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Home / Academics / Division of Math & Science / Faculty / Christopher Jones / Dissertation / Chapter 3-Section 3.1

3.1 Polymerization Scheme of Polypyrrole

Polypyrrole was the first conducting polymer to be synthesized electrochemically.7 A wide variety of other conducting polymers have been synthesized since that time. The polymerization of pyrrole can be accomplished by chemical or electrochemical methods. Each method involves the oxidation of the pyrrole monomer to initiate polymerization. Illustration 3.2(a) shows the oxidation of pyrrole, which yields a radical-cation species. In Illustration 3.2(b)-(c), radical-cation monomers can combine at the a positions to form a pyrrole dimer with the elimination of two protons. This dimer can undergo further oxidation at even lower oxidation potentials58 (as seen in Table 3.1) and form longer oligomers as seenin Illustration 3.2(d).

Displayed are schematics of the following growth patterns (A) Frank-van der Merwe,(B) Stranski-Krastanov (C) Volmer-Weber (columnar) (D) Volmer-Weber (droplet-like)

Illustration 3.1:Displayed are schematics of the following growth patterns (A) Frank-van der Merwe,(B) Stranski-Krastanov (C) Volmer-Weber (columnar) (D) Volmer-Weber (droplet-like).


Species

Oxidation Potential (Volts)

pyrrole

bi-pyrrole

ter-pyrrole

polypyrrole

1.2

0.55

0.26

-0.1

thiophene

bi-thiophene

ter-thiophene

quartre-thiophene

quinque-thiophene

polythiophene

2.07

1.31

1.05

0.95

0.83

0.7

Table 3.1:Oxidation potentials of pyrrole and thiophene oligomers of different chain lengths.58

 

The steps to the polymerization of pyrrole are a) the oxidation of the monomer to form a radical cation species, b) the formation of a pyrrole dimer before the elimination of hydrogen, c) the elimination of hydrogen, and d) the continued polymerization of polypyrrole.

Illustration 3.2:The steps to the polymerization of pyrrole are a) the oxidation of the monomer to form a radical cation species, b) the formation of a pyrrole dimer before the elimination of hydrogen, c) the elimination of hydrogen, and d) the continued polymerization of polypyrrole.

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Updated on: April 15, 2010 8:26 PM