EPR Spectra of Multispin Systems. Application to Poly-m-p-Aniline

In this communication we present NiceMagnetic, software for simulations and analysis of EPR spectrum and SQUID measurements. Systems of arbitrary number N of spin-only magnetic moments (S ≤ 0 and L = 0) were considered within the lines of the Heisenberg and Zeeman Hamiltonians. Effective algorithms used for the computations are discussed. This includes modified secant method adapted to calculate resonance fields with demanded precision. Finally, application of NiceMagnetic to experimental SQUID magnetization and EPR spectra of poly-m-p-aniline, one of recently synthesized high spin polymers containing unpaired electrons will be presented. As a result, exchange integral between electron and nitrogen nuclei spins (ligand hyperfine interaction) J = 6.3 × 10$\text{}^{-4}$ cm$\text{}^{-1}$ was estimated

Electrochemical and Raman spectroelectrochemical investigation of single-wall carbon nanotubes-polythiophene hybrid materials

International audienceTwo types of polythiophene-single-wall carbon nanotubes (SWCNTs) composites are comparatively studied. Composites of the first type consisted of nonmodified SWCNTs and nonmodified regioregular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT) or poly(dioctylterthiophenes) (PDOTT). Composites of the second type (Molecular composites) were obtained by grafting carboxylic acid functionalized poly(alkylthiophene)s on amine functionalized SWCNTs. In AFM images of the composites of nonfunctionalized components, individual carbon nanotubes can be easily distinguished, which are well dispersed in the polymer matrix showing fibrilar morphology. Cyclic voltammetry and Raman spectroelectrochemical experiments unequivocally show that all characteristic redox and spectroscopic features of both SWCTs and the polymer are retained in the composite material. Moreover the percolating network of SWCTs facilitates the electrochemical doping of the polymeric component. These new, solution processible materials are good candidates for printable contact electrodes in organic electronics. Molecular composites obtained by grafting show a different morphology. It is characterized by a network of fibers of diameters ranging from few dozens to few hundreds nm. Individual composite components cannot be distinguished which is an obvious consequence of the grafting reaction. Combined voltammetric and Raman spectroelectrochernical studies show that the grafting reaction lowers the electrochemical activity of the polymer component and the resulting maximum doping level is, in this case, lower than that found in composites of nonmodified components

EPR Spectra of Multispin Systems. Application to Poly-m-p-Aniline

In this communication we present NiceMagnetic, software for simulations and analysis of EPR spectrum and SQUID measurements. Systems of arbitrary number N of spin-only magnetic moments (S ≤ 0 and L = 0) were considered within the lines of the Heisenberg and Zeeman Hamiltonians. Effective algorithms used for the computations are discussed. This includes modified secant method adapted to calculate resonance fields with demanded precision. Finally, application of NiceMagnetic to experimental SQUID magnetization and EPR spectra of poly-m-p-aniline, one of recently synthesized high spin polymers containing unpaired electrons will be presented. As a result, exchange integral between electron and nitrogen nuclei spins (ligand hyperfine interaction) J = 6.3 × 10$\text{}^{-4}$ cm$\text{}^{-1}$ was estimated

Complexation of polyaniline with Lewis acids - a Mössbauer spectroscopy study

Doping with Lewis acid is a new method for improving solution processibility of conductive polyaniline. We report here detailed Mössbauer spectroscopy studies of polyaniline complexed with Lewis acids containing Mössbauer active nuclei, namely SnCl4 and FeCl3. Films of Lewis acid doped polyaniline cast from nitromethane solutions show stoichiometries of PANI(MeCln)1(CH3NO2)1 (where n = 3 or 4, Me denotes Sn or Fe and PANI denotes one aniline repeat unit), which means that both types of polyaniline nitrogens (imine and amine) participate in the complexation reaction, and one solvent molecule is introduced in the polymer matrix per one Lewis acid molecule. Mössbauer parameters of polyaniline doped with SnCl4 are consistent with hexacoordinated Sn(IV) in an environment of non-equivalent ligands. The spectrum of PANI doped with FeCl3 consists of two doublets with distinctly different Mössbauer parameters, which can be ascribed to two types of complexing sites (amine and imine nitrogens). From the temperature dependence of the isomer shift and the recoil free absorption, we have calculated the Mössbauer lattice temperature, ?m, as probed by both complexing sites, which are 83 K for amine and 126 K for imine sites

Poly(alkylthiophene) with Pendant Dianiline Groups via Postpolymerization Functionalization: Preparation, Spectroscopic, and Spectroelectrochemical Characterization

International audienc