Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1996-03-05
2001-11-06
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S127000, C526S160000, C526S170000, C526S281000, C526S308000, C526S335000, C526S340200, C526S348000, C526S348500, C526S352000, C526S943000
Reexamination Certificate
active
06313239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to Group 4 metal-containing organosilicon dendrimers, methods of preparation thereof, and methods of use thereof.
2. Description of the Prior Art
Dendrimers are chemical compounds characterized by a regular, highly branched structure as shown schematically in FIG.
1
. Dendrimer
10
of
FIG. 1
is a second generation dendrimer, denoted by a generation number, G
n
, equal to G
2
. Dendrimer
10
includes an initiator core
12
from which branches, whose number is denoted by N
n
and characterized by length l, emanate. Four main branches (N
1
=4) emanate directly from initiator core
12
and form four primary branch points
14
from each of which three new branches (N
2
=3) emanate and form secondary branch points
16
as the next generation polymer is produced. Branches that emanate from branch points
16
terminate in end groups
20
.
Dendrimers are ideally monodisperse, i.e., they consist of single, identical species, all of which have the same composition and molecular weight. Dendrimers can be characterized by a range of molecular weights, ranging from relatively low oligomeric molecular weight, to relatively high polymeric molecular weights. Dendrimer molecular weights can depend on several factors including length of the arms, the extent of arm branching, the functionality of the branching groups in the arms, the length of connecting groups between branching sites and the functionality of the dendrimer core. Typically, dendrimers are soluble in organic solvents and their solubility in a particular solvent can be optimized by the choice of appropriate functional groups for the end groups. However, end groups may be chosen so as to result in water solubility. Dendrimers of intermediate generation number, G
n
, typically with n in the range of from about 1 to about 10, depending upon the dendrimer system, are characterized by an uncongested periphery with empty space between neighboring end groups. As such, intermediate generation number dendrimers have high surface areas and a relatively large proportion of unoccupied dendrimer interior volume.
Dendrimers can be synthesized using a “divergent procedure”, according to which dendrimers are grown outward by repetitive chemical steps using a multifunctional central core molecule as the starting material. Alternatively, a “convergent procedure” can be used to synthesize dendrimers by preparing segments of the dendrimer first and then attaching the segments to a central core molecule.
A type of organosilicon dendrimers, carbosilane dendrimers, and their preparation are described in Seyferth et al., Organometallics, 13 (1994) 2682-2690. A typical dendrimer prepared in the foregoing study is shown in FIG.
2
.
Thus, it would be highly desirable to exploit the foregoing dendrimer characteristics, including relatively high surface area and relatively high porosity, for applications including catalysis by preparation of dendrimers having end or interior group substituents with a desired chemical activity.
SUMMARY OF THE INVENTION
Many of the foregoing needs are met by an organosilicon dendrimer with one or more dendrimer arms containing a Group 4 metal such as Ti, Zr, or Hf or mixtures thereof. The invention provides dendrimers with Group 4 metal-containing end or interior group substituents, methods for making the dendrimers and polymerization methods that use the Group 4 metal-containing dendrimers as catalysts.
According to one aspect of the invention, a method for synthesizing such a dendrimer including a Group 4 metal substituent is provided. The method includes steps of (a) providing a core molecule containing one or more reactive functional groups; (b) providing a silicon hydride with an appropriate reactive functionality such as a silicon-halogen bond; (c) providing a hydrosilylation catalyst; (d) reacting the silicon hydride with the core molecule in the presence of the hydrosilylation catalyst to produce an intermediate organosilicon dendrimer; (e) reacting the intermediate organosilicon dendrimer to introduce an unsaturated organic functional group; (f) repeating steps (b), (c), (d), and (e) n times using the intermediate organosilicon dendrimer as formed in step (e) as the core molecule to produce a G
n
generation organosilicon dendrimer wherein n is an integer in the range of from about 1 to about 10 and G
n
is the generation number; and (g) reacting the G
n
generation organosilicon dendrimer with a Group 4 metal-containing reagent to form an organosilicon dendrimer including a Group 4 metal.
Another aspect of the invention provides a method for polymerizing an olefin including steps of contacting olefin monomers with an organosilicon dendrimer catalyst including a Group 4 metal, such as Ti, Zr, or Hf, or mixtures thereof, so that the olefin monomers are polymerized to form a polyolefin.
Yet another aspect of the invention is a dehydrogenative condensation polymerization of silane monomers, RSiH
3
, to form a polysilane using the dendrimers of the invention as a catalyst.
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Seyferth et al., “Synthesis of an Organosilicon Dendrimer Containing 324 Si-H Bonds”,Organometallics,vol. 13, No. 7, 1994, pp. 2682-2690.*
Muzafarov et al., “Organosilicon Dendrimers: Volume-Growing Polyallylcarbosilanes”,Polymer Science,vol. 35, No. 11, 1993.*
Rubinsztajn, S., “Synthesis and Characterization of New Poly(siloxysilanes)”,Journal of Inorganic and Organometallic Polymers,vol. 4, No. 1., 1994, pp. 61-73.*
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Becke Sigurd
Franz Uli W.
Seyferth Dietmar
Wyrwa Ralf
Bayer Corporation
Teskin Fred
Wolf Greenfield & Sacks P.C.
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