Miroslava Trchová

Synthesis and structural study of polypyrroles prepared in the presence of surfactants

Abstract Conducting and stable polypyrrole (PPy) was synthesized by chemical oxidative polymerization of pyrrole in aqueous solution containing an oxidant, ferric sulfate, and a surfactant. Anionic surfactants: sodium dodecylbenzenesulfonate, dodecylbenzenesulfonic acid, sodium dodecyl sulfate, poly(ethylene oxide)- n -alkyl-3-sulfopropyl ether potassium salt; cationic surfactant: tetradecyltrimethylammonium bromide; and non-ionic surfactants: poly(ethylene oxide) (10) iso- octylphenyl ether (Triton ® X-100), poly(ethylene oxide) (20) sorbitan monolaurate (Tween ® 20) and poly(ethylene oxide) (20) sorbitan monostearate (Tween ® 60) were used as additives. Results of the elemental analysis and FTIR spectroscopy proved that only the anionic surfactants were incorporated into PPy similarly as the doping anion. This leads to a better stability towards the deprotonation. Also thermal stability, checked by TGA in air, was improved. Scanning electron microscopy studies showed that the presence of the anionic surfactant strongly influenced the morphology of the polymer product.

Polyaniline: The infrared spectroscopy of conducting polymer nanotubes (IUPAC Technical Report)*

Polyaniline (PANI), a conducting polymer, was prepared by the oxidation of aniline with ammonium peroxydisulfate in various aqueous media. When the polymerization was carried out in the solution of strong (sulfuric) acid, a granular morphology of PANI was obtained. In the solutions of weak (acetic or succinic) acids or in water, PANI nanotubes were produced. The oxidation of aniline under alkaline conditions yielded aniline oligomers. Fourier transform infrared (FTIR) spectra of the oxidation products differ. A group of participants from 11 institutions in different countries recorded the FTIR spectra of PANI bases prepared from the samples obtained in the solutions of strong and weak acids and in alkaline medium within the framework of an IUPAC project. The aim of the project was to identify the differences in molecular structure of PANI and aniline oligomers and to relate them to supramolecular morphology, viz. the nanotube formation. The assignment of FTIR bands of aniline oxidation products is reported.

Poly(L-lysine)-modified iron oxide nanoparticles for stem cell labeling.

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide and oxidation of the resulting magnetite with sodium hypochlorite, followed by the addition of poly( L-lysine) (PLL) solution. PLL of several molecular weights ranging from 146 ( L-lysine) to 579 000 was tested as a coating to boost the intracellular uptake of the nanoparticles. The nanoparticles were characterized by TEM, dynamic light scattering, FTIR, and ultrasonic spectrometry. TEM revealed that the particles were ca. 6 nm in diameter, while FTIR showed that their surfaces were well-coated with PLL. The interaction of PLL-modified iron oxide nanoparticles with DMEM culture medium was verified by UV-vis spectroscopy. Rat bone marrow stromal cells (rMSCs) and human mesenchymal stem cells (hMSC) were labeled with PLL-modified iron oxide nanoparticles or with Endorem (control). Optical microscopy and TEM confirmed the presence of PLL-modified iron oxide nanoparticles inside the cells. Cellular uptake was very high (more than 92%) for PLL-modified nanoparticles that were coated with PLL (molecular weight 388 00) at a concentration of 0.02 mg PLL per milliliter of colloid. The cellular uptake of PLL-modified iron oxide was facilitated by its interaction with the negatively charged cell surface and subsequent endosomolytic uptake. The relaxivity of rMSCs labeled with PLL-modified iron oxide and the amount of iron in the cells were determined. PLL-modified iron oxide-labeled rMSCs were imaged in vitro and in vivo after intracerebral grafting into the contralateral hemisphere of the adult rat brain. The implanted cells were visible on magnetic resonance (MR) images as a hypointense area at the injection site and in the lesion. In comparison with Endorem, nanoparticles modified with PLL of an optimum molecular weight demonstrated a higher efficiency of intracellular uptake by MSC cells.

Conducting carbonized polyaniline nanotubes

Conducting nitrogen-containing carbon nanotubes were synthesized by the carbonization of self-assembled polyaniline nanotubes protonated with sulfuric acid. Carbonization was carried out in a nitrogen atmosphere at a heating rate of 10 degrees C min(-1) up to a maximum temperature of 800 degrees C. The carbonized polyaniline nanotubes which have a typical outer diameter of 100-260 nm, with an inner diameter of 20-170 nm and a length extending from 0.5 to 0.8 microm, accompanied with very thin nanotubes with outer diameters of 8-14 nm, inner diameters 3.0-4.5 nm and length extending from 0.3 to 1.0 microm, were observed by scanning and transmission electron microscopies. Elemental analysis showed 9 wt% of nitrogen in the carbonized product. Conductivity of the nanotubular PANI precursor, amounting to 0.04 S cm(-1), increased to 0.7 S cm(-1) upon carbonization. Molecular structure of carbonized polyaniline nanotubes has been analyzed by FTIR and Raman spectroscopies, and their paramagnetic characteristics were compared with the starting PANI nanotubes by EPR spectroscopy.

Infrared spectroscopic study of solid-state protonation and oxidation of polyaniline

Infrared spectrum of the polyaniline sulfate was compared with the spectrum of the polyaniline base after solid-state protonation with an equimolar amount of camphorsulfonic acid and with the spectrum of the polyaniline base after solid-state oxidation with ammonium peroxodisulfate. In both cases electrically conducting product was obtained. The bands characteristic of conducting protonated or oxidized form were identified in the spectra of the blends.

Spectroscopy of thin polyaniline films deposited during chemical oxidation of aniline

Any surface immersed in the aqueous reaction mixture used for the preparation of polyaniline becomes coated with a polyaniline film of submicrometre thickness. In this way, various materials can be modified by an overlayer of conducting polymer. The present review illustrates the role of infrared, Raman, and UV-VIS spectroscopies in the studies of polyaniline film growth. Spectroscopic methods are crucial in the evaluation of the performance of polyaniline films alone or in combination with nanoparticles of noble metals. The assessment of film ageing and stability can be followed conveniently by these methods. Carbonization of polyaniline films to nitrogen-containing carbon analogues is also discussed.

In-situ polymerized polyaniline films: 5. Brush-like chain ordering

The polymerization conditions for preparation of ordered in-situ polymerized polyaniline (PANI) films were established. The thickness of films deposited on glass can be controlled by the time spent in the reaction mixture and varied up to ca. 250 nm. The PANI chains initiated on the glass surface are expected to grow mostly perpendicularly to the support. The concept of brush-like ordering of PANI macromolecules in the films is discussed on the basis of optical anisotropy measurements. The observed linear relation between film thickness and molecular weight of PANI also supports the ordering hypothesis. The differences observed in absorption FTIR spectra of PANI films and powders are discussed.

Synthesis and characterization of conducting polyaniline 5-sulfosalicylate nanotubes

Conducting polyaniline 5-sulfosalicylate nanotubes and nanorods were synthesized by the template-free oxidative polymerization of aniline in aqueous solution of 5-sulfosalicylic acid, using ammonium peroxydisulfate as an oxidant. The effect of the molar ratio of 5-sulfosalicylic acid to aniline on the molecular structure, molecular weight distribution, morphology, and conductivity of polyaniline 5-sulfosalicylate was investigated. The nanotubes, which have a typical outer diameter of 100-250 nm, with an inner diameter of 10-60 nm, and a length extending from 0.4 to 1.5 microm, and the nanorods, with a diameter of 80-110 nm and a length of 0.5-0.7 microm, were observed by scanning and transmission electron microscopies. The presence of branched structures and phenazine units besides the ordinary polyaniline structural features was revealed by infrared and Raman spectroscopies. The stacking of low-molecular-weight substituted phenazines appears to play a major role in the formation of polyaniline nanorods. The precipitation-dissolution of oligoaniline templates as a key element in the formation of polyaniline nanotubes is proposed to explain the crucial influence of the initial pH of the reaction mixture and its decrease during the course of polymerization.

Fluorescent magnetic nanoparticles for biomedical applications

The simultaneous combination of optical and magnetic resonance imaging (MRI) would greatly benefit in vivo disease diagnosis as well as in situ monitoring of living cells. In order to design dual detection of cells involving simultaneous imaging by fluorescent microscopy and MRI, nanoparticles with two reporters, a fluorescent dye and a superparamagnetic core, included in one particle were synthesized and characterized. The γ-Fe2O3 nanoparticles obtained by coprecipitation and oxidation were coated with silica (SiO2) or carboxymethyl chitosan (CMCS) and labeled with fluorescein isothiocyanate (FITC). The fluorescent label was covalently bound to the nanoparticles and was not quenched by the iron oxide core. The nanoparticles successfully labeled rat mesenchymal stem cells (rMSCs) in vitro. Relaxation time measurements found large amounts of iron inside the cells with FITC-labeled γ-Fe2O3–SiO2-AP nanoparticles. Both MR and fluorescent imaging of a rat brain with implanted rMSCs labeled with FITC-labeled CMCS-modified silica-coated γ-Fe2O3 nanoparticles were performed.

Conductivity ageing in temperature-cycled polyaniline

The conductivity of polyaniline (PANI) hydrochloride was measured in situ during successive temperature cycles from room temperature to 85, 115, 146 and 179 °C. FTIR spectroscopy, gel-permeation chromatography and X-ray diffraction assessed the changes in polymer structure after each run. The conductivity ageing of PANI in terms of deprotonation, degradation and crystallinity reduction is discussed. The behaviour of PANI in compressed pellets and as powders is compared.