Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-08-03
2001-06-26
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S452000, C525S454000, C525S395000, C525S440030, C528S044000
Reexamination Certificate
active
06252014
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns star shaped polymers and polymeric nanoparticles that include non-vinyl polymeric arms and non-vinyl polymeric cores, and a method for making the star shaped polymers and polymeric nanoparticles. In one embodiment, the method involves the reaction of functionalized non-vinyl polymer chains (typically mono-functionalized non-vinyl polymer chains) with crosslinkable non-vinyl monomers to form star polymers or nanoparticles, depending upon the reaction conditions.
BACKGROUND OF THE INVENTION
Star polymers with vinyl polymer arms have been synthesized traditionally by the reaction of an anionic living chain end of the vinyl polymer with a multi-functional compound. Silicon tetrachloride was the first such multi-functional compound to be reacted with living chains to yield a star molecule. Other silyl chloride compounds have been used to form stars with a greater number of arms. The reaction of an anionic living chain end with a divinylic monomer such as divinyl benzene was the next innovation in the synthesis of star polymers. The anionic sites of the living polymer react with the divinylic monomer to form stars with small crosslinked cores. Modification of this synthetic route has been analogously applied to living cationic chains. Both of these syntheses can lead to soluble, star-shaped polymers with highly crosslinked cores. Although the core is crosslinked, the polymer remains soluble due to the solubilizing effect of the arms. This core is also usually considered to be negligible in size relative to the weight fraction of the arms and the core fraction is typically less than five percent of the total weight of the molecule. Materials have also been formed by increasing the weight fraction of the star's core while still obtaining materials that are soluble or colloidally dispersible. For example, a large, calculated amount of divinylbenzene can be added to living polystirene chains, resulting in stars with crosslinked cores of varying weight fraction. It has been found that in this manner stars with crosslinked cores of 30 percent by weight of the total star could be formed while still retaining solubility of the material. Similarly and more recently, living cationic polymerizations were utilized to form stars with polyvinyl polymer arms with crosslinked cores on the order of 35 weight percent. These materials also remained soluble with the large core allowing a large number of arms to fit around it. These multiarm stars showed interesting solution properties due to their architecture. Other syntheses of stars with large, crosslinked cores include synthesizing them from block copolymers where one of the blocks contains crosslinkable functionalities. These block copolymers can form micellar structures in the proper solvent and if the crosslinkable block forms the core of the micelle, the structure of the micelle can be locked in through subsequent crosslinking reactions resulting in star polymers or nanoparticles. This method requires the synthesis of well defined block copolymers by living techniques similar to the requirements of living techniques for other known methods of star formation.
The prior star polymer work involved only vinyl polymers, which severely limits the usefulness of the prior synthesis techniques. This is because vinyl starting materials tend to be expensive and because vinyl polymers are less than ideal for many applications. There is a significant need for techniques to synthesize star polymers of non-vinyl materials and the star polymers that may be made by such techniques.
SUMMARY OF THE INVENTION
With the present invention, it has been found that non-vinyl materials may be used to prepare star-shaped non-vinyl polymers of a great variety of compositions. In one aspect of the invention, a method is provided for making such a star-shaped polymeric material. The method involves reacting functionalized non-vinyl polymer pre-arms with crosslinkable non-vinyl reactants to form a crosslinked core covalently linked to non-vinyl polymeric arms formed from the pre-arms. In a preferred embodiment, the polymeric arms are linked to the core through other than carbon—carbon linkages. These linkages typically are the reaction residue between the functionality of the functionalized non-vinyl polymer pre-arms and the crosslinkable non-vinyl reactants. Some examples of suitable linkages include ester, ether and amide linkages.
In another aspect of the invention, a star-shaped polymeric material is provided, which is manufacturable according to the previously noted method. The star-shaped material includes a polymeric core comprising a crosslinked non-vinyl polymer and a plurality of polymeric arms covalently linked to the core and extending from the core, with the polymeric arms each comprising at least a segment of non-vinyl polymeric material. In one embodiment, the arms impart water solubility or dispersability to the material, even when the core is hydrophobic. Such materials are useful for imbibing organic contaminants for water purification and for trapping hydrophobic drug molecules in the core for sustained drug release. Other uses for the star-shaped materials of the invention, depending upon composition, include toughening agents, size standards, additives for liquid rheology modification, additives for coating materials, and applications when colloidal materials are required. As one example, material with poly(ethylene oxide) arms and a crosslinked polyurethane core may be used for water purification purposes. As another example, material with arms of a nylon polymer and a core of a crosslinked epoxy could be used as a toughening agent. As a further example, material with arms of polyphenylene oxide and a core of a crosslinked polyester could be used as a modifier to reduce brittleness in a bulk phase mixture of polystirene and polyphenylene oxide.
As used herein, crosslinked does not require an infinite network. In that regard, the cores are of finite dimensions, which are highly branched and are formed by linking together a number of crosslinkable monomer units.
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Colorado School of Mines
Dawson Robert
Holme Roberts & Owen LLP
Kulish, Esq. Christopher J.
Zimmer Marc S.
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