Polyaniline and polypyrrole: A comparative study of the preparation

Structure and effects of gold nanoparticles in bacterial cellulose–polyaniline conductive membranes

Bacterial cellulose (BC) and poly(aniline) (PANI) composites were successfully synthesized by in situ polymerization of aniline by ammonium persulphate (APS) in the presence and absence of gold nanoparticles.

Constructing Uniform Core-Shell PPy@PANI Composites with Tunable Shell Thickness toward Enhancement in Microwave Absorption

Highly uniform core-shell composites, polypyrrole@polyaniline (PPy@PANI), have been successfully constructed by directing the polymerization of aniline on the surface of PPy microspheres. The thickness of PANI shells, from 30 to 120 nm, can be well controlled by modulating the weight ratio of aniline and PPy microspheres. PPy microspheres with abundant carbonyl groups have very strong affinity to the conjugated chains of PANI, which is responsible for the spontaneous formation of uniform core-shell microstructures. However, the strong affinity between PPy microspheres and PANI shells does not promote the diffusion or reassembly of two kinds of conjugated chains. Coating PPy microspheres with PANI shells increases the complex permittivity and creates the mechanism of interfacial polarization, where the latter plays an important role in increasing the dielectric loss of PPy@PANI composites. With a proper thickness of PANI shells, the moderate dielectric loss will produce well matched characteristic impedance, so that the microwave absorption properties of these composites can be greatly enhanced. Although PPy@PANI composites herein consume the incident electromagnetic wave by absolute dielectric loss, their performances are still superior or comparable to most PANI-based composites ever reported, indicating that they can be taken as a new kind of promising lightweight microwave absorbers. More importantly, microwave absorption of PPy@PANI composites can be simply modulated not only by the thickness of the absorbers, but also the shell thickness to satisfy the applications in different frequency bands.

Effect of multiwalled carbon nanotubes on the kinetics of the aniline polymerization: the semi-quantitative OCP approach

We demonstrate applicability of the open-circuit potential (OCP) method for kinetic analysis of the oxidative chemical polymerization of aniline both in clear solution and in dispersions of multiwalled carbon nanotubes (MWCNT). The characteristic points and the shape of the OCP profile are used to estimate the kinetic parameters of the main stages of the known two-step polymerization mechanism of aniline. We have found that the reciprocal values of the duration of the main polymerization stages namely the induction period, pernigraniline (PN) accumulation and reduction of PN with residual aniline are the linear functions of the weight fraction of MWCNT. To compare the kinetic data of the proposed OCP and known approaches the last two stages have been considered as a single heterogeneous stage of emeraldine (EM) formation. The kEM rate constant calculated by the OCP profiles for this EM stage in the solution and dispersion media is in a very good agreement with the known k2 values.

Evaluation of poly(pyrrole-2-carboxylic acid) particles synthesized by enzymatic catalysis

In this study an environmentally friendly synthesis of poly(pyrrole-2-carboxylic acid) (PCPy) particles dispersed in water–ethanol medium using enzymatic catalysis is proposed.

Coaxial conducting polymer nanotubes: polypyrrole nanotubes coated with polyaniline or poly(p-phenylenediamine) and products of their carbonisation

Polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in a reaction mixture containing methyl orange. They were subsequently coated with polyaniline or poly(p-phenylenediamine) in situ during the oxidation of respective monomers in their presence. A part of the coaxial nanotubes was deprotonated using ammonia solution. The conductivity of polypyrrole nanotubes of 60 S cm

Investigation of a Branchlike MoO(3)/polypyrrole hybrid with enhanced electrochemical performance used as an electrode in supercapacitors

A branchlike MoO3/polypyrrole conductive nanocomposite was facilely prepared by wrapping a homogeneous polypyrrole (PPy) layer around MoO3 nanobelts via the in situ oxidative polymerization of a self-assembled pyrrole monomer. X-ray powder diffraction characterization demonstrated that the PPy polymer does not hinder the crystallization of the MoO3 nanobelts substrate. The electrochemical tests show that the specific capacitance of 129 F g(-1) for the MoO3/PPy hybrid is higher than both pristine MoO3 and pure PPy. Moreover, the hybrid electrode with good electrical conductivity displays good cyclic stability of 90% retention after 200 cycles of charge/discharge. These results indicate a promising potential application of the MoO3/PPy nanocomposite for use as an effective electrode material in supercapacitors.

Electrically pressure sensitive poly(vinylidene fluoride)/polypyrrole electrospun mats

Non-woven mats with highly pressure-sensitive electrical conductivity have been prepared by electrospinning of poly(vinylidene fluoride) (PVDF) containing up to 23 wt% of polypyrrole (PPy) particles synthesized by using dodecylbenzenesulfonic acid (DBSA) as a dopant.

Synthesis and characterization of polypyrrole/H-Beta zeolite nanocomposites

Transmission electron micrographs of (a) H-Beta-25, (b), (c) and (d) 1 ml PPy/H-Beta-25 composite.

Structure-Property Relationship of Dodecylbenzenesulfonic Acid Doped Polyaniline

Dodecylbenzenesulfonic acid (DBSA) doped polypanilines (PANIs) were chemically synthesized in different molar ratios of aniline (An) to ammonium persulfate (APS) and An to DBSA. The microstructures of these PANIs were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared (FTIR). UV-Vis spectrometer, semiconductor parameter analyzer, ubbelohde viscometer and electrospinning technique were used to characterize the optical, electrical properties, viscosity and solubility of these PANIs. The results show that the molar rations of An to APS and An to DBSA had strong effect on the microstructure, molecular weight, degree of crystallinity, optical property, solubility and conductivity of obtained DBSA doped PANI. With the increase of the molar ratios of An to APS and An to DBSA, the conductivities and molecular weight of DBSA doped PANIs decreased, while the degree of crystallinity and solubility of DBSA doped PANIs increased. The DBSA doped PANI could dissolve in dichloromethane or HFIP and could be fabricated short fibers by electrospinning. Moreover, the solution of DBSA doped PANIs in concentrated sulphuric acid showed liquid crystal property.

Novel polypyrrole-coated polylactide scaffolds enhance adipose stem cell proliferation and early osteogenic differentiation

An electrically conductive polypyrrole (PPy) doped with a bioactive agent is an emerging functional biomaterial for tissue engineering. We therefore used chondroitin sulfate (CS)-doped PPy coating to modify initially electrically insulating polylactide resulting in novel osteogenic scaffolds. In situ chemical oxidative polymerization was used to obtain electrically conductive PPy coating on poly-96L/4D-lactide (PLA) nonwoven scaffolds. The coated scaffolds were characterized and their electrical conductivity was evaluated in hydrolysis. The ability of the coated and conductive scaffolds to enhance proliferation and osteogenic differentiation of human adipose stem cells (hASCs) under electrical stimulation (ES) in three-dimensional (3D) geometry was compared to the noncoated PLA scaffolds. Electrical conductivity of PPy-coated PLA scaffolds (PLA-PPy) was evident at the beginning of hydrolysis, but decreased during the first week of incubation due to de-doping. PLA-PPy scaffolds enhanced hASC proliferation significantly compared to the plain PLA scaffolds at 7 and 14 days. Furthermore, the alkaline phosphatase (ALP) activity of the hASCs was generally higher in PLA-PPy seeded scaffolds, but due to patient variation, no statistical significance could be determined. ES did not have a significant effect on hASCs. This study highlights the potential of novel PPy-coated PLA scaffolds in bone tissue engineering.

Synthesis and Physicochemical Characterization of Chitin Derivatives

Firstly, chitin derivatives were synthesized. For this purpose, chitin was modified via ring-opening reaction with cyclic anhydrides in lithium chloride/N,N-dimethylacetamide. Then, chitin derivatives synthesized were characterized by FTIR,1H NMR,13C NMR, and U-Vis spectroscopies and scanning electron microscopy. Thermogravimetric analysis was performed to investigate the thermal stability of chitin derivatives. Thermogravimetric analysis results showed that chitin modified with trimellitic anhydride is thermally more stable than chitin modified with phthalic anhydride. In addition, the electrical conductivity of chitin modified with phthalic anhydride and trimellitic anhydride was also measured. Electrical conductivity measurement results showed that the electrical conductivity of chitin modified with trimellitic anhydride ( S cm−1) is higher than that of chitin modified with phthalic anhydride ( S cm−1).

Investigação do processo de absorção de água de hidrogéis de polissacarídeo: efeito da carga iônica, presença de sais, concentrações de monômero e polissacarídeo

Neste trabalho foi reportada a caracterização de hidrogéis constituídos por metilcelulose (MC) e poliacrilamida (PAAm) preparados pelo processo de reticulação cruzada. As propriedades espectroscópicas e morfológicas foram investigadas por espectroscopia no infravermelho com transformada de Fourier e microscopia eletrônica de varredura, respectivamente. O efeito da carga iônica, presença de sais, concentrações de monômero AAm e polissacarídeo MC na absorção de água e nas propriedades cinéticas dos hidrogéis foi detalhadamente investigado. Os resultados indicaram que o decréscimo da concentração de MC ou aumento da concentração de AAm, carga iônica do contra-íon do sal de cloreto e a presença de fertilizante no meio externo de intumescimento provocaram diminuição significativa na absorção de água dos hidrogéis. O mecanismo de absorção de água dos hidrogéis de PAAm-MC em água seguiu o modelo de difusão Fickiana; já o mecanismo dos hidrogéis intumescidos em sais (cloreto ou fertilizante) seguiu o modelo de transporte anômalo. Pela alta e rápida absorção de água, as matrizes porosas e tridimensionais compostas por PAAm e MC podem em potencial ser aplicadas na agricultura como veículos carreadores.

Preparation and Characterization Flexible Conductive PPy/BC Nanocomposite Membrane

Polypyrrole (PPy) is an intrinsically conducting polymer that has a wide variety of potential applications on electrical devices, sensors, electrode material, anticorrosion and antistatic coatings. Bacterial cellulose (BC), a natural nano-material with outstanding properties, can be used as a template material. In this study, water-wet BC was firstly used to prepare PPy/BC nanocomposite membrane by combining with PPy. The obtained nanocomposite showed excellent performances such as high conductivity, considerable mechanicl behavior and perfect flexibility. Effects of pyrrole concentration and reaction time on the electrical conductivity of the membrane were investigated. Besides, FT-IR, FE-SEM and mechanical properties were studies. The results revealed that it was possible to develop a novel PPy/BC nanocomposite with potential applications on flexible displays or sensors.