Improving Electrical Conductivity, Thermal Stability, and Solubility of Polyaniline-Polypyrrole Nanocomposite by Doping with Anionic Spherical Polyelectrolyte Brushes
Su Nanoscale Research Letters
Improving Electrical Conductivity, Thermal Stability, and Solubility of Polyaniline- Polypyrrole Nanocomposite by Doping with Anionic Spherical Polyelectrolyte Brushes
Na Su 0
0 School of Printing and Packaging Engineering, Shanghai Publishing and Printing College , Shanghai 200093 , China
The extent to which anionic spherical polyelectrolyte brushes (ASPB) as dopant improved the performance of polyaniline-polypyrrole (PANI-PPy) nanocomposite was investigated. Different characterization and analytical methods including Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) confirmed that ASPB serving as dopant could improve the comprehensive properties of PANI-PPy nanocomposite. It was different from dopants such as SiO2, poly (sodium-p-styrenesulfonate) (PSS), and canonic spherical polyelectrolyte brushes (CSPB) which only enhanced the performance of PANI-PPy nanocomposite on one or two sides. The electrical conductivity of (PANI-PPy)/ASPB nanocomposite at room temperature was 8.3 S/cm, which was higher than that of PANI-PPy (2.1 S/cm), (PANI-PPy)/ PSS (6.8 S/cm), (PANI-PPy)/SiO2 (7.2 S/cm), and (PANI-PPy)/CSPB (2.2 S/cm). Meanwhile, (PANI-PPy)/ASPB nanocomposite possessed enhanced thermal stability and good solubility. In addition, the effects of polymerization temperature, the molecular weight of grafted polyelectrolyte brushes, and storage time on electrical conductivity were discussed.
Nanocomposite; Polyaniline-polypyrrole; Anionic spherical polyelectrolyte brushes; Doping; Electrical conductivity; Thermal stability; Solubility
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Background
During the last several decades, conducting polymers
have been the subject of numerous investigations due to
their excellent physical and chemical properties
originating from their unique π-conjugated system [1–3].
Among the conducting polymers studied, polyaniline
(PANI) and polypyrrole (PPy) are of particular interest
because of their promising electrical conductivity, high
environmental stability, interesting redox properties,
magnetoresistance (MR) behaviors, and electrochemical
performances [4–10]. In comparison with numerous
reports about PANI and PPy, researches on copolymers of
aniline and pyrrole are still far from enough. Because the
copolymer may overcome the shortcomings of a single
π-electron in the homopolymer, obtaining composites
with excellent property [11], studies on copolymerization
of aniline and pyrrole gradually attract people’s
attention. Electrochemical [12, 13] and chemical oxidative
polymerization methods [14, 15] are the most
common methods used in the synthesis of conducting
copolymers. However, the large-scale application of
PANI-PPy composite is sometimes limited by the
difficulty of insolubility and infusibility of the material
which can lead to poor electronic conductivity and
mechanical properties. Therefore, the improvement of
the comprehensive properties of PANI-PPy
nanocomposite is of significance.
To date, most of the published research on this topic
has been developed to improve the performance of
conducting polymers on certain aspects. Xin et al. [16]
prepared poly(aniline-co-pyrrole) nanocomposite by
chemical oxidation polymerization using iron(III)
chloride hexahydrate (FeCl3·H2O) as an oxidant and
sodium dodecylbenzenesulfonate (SDBS) as a
surfactant. They found that the nanocomposite had high
electrical conductivity by selecting proper conditions
for the synthesis process. Li et al. [17] proposed a
method to prepare poly(pyrrole-co-aniline)
nanofibrils using a template by chemical copolymerization
technique. It was reported that the length, diameter,
and thickness of copolymer nanofibers were controlled by
using AAO as a template, and the copolymer nanofibers
had good thermal stability. Moreover, as for PPy,
enhanced mechanical properties and reduced flammability
were obtained by doping with epoxy resin [18]. However,
since the properties of conducting polymers are mutually
restraining, the improvement of their comprehensive
performance is an important and difficult task.
In recent years, conducting polymers doped with
polyelectrolyte have achieved outstanding progress
[19]. Wu and coworkers [20] developed PPy, which
exhibited excellent electrical conductivity and solubility by using
different concentrations of water-soluble polystyrene
sulfonate (PSS). The reason for this may be that de-doping
does not easily happen for doped ions due to the large size
of the polyelectrolyte, so the electrical conductivity of
conducting polymers is more stable. Meanwhile, the
entanglement effect of the long flexible chains of the polyelectrolyte
can effectively hinder the growth of copolymer chains,
helping to enhance its solubility. It is undoubtedly a good
reference for the development of conducting polymers
with excellent performance. In addition, in order to
improve the thermal stability, magnetoresistance (...truncated)