Polypyrrole reinforced ZIF-67 with modulated facet exposure and billion-fold electrical conductivity enhancement towards robust photocatalytic CO_(2) reduction

The implementation of metal organic frameworks(MOFs) as the co-catalysts in hybrid photocatalytic systems puts requirements on both their charge-carrying capability and solvent stability. In the current study, in order to simultaneously promote the electrical conductivity and water stability of ZIF-67, an insitu monomer trapping strategy is deployed to synthesize polypyrrole(PPy)-reinforced ZIF-67 ensembles.Through coordination modulation, the incremental addition of pyrrole monomers enables to alter the crystal morphology of ZIF-67 from rhombic dodecahedra to truncated rhombic dodecahedra, and further to cubes. Upon polymerization, the resulted composite, in comparison to ZIF-67, demonstrates a billionfold conductivity enhancement, much improved chemical stability in pronated solvents, as well as largely retained specific surface area and porosity, enabling it functioning as an outstanding co-catalyst for catalyzing robust photocatalytic CO_(2) reduction. Furthermore, a PPy-mediated electron harvest and relay mechanism is proposed for rationalizing the enhanced photocatalytic performance.

Preparation and Characterization of Polypyrrole Microbelt via Cotton Template

Polypyrrole （PPY） microbelts are synthesized via the absorbent cotton template for the first time. PPY microbelts are characterized by Fourier transform infrared spectroscopy.The stability, the morphology and electrical conductivity of such microbelts are evaluated by means of scanning electron microscope, thermo-gravimetric analysis and four-probe con-ductivity. A possible mechanism for the formation of PPY microbelts are proposed. The conductivity is measured, and the conductivity variation mechanism of the PPY microbelts with the pyrrole monomer concentrations is analyzed.

Novel conductive polypyrrole/silk fibroin scaffold for neural tissue repair

Three dimensional（3D） bioprinting, which involves depositing bioinks（mixed biomaterials） layer by layer to form computer-aided designs, is an ideal method for fabricating complex 3D biological structures. However, it remains challenging to prepare biomaterials with micro-nanostructures that accurately mimic the nanostructural features of natural tissues. A novel nanotechnological tool, electrospinning, permits the processing and modification of proper nanoscale biomaterials to enhance neural cell adhesion, migration, proliferation, differentiation, and subsequent nerve regeneration. The composite scaffold was prepared by combining 3D bioprinting with subsequent electrochemical deposition of polypyrrole and electrospinning of silk fibroin to form a composite polypyrrole/silk fibroin scaffold. Fourier transform infrared spectroscopy was used to analyze scaffold composition. The surface morphology of the scaffold was observed by light microscopy and scanning electron microscopy. A digital multimeter was used to measure the resistivity of prepared scaffolds. Light microscopy was applied to observe the surface morphology of scaffolds immersed in water or Dulbecco＇s Modified Eagle＇s Medium at 37℃ for 30 days to assess stability. Results showed characteristic peaks of polypyrrole and silk fibroin in the synthesized conductive polypyrrole/silk fibroin scaffold, as well as the structure of the electrospun nanofiber layer on the surface. The electrical conductivity was 1 × 10^-5–1 × 10^-3 S/cm, while stability was 66.67%. A 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide assay was employed to measure scaffold cytotoxicity in vitro. Fluorescence microscopy was used to observe Ed U-labeled Schwann cells to quantify cell proliferation. Immunohistochemistry was utilized to detect S100β immunoreactivity, while scanning electron microscopy was applied to observe the morphology of adherent Schwann cells. Results demonstrated that the polypyrrole/silk fibroin scaffold was not cytotoxic and did not affect Schwann cell proliferation. Moreover, filopodia formed on the scaffold and Schwann cells were regularly arranged. Our findings verified that the composite polypyrrole/silk fibroin scaffold has good biocompatibility and may be a suitable material for neural tissue engineering.

Preparation of polypyrrole-embedded electrospun poly(lactic acid) nanofibrous scaffolds for nerve tissue engineering

Polypyrrole （PPy） is a biocompatible polymer with good conductivity. Studies combining PPy with electrospinning have been reported; however, the associated decrease in PPy conductivity has not yet been resolved. We embedded PPy into poly（lactic acid） （PLA） nanofibers via electrospinning and fabricated a PLA/PPy nanofibrous scaffold containing 15% PPy with sustained conductivity and aligned topog- raphy, qhere was good biocompatibility between the scaffold and human umbilical cord mesenchymal stem cells as well as Schwann cells. Additionally, the direction of cell elongation on the scaffold was parallel to the direction of fibers. Our findings suggest that the aligned PLA/PPy nanofibrous scaffold is a promising biomaterial for peripheral nerve regeneration.

Polypyrrole-Coated Zein/Epoxy Ultrafine Fiber Mats for Electromagnetic Interference Shielding

To reduce the environmental pollution and meet the needs for wearable electronic devices, new requirements for electromagnetic interference(EMI) shielding materials include flexibility, biodegradability, and biocompatibility. Herein, we reported a polypyrrole-coated zein/epoxy(PPy/ZE) ultrafine fiber mat which was inherently biodegradable and skin-friendly. In addition, it could maintain its ultrafine fibrous structure after coating, which could provide the mat with mechanical compliance, high porosity, and a large specific area for high EMI shielding. With the assistance of the epoxide cross-linking, the breaking stresses of the PPy/ZE fiber mats could achieve 3.3 MPa and 1.4 MPa and the strains were 40.1% and 83.0% in dry and wet states, respectively, which met the needs of various wearable electronic devices. Along with the extension in the PPy treatment duration, more PPy was loaded on the fiber surfaces, which formed more integrated and conductive paths to generate increasing conductivities up to 401.76 S·m^(-1). Moreover, the EMI shielding performance was raised to 26.84 dB. The biobased mats provide a green and efficient choice for EMI shielding materials, which may be a promising strategy to address EMI problems in multiple fields.

STUDY ON POLYPYRROLE-VISCOSE CONDUCTING FIBER

The conductivity of Polypyrrole-viscose conducting fiber prepared with author’s method can be shown up to as high as 2.106x10-2 S/cm. The main factors influencing the conductivity are the concentration of FeCl3 used as dopant and initiator, the treatment time of viscose fiber as base material in FeCl3 solution, temperature and polymerization time. It is found that the orientation and crystallization degree of viscose fiber keep constant before and after conducting treatment and the mechanical properties of conducting fiber is the same as that of base material. In addition, the distribution of polypyrrole in viscose fiber, and its effect on the conductivity were investigated in details by TEM.

Electrochemical Formation of Polypyrrole-carboxymethylcellulose Conducting Polymer Composite Films

The electrochemical preparation of polypyrrole-carboxymethylcellulose （PPY-CMC） conducting polymer composite films on indium tin oxide （ITO） glass electrode from an aqueous solution containing pyrrole monomer, ptoluenesulfonate electrolyte and carboxymethylcellulose insulating polymer is reported. The characterization by Fourier transform infrared spectroscopy （FT-IR） shows that carboxymethylcellulose （CMC） has been successfully incorporated into polypyrrole structure forming PPY-CMC polymer composite films. The conductivity of the prepared composite films was found to increase with increaseing CMC concentration in pyrrole solution, The optical microscopic results show the influence of CMC concentration in the pyrrole solution over the morphological changes of the prepared films. The dynamic mechanical analysis （DMA） on the prepared PPY-CMC film reveals the higher plastic property of the PPY-CMC composite film.

MECHANICAL PROPERTIES OF CHLORINATED POLYPROPYLENE——POLYPYRROLE FILM

The chlorinated polypropylene (PPC1)-polypyrrole (PPy) conducting films were successfully synthesized by a novel method for the first time. The mechanical properties of PPC1-PPy conducting films were investigated by means of stress-strain test and DMA. It was shown that the rupture strength and initial modulus increase with the increase of polypyrrole content , but the elongation at rupture decrease. Besides, the glass transition temperature (Tg) is increasing to a plateau when polypyrrole content attains 6%. Moreover, a new mechanical model to describe the mechanical properties of PPC1-PPy blend system is established by changing the correction factor in Mooney model. It was found that the theoretic value of the model is well coincident with the experimental results.

THE STUDY ON CHLORINATED POLYPROPYLENE (PPCI)-POLYPYRROLE (PPy) COMPOSITE FILM

The chlorinated polypropylene-polypyrrole composite film was synthesized by means of a newmethod for the first time. The effects of various conditions on polymerization and the electric con-ductivity of PPCl-PPy composite film were investigated. It was found that PPCl-FeCl3 mixturehad an excellent film-forming ability and PPCl-PPy composite film could attain high conductivityat low content of polypyrrole and was stable for heat and atmosphere.

CONDUCTIVE COMPOSITES FROM POLYPYRROLE ELECTROPOLYMERIZED IN A POLYURETHANE MATRIX

In order to improve the mechanical properties of polypyrrole, composites were made by electropolymerizing polypyrrole in a polyurethane matrix. Polypyrrole/polyurethane (PPY/PU) composite films containing CLO_4^-, BF_4^- or CH_3-C_6H_4-SO_3^- counter ions were made in a variety of solvent systems and characterized by SEM, electronic conductivity, FTIR, and mechanical properties. Composite films showing much greater fiexibility than pure polypyrrole were obtained, but their electronic conductivities were substantially lower. Measured eonductivities ranged from 0.001 to 8 S/cm, tensile strengths from 44 to 592 psi, and elongation to failure from 3 to 70%.

Studies of Stability in Electrical Property and Sensitivity of Polypyrrole Conductive Fabrics Used for Intelligent Flexible Sensors

Electrically conducting fabrics used as flexible sensors can be produced by vacuumed vapor deposition.The research of what impacts the wide and reliable application of the flexible sensors shows that the stability of flexible sensors is one of the critical issues.The electrical performance of weft knitted fabrics in course and wale direction does not show significant differences under different ambient conditions,which include time,temperature,and relative humidity.Tests of stimuli responding sensitivity of conductive fabrics indicate that the sensitivity keeps at a constant level and the average sensitivity is stable over 38 days.

Facile Synthesis of Polypyrrole/Titanate Core-Shell Nanorods and Their Electrorheological Characteristics

In this work, polypyrrole (PPy)/titanate (TN) composite nanorods were successfully synthesized using cetyl trimethyl-ammonium bromide (CTAB) as a structure-directing agent by in situ chemical oxidative polymerization. The structural characterization indicated that the new composite rods were core (TN)-shell (PPy) nanostructure with the average diameter in the range of 250-300 nm. Further, this semiconducting composite can be used as a dispersed phase in silicone oil for a new electrorheological (ER) fluid, and its ER behavior was investigated under steady and oscillatory shear. It was found that the PPy/TN fluid showed typical ER characteristics under an external electric field.

Polypyrrole Coated PET Fabrics for Thermal Applications

Polypyrrole can be chemically synthesized on PET fabrics, giving rise to textiles with high electric conductivity. These textiles are suitable for several applications from antistatic films to electromagnetic interference shielding devices. Here we discuss the thermal-electric performance and the heat generation of polypyrrole coated PET fabric samples, previously studied because of their electric conductivity and electromagnetic interference shielding effectiveness. The measured Seebeck effect is comparable with that of metallic thermocouples. Since polypyrrole shows extremely low thermal diffusivities regardless of the electrical conductivity, the low thermal conductivity gives significant advantage to the thermoelectric figure-of-merit ZT, comparable with that of some traditional inorganic thermoelectric materials. The heat generation is also investigated for possible heating textile devices. The results confirm polypyrrole as a prom- ising material for thermal electric applications due to its easy preparation in low cost processing.

Ordered Nafion ionomers decorated polypyrrole nanowires for advanced electrochemical applications

Fabrication of novel electrode materials with ordered proton-migration channels is an effective strategy to enhance the proton conductivity of the electrode for polymer electrolyte membrane fuel cells. Here we report the electrochemical fabrication of ordered Nafion？ionomers decorated polypyrrole nanowires to construct the ordered proton-migration channels. Based on the electrostatic interaction between Nafion？ionomers and the polymer intermediate, ordered Nafion？ionomers decorated polypyrrole nanowires could be fabricated via chronoamperometry with varying contents of Nafionionomers. The morphologies, charge-storage performances, electron conductivity and proton conductivity of the composites are investigated by scanning electron microscopy, cyclic-voltammetry, galvanostatic charge–discharge measurement and electrochemical impedance spectroscopy. With the modification effect of Nafionionomers on polypyrrole nanowires, the composite shows greater ordered structure relative to another without Nafion？ionomers and the electrochemical performances change with the content of Nafion？ionomers.The composite could achieve a high specific capacitance of 356 F/g at 1 A/g with a 0.62-fold enhancement compared to polypyrrole nanowires without Nafion？ionomers. It also displays a superior electrical conductivity of 49 S/cm and a quite high proton conductivity of 0.014 S/cm at working conditions of fuel cells, which are associated with the requirements of fuel cells and have the potential to be the electrode material for a large range of electrochemical energy conversion devices.

CHARACTERIZATION ON DOPING POLYPYRROLE FILMS

The conductivity of ploypyrrole films has been enhanced by electrochemical post-deposition doping with various anions.The change of conductivity was found to depend on the type and concentration of the anion.Results for the polypyrrole films doped with anions of H2SO4,(C2H5)4 N(O3SC6H4CH3),KI,CH3C8H4SO3H·H2O(p-Toluene Sulfonic acid Monohydydrate),AlCl3,KBrO3 and HNO3 showed that in the case of H2SO4,(C2H5)4N(O3SC6H4CH3) and CH3C6H4SO3H·H2O the conductivity can be enhanced by up to a factor of two,from a value of 67s cm^-1 up to 165,102 and 95 s cm^-1,respectively,Doping with I^- had a negligible effect on the conductivity which was about 71 s cm^-1,while in the case of AlCl3,KBrO3 and HNO3 the conductivity of the polypyrrole decreased significantly for certain anion concentrations.

Fabrication and Mechano-sensing Characteristics of Bending Polypyrrole Actuator

To prepare a conductive polymer actuator with decent performance,a self-built experimental platform for the preparation of polypyrrole film is employed.One of the essential goals is to examine the mechanical characteristics of the actuator in the presence of various combinations of process parameters,combined with the orthogonal test method of"four factors and three levels".The bending and sensing characteristics of actuators of various sizes are methodically examined using a self-made bending polypyrrole actuator.The functional relationship between the bending displacement and the output voltage signal is established by studying the characteristics of the actuator sensor subjected to various degrees of bending.The experimental results reveal that the bending displacement of the actuator tip almost exhibits a linear variation as a function of length and width.When the voltage reaches 0.8 V,the bending speed of the actuator tends to be stable.Finally,the mechanical properties of the self-assembled polypyrrole actuator are verified by the design and fabrication of the microgripper.

POLYMERIZATION AND CHARACTERIZATION OF HIGH CONDUCTIVITY AND GOOD ADHENSION POLYPYRROLE FILMS FOR ELECTROMAGNETIC INTERFERENCE SHIELDING

Polypyrrole（PPy） shows a favorable application in the electromagnetic interference（EMI） shielding due to its good electrical conductivity and outstanding air stability.Conducting PPy films with high conductivity and good adhesion were successfully polymerized on the surface of insulating epoxy resin substrates using chemical polymerization.The factors affecting the properties of PPy films,such as the surface morphology,adhesion between PPy film and substrate,electrical conductivity,EMI shielding effectiveness（SE）,were investigated.The adhesion was improved significantly through a three-step surface pretreatment of epoxy resin substrates including removing impurities,roughening,and surface modification with silane coupling agent.An enhancement in the conductivity of PPy films of about one order of magnitude was achieved by adding dopant in FeCl_3 solution.The higher the conductivity,the better the shielding effectiveness.Taking sodium p-toluenesulfonate doped PPy film as example,EMI SE was in the practically useful range of about 30 dB over a wide frequency range from 30 MHz to 1500 MHz.The PPy film samples were characterized by scanning electron microscopy （SEM）,infrared spectra（IR）,X-ray photoelectron spectroscopy（XPS） and the flange coaxial transmission device.The fourpoint probe method was used to measure conductivity of PPy films.

Polypyrrole-coated styrene-butyl acrylate copolymer composite particles with tunable conductivity

A series of near or monodisperse styrene-butyl acrylate (SBA) copolymer latex particles with different butyl acrylate contents were coated with polypyrrole. The struc- ture of the SBA/PPy composites was characterized by trans- mission electron microscopy (TEM), scanning electron mi- croscopy (SEM), diffuse reflectance infrared Fourier trans- form spectroscopy (DRIFT), X-ray photoelectron spectros- copy (XPS), differential scanning calorimetry (DSC) and standard four-probe method. The core-shell morphology of the SBA/PPy composite particles was confirmed. The result of DSC showed that Tg of the composite is mainly determined by the core component. The effects of the concentration of polypyrrole, the butyl acrylate content in SBA copolymer and the nature of the counter-anion on the electrical conduc- tivity of compression-moulded samples were studied. It was first found that the electrical conductivity of the samples can be tuned by varying the butyl acrylate content in SBA co- polymer and the highest conductivity of the core-shell com- posite was 0.17 S·cm?1.

Conducting polypyrrole in tissue engineering applications

Polypyrrole （PPy）, the earliest prepared conducting polymer, has good biocompatibility, easy synthesis and flexibility in processing. Compared with metal and inorganic materials, doped PPy has better mechanical match with live tissue, resulting in its many applications in biomedical field. This mini-review presents some information on specific PPy properties for tissue engineering applications, including its synthesis, doping, bio-modiflcation. Although some challenges and unanswered problems still remain, PPy as novel biomaterial has promoted the development tissue engineering for its clinical application in the future.