V.M. Kobryanskii

Temperature evolution of electronic and lattice configurations in highly ordered trans-polyacetylene

We have studied the temperature evolution of the optical absorption and Raman scattering spectra of a trans-cis blend of “soluble” polyacetylene in a polyvinylbutyral/butanol mixture. On decreasing temperature a reversible restructuring of the electronic and lattice systems of trans-(CH)x occurs: the electronic energy gap contracts at the high rate of 0.4 meV/K, and the vibrational modes are modified. The experimental data obtained are interpreted in terms of a peculiar interaction of π-conjugated electrons with lattice fluctuations.

New dopant-solvent system for conductive PAN films production

Abstract We have offered a new pathway for preparation of the water-soluble polyaniline (PAN) using sulfoacid CF 3 -CF 2 -O-CF 2 -CF(CF 3 )-O-CF 2 -CF 2 -SO 3 H. We have found then that in the presence of this sulfoacid emeraldine base becomes soluble in the mixture of m -cresol and hexafluor- iso -propanol. High quality films were cast from this solution. Their conductivity reached 10 S/cm. For comparison, we have prepared well-known system “camphorsulfonic acid — m -cresol” with the same sample of PAN and obtained high-quality films with conductivity of ca. 200 S/cm. Some aspects of “secondary doping” concept are discussed.

Thermochromism, Raman activity, and electroabsorption in highly ordered trans-and cis-polyacetylene

Abstract We report the results of thermochromism, electroabsorption, and Raman scattering spectroscopy studies for trans-cis blend of ’soluble’ polyacetylene. We have observed that the properties of the trans and cis isomers differ dramatically: the trans isomer reveals considerably higher Raman scattering activity, electroabsorption, thermochromism, and sensitivity of vibrational modes to temperature.

Effect of storage of precursor polymer solution on the electronic and physical structure of poly-(p-phenylenevinylene)

Abstract Structure and photoluminescent properties of poly (p-phenylenevinylene) (PPV) prepared via the precursor route were investigated. The results obtained offer an assumption that the long-term storage of the precursor solutions at 0–5°C brings about formation of double bonds and methoxy groups in the polymer chain. Preparing of films from the such precursor solutions is accompanied by formation of a solid phase with highly ordered conjugated areas.

Electroabsorption spectroscopy of trans-cis blend of highly ordered polyacetylene

Abstract Electroabsorption spectra have been measured for nonoriented trans-cis blend films of highly ordered ‘soluble’ polyacetylene in the spectral range 1.3 to 2.5 eV for different temperature and probe polarization. The electroabsorption spectra follow the second derivative of the absorption spectrum except the region below the absorption edge of the trans isomer. The observed electroabsorption for the cis isomer is considerably weaker than that for the trans isomer. The non-resonant nonlinear susceptibility χ (3) (ω; ω,0,0) of the soluble’ trans -(CH): x has been estimated to be ~2×10 −11 esu.

Probing of the 2Ag state in nanopolyacetylene on the time scale from femtoseconds to milliseconds

Abstract The dynamic properties of the 2A g state in films of nanopolyacetylene have been measured using photoinduced spectroscopy and photoinduced polarimetry methods both in the transient and cw regime. The excitation density per polyacetylene nanoparticle was no more than one absorbed pump photon. Using femtosecond pulses, we evaluated the rise time (≤0.2xa0ps) and the decay time (≈1xa0ps) of the photoinduced response from the 2A g state of trans- nanopolyacetylene. The longest relaxation time ≈7xa0μs was measured at room temperature. Using picosecond pulses and a novel photoinduced polarimetry method, we have done the first measurements of the transient polarization response of a conjugated material. The observed polarization signal is associated with a small photoinduced dichroism and birefringence in the 2A g state. The decay time of the polarization signal was ≈0.3xa0ns.

Photoinduced steady-state spectroscopy of a highly stable soluble polyacetylene blend: neutral soliton states and thermal effects

Abstract We have investigated steady-state photoabsorption spectra of a soluble polyacetylene prepared by a recently devised technique. Measurements were carried out both on solutions and trans -isomerized films. We have found that photoexcitation of the polyacetylene transforms only into neutral solitons in the temperature range 85–300 K. Simultaneously, photoabsorption spectra of films show thermal bands due to temperature modulation of the absorption edge.

Faraday effect in nanopolyacetylene

We measured small Faraday polarization rotation in nanopolyacetylene in a magnetic field approximately 150 Oe. We found that approximately 1% polyacetylene nanoparticles increase up to 50% the polarization rotation angle of the transparent matrix containing them when probed near and at the NPA absorption band. The rotation angles were in the range 1 - 15 (mu) rad.

Photothermal probing Ag states of trans-nanopolyacetylene in its transparency range

Dipole-forbidden states of trans-nanopolyacetylene in the near infra-red are probed by a photothermal method at room temperature. We found that light absorption at approximately 1 micrometers is four orders weaker than that corresponding to the main dipole-allowed transition.

Wavelength dependence of ultrafast and large third-order non-linear optical response of polyacetylene nanoparticles

Abstract The third-order optical non-linearity was measured in nanopolyacetylene using femtosecond optical Kerr effect technique at wavelength from 790 to 860 nm. The ultrafast non-resonant effective second-order hyperpolarizibility for single polyacetylene nanoparticle was estimated to be as large as 1.0×10 −27 esu, which corresponding to the γ c of single carbon atom contribution equals to 5.0×10 −33 esu. We ascribed the observations to the highly ordered structure of nanopolyacetylene and delocalization of the π electrons along the conjugated chains was supposed to be responsible for such properties.