A. Proń

SERS spectra of poly(3-hexylthiophene) in oxidized and unoxidized states

Surface enhanced Raman scattering (SERS) is being increasingly used for the study of the structural properties of conducting polymer thin films. It is generally accepted that the enhancement process has an electromagnetic origin, arising from the excitation of surface plasmons in the metal support on which the polymer film is deposited. However, the electromagnetic enhancement is also accompanied by a chemical process, for which available experimental data are scarce. The chemical process originates from the increase in the polarizability of the molecules at the metal surface under the action of the incident radiation, which leads to the formation of new chemical bonds with the atoms of the metal support. The present work was devoted to the study of the SERS spectra of poly(3-hexylthiophene) deposited on rough Ag and Au supports by evaporating the solvent from a solution of known concentration. The experiments revealed the existence of a chemical surface effect. The results obtained show that the SERS spectra depend on the oxidizing properties of the metal surface and on the nature of the solvent. This dependence is explained by the existence of some interfacial reactions that lead to the formation of interface compounds of the type MeX (Me=Ag or Au, X=Cl or O). The SERS measurements reported here reveal an increase in the intensities of the Raman lines, accompanied by a modification of the corresponding intensity ratios, when the degree of doping is increased. It was observed for the first time by SERS spectroscopy that the doping of 3-PHT with FeCl3 leads to the appearance of a state of disorder in the structure of the macromolecular chain, as a result of steric hindrance effects.

Vibrational spectroscopic studies of the isotope effects in polyaniline

Comparative Raman spectroscopy studies of nondeuterated polyaniline and polyaniline deuterated on the ring and on the nitrogen enabled us to confirm the assignments of principal Raman modes. Spectroelectrochemical studies carried out for these two isotopically different polymers indicate the creation of two types of structures upon electrochemical doping, namely polaron lattice and bipolaronic structure.

Polyaniline based optical pH sensor

Abstract Thin layers of polyaniline are suitable to measure optically the pH in the range of 2–12 in the near infrared region. The deposition of such layers is strongly facilitated by the use of solution-processable polyaniline. Previously unconsidered hysteresis effects are observed in the titration curves. Testing the sensor layers over a period of 300xa0h and up to 500 titration cycles revealed excellent reproducibility and stability. An absorbance drift lower than 1% per day (corresponding to about 30 titration) was observed.

Thermally processable conducting polyaniline

Abstract Protonation of polyemeraldine base with aryl phosphoric acid diesters have been studied with the main goal to obtain thermally processable conducting polymers. Polyaniline protonated with aryl diesters exhibits excellent thermal properties. Since diesters plasticize polyaniline in addition to its protonation conductive blends of PANI and plasticized PVC with low (ca. 6 wt%) percolation threshold can be prepared by hot pressing.

Chemical preparation of polyaniline containing heteropolyanions

Abstract Polyaniline containing anions of phosphotungstic acid has been prepared in a one-step reaction involving oxidation of aniline with ammonium persulfate in the presence of phosphotungstic acid. The presence of heteropolyanions (so-called structural Keggin units) in the polymer has been confirmed by elemental analysis and IR spectroscopy which showed the existence of the five strongest modes of the inserted anion in addition to the features characteristic of the protonated polyaniline chain. The anions enter the polymer matrix in their highest oxidation state (all tungstens at +6 oxidation level) since EPR spectra show only one single line characteristic of the polyaniline radical with no lines attributable to the reduced form of tungsten. The obtained product seems to be an excellent candidate for application in heterogeneous catalysis involving acid-base processes because, despite the fact that it deteriorates electrically at elevated temperatures, it retains catalytically active Keggin units.

Polyaniline containing palladium — new conjugated polymer supported catalysts

Abstract Palladium can be incorporated into polyaniline (PANI) in the polyemeraldine base form via its treatment with PdCl 2 aqueous solutions containing various amounts of HCl. PANI is doped in all the cases, but the oxidation level of palladium introduced into the polymer matrix depends upon the acidity of the PdCl2 solution. After the reaction in highly acidic solutions Pd 2+ is exclusively present in the matrix, whereas upon PANI contact with the solutions of low acidity partial reduction of Pd 2+ to Pd 0 with simultaneous oxidation of the polymer takes place. PANI-Pd systems are active in the catalytic hydrogenation of 2-ethylanthraquinone. Their activity depends on preparation conditions.

Mőssbauer spectroscopy studies of polyacetylene doped with iron chloride complexes

Abstract The 57 Fe Mossbauer resonance has been applied to study polyacetylene films doped chemically and electrochemically to different doping levels. Both methods lead to the insertion of a high spin Fe III complex with Mossbauer parameters characteristic of FeCl − 4 . Degradation of [CH(FeCl 4 ) y ] x in air leads to gradual transformation of Fe III into a high spin Fe II .

Highly conductive composites of polyaniline with plasticized cellulose acetate

Abstract Highly transparent, conductive blends can be prepared from plasticized cellulose acetate and polyaniline protonated with sulphonic acids, phosphonic acids and phosphoric acid diesters. Films cast from m-cresol solution exhibit percolation threshold below 0.5 wt% and excellent mechanical properties of plasticized cellulose acetate.

Thermally processable polyaniline protonated with diphenyl phosphate — preparation and structural aspects

Polyaniline free-standing films with enhanced conductivity (65 S/cm) can be prepared by hot pressing of polyaniline protonated with diphenyl phosphate in chlorobenzene. The resulting films show high crystallinity, similar to films of camphor sulfonic acid-polyaniline cast from m-cresol.

Raman spectroscopic studies of polyaniline protonation with bis(2-ethylhexyl) hydrogen phosphate

Abstract Protonation of polyaniline with bis(2-ethylhexyl) hydrogen phosphate leads to its plastification. Plasticized polyaniline can be, in turn, thermally processed, which is very important from a technological point of view. Using UV-Vis-NIR and Raman spectroscopies we have demonstrated that plasticized polyaniline is effectively protonated with the ester. Raman studies, using different excitation lines (from blue (457.9 nm) to near-infrared (1064 nm)), of polyaniline protonated with bis(2-ethylhexyl) hydrogen phosphate are presented.