Controllable fabrication of porous free-standing polypyrrole films via a gas phase polymerization

Fabrication of Polypyrrole Hollow Nanospheres by Hard-Template Method for Supercapacitor Electrode Material

Conducting polymers like polypyrrole, polyaniline, and polythiophene with nanostructures offers several advantages, such as high conductivity, a conjugated structure, and a large surface area, making them highly desirable for energy storage applications. However, the direct synthesis of conducting polymers with nanostructures poses a challenge. In this study, we employed a hard template method to fabricate polystyrene@polypyrrole (PS@PPy) core-shell nanoparticles. It is important to note that PS itself is a nonconductive material that hinders electron and ion transport, compromising the desired electrochemical properties. To overcome this limitation, the PS cores were removed using organic solvents to create hollow PPy nanospheres. We investigated six different organic solvents (cyclohexane, toluene, tetrahydrofuran, chloroform, acetone, and N,N-dimethylformamide (DMF)) for etching the PS cores. The resulting hollow PPy nanospheres showed various nanostructures, including intact, hollow, buckling, and collapsed structures, depending on the thickness of the PPy shell and the organic solvent used. PPy nanospheres synthesized with DMF demonstrated superior electrochemical properties compared to those prepared with other solvents, attributed to their highly effective PS removal efficiency, increased specific surface area, and improved charge transport efficiency. The specific capacitances of PPy nanospheres treated with DMF were as high as 350 F/g at 1 A/g. And the corresponding symmetric supercapacitor demonstrated a maximum energy density of 40 Wh/kg at a power density of 490 W/kg. These findings provide new insights into the synthesis method and energy storage mechanisms of PPy nanoparticles.

Maintaining Antibacterial Activity against Biofouling Using a Quaternary Ammonium Membrane Coupling with Electrorepulsion

Antibacterial modification is a chemical-free method to mitigate biofouling, but surface accumulation of bacteria shields antibacterial groups and presents a significant challenge in persistently preventing membrane biofouling. Herein, a great synergistic effect of electrorepulsion and quaternary ammonium (QA) inactivation on maintaining antibacterial activity against biofouling has been investigated using an electrically conductive QA membrane (eQAM), which was fabricated by polymerization of pyrrole with QA compounds. The electrokinetic force between negatively charged Escherichia coli and cathodic eQAM prevented E. coli cells from reaching the membrane surface. More importantly, cathodic eQAM accelerated the detachment of cells from the eQAM surface, particularly for dead cells whose adhesion capacity was impaired by inactivation. The number of dead cells on the eQAM surface was declined by 81.2% while the number of live cells only decreased by 49.9%. Characterization of bacteria accumulation onto the membrane surface using an electrochemical quartz crystal microbalance revealed that the electrorepulsion accounted for the cell detachment rather than inactivation. In addition, QA inactivation mainly contributed to minimizing the cell adhesion capacity. Consequently, the membrane fouling was significantly declined, and the final normalized water flux was promoted higher than 20% with the synergistic effect of electrorepulsion and QA inactivation. This work provides a unique long-lasting strategy to mitigate membrane biofouling.

High performance polypyrrole/SWCNTs composite film as a promising organic thermoelectric material

Conducting polymer thermoelectric (TE) materials have received great attention due to their unique properties. In this work, polypyrrole (PPy)/single-walled carbon nanotubes (SWCNTs) composite films with improved TE performance have been prepared by chemical interfacial polymerization at the cyclohexane/water interface under a controlled temperature. Attributed to the smooth surface, higher conjugation length and more ordered molecular structure of the interfacial polymerized PPy film, the electrical conductivity can be as high as ∼500 S cm⁻¹. To further enhance the TE properties of PPy, SWCNT was added to construct a PPy/SWCNTs composite. Due to the synergistic effect between the two phases and the energy filtering effect at the interfaces between PPy and SWCNTs, the Seebeck coefficient of the composite enhanced significantly with the increase SWCNTs content. The composite shows an optimal power factor of 37.6 ± 2.3 μW mK⁻² when the content of SWCNTs is 0.8 mg. This value is one of the largest values among the reported PPy based composites fabricated by the chemical polymerization method. The results indicate that interfacial polymerization under a controlled temperature is a promising way to improve the TE performance of conducting polymer based composite materials.

PPy/SWCNTs composite films with high thermoelectric performance were prepared by chemical interfacial polymerization under a controlled low temperature.

Vapor/liquid polymerization of ultraporous transparent and capacitive polypyrrole nanonets

Freestanding, contiguous, and translucent polypyrrole nanonets are prepared within 90 minutes at room temperature in Petri dishes by exposing aqueous oxidant to static pyrrole vapor. The nanonets are 150 nm thick, with variable densities depending on polymerization time. The nanonets maintain a low sheet resistance of 29.1 Ω□^-1 at 30% optical transmission, and 423 Ω□^-1 at 50% transmission. A mechanism is proposed in which polypyrrole islands serve as nucleation sites for further surface-tension constrained polymerization. The nanonets exhibit a high degree of electrochemical dopability (over 24%). Nets are robust and processable, as evidenced by their ability to drape over 2D and 3D substrates. Large areas of films are manually twisted into highly porous sub-millimeter diameter conductive wires, able to recover their two-dimensional structure upon immersion in solvents. Moreover, nanonets exhibit a high specific capacitance of 518 F g^-1 for a 1.2 V potential window. Electrochemical capacitors fabricated with nanonet active electrodes show a high energy density of 9.86 W h kg^-1 at 1775 W kg^-1 when charged to 0.8 V.

Free-standing polypyrrole/polyaniline composite film fabricated by interfacial polymerization at the vapor/liquid interface for enhanced hexavalent chromium adsorption

Interfacial polymerization is an innovative technique for the fabrication of polymeric films. However, the majority of studies on interfacial polymerization has focused on liquid/liquid interfaces, and little work has been done on vapor/liquid interfaces. In this paper, we present the fabrication of free-standing polypyrrole/polyaniline (PPy/PANI) composite films by interfacial polymerization at a vapor/liquid interface using FeCl₃ as an oxidant. The obtained PPy/PANI composite films were characterized using Fourier transform infrared spectroscopy, X-ray diffractometry, and scanning electron microscopy. It was found that the PPy/PANI composite films consist of PANI particles evenly distributed on porous PPy film. The influence of FeCl₃ concentration on the morphology of the resulting composite films was investigated. The PPy/PANI composite films show an excellent Cr(vi) adsorption capacity of 256.41 mg g⁻¹, much higher than that of PPy-based absorbents prepared from chemical and electrochemical polymerization routes. This work thus suggests a new route for the fabrication of PPy/PANI films with highly enhanced Cr(vi) adsorption capacity for practical applications.

Free-standing polypyrrole/polyaniline composite film fabricated by interfacial polymerization at vapor/liquid interface.

A Wearable Supercapacitor Engaged with Gold Leaf Gilding Cloth Toward Enhanced Practicability

Flexible energy storage devices have attracted wide attention because of the increasing requirement of wearable electronics. However, comfortability, productivity, and feasibility, to name a few, are still far from satisfactory in the current wearable supercapacitors (SCs). This is largely due to the missing of an ideal low-cost flexible substrate/current collector that should not only exhibit high conductivity, but also be compatible with modern textile technologies. Herein, we apply the traditional gilding technique to cloth and successfully convert the cloth to be an excellent current collector which is available at a reasonable cost and compatible with textile technologies. Thanks to the strong electrostatic interaction, we found that a positively charged gold leaf could be laminated on a negatively charged polyester cloth intimately. This substrate could perfectly act as an integrated compact electrode after the electrodeposition of polypyrrole nanorods. The resulting electrode is mechanically strong enough to withstand the tortures of repeated bending, cutting, or puncturing, and is readily assembled into wearable SCs and energy cloth with outstanding practicability, for example, safety and breathability. It is foreseeable that our work will inspire a series design of wearable electronics based on the fascinating gilding art.

Design and Fabrication of an All-Solid-State Polymer Supercapacitor with Highly Mechanical Flexibility Based on Polypyrrole Hydrogel

A conducting polymer-based hydrogel (PPy/CPH) with a polypyrrole-poly(vinyl alcohol) interpenetrating network was prepared by utilization of a chemical cross-linked poly(vinyl alcohol)-H₂SO₄ hydrogel (CPH) film as flexible substrate followed by vapor-phase polymerization of pyrrole. Then an all-solid-state polymer supercapacitor (ASSPS) was fabricated by sandwiching the CPH film between two pieces of the PPy/CPH film. The ASSPS is mechanically robust and flexible with a tensile strength of 20.83 MPa and a break elongation of 377% which is superior to other flexible conducting polymer hydrogel-based supercapacitors owing to the strong hydrogen bonding interactions among the layers and the high mechanical properties of the PPy/CPH. It exhibits maximum volumetric specific capacitance of 13.06 F/cm³ and energy density of 1160.9 μWh/cm³. The specific capacitance maintains 97.9% and 86.3% of its initial value after 10 000 folding cycles and 10 000 charge-discharge cycles, respectively. The remarkable electrochemical and mechanical performance indicates this novel ASSPS device is promising for flexible electronics.

Thermoelectric Properties of Flexible PEDOT:PSS/Polypyrrole/Paper Nanocomposite Films

Flexible poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polypyrrole/paper (PEDOT:PSS/PPy/paper) thermoelectric (TE) nanocomposite films were prepared by a two-step method: first, PPy/paper nanocomposite films were prepared by an in situ chemical polymerization process, and second, PEDOT:PSS/PPy/paper TE composite films were fabricated by coating the as-prepared PPy/paper nanocomposite films using a dimethyl sulfoxide-doped PEDOT:PSS solution. Both the electrical conductivity and the Seebeck coefficient of the PEDOT:PSS/PPy/paper TE nanocomposite films were greatly enhanced from 0.06 S/cm to ~0.365 S/cm, and from 5.44 μV/K to ~16.0 μV/K at ~300 K, respectively, when compared to the PPy/paper TE nanocomposite films. The thermal conductivity of the PEDOT:PSS/PPy/paper composite film (0.1522 Wm⁻¹K⁻¹ at ~300 K) was, however, only slightly higher than that of the PPy/paper composite film (0.1142 Wm⁻¹K⁻¹ at ~300 K). As a result, the ZT value of the PEDOT:PSS/PPy/paper composite film (~1.85 × 10⁻⁵ at ~300 K) was significantly enhanced when compared to that of the PPy/paper composite film (~4.73 × 10⁻⁷ at ~300 K). The as-prepared nanocomposite films have great potential for application in flexible TE devices.

A Comparative Study on Optical, Electrical, and Mechanical Properties of Conducting Polymer-Based Electrodes

Transparent, free-standing, conducting polypyrrole (PPy) film is successfully fabricated by a simple method using the spin-coating technique. The free-standing PPy film exhibits high transparency, flexibility, electrical conductivity, and stable mechanical properties because the PPy film is composed of densely packed and highly ordered PPy nanoparticles. This approach provides feasible candidate for applications requiring flexible and conducting materials.

Insulating and semiconducting polymeric free-standing nanomembranes with biomedical applications

Free-standing nanomembranes, which are emerging as versatile elements in biomedical applications, are evolving from being composed of insulating (bio)polymers to electroactive conducting polymers.