Monolayers of amphiphilic molecules at interface provide a unique system for understanding the thermodynamic and rheological properties of quasi two-dimensional systems. They are also an excellent model accessible for studying cell membranes. The feature of longrange organization of molecular tilt azimuth in monolayers at the air/water interface is one of the most interesting findings over the past two decades, which leads to the formation rich and defined textures. By observing the changes in these textures, the transitions between tilted monolayer phases can be detected. We study the boojum and stripe textures formed in the liquid-condensed phase of pentadecanoic acid (PDA) monolayers at the air/water interface and find that they can be preserved after being transferred to glass substrates at low dipping speeds at a temperature lower than the room temperature. Frictional force microscopy confirms the long-range tilt order in the transferred boojums and stripes of PDA, implying the interaction of the PDA molecules with the glass surface does not change the tilt order. Polymerized stripe textures of pentacosadiynoic acid (PCA) monolayers can also be transferred onto solid substrates. Atomic force microscopy shows that the PCA stripe textures represent the regular variations of molecular packing densities in PCA monolayers. Furthermore, we find that the molecular orientation and packing density changes in monolayers can induce the local order of nematic liquid crystals. Due to the longrange orientation correlation of nematic liquid crystals, the boojum and stripe textures in monolayers can be observed by an optical microscope after liquid crystal optical amplification.

The formation, phase ordering, and evolution has been studied in lipid and liquid crystal (LC) colloidal aqueous mixtures as a function of LC concentration and thermal history. The lipid used was 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC) while the liquid crystal was pentylcyanobiphenyl (5CB). POPC is a naturally occurring lipid in eukaryotic cell membranes and mimics many of the properties of human cell walls. 5CB is a polar liquid crystal that exhibits a thermodynamically stable orientationally ordered (nematic) state at room temperature. Colloidal dispersions were made at various 5CB and POPC concentrations in water and studied via optical microscopy (phase contrast, confocal, florescence, and cross-polarizing) to probe phase order and evolution as well as by calorimetry to study phase transformations. Very large vesicles (larger than 100 micrometers) were observed to form that appear to use the phase separated 5CB droplets as scaffolds. Also, there appears a unique promotion of dye (used to image the lipid bilayers) crystallization within liquid crystal domains well above room temperature.

Šiame darbe tiriamos skystojo kristalo su integruotomis kobalto nanodalelėmis optinės savybės. Panaudotos medžiagos: skystasis kristalas 5CB (penkiakomponentis cianobifenilas) ir kobalto nanodalelės kurių dydis 10nm. Tiriami pavyzdėliai su skirtingomis kobalto koncetracijomis (0,05%, 0,092%, 1,04%) skystajame kristale. Išmatuoti sugerties ir LD intensyvumo spektrai bangų ruože nuo 250 iki 700nm. / In this work I studied optical and manetooptical features of liquid crystal (LC) with integrated magnetic particles in magnetic field. I observed three different samples of LC with cobalt nanoparticles. Samples were made of LC pentyl-cyanobifenyl (5CB) and ferromagnetic (cobalt) particles of about 10nm. Each sample has a different concentration of cobalt nanoparticles (0,05%, 0,092%, 1,04%). All observations were made with Perkin-Elmer UV-VIS-NIR lambda 19 and Jasco spectrometer at room temperature and wavelength ranges from 250 to 700nm. My results show that low magnetic field till 0,2T is required to change cobalt-LC suspension optical features. Shift to IR region a: 17nm, 28nm and 31nm depending from cobalt concentration are detected. Different magnetic field makes unequal influence to samples with various concentrations of cobalt nanoparticles. From experiment I found that increasing of magnetic field till 0,2T, it shifts the absorption line to longer wavelength. From results follows that the magnetically controlled optical characteristic is very promising for magnetically controlled LC devices and information processing.Pavel Cyganok Magnetooptical features of flexible system, nanoparticle – liquid crystal.

The process of forcibly dewetting a solid substrate from a bulk liquid so as to leave a thin residual layer on the surface is referred to as forced dewetting. This novel experimental approach helps to investigate interfacial species by minimizing the interference of the bulk liquid when coupled with spectroscopy. In this work, the scope of liquids investigating using this approach has been expanded from simple fluids to one type of complex fluid, a nematic liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB).In order to better understand the interfacial behavior of the simple fluids, water, chloroform, and n-pentane vapors were adsorbed onto omega-terminated SAM-modifed Ag (11-mercaptoundecanoic acid, 11-mercaptoundenanol, and undecanethiol) surfaces under vapor-saturated conditions. The kinetics of solvent adsorption on each of these surfaces were investigated and the thicknesses of the adsorbed layer were compared to predictions from Lifshitz theory of long-range van der Waals interactions. Although the predicted thicknesses do not match the experimental values for adsorbed films, the predicted thicknesses do match those observed experimentally using forced dewetting. The correlation between these predicted and observed thicknesses implies that residual film formation under the conditions of forced dewetting used in this laboratory is dictated by interfacial forces alone.The surface adsorption behavior of 5CB was investigated using surface-enhanced Raman spectroscopy with the aid of localized surface plasmon resonances-surface plasmon polaritron coupling. The results clearly indicate that 5CB is adsorbed to smooth Ag surface in a facial orientation with pi-d orbital interaction suggested.Finally, forced dewetting studies of bare, -NH2-temintaed SAM, and -CH3-temintaed SAM modified-SiO2 substrates from 5CB were undertaken. Residual layer thicknesses were monitored as a function of substrate velocity. The transition from the regime in which interfacial forces dictate residual layer thickness to the regime in which fluid dynamic forces dictate thickness was observed for the first time and was evaluated in terms of the average 5CB director orientation. Unlike simple fluids, 5CB has strong interfacial interactions from surface anchoring depending on the chemical nature of the substrate, which makes the residual layer thicknesses at least 100 times larger than observed in simple fluids.