Metallomesogens: enaminoketone derivatives of the 3-oxa, 3-thia- and 3-selena-butyric amides

Liquid crystalline Ni(II) and Cu(II) complexes of tetradentate ligands, enaminoketones and 3-oxa; 3-thia- and 3-selena-butyramides were synthesized and examined. The compounds show very low C ₁ symmetry resulting from the chiral donor atoms — oxygen, sulphur and selenium — incorporated in the butyric amide moiety. This chirality can be observed in NMR studies. The complexes exhibit enantiotropic as well as monotropic calamitic SmA and N phases.     

Influence of mesogenic core polarity and position of chains attachment on columnar phase stability

Series of new Ni(II) metalomesogens of triangular molecular shape and forming Col_h liquid crystalline (LC) phase were synthesised and described. Using in the molecular core the barbituric moieties that contain carbonyl or thiocarbonyl groups causes strong polarisation of the molecules and creates a permanent dipole moment μ, which was confirmed by quantum mechanical calculations. The relationship between molecular dipole moment and self-organisation of molecules into the columnar phase was considered. The position of alkyl and alkoxy chains substituted at phenyl ring that affects LC phase formation seems to be connected with planar conformation of the attached chains. These can broaden the mesogenic core and stabilise the Col_h mesophase.     

Comparative Study of Alternating Low-band-Gap Benzothiadiazole Co-oligomers

The benzothiadiazole – arylene alternating conjugated oligomers have been designed and synthesized via Suzuki coupling reaction. The structures and properties of the conjugated oligomers were characterized by ¹HNMR, ¹³CNMR, UV–vis absorption spectroscopy, photoluminescence (PL) spectroscopy. The luminescent measurements demonstrate that polybenzothiadiazoles are good chromophores able to form thin films by Langmuir-Blodgett (LB) technique, making them suitable for further applications. Also the electrical properties of obtained films confirm the good potential of these novel aryl-based π-conjugated polymers for the development of various electrical and electrochemical solid-state devices.     

Atomic-scale friction on stepped surfaces of ionic crystals

We report on high-resolution friction force microscopy on a stepped NaCl(001) surface in ultrahigh vacuum. The measurements were performed on single cleavage step edges. When blunt tips are used, friction is found to increase while scanning both up and down a step edge. With atomically sharp tips, friction still increases upwards, but it decreases and even changes sign downwards. Our observations extend previous results obtained without resolving atomic features and are associated with the competition between the Schw?bel barrier and the asymmetric potential well accompanying the step edges.     

Antimicrobial Activity and Barrier Properties against UV Radiation of Alkaline and Enzymatically Treated Linen Woven Fabrics Coated with Inorganic Hybrid Material

One of the directions of development in the textiles industry is the search for new technologies for producing modern multifunctional products. New solutions are sought to obtain materials that will protect humans against the harmful effects of the environment, including such factors as the activity of microorganisms and UV radiation. Products made of natural cellulose fibers are often used. In the case of this type of material, it is very important to perform appropriate pretreatment before subsequent technological processes. This treatment has the aim of removing impurities from the surface of the fibers, which results in the improvement of sorption properties and adhesion, leading directly to the better penetration of dyes and chemical modifiers into the structure of the materials. In this work, linen fabrics were subjected to a new, innovative treatment being a combination of bio-pretreatment using laccase from Cerrena unicolor and modification with CuO-SiO₂ hybrid oxide microparticles by a dip-coating method. To compare the effect of alkaline or enzymatic pretreatment on the microstructure of the linen woven fabrics, SEM analysis was performed. The new textile products obtained after this combined process exhibit very good antimicrobial activity against Candida albicans, significant antibacterial activity against the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus, as well as very good UV protection properties (ultraviolet protection factor (UPF) > 40). These innovative materials can be used especially for clothing or outdoor textiles for which resistance to microorganisms is required, as well as to protect people who are exposed to long-term, harmful effects of UV radiation.     

A Laboratory Study of Heterogeneous Catalysis in Ultrahigh Vacuum

A surface science experiment has been developed that can be used in both the undergraduate and graduate curriculum. Students study the mechanism of carbon monoxide oxidation using a platinum foil catalyst, and they also get hands-on experience with ultrahigh vacuum equipment. Using temperature programmed desorption, students study the desorption of carbon monoxide and oxygen from platinum foil in vacuum. The study allows students to determine that the Langmuir-Hinshelwood reaction mechanism operates in this catalytic system.     

Polymerization of vinyl chloride in the presence of modified Ziegler–Natta catalysts comprising long chain organoaluminum compounds

Polymerization of vinyl chloride in the presence of systems containing a transition metal compound/Lewis base and an organoaluminum compound of a different length of carbon chain have been carried out. The influence of the structure and the concentrations of particular components on the polymerization yield and molecular weight of the products has been determined. The polymerization of vinyl chloride proceeds according to the free radical mechanism, and the effectiveness of such types of initiators decreases with an increase in the length of the substituent chain in the organoaluminum chain. When using ethyl derivatives, the maximum degree of vinyl chloride conversion is about 75%, and for polystyryl or polyisoprenylaluminum of an average polymerization degree of 50–100, the conversion did not exceed 0.5%. The maximum polymerization degree of vinyl chloride in block copolymers containing polyisoprenyl or polystyryl units was 90–300.     

On modified Picard and Gauss—Weierstrass singular integrals

We introduce a certain modification of the Picard and Gauss—Weierstrass singular integrals and prove approximation theorems for them. Published in Ukrains’kyi Matematychnyi Zhurnal, Vol. 57, No. 11, pp. 1577–1584, November, 2005.     

1,2-O-(1-Ethylpropylidene)-α-d-glucofuranose, a low molecular mass organogelator: benzene gel formation and their thermal stabilities

Fourier transform infrared spectroscopy has demonstrated that hydrogen bonds are responsible for the aggregation of 1,2-O-(1-ethylpropylidene)-α-d-glucofuranose molecules in solid and benzene gels. The thermal stability of the studied gel is described by its melting temperature T_GS and thermal parameters. The deduced value of the gel-sol transition enthalpy is 50 kJ/mol. Viscosity is the major factor which influences the dynamics of the benzene molecules in the gels, as proved by the relaxation measurements.     

Voltammetry of Undiluted Red‐Ox Systems. Electrochemical ESR‐ and Electrochemical Impedance Spectroscopy Evidence for Formation of Ionic Liquid at Microelectrode Surface

It is believed that voltammetry of undiluted red‐ox liquids can lead to the formation of stable thin layers of ionic liquids at the microelectrode surface. Such situation was postulated for several liquids (solvents), however, so far no hard evidence supporting this expectation was obtained. By using electron spin resonance in combination with voltammetric experiments and electrochemical impedance spectroscopy we have shown that the concentration of the cation radicals at the microelectrode surface may be high (nitrobenzene) and the overall resistance of the solution abruptly drops (methanol) when the potential at the microelectrode corresponds to the wave plateau of the undiluted organic liquid. Both facts constitute a good evidence for the formation of microlayers of ionic liquids at the microelectrode surface during electrolysis of undiluted red‐ox systems.