Synthesis, Structure, Infrared Spectra, and Iodine Doping of Unsubstituted Polyazines
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SYNTHESIS, STRUCTIURE, INFRARED SPECTRA, AND IODINE DOPING OF UNSUBSTI¶IUTED POLYAZINES WILLIAM B. EULER and BENJAMIN C. GILL Department of Chemistry, University of Rhode Island, Kingston, RI
02881
ABSTRACT Polyazines, -[N=CH-CH=N] x-, are environmentally stable conjugated polcan be doped with iodine into an electrically conductive state.
ymers that
These polymers
are prepared by the condensation of glyoxal and glyoxal di-
hydrazone with
acid catalysis.
pendent of
IR spectra of the undoped polymers, indeconditions, exhibit a broad band centered around
the synthetic
3240 cm-1
indicative of the presence of OH groups in the polymer. Solid state NMR spectra show that the OH groups are covalently bound to the polymer chain so that the polymer chain has a number of defect and/or crosslinking sites present. The polymer can be doped with iodine into a poorly conducting state. Iodine doping introduces one new vibrational band into the IR spectra at 1490 cm-l, associated with a bipolaronic charge carrier.
INTRODUCTION We have
recently reported [1] the physical and chemical properties of -[N=C(CH 3 )-C(CH3 )=NJx-. Permethyl polyazine forms in
permethyl polyazine, the all
trans conformation
NMR spectroscopy ducting powder
[2].
as demonstrated by both IR (1] and solid state
Iodine doping
of permethyl polyazine gives a contemperature pressed pellet conductivities of 0.1 heavily doped material [1,3]. Because it is known
with room
Q-icm-i for
the most
that methyl dertook the
groups inhibit the conductivity in polyacetylenes [4], we unsynthesis and doping of the unsubstituted polyazine, -[N=CH-
CH=N]x-
(PAZ), with hopes of improving the conductivity properties of this class of materials. We have found that the synthetic conditions leading to PAZ introduces defect sites that are probably tetrahydroxypiperazines and ci-amino alcohols. these polymers 10-6
Because
of the
loss of
conjugation from the defects,
can only be doped into a poorly conductive state, about 1 x
Q- 1cm- 1 for the most heavily doped powders at room temperature.
Mat. Res. Soc. Symp. Proc. Vol. 173. @1990 Materials Research Society
376
EXPERIMENTAL Polyazine is prepared by the acid catalyzed (acetic acid) condensation of equimolar
amounts of
glyoxal (obtained
from Aldrich
as a 40% aqueous
solution) and glyoxal dihydrazone (prepared by adding glyoxal to excess hydrazine hydrate) and stirring at room temperature or at reflux for at least 24 hours. Solvents used were methanol, ethanol, n-propanol, and nbutanol with only minor differences in the IR spectra of the products obtained.
Doping was
accomplished by stirring a chloroform solution of io-
dine with the polymer for 24 hours. IR spectra were obtained between 600 and 4000 cm-1 as KBr pellets on a Perkin-Elmer 281B
instrument. Conductivities were measured at room temperature on pressed pellets using the vanderPauw technique using an instrument built by Research Specialties (Chicago, IL) [1].
RESULTS Polyazines are formed by the acid oxO-dicarbonyl and an o,O-dihydrazone:
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