bluuebunny/crossref_metadata_2025_split huggingface dataset:
“Homodoping” strategy for building conducting Langmuir‐Blodgett films
Authors: Bourgoin J‐P , Ruaudel‐Teixier A , Vandevyver M , Roulliay M , Barraud A , Lequan M , Lequan R‐M 
Published: March 2011

AbstractA strategy leading to the formation of conducting LB films without any doping treatment is investigated. The method consists of mixing, within the same layer, semi‐amphiphilic and amphiphilic derivatives of the same electroactive nucleus (here Tetracyanoquinodimethane (TCNQ)). LB films obtained in this way with the sulphonium TCNQ salt as the semi‐amphiphilic molecule and the octadecyl TCNQ as the amphiphilic one in the molecular ratio 1 to 2, are of high optical quality. Such films show a d.c. conductivity which is almost constant with variation in the number of layers, down to one bilayer. Preliminary results obtained by changing the nature of the counterion in the semi‐amphiphilic molecule are in good agreement with those of the sulphonium TCNQ‐octadecyl TCNQ0.
Membrane: A program for simulation and analysis of x‐ray diffraction patterns of thin multilayer films
Authors: Kastowsky Manfred , Sabisch Andreas , Bradaczek Hans 
Published: March 2011

AbstractInvestigations of multibilayered films by X‐ray diffraction have successfully been applied to biological material and contributed a lot of structural information about biological membranes.Analysis of the intensity data obtained from a simple powder diffraction experiment yield the one‐dimensional electron‐density distribution normal to the membrane plane. It is however desirable to deduce the three‐dimensional molecular structure of the membrane constituents. For this purpose the program MEMBRANE was developed.The three main applications of MEMBRANE are:‐ the calculation of the one‐dimensional electron‐density distribution by Fourier transform of the diffraction pattern and deconvolution of the Q function‐ the calculation of the electron‐density projection of a three‐dimensional molecular model, generation of the bilayer‐stack electron density and generation of the theoretical diffraction pattern‐ the simulation of the effect of different experimental aspects on the bilayer‐stack electron‐density, e.g. solvent molecules, cations, number of bilayer stacks.We have applied MEMBRANE for the refinement of the three‐dimensional architecture of some simple amphiphilic molecules and also to the complex lipid anchor of bacterial lipopolysaccharides.
Electrical insulating properties of metal‐LB layers‐metal devices
Authors: Schindler T. , Scheunemann U. , Hickel W. 
Published: March 2011

AbstractTo investigate the electrical insulating properties of LB films, a metal‐insulator‐metal structure was chosen. The metals used were aluminium and gold. Fundamental issues concerning the junction geometry like a) metal surface roughness and subsequent LB film deposition and b) LB film damage by top metal electrode evaporation were treated. Current versus time (I(t), V‐const), current versus voltage (I/V) and charge versus time (Q(t)) curves of junctions were recorded using the polycondensate PK 08 as LB film material. The static capacitance of the junctions and the dielectric constant of PK 08 have been calculated with Q(t) curves.
Conducting LB films based on metal complexes of sulphur donor ligands
Authors: Taylor D. M. , Underhill A. E. , Gupta S. K. , Wainwright C. E. 
Published: March 2011

AbstractPreliminary studies are reported on the film forming characteristics of compounds such as dialkyldimethylammonium‐M (dmit)2 and dialkyldimethylammonium‐M (mnt)2 where M = Ni, Pt or Pd. All materials investigated show good monolayer behaviour and deposit readily onto evaporated aluminium or gold films. This is confirmed by surface potential and FTIR measurements. The lateral conductivity of deposited films increases by many orders of magnitude when exposed to bromine vapour.
Optical data storage in Langmuir‐Blodgett‐Kuhn multilayer assemblies of azo‐dye side chain LC‐polymers
Authors: Sawodny M. , Schmidt A. , Urban C. , Ringsdorf H. , Knoll W. 
Published: March 2011

AbstractWe describe the preparation of LB‐films of novel polymers containing azobenzene dye side chains. X‐ray refection measurements, surface‐plasmon experiments were used to determine the structure of LB‐films which had been transferred onto a substrate. Illumination with UV‐light causes trans‐cis isomerisation of the azobenzene side groups. This effect can be used for optical data storage and will be discussed in detail.
Low‐temperature plasma treatment of Langmuir‐Blodgett films from tetra(methoxy)‐tetra (octyloxy)‐phthalocyaninato‐polysiloxane and polydiethylsiloxane
Authors: Kalachev Alexei A. , Wegner Gerhard 
Published: March 2011

AbstractIt was found that under the influence of glow discharge, several processes occur in Langmuir‐Blodgett (LB) layers: etching, molecular rearrangement and introduction of new functionalities in the LB‐structure. Molecular rearrangement (“ordering” or “disordering” of molecular packing) and etching rate are dependent on plasma conditions, initial molecular order and number of LB‐layers. Etching rate shows a maximum at a given number of LB‐layers and it is assumed that the position of this maximum corresponds to the depth of the etching action of plasma.
Photoablation experiments of thin polysilane‐films prepared by the Langmuir‐Blodgett‐Kuhn technique
Authors: Sawodny M. , Embs F. , Miller R. D. , Aussenegg F. , Stumpe J. , Wegner G. , Knoll W. 
Published: March 2011

AbstractWe give a brief survey of our recent research on polysilane Langmuir‐Blodgett‐Kuhn films. Surface‐plasmon experiments, IR and flourescence‐lifetime measurements have been performed to study the complex photophysical and photochemical processes in these materials following UV irradiation. Quenching effects of the polysilane backbone and their influence on the ablation‐kinetics are discussed.
Excimer laser ablation of Langmuir‐Blodgett films
Authors: Magan J. , Lupo D. , Praß W. , Scheunemann U. , Lemoine P. , Blau W. , Hogan M. 
Published: March 2011

AbstractPhotoablation of several Langmuir‐Blodgett (LB) films on Silicon substrates was performed at the excimer laser wavelength of 248 nm. This is a fast, solvent‐free, one‐step method for structuring thin organic films. Structures were produced both by projection of a mask and also using direct writing of the laser beam, yielding feature sizes on the order of microns. Spectral analysis of the remaining material showed no change compared to the unexposed material, suggesting that no degradation has occurred. This technique appears to be viable for use in the lithography of LB films.
Order in amphiphilic polyimides: Cast and Langmuir films
Authors: Tsukruk Vladimir , Mischenko Nikolay , Scheludko Evgeniy , Tolmachev Aleksandr 
Published: March 2011

AbstractAmphiphilic polyimides with side methylene tails and various chemical structure of the backbones have been studied in the “bulk” state (cast films) and in the form of multilayered molecular films (Langmuir films) by means of calorimetry, X‐ray scattering and pressure‐area diagrams.
Monolayer investigations on the bacterial amphiphile lipoteichoic acid and on lipoteichoic acid/dipalmitoyl‐phosphatidylglycerol mixtures
Authors: Gutberlet Thomas , Markwitz Sabine , Labischinski Harald , Bradaczek Hans 
Published: March 2011

AbstractLipoteichoic acid (LTA) and mixtures of LTA with dipalmitoyldiphosphatidylglycerol (DPPG) were investigated with Langmuir‐Blodgett techniques. In spite of its large hydrophilic portion LTA formed a monolayer when spread from a chloro‐form/n‐propanol/water system. In DPPG/LTA‐mixed monolayers LTA influenced strongly the compression isotherms, indicating a stabilizing effect of LTA on DPPG monolayers. At higher concentrations of LTA phase separation was observed.
Structural temperature‐induced transitions in polar Langmuir‐Blodgett films of p‐(p‐octadecyloxyphenylazo)benzenesulfonamide
Authors: Feigin L. A. , Lvov Yu. M. , Novak V. R. , Myagkov I. V. 
Published: March 2011

AbstractWe have studied the temperature dependence of the pyroelectric coefficient, dielectric constant and spacings of polar LB‐films building from molecules of p‐(p‐octadecyloxyphenylazo)benzenesulfonamide (18‐OABS) with a large dipole moment. The films were deposited by the Langmuir‐Schaefer method. A significant pyroelectric effect in the films proved them to be polar. The periodicity of structure in films was approximately equal to the length of the molecules used. An irreversible transition at 90°C from polar to nonpolar phase has been observed in these films. At this transition the structural period of the films changes (39Å ⟹ 69Å). Also these LB‐films exhibited several structure transitions. The films did not show a single solid‐to‐liquid transition but were liquid‐crystalline. In the liquidcrystal state the films have several smectic mesophases. Transitions to the mesophases take place at 124°C (69Å ⇔︁ 63Å) and at 136°C (63Å ⇔︁ 41Å). During the transitions the structural periods of the films and the value of dielectric constant change.
Heavy ion induced desorption (HIID) mass spectrometry of Langmuir‐Blodgett films built from CD‐salts of fatty acids
Authors: Schmidt R. , Brandl D. , Schoppmann Ch. , Voit H. , Johannsmann D. , Kröhl T. , Knoll W. 
Published: March 2011

AbstractLangmuir‐Blodgett films made from cadmium salts of fatty acids have been analyzed by means of the heavy ion induced mass spectrometry in which megaelectronvolt ions are used to desorb sample specific molecules. The method is a useful tool for detecting incomplete salt formation at the subphase and the replacement of the original counter‐ion by ions from the substrate surface. The method exhibits a depth sensitivity which can be varied between 2 to 14 layers depending on the energy loss of the heavy ion.
Local control of antibody binding to hapten‐presenting interfaces: Steric and electrostatic interaction
Authors: Piepenstock Michael , Lösche Mathias , Möhwald Helmuth 
Published: March 2011

AbstractThe binding of labeled antibodies to hapten substituted monolayers at the air/water interface has been studied by means of fluorescence microscopy. Haptens with various spacer lengths between the epitope and a hydrocarbon chain, anchoring the molecule to the interface, have been synthesized. With DMPC,a unspecific binding has been shown to predominate over specific binding due to electrostatic interactions. At high surface pressures the bound antibody is detached because of steric interference with the lipid head groups. Due to a reduction of electrostatic interactions, no unspecific binding is observed to monolayers of cholesterol, which carries a small dipole moment. Mixed monolayers of cholesterol and DMPC separate into two fluid phases, with preferential antibody binding to the cholesterol‐enriched phase.
Buildup of ultrathin multilayer films by a self‐assembly process, 1 consecutive adsorption of anionic and cationic bipolar amphiphiles on charged surfaces
Authors: Decher Gero , Hong Jong‐Dal 
Published: March 2011

AbstractAn anionic and a cationic bipolar amphiphile containing rigid biphenyl cores were synthesized. The compounds were dissolved in a mixture of dimethylsulfoxide (DMSO) and water and pure water, respectively. When a solid substrate with a positively charged planar surface is immersed in the solution containing the negatively charged bipolar amphiphile, a monolayer of the amphiphile is adsorbed and due to its bipolar structure the surface charge is reversed. After rinsing in pure water the substrate is immersed in the solution containing the positively charged bipolar amphiphile. Again a monolayer is adsorbed but now the original surface charge is restored. By repeating both steps in a cyclic fashion alternating multilayer assemblies of both compounds are obtained. It is demonstrated that multilayer films, composed of at least 35 consecutively alternating layers, which corresponds to a total film thickness of 170 nm can be assembled.
Crystallization of isotactic poly(methylmethacrylate) in monolayers and thin films
Authors: Brinkhuis R. H. G. , Schouten A. J. 
Published: March 2011

AbstractLangmuir‐Blodgett monolayers of isotactic PMMA exhibit a pressure‐induced transition upon compression, that can be described in terms of a two‐dimensional crystallization process, analogous to a normal melt crystallization.These water surface crystallized monolayers can be used to prepare highly crystalline thin films of isotactic PMMA with tailor‐made orientational characteristics.
Polysiloxanes at the air/water interface and after transfer onto substrates
Authors: Kalachev Alexei A. , Litvinov Victor M. , Wegner Gerhard 
Published: March 2011

AbstractSurface/area isotherms, surface potential measurements and FT‐IR data suggest that polydimethylsiloxane (PDMS) forms an uniform layer at the air/water interface, where each oxygen atom of PDMS is in contact with water and the specific area corresponds ca. 20 Å2 per monomeric unit. Under compression the PDMS‐layer is reversibly folded from 18 to 5 Å2/unit and then collapses irreversibly. Collapse pressure and specific area are dependent on the subphase temperature. Polydiethyl‐siloxane (PDES) forms, after spreading, an island‐like structure which is integrated under compression. Thickness and structure of this PDES‐film is a result of several simultaneous processes: spreading of the molecules, evaporation of solvent and PDES‐mesophase formation. The resulting structure is specifically oriented and is obviously different from the PDES‐bulk in its normal mesophase.
Experiments on convective in‐plane orientation of monolayers
Authors: Kurthen Christof , Nitsch Walter , Stöckelhuber Werner 
Published: March 2011

AbstractFlow‐compressed monolayers of stiff rod‐like polymers (poly‐glutamates) mixed with oleophilic tracer dyes showed significant in‐plane dichroism of dye absorption at the water surface, indicating lateral ordering of polyglutamate‐rods more or less “perpendicular” to flow direction. During LB‐deposition the lateral orientation of dye‐ and polymer‐molecules was maintained, in‐plane orientation of the LB‐film was thus depending on substrate‐orientation relative to flow‐direction. Identical monolayers compressed in a regular Langmuir‐trough (with moving barrier) showed no large‐scale ordering at the water surface, but during film‐transfer polymer matrix and dye were oriented in dipping direction, irrespective of substrate orientation relative to compression direction.
A new liquid surface neutron reflectometer and its application to the study of DPPC in a monolayer at the air/water interface
Authors: Vaknin D. , Kjaer K. , Als‐Nielsen J. , Lösche M. 
Published: March 2011

AbstractA constant wavelength neutron reflectometer is described. Using this reflectometer, the neutron reflectivities from phosphatidylcholine monolayers in the highly condensed LC phase on ultra pure H2O and D2O have been measured on a Wilhelmy film balance. The neutron reflectivities have been carefully compared with those obtained by the X‐ray method applied to the same monolayer under similar conditions. A new approach to analyzing a combined set of data composed of X‐ray and neutron reflectivities has been used. From the analysis it is concluded that despite their limited qz range neutron reflectivities are as essential as X‐ray reflectivities for the unique determination of the monolayer structure.
Ellipsometric studies of behenic acid at the air‐water interface
Authors: Paudler Michaela , Ruths Jens , Alberti Bernhard , Riegler Hans 
Published: March 2011

AbstractThe rich phase behaviour of monolayers of behenic acid (=docosanoic acid) has been analyzed by null ellipsometry in isothermic and isobaric measurements. By using structural data known from x‐ray measurements the anisotropy and refractive indices in the vicinity of the S‐CS phase transition have been calculated with a minimum of model assumptions. The calculated values are: nsx=1.47. ncsx=1.48. nsz=1.54. ncsz=1.55. and anisotropy γ=nx/nz ≈︁0.95. It is also shown that ellipsometry is a very sensitive and convenient method of detecting phase transitions. Its value for quantifying the roughness of the monolayer in the close vicinity of phase transitions due to thickness and density fluctuations is shown by the measurement of the parabolic intensity variations of the ellipsometric angle δΔ. The intensity minimum at the phase transition is much wider than in the adjacent homogeneous phases.
Fluorescence studies of hydrophobically‐modified poly(N‐isopropylacrylamides) or how to play accordion on a liposome
Authors: Ringsdorf Helmut , Venzmer Joachim , Winnik Francoise M. 
Published: March 2011

AbstractThe coil/globule transition of polymers in solution is a favourite topic of discussion among polymer theoreticians. Here, this phenomenon is used to play a “molecular accordion” built with a thermosensitive polymer anchored to liposomes, a tune which mimics a natural process occuring in cell membranes.
From monomolecular films to bulk liquid crystals
Authors: Rapp Bertram , Eberhardt Mathias , Gruler Hans 
Published: March 2011

AbstractMolecules forming thermotropic liquid crystal bulk phases, were investigated at the air‐water interface. With nematic and smectic substances, compression of the film resulted in an increase of the lateral pressure, provided the molecules had an amphiphilic character. Two types of π‐A‐diagrams were found for areas below a threshold value: (i) A single coexistence region (constant pressure at different areas) is obtained for molecules forming nematic liquid crystal bulk phases. The original monomolecular film grew in the third dimension to form a nematic liquid crystal at the interface. (ii) The π‐A‐diagram showed several coexistence regions with constant pressures if the molecules had the capacity to form smectic bulk phases. The “collapses” were at areas in the relation 1 : 1/2 : 1/3 etc. suggesting that smectic layers have been formed. The aqueous subphase is found to make a large contribution to the latent heat. The initial layer (together with the subphase) is found to be of lower symmetry than the upper layer(s). The transition is first order at low temperature (< 30°C) and second order at high temperatures. Evidences are given for a smectic Shubnikov phase where the layer‐to‐layer material flow is concentrated in flux lines.
Growth of anisotropic domains in a Langmuir monolayer
Authors: Muller Pierre , Gallet François 
Published: March 2011

AbstractWe studied the growth of solid anisotropic domains in a monolayer made of pure NBD‐stearic acid spread on water. These domains have a needle‐like shape. We found that the growth process is limited by the interface kinetics, and not by the diffusion of impurities. Moreover the longitudinal growth velocity of these needles is simply proportional to the overpressure, as for a rough interface. No such law was found for the width of the needles.
Polymorphic domains in monolayers of isomeric triple‐chain phospholipids
Authors: Dietrich A. , Möhwald H. , Brezesinski G. 
Published: March 2011

AbstractMonolayers of two isomeric branched chain phosphatidyl cholines at the air/water interface have been studied by means of fluorescence microscopy. The lipids differ in the position of the branched chain at the glycerol backbone and carry three chains per headgroup of almost equal length. Most qualitative features of the compression isotherms are similar except a difference of 4 Å2/molecule in the minimum molecular area at high lateral pressures. This indicates a more condensed solid phase of compound C2 and is also reflected in the shapes of domains observed in the LE/LC phase coexistence range: domains with sharp edges and a mostly hexagonal shape are formed. On the other hand, the compound C1 with a larger limiting molecular area exhibits a smooth domain boundary and a shape instability as theoretically predicted.
J‐aggregates prepared by adsorption at monolayer/water interfaces
Authors: Kirstein S. , Möhwald H. 
Published: March 2011

AbstractBy adsorption of anionic cyanine dyes at positivly charged lipid monolayers large J‐aggregates are formed. Absorption and fluorescence spectra are measured at the air/water interface during the crystallization process. The influence of the lipid/dye interaction on the aggregate structure is studied for two different systems. It is shown that the aggregate structure can be improved by growing crystals from a seed.
Recent studies on radical polymerization
Authors: Farina Mario , Di Silvestro Giuseppe , Sozzani Piero , Yuan Cui Ming 
Published: March 2011

AbstractDifferent aspects of radical polymerization have been investigated in the author&s laboratory.1) Radical oligomerization has been studied by GC‐MS and some kinetic parameters obtained in this way (chain transfer and reinitiation constants, reactivity ratios) compared with the results of classical experiments.2) Star‐shaped polymers have been obtained by using a series of polyfunctional chain transfer agents; the experimental results agree very well with the theoretical expectations. 3) A reexamination of the copolymerization equation showed that the steady‐state assumption is not a necessary condition for the kinetic derivation and that all approaches are conceptually equivalent. 4) The structure and the 2D NMR spectra of hemiisotactic polypropylene obtained by radical inclusion polymerization are discussed.
New processes and designed polymers by cationic techniques
Authors: Kennedy Joseph P. 
Published: March 2011

AbstractThe most important recent development in cationic polymerizations is the emergence of living polymerizations leading to a variety of new potentially useful well‐defined macromolecules under conventional laboratory conditions. Three requirements have to coexist for living carbocationic polymerization to occur: Controlled initiation controlled chain‐transferless propagation and controlled (quasiliving) termination. The first part of this presentation will briefly discuss the road to these three key requirements. The second part will concern practical consequences and select systems. The synthesis of narrow‐molecular‐weight‐distribution (M̄w/M̄n = 1.1 ‐ 1.3) tert‐chlorine telechelic polyisobutylenes over a wide molecular weight range (M̄n from ∼1000 to ∼125, 000 g/mole) will be outlined together with recent work on aromatic olefins, e.g., styrene, tert‐butylstyrene and p‐chlorostyrene. These developments led to the combination of these living systems for the synthesis of block copolymers by sequential monomer addition. Tri‐ or higher block copolymers comprising glassy outer segments and rubbery inner segments, for example, poly(styrene‐b‐isobutylene‐b‐styrene, poly(p‐chlorostyrene‐b‐isobutylene‐b‐p‐chlorostyrene), have been prepared. These new thermoplastic elastomers exhibit phase‐separated microstructures and an interesting combination of physical‐mechanical properties.
A novel high‐vacuum and variable‐temperature stopped‐flow device for high‐purity polymerization kinetics
Authors: Villesange M. , Rives A. , Bunel C. , Vairon J‐.P. , Froeyen M. , van Beylen M. , Persoons A. 
Published: March 2011

AbstractA one‐block all‐glass custom‐designed stopped‐flow instrument is presented. It can be filled under high vacuum with purified reagents stored under vacuum and works over a wide temperature range. Preliminary observations, obtained with this instrument, on the styrene‐triflic acid cationic polymerization system, are reported.
Stereochemical behavior of oxirane and bioxirane in their polymerizations initiated with an organozinc complex having chair‐type structure
Authors: Tsuruta Teiji 
Published: March 2011

AbstractA well‐defined organozinc complex, [MeOCH2CH(Me)OZn‐OCH(Me)CH2OMe]2[EtZnOCH(Me)CH2OMe]2 ([Zn‐MP]2, 2), is a very unique and versatile initiator for polymerization of oxirane and bioxirane. [Zn‐MP]2, 2 induced “pure” isospecific polymerization of tert‐butylethylene oxide. The two to two complex, however, became a syndiospecific initiator for cis‐α, β‐disubstituted oxirane. Regioselective nature of [ZnMP]2, 2 complex against bioxirane made it possible to prepare a soluble polyether having pendant oxirane rings.