Inorganic PolymersACCE 4111 : Polymer Science

4th Year : Odd Semester

Section : B (Chapter - 7)

2 November 2015

Course Outline

1. Inorganic Polymers, Homopolymers and heteropolymers

2. Silicon polymers

3. Polysilane polymers, preparation and chemical modification of

polysilane polymers

4. Properties and uses of polysilane polymers.

5. Polysiloxane and polysilicate polymers, polyphosphazene polymers

6. Coordination polymers and sol-gel.

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Inorganic polymers

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Inorganic polymers are polymers with a skeletal structure that does not

include carbon atoms in the main backbone.

1.(inorganic chemistry) Any giant molecule linked by covalent bonds, but having no (or

few) carbon atoms in the main molecular backbone.

Carbon fibres, graphite and diamond are,

however, considered to be inorganic

polymers.

Reference: E-Books

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In terms of the composition of the main chain, they are classified as

Homochain polymers ([—M—] n)

Heterochain polymers ([—M—M’—] n or [—M—M’—M”—] n),

Inorganic polymers

Homopolymers

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Homochain polymers with one kind of atom in the main chain:

•Silicon-silicon: polysilanes; precursors to fibrous silicon carbide

•Germanium-germanium: polygermanes

•Tin-tin: polystannanes

Heteropolymers

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Heterochain polymers with more than one type of atom in the main chain, mostly two types of

atoms alternate along the main chain, ranked by atomic weight of in-chain elements.

* Boron-nitrogen: polyborazylenes

* Silicon-oxygen:polysiloxanes

like the polydimethylsiloxane (PDMS), polymethylhydrosiloxane (PMHS) and polydiphenylsiloxane

* Silicon-nitrogen: polysilazanes

PolyborazylenesPolysiloxane

Silicon Polymers

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Silicones are mixed inorganic-organic polymers with the chemical

formula [R2SiO]n or [R2Si]n where R is an organic group such as methyl,

ethyl, or phenyl. Various silicon polymers are as follows:

1. Polysilane Polymer

2. Polysiloxane Polymer

3. Polysilicate polymer

Polysilane Polymer

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Polysilanes which cover one of the most attractive and challenging fields, are high molecular

weight polymers with inorganic elements in their backbone. These materials have silicon atoms

in their main chain and exhibit unique properties resulting from the easy delocalization of sigma

electrons in the Si─Si bonds.

Reference: E-Books

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Preparation of Polysilane

Reference: E-Books

Properties of Polysilane

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Polysilane is an unique inorganic polymer and hey exhibit distinctive optical

and electrical properties. The special properties are:

1. Rubbery elastomers

2. Stable at 300° C temperature

3. Shows photoconductivity

4. Conducts Electricity/Semiconductor

5. They are not easily hydrolyzed.

6. Degrade when exposed to ultraviolet light.

7. Inert to oxygen at normal temperatures

Reference: E-Books

Uses of Polysilane

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There are many technical uses as well as applications of these materials such as:

1. Precursors of silicon carbide ceramics

2. A strengthening agent in porous ceramic

3. Imaging materials in microlithography

4. Photoiniting in radical reactions and

5. Photo conducting, conducting, and semiconducting which are due to the unusual

mobility of sigma electrons.

Reference: E-Books

Polysiloxane Polymer

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Polysiloxane is an inorganic polymer with Si-O-Si linkage. It has siloxane

repeating unit. The formula is (C2H6OSi)n.

Reference: E-Books

Preparation of Polysiloxane Polymer

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Properties of Polysiloxane

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1. Flexible

2. Low surface energy

3. Permeability to gases

4. Transition temperatures

5. Low internal pressure,

6. Low bulk viscosity

7. Low temperature coefficient

8. Low entropy of dilution

9. Low excess volume upon mixing.

10. Optically clear, and, in general, inert, non-toxic, and non-flammable.

Reference: E-Books

Uses of Polysiloxane

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1. Artificial organs, facial reconstruction, catheters, artificial skin, contact

lenses.

2. Drug delivery systems while the non-medical applications include high-

performance elastomers.

3. Electrical insulators, water repellants.

4. Anti-foaming agents, mold release agents, adhesives and protective

coatings.

5. Agricultural chemicals, and hydraulic, heat-transfer, and dielectric fluids.

Polysilicate Polymers

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Polysilicates are geochemically important compounds formed by the reaction of the

acidic oxide SiO2 (silica) and basic metal oxides. These compounds possess definite

silicon oxo anions having covalent Si-O bonds but do not have the simple silicate ion

SiO44-. Rather, they have many 2-coordinate oxygen atoms linking the silicon atoms into

oligomeric or polymeric structures. In almost all silicates, silicon has a coordination

number of 4.

Polyphosphazene Polymers

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Polyphosphazenes include a wide range of hybrid inorganic-organic polymers with a number of

different skeletal architectures that contain alternating phosphorus and nitrogen atoms. Nearly

all of these molecules contain two organic or organometallic side groups attached to

each phosphorus atom. These include linear polymers with the formula (N=PR1R2)n, where R1 and

R2 are organic or organometallic side groups.

Reference: E-Books

Synthesis of Polyphosphazene

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Co-ordination Polymers

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A coordination polymer is an inorganic or organometallic polymer structure containing

metal cation centers linked by organic ligands. More formally a coordination polymer is a

coordination compound with repeating coordination entities extending in 1, 2, or 3

dimensions

Sol-gel

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• The sol-gel process is a method for producing solid materials from small molecules.

• The method is used for the febrication of metal oxides

• The process involves conversion of monomers into a collidal solution (sol) that acts

as the precursor for an integrated network (gel) of either discrete particles or

network polymers.

Reference: E-Books

Uses of Sol-Gel

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Sol-gel is a fabrication technique mainly used to make oxide ceramics, or polymer-ceramic

composite materials. These materials can be in the form of powders, coatings, bulk monoliths

or fibres. The two most common (i.e. economically viable) being powders and coatings.

Powders

Coatings

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Powders

The first significant industrial products of sol-gel technology were mixed oxide powders of

radioactive elements such as uranium and thorium. Being a solution-based technique sol-gel

produces no dust during fabrication, eliminating problems with the management of radioactive

dust and decontamination of the preparation areas. Both these issues had previously demanded

significant resource when conventional powder routes were used.

A second example of a sol-gel derived powder being used industrially is that of alumina for

abrasive applications. Conventional melting and crushing gives a relatively low yield of alumina

particles that are suitable for use in abrasive wheels and papers. Fabrication of these powders

using sol-gel methods gives a much better yield because the grain size can be more readily

controlled.

Uses of Sol-Gel

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Coatings

Coatings of sol-gel derived materials are used in a variety of applications, for example as

architectural coatings. The best known example of this is the European Patent House in Frankfurt,

which has a sol-gel coating on the windows. The coating controls the transmission and adsorption

of different wavelengths of light to give a uniform reflective appearance that is aesthetically

pleasing, whilst also minimising the "greenhouse effect" in the building and reducing cooling costs

during the summer.

Other examples of sol-gel coatings include the "self-cleaning" wing mirror on some premium car

brands, anti-reflective coatings on the interior mirrors of cars and corrosion protection coatings

for metals.

Uses of Sol-Gel

SOL-GEL PROCESS TECHNOLOGY AND CHEMISTRY

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SOL-GEL PROCESS TECHNOLOGY AND CHEMISTRY

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Thank you all

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