Palladium (II) catalyized polymers of norbornene and acrylates

Details Palladium (II) catalyized polymers of norbornene and acrylates Palladium (II) catalyized polymers of norbornene and acrylates

2000-05-05

2001-10-09

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S172000, C526S328000, C526S329000, C526S329700, C526S281000

Reexamination Certificate

active

06300440

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a novel catalyst that is suitable for use in the homopolymerization of norbornenes, in the homopolymerization of acrylates, and in the copolymerization of norbornenes with acrylates. The invention relates, further, to a process for homopolymerizing norbornenes and acrylates using the present catalyst, to a process for copolymerizing norbornenes with acrylates using the present catalyst, and to novel copolymers of norbornenes with acrylates.
BACKGROUND OF THE INVENTION
Considerable interest has existed in the copolymerization of acrylates with norbornenes because of the potential benefits of combining the useful properties of the homopolymers of the two monomers. For example, polyacrylates are valued for their extreme hardness and adhesive properties, and are used to form clear, glass-like materials such as Lucite® and Plexiglas®. Polynorbornenes, on the other hand, are capable of resisting high temperatures and, thus, typically are employed in applications that necessitate high-temperature stability.
Until the present invention, attempts to copolymerize acrylates with norbornenes have been unsuccessful because of a disparity in the mechanisms by which the respective monomers polymerize. Typically, acrylates polymerize in the presence of radical or anionic initiators, whereas norbornenes do not follow radical pathways and normally are polymerized by cationic or insertion mechanisms. Therefore, in order to effect the copolymerization of acrylates with norbornenes, it was necessary to develop a catalyst system that would be effective for polymerizing both types of monomers.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a catalyst system that is capable of copolymerizing acrylates with norbornenes.
It is another object to provide a catalyst system that is useful for the homopolymerization of both acrylate monomers and norbornenes.
It is yet another object to provide a novel catalyst system that is useful both for the homopolymerizing of acrylate monomers and norbornene monomers, and for the copolymerization of acrylates with norbornenes.
Still another object of the invention is to provide novel copolymers of acrylates with norbornenes.
DETAILED DESCRIPTION OF THE INVENTION
The above and other objects and advantages of the invention are accomplished in one embodiment by providing a Pd(II)-based catalyst system which homopolymerizes acrylates to high molecular weight polymers, which homopolymerizes norbornenes to polymers, and which copolymerizes acrylates with norbornenes to high molecular weight polymers. The copolymers prepared in accordance with this invention are characterized by advantages and properties attributable to the respective acrylate and norbornene monomers from which they are derived. The copolymers can be tailored in norbornene to acrylate ratio by varying the ratio of the respective monomers in the reaction mixture and by varying the ligands utilized in the catalyst system.
As used in this specification and claims, the term “acrylates” is meant to include compounds of the general formula H
2
C═CHCOOR, where R is an alkyl group, such as methyl (CH
3
), ethyl (CH
2
CH
3
), propyl (CH
2
CH
2
CH
3
), n-butyl (CH
2
CH
2
CH
2
CH
3
) or t-butyl (C—(CH
3
)
3
), or an aryl group, such as phenyl (C
6
H
6
) or p-tolyl (C
7
H
8
). Other acrylates which do not conform to the above formula, but which are nonetheless suitable for use in the present invention and are intended to be included within the scope of the term “acrylates”, include such acrylates as 2-hydroxy ethyl methacrylate and methyl methacrylate. Specific, non-limiting examples of acrylates contemplated for use in the present invention include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylamide, 2-hydroxy ethyl methacrylate, methyl methacrylate, acrolein, ethyl methacrylate, acryloyl chloride and phenyl acrylate.
The term “norbornenes” is meant to include norbornene, as well as norbornene derivatives, such as norbornadiene and compounds conforming to the general formulas 5-norbornene-2-R
1a
, 5-norbornene-2,2-R
1a
, 5-norbornene-3-R
1a
, 5-norbornene-3,3-R
1a
, 5-norbornene-2,3-R
1a
, or 5-norbornene-2-R
1a
-3-R
1b
, where R
1a
and R
1b
, independently, represent an alkyl or aryl group. Specific, non-limiting examples of norbornenes contemplated for use in the present invention include norbornene, 5-norbornene-2-methanol, cis-5-norbornene-endo-2,3-dicarboxylic anhydride, 5-norbornene-2,2-dimethanol, 5-norbornen-2ol, norbornadiene, 5-norbornene-2,3-diphenyl, cis-5-norbornene-endo-2,3-dicarboxylic acid dimethyl ester, 5-norbornen-2-yl-acetate and 5-norbornene-2-carboxyaldehyde.
The Pd(II)-based catalyst system of the present invention is a dimer catalyst that may be characterized by the formula [(L)Pd(R)(X)]
2
.
In this dimer catalyst, L is a monodentate phosphorus or nitrogen ligand. In general, suitable monodentate phosphorus ligands are those which conform to the formula R
2
3
P, where R
2
is alkyl and/or aryl group. Non-limiting examples of such monodentate phosphorus ligands include triphenyl phosphine (PPh
3
), tricyclohexyl phosphine (PCy
3
), trimethyl phosphine (PMe
3
), triethyl phosphine (PEt
3
), tri-n-propyl phosphine (P(n-Pr)
3
), tri-n-butyl phosphine (P(n-Bu)
3
), tri-t-butyl phosphine (P(t-Bu)
3
) and tri-p-tolyl phosphine (P(p-Tol)
3
). Specific, non-limiting examples of mixed alkyl and aryl phosphines that are suitable for use in the invention include methyldiphenyl phosphine (P(Me)(Ph)
2
), phenyidimethyl phosphine (PPh(Me)
2
), ethyldiphenyl phosphine (P(Et)(Ph)
2
), and ethyldiphenyl phosphine (PPh(Et)
2
).
Generally, monodentate nitrogen ligands which may be used in the present invention are aromatic or heterocyclic amines, such as pyridine, t-butyl pyridine, aniline, trimethyl aniline and imidazole, or compounds that conform to the formula R
3
3
N, where R
3
is an alkyl group, such as methyl (CH
3
), ethyl (CH
2
CH
3
), propyl (CH
2
CH
2
CH
3
), n-butyl (CH
2
CH
2
CH
2
CH
3
), or t-butyl (C—(CH
3
)
3
), or an aryl group, such as phenyl (C
6
H
6
) or p-tolyl (C
7
H
8
).
X is an anionic group, such as chlorine or bromine, or a carboxylate, such as acetate, propionate, trifluoroacetate, and benzoate; and R is an alkyl group, such as methyl (CH
3
), ethyl (CH
2
CH
3
), propyl (CH
2
CH
2
CH
3
), n-butyl (CH
2
CH
2
CH
2
CH
3
or t-butyl (C—(CH
3
)
3
), or an aryl group, such as phenyl (C
6
H
6
) or p-tolyl (C
7
H
8
).
Typically, the catalyst is formed by reaction of 1 equivalent of the monodentate ligand with [(1,5-cyclooctadiene)Pd(Me)(X)] in situ, as illustrated by the equation (using X=chlorine):
Catalyst formation may be monitored by
1
H and
31
P{
1
H} NMR. For the PCy
3
analog, the movement of the methyl signal in the proton spectrum from a singlet at 1.12 ppm in the starting material to a triplet at 0.11 ppm in the dimer upon addition of 1 equivalent PCy
3
indicates the formation of the desired product. Additionally, the appearance of uncoordinated 1,5-cyclooctadiene signals at 5.55 and 2.34 ppm in the proton NMR and a 25.6 ppm
31
P{
1
H} NMR signal for [(PCy
3
)Pd(Me)(Cl)]
2
are observed.
The relevance of the alkyl (or aryl) group in the present dimer catalyst system was explored by attempting to homopolymerize methyl acrylate using a dimer catalyst that was devoid of alkyl (or aryl) groups. It was found that methyl acrylate would not polymerize when reacted in the presence of a Pd(II) catalyst that was prepared by reacting [(1,5-cyclooctadiene)Pd(Cl)
2
] with 1 equivalent of tricyclohexyl phosphine (PCy
3
). This indicated that the alkyl (or aryl) group is essential to the polymerization mechanism.
The copolymers of the present invention may be tailored in norbornene to acrylate ratio by varying the ratio of the respective monomers in the reaction mixture and by varying the ligands utilized in the catalyst system. Typically, the ratio of norbornene monomer to acrylate monomer in the sta

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