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Introduction toIntroduction to

INORGANIC POLYMERSINORGANIC POLYMERS

ISLAMIC AZAD UNIVERSITY - KARAJ BRANCHFACULTY OF GRADUATE STUDIES

DEPARTMENT OF CHEMISTRY

By:Mohammad BarkhiMohammad Barkhi

What is a Polymer ?

► A polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. The term is derived from the Greek words: polys meaning many, and meros meaning parts.

What is an inorganic polymer ?What is an inorganic polymer ?► Inorganic by its name implies nonorganic or nonhydrocarbon. The most obvious definition for an inorganic polymer is a polymer that has inorganic repeating units in the backbone.

► A giant molecule linked by covalent bonds but with an absence or near-absence of hydrocarbon units in the main molecular backbone.

► A polymer that don't have any carbon atoms in the backbone chain.

Why inorganic polymers ?► The main reasons for scientist to be interested in inorganic-base macromolecules are connected with their unique property profiles that make them different from their totally organic counterparts.

► The number and variety of elements found in these polymers.

► The relative high abundance of inorganic elements in the earth's crust.

► Stronger bond formation, which are more resistant to cleavage reactions (Si-O 110, P-N 140, and C-C 85 kcal/mol).

► Different valancies for attachment of side groups.

► Stability at high temperature.

► Tailoring new and interesting structures with many variations, which seem endless.

► And finally, regarding the fact that most of the organic polymers are made of oil, according to the decrease of oil storages, the existence of them will one day restricted.

Classification schemes► Inorganic polymers represent a rapidly growing field of chemical research and already have many applications and any classification is necessarily somewhat arbitrary.

► N. H. Ray, in his book on inorganic polymers(1978), uses connectivity as a method of classifying inorganic polymers.

► The other classifying will be introducedin the following: - wholly inorganic polymers - inorganic-organic polymers - organometallic polymers - hybrid organic-inorganic polymers

Classification by connectivities

► Ray defines connectivity as the number of atoms attached to a defined atom that are a part of the polymer chain or matrix. This polymer connectivity can range from 1 for a side group atom or functional group to at least 8 or 10 in some metal-coordination and metal-cyclopentadienyl polymers, respectively.

Connectivities of 1

► Anchored metal-containing polymers used for catalysis can have connectivity values as low as 1 with respect to the polymer chain.

Schematic of anchored metal-containing polymer with a connectivity of 1, where M might be palladium or platinum with three other ligands. For catalytic activity, at

least one of the three must be easily removed by a substrate.

Connectivities of 2

Examples of inorganic polymeric species with connectivity of 2 :(a )poly-)sulfur nitride(; )b( linear polyphosphate; )c( poly)dichlorophosphazene(

a b

c

Connectivities of 3

Examples of connectivity of 3: )a( boric acid, )b( arsenic)III( sulfide,

Mixed Connectivities of 2 and 3

Example of polymeric inorganic species with mixed connectivities of 2 and3: an ultraphosphoric acid

Connectivities of 4

Examples of polymeric inorganic species with mixed connectivities of 4:)a( silica with silicon atoms of connectivities of 4 and )b( boron phosphate with

both phosphorus and boron atoms with connectivities of 4.

Connectivities of 6

Mixed Connectivities of 4 and 6

An orthophosphate of mixed connectivites of 4 and 6.

Connectivities of 8

A Schiff-base polymer of zirconium with a connectivity of 8.

wholly inorganic polymers► Inorganic polymers in this class constitute the major components of soil, mountains and sand, and they are also employed as abrasives and cutting materials (diamond, silicon carbide (carborundum)), fibres (fibrous glass, asbestos, boron fibres), coatings, flame retardants, building and construction materials (window glass, stone, Portland cement, brick and tiles), and lubricants and catalysts (zinc oxide, nickel oxide, carbon black, silica gel, aluminium silicate, and clays).

Structure of a typical silicon dioxide intensive glass

Inorganic-organic Polymers► inorganic polymers containing organic portions attached to inorganic elements in their backbone. The area of inorganic-organic polymers is very extensive. Some examples of this class are: Polysilanes, Polysiloxanes, Polyphosphazenes.

Organometallic Polymers►Organometallic polymers are made of over 40 elements including main group of metals )Si or Ge(, transition metals or rare earth elements in addition to the 10 elements )C, H, N, O, B, P, halides( which is found in organic polymers )Figure 10(.The variations of organometallic polymers seem endless. Organometallic polymers are new materials which combine the low density and structural variations and functional group varieties of organic materials with electrical conductivity and the high temperature stability features of inorganic compounds.

Different structures found in organometallic polymers

Hybrid organic-inorganic polymers

► Hybrid organic-inorganic networks, prepared via sol-gel process, are multi-functional materials offering a wide range of interesting properties. Since there are countless different combinations of the organic and inorganic moieties, a large number of applications are possible by incorporation of inorganic building blocks such as silica networks, porous materials and metals.

π-Conjugated polymers prepared via organometallic condensation reactions

INORGANIC POLYMERS SYNTHESIS

A classification of polymerization reactions

► Several methods proposed for inorganic polymers synthesis. We focus our discussion on some of them.

► Polyphosphazenes are inorganic polymers with a phosphazene repeating unit and general structure )-RR'P=N-(. They are generally prepared from the intermediate poly)dichlorophosphazene( and either amines or sodium salts of alcohols. Poly)dichlorophosphazene( is prepared from the ring opening polymerization of hexachlorocyclotriphosphazene.

► In 1949, Burkhard was invented a polysilane called polydimethylsilane that it wasn't much good for anything. It formed crystals that were so strong that nothing could dissolve them. In the seventies, some scientists got the notion to make small rings of silicon atoms. But unwittingly did something similar to what Burkhard had done. They reacted sodium metal with dichlorodimethyl silane, but they also added some dichloromethylphenylsilane to the brew. But they didn't get the rings they wanted. they got a copolymer that was soluble and can be processed and played with and studied.

► The major route to produce polysiloxane is Rochow process in which ground silicon is reacted with chloromethane using a catalyst, such as copper. These compounds react with water forming dihydroxysilanes that in turn will be condensed, splitting out water, eventually forming polysiloxanes.

A dual thermal ring-opening polymerization reaction between asilyl-bridged ferrocene and a cyclic silane.

The cationic initiated polymerization of divinylferrocene.

The synthesis and electropolymerization of copper)II( and nickel)II(3,4-bis)salicylaldimino(thiophene Schiff-base chelates

The photo activated platinum-catalyzed hydrosilylation polymerization ofvinyldimethylsilane

The synthesis of lanthanide polyelectrolytes with Condensation Through Bridging Ligand Coordination.

)bis)tetradentate( Schiff-base bridging ligand(.

General synthesis pathway for hard type triazene polyurethanes wereobtained by a polyaddition performed in dry DMF

APPLICATIONSOF

INORGANIC POLYMERS

► Amorphous silicon dioxide-intensive materials include a wide variety of glasses such as fibreglass, window glasses, Vycor glasses, borosilicate glass, which can be shaped by drawing, pressing, casting, and blowing. Colourless optical glasses, luminescence and laser glasses are produced by using rare earth elements as components of these special glasses. A scintillating glass with fluorescence properties uses PbO-Bi2O3 heavy-metal oxides based materials. A new superionic glasses )solid electrolyte( based on silver iodide with organic monomer ions is reported, which exhibits high ionic conductivity comparable to that of oxides based superionic glasses, but 10 to 10000 times larger than of typical Li+ polymer electrolytes.

► Poly (sulphur nitride) is the first reportednon-metallic covalent polymer, with electronic conductivity properties comparable to that of metal, and is the first example of a polymeric superconductor.It is used as conductive material in the manufacturing of a plasma display panel and in electrically conductive plastic light sources such as battery-powered flash lights and lanterns. Battery housing or head assemblies for light sources are formed from electrically conductive polymers such as poly)sulphur nitride(.

► Polysilanes are useful as precursors to silicon carbide ceramics as photoresists, in microelectronics as photoinitiators for radical reactions and as photoconductors.

silicon carbide ceramics

► Siloxane polymers have numerous medical applications such as: prostheses, artificial organs, facial reconstruction and tubing and catheters take advantage of the inertness, stability, and pliability of these polymers; artificial skin, contact lenses, and drug delivery systems utilize their high permeability as well. A wide range of medical-purpose items were manufactured using of unsaturated siloxane rubbers with silicon hydrides of various structures. These materials are biologically-compatible with a high complex of medicals.

b

b)a(Siloxane artificial pacemakers and )b( polysiloxane rubber being used to make vinyl sheet with detailed surface.

a

► Polyphosphazenes or phosphonitrilic polymers are the most interesting and commercially promising inorganic Polymers. Applications based on structure-property correlations in technology or medicine are as follows:

- Advanced elastomers, design for a rechargeable lithium battery based on the conductivity of lithium triflate in solid poly[bis-)methoxyethoxyethoxy( phosphazene.

- The extreme hydrophobicity of the surface minimizes the foreign body interactions that normally occur when non-living materials are implanted in contact with living systems, including blood.

- Solid polymer electrolytes have been extensivelyinvestigated for their potential applications in highenergydensity batteries.

► Polymeric copper phthalocyanine containing peripheral carboxyl groups is converted into polyimides through polycondensation with aromatic diamine to obtain a processable material for potential application in the fabrication of electronic devices.

EPILOGUE► Numerous uses for inorganic polymers have been developed. For many of these uses, the inorganic polymers have advantages over their organic counterparts, but often relatively high cost has precluded the use of the inorganic polymers, except where the cost differential is less than the advantage perceived for the polymer. As simpler synthetic methods and larger scale use occur, the differential will diminish and more uses will flourish. For some uses where no organic counterpart is satisfactory, the inorganic polymers have been accepted.

Inorganic polymers will undoubtedly be featured in future high-tech nanoscale materials, where cost may be less of a factor.

Thus the ultimate fate of inorganic polymers rests on future practitioners in the field and the uses for which the polymers are found to be superior over their organic counterparts. If recent developments are a guide to the future, the future for inorganic polymers is very bright indeed.

Acknowledgement:► Dr. Mohammad. R. Melardi; Dep. Of Chem. Karaj I.A.U.

► Dr. Fariba Shokrolahi; Iranian Polymer & Petrochemical Institute.

Refrences:► INORGANIC AND ORGANOMETALLIC POLYMERS; RONALD D. ARCHER; A John Wiley & Sons, Inc., Publication

► Inorganic and Organometallic Polymers: A Review; Azam Rahimi; Iranian Polymer Journal 13 )2(, 2004, 149-164.

► Bianconi et al; Macromolecules,1989, 22, 1697; © 1989 American Chemical Society.

► E.C. Buruiana et al. / Journal of Photochemistry and Photobiology A: Chemistry 171 )2005( 261–267

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