2' azoisobutyronitrile, was
recrystallized twice from ether. Poly(ethyl vinyl ether), 20 repeat
units, was generously donated by BASF Corporation (Ludwigshafen,
GER).
[0132] All other chemicals were obtained from Aldrich Chemicals and
used as received, unless otherwise noted.
Synthesis of Acetate Functionalized Poly(Epichlorohydrin)
[0133] Low molecular weight poly(epichlorohydrin) was used as the
starting material to produce acetate-modified polymers with varying
acetate content. In a typical polymerization reaction, boron
trifluoride diethyl ether (1.5 ml, 0.0118 moles) was added dropwise
to a solution of 20 ml epichlorohydrin (0.2557 moles) in 44 ml of
toluene over 30 minutes at room temperature. After 4 hours the
catalyst was deactivated with aqueous NaOH, and the organic phase
was separated and dried over CaCl.sub.2. The solvent was removed
under reduced pressure at 50.degree. C. and the polymer analyzed
using NMR and GPC. Poly(epichlorohydrin) with 7 repeat units was
produced with a yield of 90-95%. To generate higher molecular
weight polymer (e.g. 25 repeat units), methylaluminoxane (kindly
supplied by Akzo Nobel) was used as the initiator. The
polymerization was stopped with methanolic hydrochloric acid and
the polymer solution was filtered and processed as above.
[0134] For modification with acetate groups, the polymer was
reacted with potassium acetate using a phase transfer catalyst
(benzyltrimethyl ammonium chloride) in toluene (FIG. 2). The
reaction mixture was heated to 50-80.degree. C. for 24 hours. The
solution was allowed to cool to room temperature and the remaining
catalyst and potassium acetate were removed by filtration. The
polymer solution was washed rapidly three times with cold water to
remove any unreacted potassium acetate, then dried with magnesium
sulfate. The solvent was removed under reduced pressure. The amount
of acetate incorporated was determined by .sup.13C NMR from the
ratio of the CH.sub.2Cl peak at 43-45 ppm and CO peak from acetate
at 170-171 ppm. Maximum degree of modification was 45%.
Synthesis of Poly(Glycidyl Acetate)
[0135] Polymers containing only acetate groups in the side chain
were synthesized by polymerization of glycidyl acetate in a similar
manner as epichlorohydrin, using a sterically hindered aluminum
catalyst of the type
((H.sub.5C.sub.6).sub.3C--O).sub.2--Al--O--CH(CH.sub.3).sub.2. The
glycidyl acetate was synthesized according to known procedures
described in the literature. See Davies, A. G.; Alwyn, G.; Hawari,
J. A. -A.; Muggleton, B.; Tse, M. -W. J. Chem. Soc. Perkin Trans.,
2, 1981, 1132.
Synthesis of Catalysts for Oxirane/CO.sub.2 Copolymerization
[0136] These catalysts were synthesized under argon, in glass
flasks that were heated to 200.degree. C. and then evacuated and
flushed with inert gas three times. The catalysts used for the
copolymerization of propylene oxide and carbon dioxide were
monofunctional (1) or difunctional (2) sterically-hindered aluminum
alkoxides or phenoxides (FIG. 6). First, triisobutylaluminum was
reacted with tri(phenyl)methanol or a sterically hindered phenol,
then with an appropriate alcohol or glycol. The .sup.27Al-NMR
spectra of the catalysts showed that the sterically hindered
aluminum catalysts exhibited essentially only pentacoordination. If
Al atom was hexacoordinated then then .sup.27Al NMR would also show
a peak at 0 ppm but the pentacoordinated species only showed a peak
at appoximately 60 ppm. These NMR results suggest that the
catalysts exhibited one species of active site (unlike previously
reported catalysts for the polymerization of oxiranes and carbon
dioxide); which perhaps explains the living character of the
polymerizations subsequently observed.
[0137] In a typical experiment 10 mL tri-isobutyl aluminum (TIBA),
as a 1.0 molar solution in toluene, was reacted with 5.207 g (0.02
mol) tri(phenyl)methanol at 40.degree. for 2-4 hours and then 0.77
mL (0.01 mol) isopropanol was added dropwise, and the mixture was
stirred for two hours. The suspension of catalyst in toluene was
then cooled to room temperature, the solvent was removed with a
syringe and the catalyst washed twice with a small amount of dried
toluene. The remaining solvent was then removed under vacuum at
50.degree. C. The aluminum catalysts with sterically hindered
phenoxide substituents were used as a toluene solution.
Copolymerization of Cyclic Ethers and Carbon Dioxide
[0138] Copolymerization of cyclic ethers and carbon dioxide was
performed in either a 25 mL or 35 mL high-pressure reactor equipped
with magnetic stirrer and pressure and temperature indicators.
Prior to the experiment the reactor was heated to 200.degree. C.,
evacuated, and then cooled to room temperature under an argon
blanket. The desired amount of aluminum catalyst was introduced to
the reactor under an argon blanket, the reactor was sealed and
evacuated for 15-20 minutes, then finally flushed with argon. The
soluble aluminum compounds were used as a toluene solution and
introduced with a syringe. The oxirane was added alone using a
syringe, or as a mixture with CO.sub.2 using a high-pressure
syringe pump (High Pressure Equipment Co.). After injection of the
reagents, the reactor was isolated and heated to the prescribed
temperature (40-60.degree. C.). After the desired time the pressure
was slowly released, and the reaction was terminated with
methanolic hydrochloric acid. The polymer solution was filtered,
processed and analyzed. The amount of carbonate incorporated into
the polymer was determined from the integrals of the ether protons
peaks at approximately 3.4-3.6 ppm and the carbonate bound protons
at 4.8 ppm from .sup.1H-NMR. The reaction of cyclic ethers and
carbon dioxide produced copolymers including both ether and
carbonate linkages.
Synthesis of Acetate Terminated Poly(Propylene Oxide)
[0139] Poly(propylene) oxide (monobutyl ether) with 7 or 21 repeat
units was reacted with an excess of acetyl chloride in toluene for
24 hours. The residual reactant and solvent were subsequently
removed under vacuum.
Synthesis of Poly(Vinyl Acetate)
[0140] A three-neck glass flask evacuated with argon was charged
with 10 ml (0.1085 moles) of vinyl acetate, 20 ml of toluene, and
0.228 g of 2,2' azoisobutyronitrile (0.00139 moles). The reaction
mixture was then heated to 60.degree. C. for 4 hours. n-Butyl
mercaptan was used as chain transfer agent; amounts employed varied
as the desired molecular weight varied.
Synthesis of Poly(Ethyl Vinyl Ether)
[0141] A three-neck glass flask evacuated with argon was charged
with 10 ml (0.1279 moles) of ethyl vinyl ether and 20 ml of
toluene. Boron trifluoride diethyl etherate (0.250 ml, 0.0016
moles) was added dropwise to the EVE solution, which was kept at
20.degree. C. throughout the reaction. The reaction was allowed to
proceed for 24 hours and then was terminated with dilute aqueous
sodium hydroxide. The resulting mixture was extracted with ether to
remove the polymer and the ether solution was re-washed with
aqueous dilute sodium hydroxide to remove the residual catalyst
residue. The ether solution was then dried with magnesium sulfate
and filtered.
Synthesis of Poly(Vinyl Acetate Co-Ethyl Vinyl Ether)
[0142] In a typical reaction, a stainless steel reactor (50
cm.sup.3, manufactured at the University of Pittsburgh) was charged
with 10 ml of ethyl vinyl ether (0.1046 moles), 2 ml of vinyl
acetate (0.0217 moles), and 0.228 g of 2,2' azobis(isobutyrnitrile)
(0.00139 moles). The reactor was sealed and then submersed in an
oil bath. The temperature in the oil bath was raised to 60.degree.
C. and the reaction was allowed to proceed at the vapor pressure of
the monomer mixture for 4 hours. The polymer was recovered with
methanol. The solvent was subsequently removed under reduced
pressure.
Phase Behavior Measurements
[0143] The phase behavior of the copolymers was measured using a
high-pressure, variable-volume view cell (D. B. Robinson &
Assoc.). This cell is a quartz tube containing a floating piston.
The entire tube assembly is encased in a windowed, stainless steel
vessel capable of supporting pressures up to 500 bar. A known
amount of solute was added to the view-cell chamber above the
piston. The chamber was then sealed and charged with liquid
CO.sub.2. The pressure on the sample was altered at constant
composition via injection of silicone oil, which moved the floating
piston higher in the quartz tube. Initially, the pressure was
raised to the point where a clear, single-phase solution was
obtained. The phase boundary (cloud point, or miscibility) was
found subsequently by lowering the pressure until the solution
became cloudy.
Analyses
[0144] All .sup.1H NMR spectra were recorded on a Bruker DMX 300
instrument where the polymers were dissolved in d-chloroform with
tetramethylsilane used as the internal reference. The .sup.27Al-NMR
(75.468 MHz) spectra of the catalysts were recorded as known in the
art. Molecular weights of the product polymers were determined
using a Waters 150CV gel permeation chromatograph, equipped with
10.sup.4, 10.sup.3, 500 and 100 A ultrastyragel columns. THF was
used as eluent and calibration was performed using polystyrene
standards. IR spectra were recorded on a Mattson Genesis II FTIR.
Phase behavior of the polymers was studied in a variable volume
high pressure view cell, equipped with stirrer and temperature and
pressure controllers.
[0145] Molecular weight and the molecular weight distribution of
the polymers were measured using a Waters 150 CV gel permeation
chromatograph, equipped with 10.sup.4, 10.sup.3, 500 and 100 .ANG.
Ultrastyragel columns.
[0146] Although the present invention has been described in detail
in connection with the above examples, it is to be understood that
such detail is solely for that purpose and that variations can be
made by those skilled in the art without departing from the spirit
of the invention except as it may be limited by the following
claims.
* * * * *