2 research outputs found
Influence of Dispersed Nanoparticles on the Kinetics of Formation and Molecular Mass of Polyaniline
Using a combination of the open circuit
potential and pH profiles
of aniline (An) polymerization and their mathematical treatment, we
develop a new convenient semiquantitative approach to determine the
influence of the dispersed nanoparticles (e.g., TiO<sub>2</sub> nanoparticles)
on the kinetic features of this process and molecular mass of the
formed polyaniline (PANI). It is revealed
that the reciprocal values of the polymerization stages, namely, the
duration of the induction period, of homogeneous and heterogeneous
pernigraniline (PN) accumulation, and of PN reduction with An, are
linear functions of the weight fraction of the nanoparticles. We found
that when nanoparticles are added the weight-averaged molecular weight
of PANI initially increases from 56 000 to 79 000 and
the polydispersity index drops from 3.9 to 1.7. However, at high TiO<sub>2</sub> concentrations, the former dramatically decreases, whereas
the latter increases. We use the relative proton concentration as
a function of time and the different extents of acceleration of the
consecutive stages of An polymerization to explain the changes in
the molecular weight distribution of PANI with different contents
of TiO<sub>2</sub> nanoparticles in the polymerization medium
Evolution and Interdependence of Structure and Properties of Nanocomposites of Multiwall Carbon Nanotubes with Polyaniline
Structure–property
relationships of nanocomposites of multiwall
carbon nanotubes (MWCNTs) and polyaniline (PANI) doped with dodecylbenzenesulfonic
acid (DBSA) are studied and discussed in terms of contribution of
the PANI phase properties. Two phases of PANI-DBSA with different
properties, such as a shell-wrapping carbon nanotube and separate
neat PANI-DBSA domains, are revealed for the first time in the nanocomposites
with a high or medium PANI-DBSA content. In the nanocomposites with
lower PANI-DBSA contents (<40 wt %), only a core–shell morphology
with ∼3 nm or lower thickness PANI shell on the nanotubes is
observed. Under this condition, the degree of crystallinity of the
PANI-DBSA shell increases almost 2-fold, and thermal stability of
the nanocomposite grows sharply. As compared with the neat PANI-DBSA,
this special PANI shell phase has more perfect molecular structure
and is characterized by a reduced amount of DBSA. It is found that
the latter is caused by a competition between the processes of doping
of the formed PANI in the shell by the protonic acid and p-doping
caused by the MWCNT surface. The nanocomposites demonstrate ppm/ppb
range sensitivity to ammonia/methylamine gases with response times,
which inversely depend on the PANI-DBSA contents and thickness of
the shell