508
O. Aksimentyeva et al.
(“core-shell”) or the insertion, intercalation, or other mechanisms of embedding of
inorganic component into a polymer matrix with the formation of coordination,
covalent, hydrogen, or ionic bonds [8–10].
For the creation of composites of semiconductor or metallic nanoparticles with
polymeric matrices, organic polymers with their own electronic conductivity, of
which polyaniline is a prime representative, are increasingly being considered. Due
to the high stability, uniqueness, and variety of electronic properties, this polymer
is attracting increasing attention of scientists around the world [11–15]. Control
over the formation of the properties of metal-polyaniline composites consists of the
ability to establish the relationship between the conditions of synthesis, structure,
and physicochemical characteristics of the resulting hybrid systems [16–18]. Various
approaches, including both single-step (one-step) and multistage synthesis, are used
for the synthesis of nanocomposites [19, 20]. The multistage synthesis includes a
three-step pathway: the synthesis of charged inorganic nanoparticles, the modification of their surface (“passivation-compatibilization”), and their introduction into the
organic matrix [21].
One-step synthesis is based on the direct oxidation of the monomer by metal ions
in solution in the absence of additional oxidants. The latter involves the formation
of nanoparticles directly in the presence of the polymer, so that the nanocomposite
is the product of the one-step reaction. The direct method is faster, but it is not able
to produce contact-free identical nanoparticles. With such techniques, the inorganic
precursor is usually introduced in the polymeric matrix and, by consequent chemical
reduction, the desired product is obtained [19].
We used this approach to obtain PAn composites with noble metals. Studies
show that such synthesis, in the absence of additional stabilizers, in most cases
does not lead to the formation of nanoparticles. However, at a metal to polymer
ratio of 0.1, it was possible to obtain 7 nm spherical particles [17]. The use of
substances with bulk anions such as dodecylbenzenesulfonate, polystyrenesulfonate,
or camphorsulfonic acid, which act both as dopant and stabilizer, results in the
production of nanoparticles [20].
Attempts have also been made to use organic media for the one-step synthesis
of PAn-Au [21], PAn in the form of nanoballs-Au [18], and palladium-poly (3,5dimethylaniline) [19] composites. Interesting is the phase-boundary synthesis, which
used aniline dissolved in chloroform as the lower phase and chloroplatinic acid with
polystyrenesulfonate dissolved in water as the upper phase [20]. In the obtained
composite, the particles were uniformly distributed in the polymer matrix.
In most works about single-stage synthesis, attention is focused on the reaction
characteristics, the size and distribution of particles in the polymer matrix. Only
in some cases, the conductivity or thermal stability of the composites is indicated.
Regarding conductivity, the incorporation of metal into the polymer does not produce
a definite result and causes both its growth [21–24] and decrease [25, 26] compared
to the pure polymer. Conductivity depends not only on the amount of metal in the
composite, but also on the state of the structure and the degree of oxidation of the
polymer.
O. Aksimentyeva et al.
(“core-shell”) or the insertion, intercalation, or other mechanisms of embedding of
inorganic component into a polymer matrix with the formation of coordination,
covalent, hydrogen, or ionic bonds [8–10].
For the creation of composites of semiconductor or metallic nanoparticles with
polymeric matrices, organic polymers with their own electronic conductivity, of
which polyaniline is a prime representative, are increasingly being considered. Due
to the high stability, uniqueness, and variety of electronic properties, this polymer
is attracting increasing attention of scientists around the world [11–15]. Control
over the formation of the properties of metal-polyaniline composites consists of the
ability to establish the relationship between the conditions of synthesis, structure,
and physicochemical characteristics of the resulting hybrid systems [16–18]. Various
approaches, including both single-step (one-step) and multistage synthesis, are used
for the synthesis of nanocomposites [19, 20]. The multistage synthesis includes a
three-step pathway: the synthesis of charged inorganic nanoparticles, the modification of their surface (“passivation-compatibilization”), and their introduction into the
organic matrix [21].
One-step synthesis is based on the direct oxidation of the monomer by metal ions
in solution in the absence of additional oxidants. The latter involves the formation
of nanoparticles directly in the presence of the polymer, so that the nanocomposite
is the product of the one-step reaction. The direct method is faster, but it is not able
to produce contact-free identical nanoparticles. With such techniques, the inorganic
precursor is usually introduced in the polymeric matrix and, by consequent chemical
reduction, the desired product is obtained [19].
We used this approach to obtain PAn composites with noble metals. Studies
show that such synthesis, in the absence of additional stabilizers, in most cases
does not lead to the formation of nanoparticles. However, at a metal to polymer
ratio of 0.1, it was possible to obtain 7 nm spherical particles [17]. The use of
substances with bulk anions such as dodecylbenzenesulfonate, polystyrenesulfonate,
or camphorsulfonic acid, which act both as dopant and stabilizer, results in the
production of nanoparticles [20].
Attempts have also been made to use organic media for the one-step synthesis
of PAn-Au [21], PAn in the form of nanoballs-Au [18], and palladium-poly (3,5dimethylaniline) [19] composites. Interesting is the phase-boundary synthesis, which
used aniline dissolved in chloroform as the lower phase and chloroplatinic acid with
polystyrenesulfonate dissolved in water as the upper phase [20]. In the obtained
composite, the particles were uniformly distributed in the polymer matrix.
In most works about single-stage synthesis, attention is focused on the reaction
characteristics, the size and distribution of particles in the polymer matrix. Only
in some cases, the conductivity or thermal stability of the composites is indicated.
Regarding conductivity, the incorporation of metal into the polymer does not produce
a definite result and causes both its growth [21–24] and decrease [25, 26] compared
to the pure polymer. Conductivity depends not only on the amount of metal in the
composite, but also on the state of the structure and the degree of oxidation of the
polymer.