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Particulate materials

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Title: Particulate materials.
Abstract: The present invention provides the use of a particulate polymer material as a support for an active agent, characterised in that said polymer material is a polymer produced by copolymerising an unsaturated heterocyclic monomer and squaric or croconic acid or a derivative thereof. ...


Inventor: Daniel Eric Lynch
USPTO Applicaton #: #20120064348 - Class: 428407 (USPTO) - 03/15/12 - Class 428 
Stock Material Or Miscellaneous Articles > Coated Or Structually Defined Flake, Particle, Cell, Strand, Strand Portion, Rod, Filament, Macroscopic Fiber Or Mass Thereof >Particulate Matter (e.g., Sphere, Flake, Etc.) >Coated >Including Synthetic Resin Or Polymer

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The Patent Description & Claims data below is from USPTO Patent Application 20120064348, Particulate materials.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 11/579,271, filed Oct. 31, 2006.

BACKGROUND OF THE INVENTION

This invention relates to particulate polymers and particulate glasses prepared therefrom, to their use as reservoirs or encapsulating agents, to reservoir and encapsulating agent compositions and to materials containing such compositions, in particular to materials in which the basic polymer is prepared using the combination of an unsaturated heterocyclic monomer and a mono-unsaturated four or five membered dihydroxyl, di- or tri-oxo monomer, i.e. squaric acid or croconic acid, or an activated derivative thereof.

In many technical fields, particulate substrate materials are used as reservoirs for or to encapsulate chemical compounds having desirable properties, e.g. colorants, diagnostic agents, catalysts, growth media, etc.

Typical such particular substrate materials include porous, solid and hollow organic (e.g. polymeric) and inorganic (e.g. silicaceous) particles.

In the case of these particulate substrate materials, it is frequently complex or expensive to achieve the desired properties in terms of particle size, particle size distribution, porosity, loading characteristics, release characteristics, solvent penetrability, etc. This is particularly the case for hollow particulate substrates. Accordingly there is a continuing need for new materials having desirable properties as substrates.

A class of polymers produced by copolymerisation of unsaturated heterocyclic monomers and squaric or croconic acid has been investigated for their optoelectronic properties. See for example the review article by Ajayaghosh in Chem. Soc. Rev. 32: 181-191 (2003), the contents of which is hereby incorporated by reference. Such polymers however have not been suggested to have any utility as substrate materials and indeed many were dismissed as useless in view of their “intractable nature” (see Ajayaghosh (supra) at page 186, left hand column) as they formed an insoluble material on solution polymerisation.

We have found however that such intractable materials have properties which make them particularly suitable for use as particulate substrates, in particular their abilities to absorb compounds of interest, to be coated with inorganic glass layers, to shrink in a controlled manner upon heating, to produce hollow permeable glass spheres on thermal degeneration of the polymer core, etc.

Thus viewed from one aspect the invention provides the use of a particulate polymer material as a support for an active agent, characterised in that said polymer material is a polymer produced by copolymerising an unsaturated heterocyclic monomer and squaric or croconic acid or a derivative thereof.

Viewed from a further aspect the invention provides the use of a hollow particulate glass as a support for an active agent, characterised in that said hollow particulate glass is produced by pyrolysis of a glass-coated polymer produced by copolymerising an unsaturated heterocyclic monomer and squaric or croconic acid or a derivative thereof.

The particulate polymer material used according to the invention is preferably one prepared by solution polymerisation of the monomers in a solvent in which the growing polymer becomes insoluble, i.e. such that insoluble polymer particles form within the polymerisation mixture. The solvent used may be any appropriate organic solvent, preferably an alcohol, e.g. a C1-14 alkanol such as butan-1-ol, hexan-1-ol, decan-1-ol, tetradecanol and hexadecanol, preferably a C2-8 alkanol, more preferably butan-1-ol.

The heterocyclic monomer may comprise a single heterocyclic ring (preferably a pyrrole ring) or two or more heterocyclic rings linked via a fused ring, a bond, or a non-fused ring or a chain optionally incorporating a ring structure. The heterocycle ring(s) taking part in the polymerisation reaction are preferably five membered rings containing a nitrogen atom which either are unsubstituted at a position adjacent the nitrogen (or at both positions adjacent the nitrogen if only one heterocyclic ring is active in the polymerisation reaction) or are substituted at that position by a methylene group. Examples of the types of structure feasible are shown in Ajayaghosh (supra). Particularly preferably the heterocyclic group is a 2,5-unsubstituted pyrrole or a 5,5′-unsubstituted-2,2′-bis-pyrrole. In such compounds the 1, 3 and 4 positions may if desired be substituted, e.g. by optionally substituted alkyl, aralkyl or aryl groups. Typically optional substitution of such groups might be by hydroxy, thiol, amino, oxo, oxa, carboxy, etc. groups and substituted versions thereof (e.g. with alkoxy, alkylamino, carboxyalkyl, alkyl, aryl or alkaryl substitution). In the case of the 2,2′-bis pyrroles, linkage of the pyrrole groups may be for example via a bond, a chain (e.g. a methylene or polymethylene chain or a substituted chain such as 9-ethylcarbyl), a saturated or unsaturated ring (e.g. a furan, thiophene, benzene, bisphenyl, pyridine, anthracene or stilbenzyl ring) or a chain interrupted by a ring (e.g. vinyl-phenyl-vinyl). Desirably the monomer is selected such that in the backbone of the polymer product double bonds are in alternating positions, i.e. such that a delocalised electron system along the polymer is feasible.

Thus in a particularly preferred embodiment, the polymer has the structure

where each R, which may be the same or different, is hydrogen or optionally substituted alkyl; X is a bond or a bridging group; y is zero or a positive integer (e.g. 1, 2, 3 or 4) and z is a positive integer the value whereof determines the molecular weight of the polymer

As may readily be realised, where y>1, the heterocyclic monomer may itself be a pre-prepared polymer or oligomer.

In the heterocyclic monomer, the ring nitrogen is preferably unsubstituted or alkyl, especially methyl, substituted.

In the monomers used, any alkyl or alkylene moiety, unless otherwise specified, preferably contains up to 6 carbon atoms; any ring is preferably 5, 6 or 7 membered containing 0, 1 or 2 heteroatoms, especially O, N or S atoms; and any fused ring system preferably contains 2 or 3 rings.

The polymer beads formed in this way will typically be substantially monodisperse with a particle size of 0.1 to 5 μm (defined as the maximum diameter for which at least 90% by volume are as large or no larger—this can be determined using a Coulter particle size measuring apparatus). The particle size may be reduced, substantially uniformly, by heating to a temperature beneath that at which pyrolysis begins, e.g. to a temperature of 400-500° C., especially 430 to 450° C.

The “active agent” (or its precursor) may be absorbed into such particles from solution, e.g. in an aqueous or organic solvent. The active agent or precursor used in this respect may be any organic or inorganic compound or compound mixture capable of exhibiting desired characteristics in the end product. Thus for example it may be an organic or inorganic dye or dye precursor (a term which is used herein to include visible light absorbers as well as fluorescent and phosphorescent materials), an organic, inorganic or organometallic catalyst or catalyst precursor, a biological material (e.g. a bacterium or virus), a radiochemical, a diagnostic agent (e.g. a paramagnetic or super-paramagnetic material, an X-ray opaque material, a fluorocarbon etc.), a binding agent (e.g. an antibody or antibody fragment), etc. If desired, the particles may be used to carry a compound mixture (i.e. at least two compounds) rather than a single “active” compound. Where this is to be done, the particle may be impregnated sequentially or simultaneously with solutions of the compounds to be impregnated into the particles. If desired, the active agent may be a reagent for a desired reaction and indeed different batches of particles may be loaded with different reagents and then mixed so that reaction occurs when the reagents are released. In general however, where the polymer substrate is to be pyrolysed, either the material loaded onto the particles is a metal or pseudo-metal compound (e.g. an inorganic compound) or the material is loaded after pyrolysis of glass coated polymer particles.

In a particularly preferred embodiment of the invention, the uncoated polymer particles are loaded with a metal compound in dissolved form, e.g. a dissolved oxide, chloride, sulphate, nitrate, phosphate, acetate, etc. or with an organometallic compound, e.g. a metal alkyl or alkoxide. In this way it appears that virtually any element may be loaded into the particles.

If it is desired to produce glass-coated or hollow glass particles, the polymer particles may be contacted with a ceramic precursor, e.g. a metal or pseudo-metal alkoxide. Heating such treated polymer particles generates a glass (i.e. ceramic) shell by virtue of the decomposition of the alkoxide. Heating to the temperature at which the polymer pyrolizes generates a hollow glass particle containing the preloaded active agent (if any). Typically such pyrolysis occurs at temperatures above 600° C., e.g. 650-700° C. In this context it will be realised that the “glass” need not be a silica glass but may be any other metal or pseudo-metal ceramic, e.g. zirconia, titania, hafnia, etc. As zirconia, etc. may function catalytically, the glass shell itself may be or contain the “active agent”.



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stats Patent Info
Application #
US 20120064348 A1
Publish Date
03/15/2012
Document #
13373460
File Date
11/15/2011
USPTO Class
428407
Other USPTO Classes
65 214, 428402, 526263
International Class
/
Drawings
0



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