TY  - JOUR
A1  - Reiche, Jürgen
A1  - Dietel, Reinhard
A1  - Lemmetyinen, Helge
A1  - Janietz, Dietmar
A1  - Lemmetyinen, Helge
A1  - Brehmer, Ludwig
T1  - Edge-on Langmuir-Blodgett multilayers derived from disc-shaped multiyne mesogens
N2  - Langmuir-Blodgett(LB) multilayers were prepared from disc-shaped multiyne mesogens based on amphiphilic alkyl pentakis(aryl-ethynyl)benzene ethers. The two compounds used are characterized by five hydrophobic flexible chains and one hydrophilic substituent at the terminal position of the alkoxy chain. The LB films were analysed by X-ray scattering and spectroscopic measurements. An edge-on arrangement of the two discotic pentaalkynes within Y-type bilayers with a different packing density proved to be possible for the LB films of both compounds.
Y1  - 1992
ER  - 
TY  - JOUR
A1  - Reiche, Jürgen
A1  - Pietsch, Ullrich
A1  - Fink, Hans-Peter
A1  - Lemmetyinen, Helge
T1  - A comparison fo x-ray methods for structure refinement of Langmuir-Blodgett multilayers
N2  - The possibilities and limits of structure refinement of Langmuir-Blodgett films by means of symmetrical reflection of X- rays are described using the example of a stearic acid multilayer. Three different techniques for the determiantion of the electron density profile from reflectivity data are compared; a Fourier method, a Patterson method, and model calculations. The important role of the a priori information for finding the besft structure model is outlined.
Y1  - 1992
ER  - 
TY  - JOUR
A1  - Angelova, Angelina
A1  - Reiche, Jürgen
A1  - Ionov, Radoslav
A1  - Janietz, Dietmar
A1  - Lemmetyinen, Helge
A1  - Brehmer, Ludwig
T1  - Control of the structure of Langmuir-Blodgett films of a discotic liquid crystalline compound via the subphase composition and the adjacent molecular environment
N2  - Changes of the molecular arrangenemt that can be induced by means of the LB technique in the multilayers of a disc-shaped multialkynyl amphiphile are monitored by means of small angle X-ray diffraction. Studies of the monolayers at the air-water interface reveal "edge-on" orientation of the discs. Specific effects of the counter- ions (Na+, Cd²+, Pb²+, and Ba²+) and sub-solution pH on the monolayer collapse pressure, transfer efficiency and molecular order in the multilayers are found. A correlation between the monolayer properties and the ability for formation of periodic discotic structures in the presence of divalent counterions is established. The discotic molecules retain their "edge-on" arrangement in the highly compressed transferred films with slight irregular interdigtation of the flexible wings and inclination to the substrate normal. The tilt and the inter- digitation are reduced when the discotic monolayers are deposited in alternating LB films with barium arachidate spacer layers.
Y1  - 1994
ER  - 
TY  - JOUR
A1  - Jutila, Arimati
A1  - Janietz, Dietmar
A1  - Reiche, Jürgen
A1  - Lemmetyinen, Helge
T1  - Photophysical investigation of Langmuir-Blodgett films of amphiphilic discotic penta-alkynes
N2  - Amphiphilic discotic pentakis (arylethynyl) benzene compounds 1 and 2 containing an enlarged aromatic core functioning as a chromophoric p-electron system were studied with regard to their photophysical properties within Langmuir-Blodgett (LB) films. The results obtained from steady-state absorption as well as fluorescence excitation and emission measurements will be discussed with regard to interchromophoric interactions in the LB films. Time-resolved fluorescence inves6igations revealed the formation of a ground-state complex as well as excimer formation. Thermal treatment causes irreversible destruction of the LB film structure of the discotic amphiphiles. Within droplets the reorganization of the original nematic-discotic (ND) mesophase of the bulk materials was found for the alcohol 2 as indicated by a Maltese Cross texture, whereas the acid 1 remained isotopic.
Y1  - 1995
ER  -