Folyadékkristályok és polimerfilmek kölcsönhatása = Interaction between liquid crystals and polymer films

A folyadékkristály-polimer határfelületi kölcsönhatás vizsgálatában azt a fő gondolatot igyekeztünk követni, hogy a két rendszer egymás rendezettségét kölcsönösen befolyásolja. A folyadékkristály nemcsak passziv szerepet játszik a folyamatban, hanem képes a felület közelében elhelyezkedő polimerláncok rendezésére is. Ezzel magyaráztuk a felületi rendezettség memóriaeffektusát, a fotoorientáció kinetikájának függését a folyadékkristályos fázistól és a direktor-csúszás felgyorsulását az üvegesedési hőmérséklet közelében. Megadtuk a kölcsönhatás általános modelljét. A munkákban nagy szerepet kapott a fénnyel keltett jelenségek tanulmányozása. Vizsgáltuk a fénnyel keltett optikai anizotrópiát azo festékkel doppolt nagy-viszkozitású folyadékokban, fotoizomerizációval indukált fázisátmenetet valamint vizben oldott folyadékkristály cseppecskék cirkuláris fény hatására bekövetkező forgását. Ezeket a munkákat nemzetközi együttműködés keretében végeztük. | In the study of the interaction of liquid crystals with polymer layers we followed the idea that the two sub-systems influence mutually each others order. The liquid crystal does not play only a passive role in the process, but it is able to orient the polymer chains near the surface. With this suggestion we were able to explain the memory effect of the surface orientation, the dependence of the kinetics of photo-orientation on the liquid crystalline phase and the speeding up of director gliding in the vicinity of the glass transition temperature. We presented a general model for these processes. In the works a big attention was given to light-induced processes. We studied light-induced optical anisotropy in dye-doped high-viscosity fluids, phase transition induced by photo-isomerization and rotation of liquid-crystal droplets in water induced by circularly polarized light. This latter works were accomplished in international co-operations

Aminosavak és peptidek folyadékkromatográfiája. Királis elválasztások. = Chromatography of amino acids and peptides. Chiral separations.

Munkánk során nagyhatékonyságú folyadékkromatográfiás és kapilláris elektroforetikus módszereket fejlesztettünk különböző biológiai és gyógyszeripari szempontból fontos vegyületek (elsősorban ?-, ß- és ?-aminosavak, ß-laktámok, naftol analógok és opioid peptidek) sztereoizomerjeinek elválasztására. Vizsgáltuk a mozgófázis összetételének és hőmérsékletének, illetve különféle királis szelektorok hatását a kromatográfiás viselkedésre. Tanulmányoztuk különböző új fejlesztésű királis kolonnák elválasztóképességét, illetve vizsgáltuk a különféle királis szelektorok és a modellmolekulák közötti kölcsönhatásokat. A hőmérsékletfüggésből nyert termodinamikai adatok és a kémiai szerkezettől való függés alapján következtetést vontunk le az elválasztás mechanizmusára vonatkozóan. Feltérképeztük a molekulaszerkezet és kromatográfiás viselkedés között fennálló kapcsolatokat. Eredményeinket rangos nemzetközi folyóiratokban publikáltuk. | The goal of the present project was to develop new chromatographic and electrophoretic methods for the analysis of the stereoisomers of biologically and/or pharmaceutically important compounds (e.g. ?-, ß- and ?-amino acids, ß-lactams, naphthol analogs and opioid peptides). The effects of the mobile phase composition, temperature, and different chiral selectors on the retention have been studied. The separation efficiency of newly developed chiral stationary phases and interactions between chiral selectors and model compounds have been investigated. By variation of the chromatographic parameters, the separation of the stereoisomers has been optimized. Mechanistic aspects of the chiral recognition process have been studied with respect to the structures of the analytes. Based on variable-temperature studies it could be concluded that the enantioseparations were in most cases enthalpy-driven but entropy-driven separation was also observed. Results have been published in international journals and conferences

Study on the antioxidant activity during the formulation of biological active ingredient

Background& Aims:This study examined the antioxidant activity of different extract of parsley (Petroselinum crispum) with DPPH method. This assay is one of the most commonly used because of its simplicity and efficiency. Parsley is a widely known culinary plant and herbal medicine in Europe since ancient times. It is easy to grow and many biological activities are attributed to the flavonoids in the leaf. Biological active herbal medicines have an advantage over drugs because they are safer and cheaper. Methods: The antioxidant activities of the main flavonoid and its glycosides were measured. With previously optimized extraction procedure, the effect of particle size and extraction temperature were tested regarding the radical scavenging activity and drug content with spectrophotometric and HPLC-UV method. The antioxidant capacity of the extracts for 7 days were also investigated. Results: The aglicon possesses bigger antioxidant activity over the glycosidic forms. The scavenging activity was decreased with smaller the particle size of the dried leaves and higher temperature, but the flavonoid content was increased. Conclusion: The use of medicinal plants in the therapy is emerging. The exact dose and mode of action of the medicinal plants are still an unfolding area therefore the study on the main mode of action - the antioxidant activity – influenced by the formulation is important

The role of onium salts in the oxidation of hydrocarbons by O2 catalysed by cationic phase-transfer reagents

Experimental and theoretical evidence is presented that cationic phase-transfer catalysts promote the homolytic decomposition of hydroperoxide initiators into radicals, this being a fundamental step in the catalysis of the oxidation of hydrocarbons by O-2. Such decomposition of the model substance tert-butyl hydroperoxide (t-BHP) results in O-2, tert-butanol (90-95%) di-tert-butyl peroxide (5-10%) and traces of CO2. The stoichiometric ratio Delta[t-BHP]/Delta O-2 was found to have a value of 2, independently of the nature of the counteranion present. It is assumed that the interaction between hydroperoxide and onium cation is mainly electrostatic in nature and that its effectivity depends on the positive charge density on the onium cation, which is controlled by the nature and dimensions of the counteranion. The role of water in the decomposition of t-BHP is also elucidated

A test on the effectiveness and selectivity of three sampling methods frequently used in orthopterological field studies

To obtain unbiased data in entomological samplings the selectivity and effectiveness of methods should be known. Sweepnetting, direct search and dish trap, which are frequently used in orthopterology, were tested to get data on selectivity and effectiveness. Based on the number of collected individuals, sweepnetting was the most labour efficient, while the highest number of species was collected by direct search. Dish traps were most selective to ground-dwelling species. Sweepnetting and direct search were sensitive to grass-dwelling species. Our results underlines that none of the methods is universal, and a combination of sweepnetting and direct search provides the greatest benefits