2. OUTLINE
• Conducting polymer
• Types of Conducting Polymers.
• Types of Conduction
• Doping
• Polyaniline (Synthesis, properties and applications)
• Polypyrrole (Synthesis, properties and applications)
• Polyacetylene (Synthesis, properties and applications)
• Conclusions
3. Conducting Polymers
• Conducting polymers are those polymers which
• Conduct electricity due to delocalization of π
electrons.
E.g- Polyacetylene, Polythiophene, Polyaniline,
Polypyrrole, etc.
4. Discovery of conducting polymers
• Discovered in the late seventies (1977) by Alan
Heegar, Dr. Hideki Shirakawa and Alan Macdiarmid
• Before that polymers were used as insulators in the
electronic industry
• Advantages over conductors
Chemical - ion transport possible, redox behavior ,
catalytic properties, electrochemical effects,
Photoactivity, Junction effects
Mechanical - light weight, flexible, non metallic
surface properties
5. What is Conductivity?
• Conductivity can be defined simply by Ohms Law.
V= IR
• Where R is the resistance, I the current and V the
voltage present in the material.
• The conductivity depends on the number of charge
carriers (number of electrons) in the material and
their mobility.
• In a metal it is assumed that all the outer electrons are
free to carry charge and the impedance to flow of
charge is mainly due to the electrons "bumping" in to
each other.
6. Types of Conduction
• Intrinsic conductors(Pure)- Conduct electricity in pure
form due to the presence of electrons & holes.
• Extrinsic conductors- By adding external
impurities.(Doping).
• Holes- Formed by removal of electrons on doping.
7. Two conditions to become conductive:
1. The first condition for this is that the polymer
consists of alternating single and double bonds,
called conjugated double bonds.
In conjugation, the bonds between the carbon
atoms are alternatevly single and double. Every
bond contains a localised “sigma” (σ) bond which
forms a strong chemical bond. In addition, every
double bond also contains a less strongly
localised “pi” (π) bond which is weaker.
8. 2. Doping
Converstion of poymer back bone to a charge π conjugated
system is called Doping.
There are diffrents types of Doping-
• Redox doping
• Non redox doping
• Photo doping
• Charge injection doping
• Electrochemical Doping
9. Types of Doping Agents
Dopants may be classified as:
• Neutral dopants: I2, Br2, AsF2, Na, K, H2SO4, FeCl3 etc.
• Ionic dopants: LiClO4, FeClO4, CF3SO3Na, BuNClO4 etc.
• Organic dopants: CF3COOH, CF3SO3Na, p-CH3C6H4SO3H
• Polymeric dopants: PVS, PPS
Effect of dopant
• Conductivity - increases upto a certain doping level
• Stability – decreases
• Morphology : due to presence of charges shape will
not be retained.
10. Polyaniline
• Polyaniline (PANI) is a conducting polymer of the semi-
flexible rod polymer family.
• Produced as bulk powder, cast films, or fibers.
• One of the oldest known conducting polymer.
• First discovered in the 19th century.
• Also known as Aniline Black.
11. Synthesis of Polyaniline
• Found in one of three idealized oxidation states.
• leucoemeraldine – white/clear & colorless (C6H4NH)n
• emeraldine – green for the emeraldine salt, blue for the emeraldine base
([C6H4NH]2[C6H4N]2)n
• (per)nigraniline – blue/violet (C6H4N)n
• The formation of leucoemeraldine can be described as follows, where [O]
is a generic oxidant.
• n C6H5NH2 + [O] → [C6H4NH]n + H2O
• The most common oxidant is Ammonium persulfate.
• The reaction is very exothermic
13. Why Polyaniline?
• High sensitive
• Very simple in detection
• Rapid
• Flexibile
• Easy in synthesis
14. Synthesis of Polyaniline Nanowires
• 1) Chemical Synthesis-Polyaniline nanowires are
formed by chemical oxidation of aniline monomers.
• 2)Electrochemical polymerization-Aniline monomers
are electrochemically oxidized and polymerized on the
surface of the anode of the electrochemical cell.
16. Polypyrrole
• Polypyyrole(PPy) first synthesised in 1968
• It is a heterocyclic conducting polymer
• Ppy is an organic polymer obtained by oxidative
polymerization of pyrrole.
• It is a solid with the formula H(C4H2NH)nH
• It is an intrinsically conducting polymer, used in
electronics, optical, biological and medical fields.
17. Synthesis of Polypyrrole
• Polypyrrole (PPy) was synthesized by chemical
oxidative polymerization technique using pyrrole
monomer and different oxidants.
• The chemical polymerization was carried out in a
beaker with distilled water by mixing different
molar ratios of pyrrole monomer, an oxidant,
and a surfactant.
20. Polyacetylene
• Polyacetylene (PA) (IUPAC name: polyethyne)
is an organic polymer discovered by Hideki
Shirakawa, Alan Heeger, and Alan MacDiarmid
with the chemical formula of (C2H2)n
• It forms by the oxidative polymerization of
acetylene monomer to form a continuous linear
chain of olefin groups.
24. Applications
• Doped PA used as electric wiring or electrode
material for light weight rechargable batteries.
• Sensor to measure glucose concentration.
• Polyacetylene is used in optoelectronics. The
conductivity of the polymer after doping is equal to
that of copper.
25. Conclusion
• For conductance free electrons are needed.
• Conjugated polymers are semiconductor
materials while doped polymers are conductors.
• The conductivity of conductive polymers
decreases with falling temperature in contrast to
the conductivities of typical metals, e.g. silver,
which increase with falling temperature.
• Today conductive plastics are being developed
for many uses.
