Oksana Krupka

Concentration Variation of Quadratic NLO Susceptibility in PMMA-DR1 Side Chain Polymer

Chemical synthesis and concentration dependence of two second order NLO tensor components: and was studied for a side chain polymer PMMA-DR1 in thin films by optical second harmonic generation techniques. The noncentrosymmetry was created by the corona poling technique. The results show that for small chromophore concentrations the susceptibility follows linearly the density number of active chromophores, reaches a maximum, than decreases and stabilizes.

Synthesis and Investigation of a Methacrylic Monomer Based on 4-[4-(Phthalimido)-Phenylsulphamido]-2,6-Dimethoxypyrimidine

ABSTRACT New sulphamide with three non-conjugated π-electron systems were synthesized and their physicochemical properties are determined by electronic absorption, fluorescence, fluorescence excitation, phosphorescence and NMR spectroscopes. Experimental results revealed the presence of efficient intramolecular excitation energy transfer between π-electron systems in the new sulphamide and its monomer and polymers. On the basis of spectral measurements the Jablonski diagrams of the ground and first excited electronic levels of π-electron systems were constructed. Experimental results were confirmed by semiempirical calculations carried out at the PM3/CI level.

The investigation of third-order hyperpolarizabilities and susceptibilities of push-pull azobenzene polymers

To estimate the potential for third-order nonlinear optical (NLO) properties of the title azobenzene polymers, the one-photon absorption (OPA) and two-photon absorption (TPA) characterizations have been determined by configuration interaction (CI) and time-dependent Hartree-Fock (TDHF) methods, respectively. The nonlinear absorption parameters (β) and third-order susceptibilities (χ(3)) have been measured by performing the Z-scan measurements. According to the ab-initio computation results, the investigated compounds exhibit averaged (isotropic) second hyperpolarizabilities (〈γ〉) with non-zero values, implying microscopic third-order optical nonlinearity. Our computed results on TPA cross-sections (δ(ω)), third-order hyperpolarizability and susceptibility values are in accord with the experimental observations of the examined molecules.

Investigation of functionalised thin films of DNA:PEDT-PSS - electrical and optical properties

We have investigated electrical, charge transport and optical properties of functionalised DNA:PEDT-PSS thin films. Current-voltage dependencies of the samples were linear and symmetrical down to 77 K temperature. Material conductivity at room temperature was about (1-5)×10-10 ¿-1 cm-1. The thermal activation energy of the conductivity measured in the dark was about 0.033 eV near the room temperature independently on the applied bias. The weakly expressed carrier trapping was identified by the thermally stimulated current method, evidencing the fast recombination of light-generated carriers. Though, at constant light excitation a bistable photoconduction below the room temperature was identified. I.e., upon excitation by light from the spectral region ~ 500 800 nm a notable increase of the photocurrent could be observed below 140 160 K by cooling the samples. Meanwhile by heating the photosensitivity remained increased up to 230 240 K. Most probably such phenomenon could be attributed to the light-induced morphology changes of the samples.

Introducing sulfonamides moiety on the polyethylene films surface

Surface photomodification of polyethylene (PE) films by using new azidobenzenesulfonamides was carried out. The wetting angles for three liquids of different polarity (water, formamide and diiodomethane) have been studied to estimate the surface modification performed. The received values of wetting angles for determining the surface free energy γS (γ) by the Owens-Wendt and Lifshitz-van der Waals γLW, acid-base γAB by the Lifshitz-van der Waals/acid-base methods.

Photochemistry and Photophysics in Phenyloxazolones

The semi-empirical calculations carried out according with the theory of the PM3/CI level has shown, that at an irradiating of their solutions by UV-light give no possibilities of the photo-Fries reaction. The calculated values are in a good accordance with the experimental ones.