Search results for "Nolay"
showing 10 items of 588 documents
Formation, phase composition, and transformations of Langmuir-Blodgett multi- and monolayers containing Fe
1992
Mono- and multilayers of ferric stearate were formed by the Langmuir-Blodgett technique. Thermodesorption of the hydrocarbon chains results in well defined thin oxidic films. Their reduction to Fe2+ and α-Fe was followed by conversion electron Mossbauer spectroscopy. Resonance lines can be observed even if the Fe coverage is less than one monolayer.
Self-organization of substituted azacrowns based on their discoid and amphiphilic nature
1989
Abstract Cyclame and hexacyclene derivatives, bearing four and six long-chain substituents respectively, were synthesized. They are discussed as monolayer-forming amphiphiles as well as liquid-crystalline-phase-forming thermotropic mesogens. The compounds investigated form ordered monolayers at the gas/water interface. In the monolayer the hydrophilic cyclic head group lies flat on the water surface, whereas the hydrophobic substituents are oriented perpendicularly with respect to the interface. Most derivatives fitted with aromatic substituents exhibit a solid condensed state exclusively. In contrast with this, solid condensed as well as expanded phases can be found when spreading the alip…
Two-Dimensional Assembly Formation of Hydrophobic Helical Peptides at the Air/Water Interface: Fluorescence Microscopic Study
1995
Monolayer formation of hydrophobic α-helical peptides, X-(Ala-Aib) 8 -Y (X=Boc-, HOOCCH 2 CH 2 CO-, biotinyl, biotinyl-(Sar) 3 -; Y=OMe, OBzl, OH), at the air/water interface was studied by the fluorescence microscopic method. Some peptides showed a mound in the π-A isotherm. When the monolayer containing a small amount of FITC-labeled peptide was held at the surface pressure corresponding to the top of the mound, bright and dark domains were observed by fluorescence microscopy. Domain formation was also observed by the addition of a cationic dye (DiIC 1 ) into the subphase underneath the peptide monolayer. The mound in the π-A isotherm is, therefore, ascribed to the phase transition from a…
Reaction kinetics in dense two-dimensional polymer solutions : an excimer probe study
1994
We report measurements of the time dependent reaction rate of excimer formation in two-dimensional solutions of a polymerized amphiphile with partially pyrene-labelled chains in monolayers at the air-water-interface. We find a time dependent reaction rate for excimer formation obeying a power law r(t) ∞ t -β . The exponent β has a value of 0.22±0.12. This value is consistent with β=1/4, as has been predicted for bimolecular diffusion-controlled reactions in two-dimensional polymer melts by de Gennes. The measurements demonstrate the usefulness of the excimer technique to explore polymer dynamics
Microstructure and lateral diffusion in monolayers of polymerizable amphiphiles
1989
Lipid analogue amphiphilic molecules containing polymerizable units were investigated in monolayers at the air/water interface by using film balance measurements, fluorescence microscopy, and photobleaching techniques. The polymerizable groups (diene-, diyne-, and methacrylate units) were introduced into the hydrophobic alkyl chains or into the polar head of the amphiphilic molecules. In the case of the diene- and diyne-containing compounds the polymerizable units are incorporated into the hydrophobic alkyl chains, enabling them to form a two-dimensional network. Due to the free chain flexibility of the monomers the lateral mobility was comparable to that of saturated lipid analogues and de…
Multilayer build-up of a reactive polymer with α,ω-functionalized chromophores
1997
Alternating multilayers with up to ten layers have been prepared by sequential reaction of a reactive polymer (poly[(1-methylvinyl isocyanate)-alt-(maleic anhydride)]) with α,ω-functionalized chromophores. For this purpose new chromophores were synthesized varying the length of the hydrophobic spacer. The analysis of the multilayer build-up shows that physisorption is more important than chemisorption for fixation of new polymer layers. Thus, a multilayer build-up is only possible with the shorter, more hydrophilic chromophore and not with the long hydrophobic spacer.
Epifluorescence microscopy studies of fatty acid monolayers: Domain formation induced by polymeric gegenions
1991
The monolayer behavior of long-chain fatty acids at the air/water interface on a poly(ethyleneimine) containing subphase was investigated. The interaction of the polymeric gegenions in the subphase leads to expanded states and permits the visualization of the aggregation behavior of different long-chain fatty acids via fluorescence microscopy. The monolayer morphologies and their variability were intensively studied by fluorescence microscopy. In addition, the transfer of the complexed fatty acid monolayers to solid substrates has been investigated.
Adsorption and structure formation of semiflexible polymers on spherical surfaces
2018
Abstract Rigid spheres with a short-range attractive potential are taken as a coarse-grained model of vesicles, which contain a solution of semiflexible polymers in their interior. Assuming good solvent conditions with an implicit description of the solvent, effective monomers experience bond-length and bond-angle potentials as well as excluded-volume interaction. Due to the attractive vesicle surface, phase separation occurs between a thin shell of adsorbed monomers at the surface and a rather dilute, and therefore, disordered polymer solution in the sphere interior. While at a planar attractive surface the wormlike chains would exhibit liquid crystalline (nematic and smectic) order, the c…
Photoinduced electron transfer in molecular organizates at the gas-water interface
1994
Abstract The influence of the molecular geometry is of fundamental importance for a better understanding of the photoinduced electron transfer mechanism. Because of their typical molecular structures, cyclophane rings have proved to be suitable for this purpose as electron acceptor molecules adsorbed under an amphiphile monolayer. We used a pyrene-labelled phospholipid derivative both as molecular anchor for the cyclophane ring and electron donor molecule. The co-spreading technique was used to prepare the complex monolayers. Surface pressure and surface potential measurements have indicated similar monolayer behaviour as with dimyristoylphosphatidic acid as anchor molecule, leading to the …
Isoreticular two-dimensional magnetic coordination polymers prepared through pre-synthetic ligand functionalization
2018
Chemical functionalization is a powerful approach to tailor the physical and chemical properties of two-dimensional (2D) materials, increase their processability and stability, tune their functionalities and, even, create new 2D materials. This is typically achieved through post-synthetic functionalization by anchoring molecules on the surface of an exfoliated 2D crystal, but it inevitably alters the long-range structural order of the material. Here we present a pre-synthetic approach that allows the isolation of crystalline, robust and magnetic functionalized monolayers of coordination polymers. A series of five isostructural layered magnetic coordination polymers based on Fe(ii) centres a…