A Facile Synthesis of Polypyrrole/Carbon Nanotube Composites with Ultrathin, Uniform and Thickness-Tunable Polypyrrole Shells
Bin Zhang
1
Yiting Xu
0
Yifang Zheng
0
Lizong Dai
0
Mingqiu Zhang
1
Jin Yang
1
Yujie Chen
2
Xudong Chen
1
Juying Zhou
1
0
College of Chemistry and Chemical Engineering, State Key Laboratory for Physical Chemistry of Solid Surfaces, Xiamen University
, Xiamen, 361005,
China
1
Key Lab Polymer Composite & Funct Mat, Key Lab Designed Synth & Applicat Polymer Mat,
School of Chemistry and Chemical Engineering, Sun Yat-Sen University
, Guangzhou, 510275,
China
2
Institute of Photonics
, SUPA,
University of Strathclyde
, Glasgow G4 0NW,
UK
An improved approach to assemble ultrathin and thickness-tunable polypyrrole (PPy) films onto multiwall carbon nanotubes (MWCNTs) has been investigated. A facile procedure is demonstrated for controlling the morphology and thickness of PPy film by adding ethanol in the reaction system and a possible mechanism of the coating formation process is proposed. The coated PPy films can be easily tuned by adding ethanol and adjusting a mass ratio of pyrrole to MWCNTs. Moreover, the thickness of PPy significantly influences the electronic conductivity and capacitive behavior of the PPy/MWCNT composites. The method may provide a facile strategy for tailoring the polymer coating on carbon nanotubes (CNTs) for carbon-based device applications.
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Introduction
Over the last two decades, carbon nanotubes (CNTs) have
been widely used as fillers in desirable combinations with
functional polymers because of their high electrical
conductivity, chemical stability, low mass density, and large
surface area [1-3]. Composite materials of CNTs and
polymers have attracted great interest because they may
possess novel combinations with superior characteristics than
either of the individual components [4-9]. Among them, it
has been already confirmed that the composites consisted
of electronically conducting polymers (ECPs) and CNTs
possess the superior electrical properties than either of the
individual components [8], which are potential materials
for the development of organic electronic devices, such as
organic photovoltaic cells, [10] biologic sensors [11] and
flexible light-emitting diodes [12]. To the best of our
knowledge, the interfacial structure between nanotube and
polymer including the morphology and thickness of
polymer is critical to tailor their structures and properties
in many potential applications [13].
So far, a variety of methods such as chemical oxidation
process, electrochemical or chemical polymerization
through surfactants and template synthesis [14-19] have
been investigated for producing composites from the
combination of CNTs with conducting polymers.
Unfortunately, CNTs have often been coated with thick and
nonuniform layers, which range from 50 to 80 nm
[14-18], and encapsulated aggregation of CNTs within
the bulk polymer matrix due to the poor solubility of
CNTs and partial exfoliation of nanotube bundles [20].
Moreover, successful results of the PPy/CNT composites
with tunable thickness of the polymer shell have rarely
been obtained [21,22]. The major problem exists in the
processibility of CNTs in solution and the controll of
interfacial bonding in polymer/CNTs composites. Due to
the hydrophobic nature and strong van der Waals
interactions between CNTs, as-produced CNTs pack into
crystalline ropes and tangle networks which are found to
act as an obstacle to most applications, especially
diminishing the special mechanical and electrical properties of
the individual tubes [23]. Furthermore, inherently weak
nanotube-polymer interactions result in the poor
interfacial adherent [24], which will lead to the agglomeration
of conjugated polymers. The polymer chains incline to
form deposits of irregular nanoparticles or sediments
with a diameter of about 50 nm [19,20,23]. Consequently,
one way to overcome these limitations is to control the
polymerization rate of the pyrrole monomers and
improve the processibility of CNTs in solution.
Herein, we report a facile approach to assemble
ultrathin and uniform PPy films onto multiwall carbon
nanotubes [MWCNTs] to form a one-dimensional hybrid
nanostructure by an improving in situ chemical
oxidation polymerization. The addition of ethanol in the
aqueous reaction system is a key point for tuning the
morphology and thickness of PPy shell by controlling
the polymerization rate [24], which overcomes the
significant challenge in enhancing the interfacial bonding
between polymer and carbon nanotubes. The PPy/
MWCNT composites possess the core (individual
MWCNT)/shell (PPy film) structure and no
agglomerations or irregular nanoparticles of polymer are found on
the surface of the composites. Furthermore, the
synthesis process does not need any surfactant assistance and
the thickness of the polymer shell can be precisely
controlled by adding ethanol and changing the mass ratio
of PPy/MWCNT. Moreover, the influences of the
thickness of coating-polymer on the electrical properties of
the PPy/MWCNT composites have been explained
systemically. The (...truncated)