Search results for "Monolayer"
showing 10 items of 584 documents
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…
Bistable Hofmann-Type FeII Spin-Crossover Two-Dimensional Polymers of 4-Alkyldisulfanylpyridine for Prospective Grafting of Monolayers on Metallic Su…
2021
Aiming at investigating the suitability of Hofmann-type two-dimensional (2D) coordination polymers {FeII(Lax)2[MII(CN)4]} to be processed as single monolayers and probed as spin crossover (SCO) junctions in spintronic devices, the synthesis and characterization of the MII derivatives (MII = Pd and Pt) with sulfur-rich axial ligands (Lax = 4-methyl- and 4-ethyl-disulfanylpyridine) have been conducted. The thermal dependence of the magnetic and calorimetric properties confirmed the occurrence of strong cooperative SCO behavior in the temperature interval of 100-225 K, featuring hysteresis loops 44 and 32.5 K/21 K wide for PtII-methyl and PtII/PdII-ethyl derivatives, while the PdII-methyl deri…
Consecutive Selective Adsorption of Pentamidine and Phosphate Biomolecules on a Self-Assembled Layer: Reversible Formation of a Chemically Selective…
1996
In situ ellipsometric film thickness measurements, FT-IR external reflectance spectroscopy, and potentiometric measurements indicated that the amphiphile pentamidine (PAM), a bisbenzamidine, associated by self-assembly with a preformed self-assembled monolayer of a mercaptoalkanoic acid on gold. The structural properties of PAM and the nature of the substrate were ideal for the formation of a densely packed monolayer. This process was fully reversible, as demonstrated by changing the pH of the surrounding medium. Thus, disassembly−reassembly occurred when the pH was cycled between 8.7 and 3. The bilayer structure, featuring a positively charged amidinium surface, was subsequently used for s…
Monolayers of Bolaform Amphiphiles: Influence of Alkyl Chain Length and Counterions
1994
We have prepared self-assembled monolayers of novel cationic bolaform amphiphiles on negatively charged substrates. Most of these amphiphiles form smooth, defect-free monolayers which can be used to reverse the substrate surface charge and thus allow subsequent adsorption of anionic molecules and construction of multilayers. Atomic force microscopy, surface force measurement, and surface plasmon spectroscopy were combined to probe the molecular orientation and ordering, mechanical properties, and surface electrical properties of the monolayers. In addition, the amphiphile aggregation behavior at an air-water interface was studied by surface tension measurement, and lyotropic phase behavior …