Polyaniline Nanostructures

Abstract

Polyaniline (PANI) is one of the most extensively studied conducting polymers because of its simple synthesis [1] and doping/dedoping chemistry [2], low cost, high conductivity, and excellent environmental stability. PANI has a wide applicability in rechargeable batteries [3], erasable optical information storage [4], shielding of electromagnetic interference [5], microwave-and radar-absorbing materials [6], sensors [7], indicators [8], catalysts [9], electronic and bioelectronic components [10], membranes [11], electrochemical capacitors [12], electrochromic devices [13], nonlinear optical [14] and light-emitting devices [15], electromechanical actuators [16], antistatic [17] and anticorrosion coatings [18]. Its electromagnetic and optical properties depend mostly on its oxidation state and degree of protonation [19]. The green emeraldine salt form of PANI is conducting ($1-10 S cm À1 for granular powders) [1]. It contains, depending on the synthetic route, variousunits (in the preceeding formulae B, Q and A À denote a benzenoid ring, quinonoid ring and dopant anion, respectively). The blue emer-The preparation of bulk quantities of conducting granular PANI is usually performed Nanostructured Conductive PolymersEdited by Ali Eftekhari by the oxidative polymerization of aniline with ammonium peroxydisulfate (APS) in an acidic aqueous solution (initial pH < 2.0) [1]. Colloidal PANI nanoparticles are prepared by dispersion polymerization of aniline in the presence of various colloidal stabilizers [20,21]. The average size of colloidal PANI nanoparticles decreases with increasing stabilizer/aniline ratio. PANI colloids often have nonspherical (rice grain, needle-like, etc.) core-shell morphology. The colloidal nanoparticle core most likely has a composite nature, i.e. it is composed of both the PANI and the incorporated stabilizer, while the shell is formed by the stabilizer. Nowadays, conducting PANI nanostructures are the focus of intense research owing to their significantly enhanced dispersibility and processability, and substantially improved performance in many applications, in comparison with granular and colloidal PANI [22][23][24][25][26][27]. The continuously growing interest in the study of zero-dimensional (0-D) (solid nanospheres), one-dimensional (1-D) (nanofibers (nanowires), nanorods (nanosticks), nanoneedles, rice-like nanostructures, nanotubes), two-dimensional (2-D) (nanoribbons (nanobelts), nanosheets (nanoplates, nanoflakes, nanodisks, leaf-like nanostructures), nanorings (cyclic nanostructures), net-like nanostructures), and three-dimensional (3-D) PANI nanostructures (hollow nanospheres, dendritic and polyhedral nanoparticles, flower-like, rhizoid-like, brain-like, urchin-like, and star-like nanostructures, etc.) has dramatically increased in recent years (Figure 2.1). The major focus of research has been the preparation, characterization, processing, and application of PANI nanofibers (PANI-NFs) and nanotubes (PANI-NTs). PANI-NFs are 1-D PANI nanoobjects of cylindrical profile with diameters ...

Enhanced Microwave Synthesis: Fine-Tuning of Polyaniline Polymerization

“…For instance, the SA of PANI nanofibers obtained with different dopant acids in conventional synthesis were reported to be in the range of ∼35–55 m 2 g –1 , while the conventionally synthesized PANI had a SA of 15 m 2 g –1 . Because microwave-enhanced synthesized PANI samples have larger specific SA, this material may act as a promising catalyst support or chemical sensor carrier . It has been reported that a classical microwave was used for preparation of hypercrosslinked PANI with permanent porous structure and SA which exceed 630 m 2 g –1 .…”

“…PANI is typically produced through the oxidative polymerization of aniline, using a strong oxidizing agent such as ammonium persulfate (APS) or potassium iodate (KIO 3 ) in a strong acidic solution such as 1 M HCl. , Synthesized in this way, PANI possesses a granular morphology and is characterized by high conductivity. However, under certain conditions PANI can form nanostructuresnanotubes, nanorods, nanofibers, and nanospheresthe formation and structural characteristics of which have been extensively studied and reported. − As the field of nanodevices becomes more commercially attractive, the widespread adoption of nanomaterials is limited by a need for the development of a methodology that can provide large-scale quality products. Over the past few years, considerable interest has emerged in the use of microwave irradiation in inorganic and organic synthesis. , In many of the published examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purities by reducing unwanted side reactions compared to conventional heating methods…”

Structure of Ultralong Polyaniline Nanofibers Using Initiators

“…Since their discovery, conducting polymers have attracted great interest due to their potential use as inexpensive and flexible organic (semi)conducting layers in various applications such as electronics, photovoltaic devices, and supercapacitors . In recent years, studies toward the formation of one-dimensional (1-D) nanostructures such as fibers, wires, rods, and tubes of conducting polymers have flourished because of the proven advantages of such materials in many applications that lead to superior performance characteristics compared to those of their currently used bulk counterparts. − Among all the conducting polymers, polyaniline (PANI) nanofibers are one of the most intensively studied systems because of their remarkable propensity to form anisotropic structures and also the unique, simple acid−base doping−dedoping chemistry . Synthetic routes toward PANI nanofibers include template-guided methods such as those using zeolites, , surfactants or bulky dopant acids, − nanowire seeding, and biotemplates .…”

Thermal behavior and matrix-assisted pulsed laser evaporation deposition of functional polymeric materials thin films with potential use in optoelectronics

“…Although the compound itself was discovered over 150 years ago [37], only since the early 1980s it has truly captured the attention of the scientific community due to its significant electrical conductivity. Amongst the family of conducting polymers and organic semiconductors, polyaniline has many appealing processing properties, being one of the most studied conducting polymers of the past 50 years: in bulk, as thin films, or as nanostructures [13,19,[38][39][40][41][42][43][44][45][46]. PAni exhibits significant absorbance in the microwave range, and it is also frequently used in gas sensors because of its capability to convert chemical interactions into electrical signals [13,19,39].…”