A Comparative Study of Two Different Media Effect on the Electropolymerization of 2-(9-ethylcarbazol-3- yliminomethyl)phenol by Cyclic Voltammetry, Impedance Spectroscopy, XPS, UV-visible Measurements and DFT Calculation | Chapter 9 | Theory and Applications of Chemistry Vol. 2
A
carbazole-based monomer, 2-(9-ethylcarbazol-3-yliminomethyl)phenol (SIC), was
first synthesized and
characterized. It was afterward polymerized by potentiostatic methods.
Oxidative polymerization of
SIC was carried out in two media. The first one (i.e. Bu4NBF4
(0.1M)/MeCN) gives the poly(2-(9- ethylcarbazol-3-yliminomethyl)phenol).
However, the second one (LiClO4/MeCN + 35mM HClO4), leads
to another polymer, the
poly(2-(9-ethylcarbazol-3-yliminomethyl)cyclohexa-2,5-diene-1,4- dione). These
two novel polymers will be abbreviated here after as PSIC and PDIC,
respectively. If the formation
of PSIC was expected, the formation of PDIC in acidic medium isn’t. It was
explained by a hydroxyl
function oxidation of SIC. The obtained polymers were then characterized by
cyclic voltammetry,
electrochemical impedance spectroscopy, XPS, IR and UV-Vis spectroscopies. Furthermore,
the corresponding electrochemical and optical bandgap values were calculated in
order to
get an idea about the conductive properties. The related results show that PDIC
and PSIC are good conductive
polymers. The electrochemical polymerisation of SIC is performed in both protic
and organic
medium. During the anodic oxidation in protic medium containing LiClO4/MeCN
+ (35mM) HClO4,
SIC undergoes hydrolysis around 1V, which modifies its structure before its
polymerization. This
reaction is very fast, and leads to the formation of two isomers, para-quinone
and ortho-quinone (DIC)
which oxidizes at the same potential and form PDIC. In the organic medium, the
SIC retains its initial
structure, and leads after oxidation to the corresponding polymer PSIC. The
electrochemical behaviour
of PSIC and PDIC supports the conductive character of both polymers and the
difference between
their structures. In an acidic medium, the imine bond undergoes a protonation
which increases
commonly the planarity of the polymeric material and subsequently, improves its
electrical properties.
The charge transfer resistance recorded for the PDIC film was much lower than
the one recorded
for the PSIC film. The electrochemical and the optical bandgaps of PDIC are
lower than those
of PSIC. The difference in structures of both polymers could explain these
results. Compared to SIC,
para-quinone and ortho-quinone compounds are formally electrons donor-acceptor
(D-A) type moieties.
In a D-A system, a charge transfer from the donor to the acceptor increases
conjugation length
through resonance which causes the decrease of its bandgap. Therefore, these
findings indicate
that PDIC is more conductive than PSIC.
Author(s) Details
Mounia Guergouri
Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.
Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.
Rafik Bensegueni
Université Mohamed Cherif Messaadia, 41000 Souk Ahras, Algeria.
Université Mohamed Cherif Messaadia, 41000 Souk Ahras, Algeria.
Ammar Khelifa
Baghdouche
Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.
Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.
Leila Bencharif
Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.
Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.
Comments
Post a Comment