Effect of processing conditions on the properties of high molecular weight conductive polyaniline fiber

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Scalable production of ultrafine polyaniline fibres for tactile organic electrochemical transistors

The development of continuous conducting polymer fibres is essential for applications ranging from advanced fibrous devices to frontier fabric electronics. The use of continuous conducting polymer fibres requires a small diameter to maximize their electroactive surface, microstructural orientation, and mechanical strength. However, regularly used wet spinning techniques have rarely achieved this goal due primarily to the insufficient slenderization of rapidly solidified conducting polymer molecules in poor solvents. Here we report a good solvent exchange strategy to wet spin the ultrafine polyaniline fibres. The slow diffusion between good solvents distinctly decreases the viscosity of protofibers, which undergo an impressive drawing ratio. The continuously collected polyaniline fibres have a previously unattained diameter below 5 µm, high energy and charge storage capacities, and favorable mechanical performance. We demonstrated an ultrathin all-solid organic electrochemical transistor based on ultrafine polyaniline fibres, which operated as a tactile sensor detecting pressure and friction forces at different levels.

Conductive, Acid-Doped Polyaniline Electrospun Nanofiber Gas Sensing Substrates Made Using a Facile Dissolution Method

A novel dissolution method that allows for the total solvation of high-concentration, high-molecular-weight polyaniline (PANi) doped with (+)-camphor-10-sulfonic acid (CSA) is reported. Preparation of 12-16 wt % 65,000 Da PANi solutions in N,N-dimethylformamide is achievable using a simple one-pot method. Doped polyaniline solutions in common organic solvents were processed into nanofibers using a convenient single-nozzle electrospinning technique. The electrospinning of PANi-CSA into nanofibrous membranes generated substrates that were subsequently employed in colorimetric gas sensing. These substrates demonstrated linearity of response upon exposure to 50-5500 ppm ammonia at ambient (50 ± 10% RH) and high (80% RH) humidity.

Synthesis and Conductivity Studies of Poly(Methyl Methacrylate) (PMMA) by Co-Polymerization and Blending with Polyaniline (PANi)

Poly(methyl methacrylate) (PMMA) is a lightweight insulating polymer that possesses good mechanical stability. On the other hand, polyaniline (PANi) is one of the most favorable conducting materials to be used, as it is easily synthesized, cost-effective, and has good conductivity. However, most organic solvents have restricted potential applications due to poor mechanical properties and dispersibility. Compared to PANi, PMMA has more outstanding physical and chemical properties, such as good dimensional stability and better molecular interactions between the monomers. To date, many research studies have focused on incorporating PANi into PMMA. In this review, the properties and suitability of PANi as a conducting material are briefly reviewed. The major parts of this paper reviewed different approaches to incorporating PANi into PMMA, as well as evaluating the modifications to improve its conductivity. Finally, the polymerization condition to prepare PMMA/PANi copolymer to improve its conductivity is also discussed.

Efficient Spin Selectivity in Self-Assembled Superhelical Conducting Polymer Microfibers

Chiral materials, natural or synthetic, have been widely studied since Pasteur's separation of enantiomers over a century ago. The connection between electron transmission and chirality was, however, established recently where one spin was preferably selected by the chiral molecules, displaying a typical chirality-induced spin selectivity (CISS) effect. Currently, this CISS effect was mainly demonstrated in the molecular-scale devices. Herein, we explored this effect in a microscale device where an efficient spin selectivity was found in the self-assembled superhelical conducting polyaniline (PANI) microfibers. A spin-selective efficiency up to 80% (not magnetoresistance) was achieved when spins traversed the ca. 2-6 μm-long helical channels at room temperature. Importantly, the long-range ordering of chiral PANI molecules is crucial to observe this efficient spin selectivity, whereas no selective transmission was found in the "amorphous" chiral PANIs. This efficient spin selectivity was subsequently rationalized by using an extended Su-Schrieffer-Heeger model where the Rashba spin-orbit coupling was considered. We expect these results could inspire the research of organic spintronics by using molecularly ordered, self-assembled, and chiral π-conjugated materials.

Radical addition polymerization: Enzymatic template-free synthesis of conjugated polymers and their nanostructure fabrication

Conjugated polymers are attractive for many applications due to their unique properties. Their molecular structure can easily be tuned, making them suitable for an enormous number of specific applications. Conjugated polymers have the potential to achieve electrical properties similar to those of noncrystalline inorganic semiconductors; however, their chemical structure is much more complex and somewhat resembles that of biomacromolecules. The molecular conformation and interactions of conjugated polymers play an important role in their functionality. The use of enzymes has emerged as a highly valuable alternative method to synthesize these polymers and is very useful in the fabrication of their nanostructures. Here, we present established strategies for the synthesis of conjugated polymers in template-free systems that do not interfere with the preparation of their nanostructures. These strategies are based on the use of peroxidases (class III; EC 1.11.1.7, donor: hydrogen peroxide oxidoreductase), which are enzymes that have the ability to catalyze the oxidation of a number of compounds (including aromatics such as aniline, pyrrole, thiophene and some of their derivatives), in the presence of hydrogen peroxide, to obtain conjugated polymers.

The Preparation and Characterization of Polyacrylonitrile-Polyaniline (PAN/PANI) Fibers

The paper presents a method of modifying polyacrylonitrile (PAN) fibers using polyaniline (PANI). The PAN fibers were doped with polyaniline that was obtained in two different ways. The first consisted of doping a spinning solution with polyaniline that was synthesized in an aqueous solution (PAN/PANI blended), and the second involved the synthesis of polyaniline directly in the spinning solution (PAN/PANI in situ). The obtained fibers were characterized by the methods: X-ray powder diffraction (XRD), scanning electron microscope (SEM), fourier-transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential scanning calorimetry (DSC). Analysis of the results showed strong interactions between the nitrile groups of polyacrylonitrile and polyaniline in the PAN/PANI in situ fibers. The results of mechanical strength tests indicated that the performance of the PAN/PANI mixture significantly improved the mechanical parameters of polyaniline, although these fibers had a weaker strength than the unmodified PAN fibers. The fibers obtained as a result of the addition of PANI to PAN were dielectric, whereas the PANI-synthesized in situ were characterized by a mass-specific resistance of 5.47 kΩg/cm².

Preparation and Application of Conductive Polyaniline-Coated Thermally Expandable Microspheres

The thermally expandable microspheres (TEMs) were prepared through suspension polymerization with acrylonitrile (AN), methyl methacrylate (MMA) and methyl acrylate (MA) as the main monomers. Simultaneously, iso-pentane, n-hexane, iso-octane and other low-boiling hydrocarbons were prepared as blowing agents under two conditions, including high-pressure nitrogen and atmospheric conditions. The above physical foaming microspheres have a core-shell structure and excellent foaming effects. A layer of polyaniline (PANI) was deposited on the surface of the prepared TEMs by emulsion polymerization to obtain conductive and heat-expandable microspheres. Afterwards, the foaming ink was prepared by mixing the conductive TEMs and water-based ink. Finally, a conductive three-dimensional picture was obtained by screen-printing technology. This paper specifically focuses on the effects of particle size, morphology and the thermal expansion properties of the microspheres. The present research methods expect to obtain microspheres with a high foaming ratio, uniform particle size and antistatic properties, which may be applied to physical foaming ink.

Two liquid adsorptive entrapment of a pluronic polymer into the surface of polyaniline films

Pluronic triblock copolymers were entrapped on the surface of polyaniline (PANI) films by first immersing the latter in N-methylpyrrolidinone (NMP) solutions of one of the Pluronics for a short time. This softened the surface of the films and allowed the Pluronic molecules to entangle with PANI segments of the swollen film on the surface. Further, the films were taken out from the NMP solution and dipped into water, which is a nonsolvent for PANI. The rapid surface deswelling of PANI by the water resulted in the entrapment of the Pluronic on its surface, with the hydrophilic blocks toward water and the hydrophobic block imbedded in the PANI films. The modified PANI obtained was examined by X-ray photoelectron spectroscopy, water droplets contact angles, scanning electron microscopy, and wide angle X-ray diffraction. The surface of the Pluronic entrapped PANI films became more hydrophilic than the hydrophobic PANI films and decreased the amount of bovine serum albumin protein adsorbed on them. This means that, by reducing the biofouling, the life of the modified polyaniline film can be extended when the latter is employed as a biosensor.

Improved surface properties of polyaniline films by blending with Pluronic polymers without the modification of the other characteristics

Films of conductive polyaniline and amphiphilic Pluronic (P105) copolymer blends were prepared by dissolving the two polymers in N-methylpyrrolidinone (NMP) followed by a slow solvent evaporation at 55 degrees C. The characteristics of both doped and undoped films were determined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water droplet contact angles, differential scanning calorimetry (DSC), thermal gravimetry analysis (TG), wide-angle X-ray diffraction (WAXD), and tensile strength measurements. The surface of the blends became more hydrophilic than that of the hydrophobic PANI film, but the other properties of the blends did not change appreciably for Pluronic content lower than 50 wt%. Compared to PANI films, the more hydrophilic surfaces decreased the amount of bovine serum albumin protein adsorbed. By preventing biofouling, the polyaniline-Pluronic blends can become more useful as biosensors than the polyaniline films.

The use of conducting polymers in membrane-based separations: a review and recent developments

As a material family, pi-conjugated polymers (also known as intrinsically conductive polymers) elicit the possibility of both exploiting the chemical and physical attributes of the polymer for membrane-based separations and incorporating its electronic and electrochemical properties to enhance the separation figures-of-merit. This review article, although by no means comprehensive, provides a current snapshot of the investigations from many research laboratories in the use of conducting polymers for membrane-based separations. The review focuses primarily on polyaniline, polypyrrole, and substituted-polythiophene and includes applications in gas separations, liquid (and/or vapor) separations, and ion separations. Additionally, we discuss the broad challenges and accomplishments in membrane formation from conducting polymers.