This document summarizes chemical and electrochemical methods for synthesizing polyaniline and polythiophene. Polyaniline can exist in three oxidation states - leucoemeraldine, emeraldine, and pernigraniline. It can be synthesized chemically using an oxidative process with an acid and oxidizing agent like ammonium persulfate or potassium dichromate. Electrochemical synthesis grows a polyaniline film on an anode. Polythiophene is also synthesized chemically using oxidative polymerization with catalysts or electrochemically by applying a potential to drive polymerization. The McCullough and Rieke methods can produce regioregular polythiophene using nickel or palladium catalysts. Both polymers find applications in

1. CHEMICAL AND ELECTROCHEMICAL METHODS OF THE SYNTHESIS
OF POLYANILINE AND POLYTHIOPHENE
NAST-622: POLYMERS AND NANOCOMPOSITES
Course Instructor:
Dr. A. SUBRAMANIA
Centre head
Center for Nanoscience and Technology
presented By:
MUGILAN N (16305012)
M.TECH Ist YEAR (NAST)

2. INTRODUCTION
POLYANILINE
 Polyaniline (PANI) is a conducting polymer of the semi-flexible rod polymer family.
 Polymerized from the inexpensive aniline monomer.
 Polyaniline can be 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
In figure, x equals half the degree of polymerization (DP).
• Leucoemeraldine with n = 1, m = 0 is the fully reduced state.
• Pernigraniline is the fully oxidized state (n = 0, m = 1) with imine links instead of amine links.
• The emeraldine (n = m = 0.5) form of polyaniline, often referred to as emeraldine base (EB).
Studies have shown that most forms of polyaniline are one of the three states or physical mixtures of these
components.

3. POLYTHIOPHENE
 Polythiophenes (PTs) are polymerized thiophenes, a sulfur heterocycle.
 They can become conducting when electrons are added or removed from the conjugated π- orbitals via doping.
 The most notable property of these materials, electrical conductivity, results from the delocalization of electrons
along the polymer backbone – hence termed as "synthetic metals".

4. SYNTHESIS OF POLYANILINE
CHEMICAL METHOD:
 It is an oxidative process
 It needs acidic medium
and a proper oxidizing
agent e.g. Ammonium per
sulfate, Potassium
dichromate etc.
 Consider a method:
(0.1 M) Aniline + Aque. H2SO4
Total volume 100 ml
Adding K2Cr2O7 Drop by Drop
Stirring
Final product filtered & washed with dilute solutions of H2SO4 acid and
dried at 60°C in vacuum for 12 Hrs.
Grinded and the product is obtained in the form of fine green
powder (Emeraldine salt)
Reaction Mechanism

5. Electrochemical Synthesis:
Electrochemical polymerization performed in a single compartment
electrochemical cell.
Stainless steel plate used as the working electrode (anode).
The counter electrode (cathode) also comprised of stainless steel plate.
Electrochemical polymerization of aniline carries out in the presence of aqueous
sulphuric acid.
Appropriate amount of aniline (0.1 M) and H2S04 (0.1 M) acid were added to
polymerization vessel.
The different voltages (0-5V) were used for the electrochemical synthesis.
The collected samples was filtered and washed with dilute solution of H2S04 acid
and driedto form powder at higher temperature around 600 °C.
DIAZ and LOGAN prepared PANI film as a typical electro conductive polymer by
means of anoidic oxidation of aniline in aquous sulphuric acid using platinum
electrode.
Noufi et al showed that deposition of PANI is possible onto the surface of several
semiconductor electrodes such as cadmium chalcogenides,si,GaAs ,GaP.

6. SYNTHESIS OF POLYTHIOPHENE
Electrochemical synthesis:
In an electrochemical polymerization, a potential
is applied across a solution containing thiophene
and an electrolyte (acetonitrile and
tetrabutylammonium tetrafluoroborate).
It produces a conductive PT film on the anode.
The potential required to oxidize the monomer
depends upon the electron density in the
thiophene ring π-system
Electron-donating groups lower the oxidation
potential, while electron-withdrawing groups
increase the oxidation potential.
Initial steps in the electropolymerization
of thiophenes.

7. Chemical synthesis:
 It offers two advantages compared with electrochemical synthesis
• Greater selection of monomers, and
• Using the proper catalysts, the ability to synthesize perfectly regioregular substituted PTs.
 The first synthesis of perfectly regioregular PATs was described by McCullough et al. in 1992
McCullough Method
 selective bromination produces 2-bromo-3-alkylthiophene.
 Followed by lithiation, transmetalation and then Kumada cross-coupling in the presence of a nickel catalyst.
 This method produces approximately 100% HT–HT couplings, according to NMR spectroscopy analysis of
the diads
Reaction Mechanism
Chloroform+ SDS
Adding Fecl3 and stirring
Adding thiophene monomer
continue stirring for upto 6 hours
Polythiophene

8. Rieke Method:
 The method subsequently described by Rieke et al. in 1993
 2,5-dibromo-3-alkylthiophene is treated with highly reactive "Rieke zinc" to form a mixture of
organometallic isomers.
 Addition of a catalytic amount of Pd(PPh3)4 produces a regiorandom polymer, but treatment with
Ni(dppe)Cl2 yields regioregular PAT in quantitative yield.
 McCullough and Rieke methods produce structurally homogenous PATs
Reaction Mechnism

9. Applications
Polythiophene
Field-effect transistors
Electroluminescent devices
 Solar cells
Photochemical resists
Nonlinear optic devices
Batteries
Diodes and
Chemical sensors
Polyaniline
 Actuators
 supercapacitors and
electrochromics.
 electrically conducting
yarns
 antistatic coatings
 electromagnetic shielding
 flexible electrodes.

10. THANK
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