Magnetic poly(N‐propargylacrylamide) microspheres: Preparation by precipitation polymerization and use in model click reactions

Magnetic poly(N‐propargylacrylamide) (PPRAAm) microspheres were prepared by the precipitation polymerization of N‐propargylacrylamide (PRAAm) in a toluene/propan‐2‐ol medium in the presence of magnetic nanoparticles (oleic acid‐coated Fe₃O₄). The effects of several polymerization parameters, including the polarity of the medium, polymerization temperature, the concentration of monomer, and the amount of magnetite (Fe₃O₄) in the polymerization feed, were examined. The microspheres were characterized in terms of their morphology, size, particle‐size distribution, and iron content using transmission and scanning electron microscopies (TEM and SEM) and atomic absorption spectroscopy (AAS). A medium polarity was identified in which magnetic particles with a narrow size distribution were formed. As expected, oleic acid‐coated Fe₃O₄ nanoparticles contributed to the stabilization of the polymerized magnetic microspheres. Alkyne groups in magnetic PPRAAm microspheres were detected by infrared spectroscopy. Magnetic PPRAAm microspheres were successfully used as the anchor to enable a “click” reaction with an azido‐end‐functionalized model peptide (radiolabeled azidopentanoyl‐GGGRGDSGGGY(¹²⁵I)‐NH₂) and 4‐azidophenylalanine using a Cu(I)‐catalyzed 1,3‐dipolar azide‐alkyne cycloaddition reaction in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

The oxidative polymerization of p‐phenylenediamine with silver nitrate: Toward highly conducting micro/nanostructured silver/conjugated polymer composites

The oxidative polymerization of p‐phenylenediamine with silver nitrate by using various oxidant/monomer mole ratios in aqueous solutions of both acetic and nitric acid was studied experimentally and computationally. The produced micro/nanostructured conducting poly(p‐phenylenediamine)–silver composites, reaching the conductivities >10⁴ S/cm, were characterized by conductivity and density measurements, gel permeation chromatography, transmission electron microscopy, UV–visible, FTIR, and Raman spectroscopies. The highest conductivity was 31,700 S/cm for poly(p‐phenylenediamine) base–silver (81.4 wt % Ag). The unexpected increase of conductivity after deprotonation of polymer component is discussed on the basis of interfacial electrical barriers and their removal. Theoretical study of the mechanism of p‐phenylenediamine oxidation has been based on the AM1 semi‐empirical quantum chemical computations of the heat of formation of the reaction intermediates, taking into account the influence of pH and solvation effects. Quantum chemical predictions of molecular structure of poly(p‐phenylenediamine) were correlated with spectroscopic findings. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Evolution of polyaniline nanotubes: the oxidation of aniline in water

The course of aniline oxidation with ammonium peroxydisulfate in aqueous solutions has been investigated. The reaction was terminated at various times and the intermediates collected. Besides the precipitates, the films deposited in situ on silicon windows have also been studied. The kinetic course of polymerization is controlled by the acidity level, which changes during the polymerization from pH 8 to a final value close to pH 1. It has two distinct exothermic phases. Gel-permeation chromatography indicates that aniline oligomers are produced at first at high pH, while polyaniline follows after the pH becomes sufficiently low. The growth of polyaniline nanotubes was observed by optical microscopy and confirmed by electron microscopy. The molecular structure of the reaction intermediates was studied in detail by FTIR spectroscopy. Oxidation products are markedly sulfonated, and they contain phenazine units. Aniline oligomers are more soluble in chloroform than the polymer fraction, which contains nanotubes.     

Intercalates of Vanadyl Phosphate with Dinitriles

Intercalates of vanadyl phosphate with aliphatic dinitriles (malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and suberonitrile) were prepared and characterized by X-ray powder diffraction, thermogravimetric analysis, IR and Raman spectroscopies. The basal spacings of all the intercalates prepared are practically identical. The dinitrile content in the intercalates decreases with increasing chain length. The dinitrile molecules are anchored to the host layers by an N–V donor–acceptor bond and their aliphatic chains are parallel to the host layers. The dinitrile intercalates are generally more stable in air (at relative humidity 40–50%) than nitrile intercalates and the guest molecules are slowly replaced by the water molecules.     

Chemical oxidative polymerization of dianilinium 5-sulfosalicylate

Dianilinium 5-sulfosalicylate was prepared in situ and then oxidized in aqueous solution with ammonium peroxydisulfate. The precipitated polyaniline 5-sulfosalicylate was soluble in polar aprotic solvents and showed conductivity of ∼0.1 S cm⁻¹. Scanning electron microscopy revealed the coexistence of nanorods and granular morphology of the polyaniline 5-sulfosalicylate. The weight-average molecular weight and poly-dispersity index were determined by gel-permeation chromatography as 53000 and 9.0, respectively. FTIR spectroscopic analysis combined with AM1 and MNDO-PM3 semi-empirical quantum chemical studies of the polymerization mechanism indicate both covalent and ionic bonding of sulfosalicylate to polyaniline chains. Raman spectroscopy proved the presence of substituted phenazine structural units besides ordinary emeraldine segments. The text was submitted by the authors in English.     

Multi-wall carbon nanotubes with nitrogen-containing carbon coating

Polyaniline coating was deposited on the surface of multi-wall carbon nanotubes of Russian and Taiwanese origin in situ during the polymerization of aniline. The deposited polyaniline film was subsequently carbonized under an inert atmosphere at various temperatures to produce coaxial coating of the carbon nanotubes with nitrogen-containing carbon. The new materials were investigated by infrared and Raman spectroscopies, which demonstrated the conversion of the polyaniline coating to a carbonized structure. X-ray photoelectron spectroscopy proved that the carbonized overlayer contains nitrogen atoms in various covalent bonding states. Transmission electron microscopy confirmed the coaxial structure of the composites. The Brunauer-Emmett-Teller method was used to estimate the specific surface area, the highest being 272 m² g^?1. The conductivity of 0.9–16 S cm^?1 was measured by the four-point method, and it was only a little affected by the carbonization of the polyaniline coating.