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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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