Chemistry International
Vol. 24, No. 5
September 2002
Highlights
from Pure and Applied Chemistry
Polyaniline.
Preparation of a Conducting Polymer (IUPAC Technical Report)
by J.
Stejskal and R. G. Gilbert
Pure and Applied
Chemistry, Vol. 74, No. 5, pp. 857-867 (2002)
Eight
persons from five institutions in different countries carried out polymerizations
of aniline following the same preparation protocol. In a "standard"
procedure, aniline hydrochloride was oxidized with ammonium peroxydisulfate
in aqueous medium at ambient temperature. The yield of polyaniline was
higher than 90% in all cases. The electrical conductivity of polyaniline
hydrochloride thus prepared was 4.4 ± 1.7 S cm-1 (average
of 59 samples), measured at room temperature. A product with defined
electrical properties could be obtained in various laboratories by following
the same synthetic procedure. The influence of reduced reaction temperature
and increased acidity of the polymerization medium on polyaniline conductivity
were also addressed. The conductivity changes occurring during the storage
of polyaniline were monitored. The density of polyaniline hydrochloride
was 1.329 g cm-3. The average conductivity of corresponding
polyaniline bases was 1.4 x 108 S cm-1, the density being
1.245 g cm-1. Additional changes in the conductivity take
place during storage. Aging is more pronounced in powders than in compressed
samples. As far as aging effects are concerned, their assessment is
relative. The observed reduction in the conductivity by ~10% after more
than one-year storage is large but, compared with the low conductivity
of corresponding polyaniline (PANI) base, such a change is negligible.
For most applications, an acceptable level of conductivity may be maintained
throughout the expected lifetime.
www.iupac.org/publications/pac/2002/7405/7405x0857.html