bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic uniaxiality in strained networks: A deuterium NMR investigation
Authors: Sotta Paul , Deloche Bertrand , Herz Jean
Published: March 2011

The orientational order generated in a polymer network by a uniaxial stress is probed using deuterium NMR. The experiments are performed on end‐linked polydimethylsiloxane networks. When a uniaxial force is applied, the observed NMR spectra show that the chain segments reorient uniaxially around the external force direction. This experimental fact appears as new evidence for cooperative orientational interactions between chain segments in the deformed networks.
Assembling networks for molecular electronics
Authors: Taylor D. Martin , Morgan Hywel , D'Silva Claudius
Published: March 2011

An investigation is described into the feasibility of assembling molecular networks by affinity polymerisation of avidin and bisbiotin. Preformed polymers have been spread as monolayers on a Langmuir trough and their surface behaviour characterised. Deposited monolayers have been imaged by TEM. In a parallel programme, chemisorption has been used to grow polymer chains normal to the surface of a gold substrate. Copper decoration indicates that areas as large as 200 μm × 200 μm can be grown entirely free of pinholes.
Correlations between chemical structure and chain packing in two‐ and three‐dimensional systems
Authors: Brezesinski Gerald , Förster Günter , Rettig Willi
Published: March 2011

Phosphatidylcholines (PCs) containing a branched chain fatty acid at the sn‐1 position of the glycerol backbone were characterized by calorimetric and X‐ray diffraction studies with bilayers as well as by thermodynamic studies with monolayers. Branching leads to altered thermal properties which are connected with a modified structural polymorphism. Gel phases with interdigitated chains or nonbilayer liquid‐crystalline phases could be found in dependence on the length of the side branches. The pressure‐area isotherms of the monobranched PCs were measured over a wide range of temperature. The critical temperatures Tc of the transition between the liquid‐expanded and condensed films were estimated and compared with the main transition temperatures Tm of the bulk phase. Tc was found to be either lower or higher or equal to Tm. The correlations between Tc and Tm are discussed in terms of chain packing in the two‐ and threedimensional systems.
Optical measurements of an acylated azacrown at the air‐water interface
Authors: Ducharme D. , Salesse C. , Leblanc R. M. , Meller P. , Mertesdorf C. , Ringsdorf H.
Published: March 2011

In this study, a cyclame derivative bearing four aliphatic chain substituents shows, like many amphiphiles, solid‐condensed as well as liquid‐expanded phases. In contrast to the classical amphiphiles, the onset of its phase transition is characterized by a bump‐like shape whose amplitude is a function of the compression speed. Ellipsometry which is very sensitive to the monolayer physical state changes, and fluorescence microscopy which has contributed significantly to the understanding of the phenomena occurring in the phase transition region have been used to investigate the monolayer behavior of this compound. This study shows that in the liquid‐expanded state, the film is homogeneous and remains as such until either the maximum amplitude of the bump is reached or the beginning of the plateau sets in. Thereafter, heterogeneity with formation of diamond‐like domains appears with domain sizes varying with compression speed. The formation of the domains coincides with a change in the ellipsometric zone differences. From this ellipsometric behavior, a change in the distribution of the orientation of the molecules is suggested to take place at the onset of the phase transition.
Ligand‐receptor interactions directly measured with the surface forces apparatus
Authors: Helm C. A. , Schmitt F. J. , Israelachvili J. N. , Knoll W.
Published: March 2011

Ligand‐receptor interactions give rise to very strong bonds due to perfect geometrical fit. Using the Surface Forces Apparatus we have studied the interactions between membrane‐bound biotin ligands and streptavidin receptors. We find an unusually strong short‐range binding force associated with equally specific molecular rearrangements‐both qualitatively and quantitatively unlike anything previously measured.
Interfacial recognition reactions as seen by fluorescence‐, surface plasmon‐and atomic force microscopies
Authors: Schmitt F.‐J. , Weisenhorn A. L. , Hansma P. K. , Knoll W.
Published: March 2011

We report on various microscopic investigations of the specific recognition and binding reaction between a biotinylated lipid layer and streptavidin. First, we present fluorescence microscopic evidence for the preferential adsorption of the protein to only the fluid matrix of a monolayer at the water‐air interface if the latter is compressed to the phase transition region where crystalline domains coexist with expanded phase. Surface plasmon microscopy shows that this selectivity is preserved also if the monofilm is first transferred to a solid support (but still in contract with the aqueous phase) and then exposed to a streptavidin‐containing solution. Finally, atomic force microscopic pictures taken at the monolayer‐electrolyte interface are presented that confirm this preferential binding.
“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

A 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

Investigations 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

To 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

Preliminary 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

We 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

It 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

We 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

Photoablation 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

Amphiphilic 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

Lipoteichoic 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

We 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

Langmuir‐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

The 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

An 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

Langmuir‐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

Surface/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

Flow‐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

A 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

The 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

The 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

Molecules 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

We 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

Monolayers 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

By 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

Different 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

The 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

A 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

A 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.
Anionic polymerization of dodecamethyl‐cyclohexasiloxane (D6) with lithium cryptate as a counterion
Authors: Lestel Laurence , Boileau Sylvie
Published: March 2011

A kinetic study of the anionic polymerization of dodecamethylcyclohexasiloxane (D6) has been carried out in toluene at 25°C with the cryptate Li+ + [211] as the counterion. The rate constants of propagation of D6 and of the formation of cyclic oligomers have been determined. The results are in good agreement with those reported previously for the anionic polymerization of D3 and D4 under the same conditions. The rate constants of propagation and of formation of D6 have been found to be equal to 1.1 l‐mol−1.h−1 and 0.05 h−1, respectively. In the case of the anionic polymerization of cyclosiloxanes with Li+ + [211] as the counterion, the order of reactivities of Dx as a function of × is as follows:
Synthesis and characterization of main‐chain thermotropic aromatic polyazomethines with siloxane spacers
Authors: Madec Pierre‐Jean , Pérès Richard , Maréchal Ernest
Published: March 2011

New main‐chain liquid crystal copolymers have been synthesized in the polyazomethine series from two polycondensation routes (polyhydrosilylation and polyimination). The mesogenic units are separated with siloxane spacers. The obtained copolymers have been characterized by size‐exclusion chromatography and NMR and FT‐IR spectroscopies; their mesomorphic behavior has been investigated by polarizing microscopy, differential scanning calorimetry and RX diffraction. Moreover, when the polycondensation reactions are carried out in solution or when the copolymers are kept in a solvent, we observed the formation of macrocyclic dimers, which have been isolated and characterized.
Electrocatalyzed step polymerization of 3, 6‐dibromo‐N‐alkylcarbazoles
Authors: Faïd K. , Adès D. , Chevrot C. , Siove A.
Published: March 2011

Poly (N‐alkyl‐3, 6‐carbazolediyl)s were synthesized by step polymerization of the corresponding 3, 6‐dibromo‐monomers, electrocatalyzed from a NiBr2/2.2&‐bipyridine complex in N, N dimethylacetamide. From both gel‐permeation chromatography analyses during the course of electrosynthesis and electrochemical behavior studies of the systems, it was deduced a coupling process occuring by step polymerization. Mechanism of formation of the growing chains, in homogeneous phase, is discussed. According to the proposed mechanism and to physical features, polymer chains have a well‐defined structure.
Polymer synthesis by means of germylene and stannylene
Authors: Kobayashi Shiro
Published: March 2011

Divalent group 14 metal species, a germylene(la) and a stannylene(lb), behaved as a comonomer(reductant monomer) in the copolymerization with p‐benzoquinone derivatives(oxidant monomer)(“oxidation‐reduction copolymerization”) and as an initiator for anionic monomers. The copolymerization took place without initiator at a lower temperature to give an alternating copolymer. N‐phenyl‐p‐quinoneimine also behaved as a reactive oxidant monomer toward la and lb. These species have been shown to induce the polymerization of anionically polymerizable monomers such as methyl methacrylate, methacrylonitrile, and 4‐vinylpyridine. Based on the mechanistic examination of the polymerization, a new alternating copolymerization between la and 2‐cyclohexene‐l‐one has been developed to produce a copolymer having a metal‐enolate structure, which involves the oxidation‐reduction process during the copolymerization.
Reactions under mixing in viscous polymeric media
Authors: Blumen A. , Sokolov I. M.
Published: March 2011

Mixing of viscous liquids is of common occurence in polymer technology. We consider the effects of mixing on the simplest bimolecular reaction A+B→O. Under mixing often lamellar arrays of striations of the A and B reactants are formed. The structure of these arrays and the thinning of the striations during mixing determine the kinetics of the reaction. We consider both a premixed situation (where the reaction is diffusion‐controlled) and also a situation where mixing and reaction take place simultaneously.
Membranes of high performance polymers
Authors: Haubs M. , Herold F. , Krieg C. , Meyer‐Blumenroth U. , Schneider J. , Wagener R. , Wildhardt J.
Published: March 2011

Membranes, as part of technical processes, are gaining more importance in areas such as chemicals, biotechnology or waste‐water treatment. The use of high performance polymers as membrane materials offers unique combinations of properties and allows new applications. Three different approaches towards membrane fabrication from high performance polymers such as polyaryls or polyaramides are discussed, i. e. maintenance of the polymer structure during processing and synthesis of better soluble structures via either polymer‐analogous reactions or tailor‐made copolymers. Examples of chemistry, property profiles and potential applications are given.
Gas permeability of cardo‐poly(ether‐ether‐ketone) and poly(phenylene sulfide)
Authors: Engelmann I. , Schultze J. D. , Böhning M. , Springer J.
Published: March 2011

The gas permeability and sorption of CO2 and N2O was measured on cardo‐poly(ether‐ether‐ketone) (C‐PEEK) and poly(phenylene sulfide) (PPS) at 298 K. The results are discussed on the basis of the dual‐mode model. Results obtained from measurements at 308 K are compared with literature data of poly(phenylene oxide) (PPO), poly(sulfone) (PSU) and poly(carbonate) (PC). While C‐PEEK shows similar transport properties as PC and PSU, the values of PPS are distinctly lower. The solubility of CO2 in the various polymers as well as the correlation of the permeability coefficients of the same polymers for He, Ar, CO2, N2, and CH4 with the kinetic molecular diameter of the gases indicate a simple relation of the transport properties with the polymer density.
Dye doped polymer films: From supramolecular photochemistry to the molecular computer
Authors: Wild Urs P. , Renn Alois
Published: March 2011

A new concept of “molecular computing” based on spectral hole‐burning, the interaction of molecular energy levels with an externally applied electric field and the interferometric properties of holography is presented. The molecular processor introduced here relies on the spectroscopic properties of a dye doped polymer film, which simultaneously can be used for image recording and for parallel processing of the stored information.
Nanostructured materials
Authors: Gleiter H.
Published: March 2011

In the cores of lattice defects (e.g. dislocations, grain boundaries, phase boundaries etc.) a special state of solid matter exists due to the forces (constraints) between the atoms (molecules) in the core region of the defects and the atoms (molecules) in the surrounding strained crystal lattices. These constraints result in the formation of a solid state structure characterized by a low density (typically 60 ‐ 80 % of the crystal density) and a very broad distribution of nearest neighbour spacings. It is the basic idea of Nanostructured Materials to utilize the atomic structures formed in the cores of defects to generate a new class of materials. This goal is achieved by incorporating so many defects into a (formerly perfect) crystal that about 50 vol % of the material consists of defect cores. The results of studies by means of electron microscopy, neutron and x‐ray diffraction, various types of spectroscopy and property measurements agree with these ideas. Nanostructured Materials exhibit properties that deviate (sometimes by many orders of magnitude) from the properties of crystals and glasses with the same chemical composition.
Reactive polymer blends with thermoplastic polyurethan
Authors: Rätzsch Manfred , Pionteck Jürgen , Rische Thomas
Published: March 2011

The paper presents the concept of reactive coupling of thermoplastics and describes the technological preconditions and the present state of development. The examples of developments of blends of thermoplastic polyurethan (TPU), and polyethylene terephthalate (PET) serve to show that different mechanisms of reactive coupling of the blend components permit to produce high‐quality blends.
Blockcopolymers with electrically conductive microphases morphology, conductivity and crystal structure
Authors: Kempf S. , Gronski W.
Published: March 2011

By synthesis of TCNQ radical anion salts of poly(1,4‐butadiene‐b‐4‐vinylpyridine)(B4VP) blockcopolymers and subsequent doping with neutral TCNQ filmforming electrically conductive materials of good mechanical stability were obtained. The improved properties are achieved either by incorporation of butadiene microparticles in a coherent conductive P4VP phase or by generation of a percolating electrically conductive crystalline micronetwork embedded in a continous butadiene phase. In comparison to the homopolymers the resistance to oxidation is enhanced.
Molding plateable micropatterns of electrically insulating and electrically conducting poly(methyl methacrylate)s by the LIGA technique
Authors: Harmening M. , Bacher W. , Menz W.
Published: March 2011

A new process of molding directly plateable molded plastic pieces has been developed for the mass fabrication of metal micropatterns of any shape by the LIGA‐technique. In this process, electrically insulating micropatterns of poly(methyl methacrylate) are molded on the surface of an electrically conducting poly(methyl methacrylate) composite. The composite is made of a methyl methacrylate casting resin. In the development process, the polymerization of casting resins was studied for various fillers and initiators. In addition, poly(methyl methacrylate)s filled with silver were subjected to studies of the electrical, thermal, and mechanical behavior of the composites as a function of the filler content.
Macromolecular engineering on the basis of the polymerization of 2‐oxazolines
Authors: Saegusa T. , Chujo Y.
Published: March 2011

Ring‐opening polymerization of 2‐methyl‐2‐oxazoline produces poly(N‐acetylethylenimine). This polymerization reaction proceeds in living mechanism under appropriate reaction conditions. The resulting polymer has high hydrophilicity and good compatibility with other organic polymers. On the basis of these characteristic properties, i.e., high hydrophilicity and the cleanness of polymerization reaction, the following three functional polymers have been explored.

1. Non‐ionic hydrogels,

2. Non‐ionic surfactants,

3. Molecular hybrid with silica gel.
Transesterification in polymer blends including polycarbonate at high temperatures
Authors: Nishi Toshio , Suzuki Takashi , Tanaka Hajime , Hayashi Takafumi
Published: March 2011

Miscibility of polycarbonate (PC)/poly (arylate) (PAr) was studied by differential scanning calorimetry (DSC), phase contrast microscopy with digital image analysis (DIA) system, FT‐IR spectroscopy, and cloud points for the PC/PAr/methylene chloride ternary systems. PC and PAr were immiscible over the whole composition range from the thermodynamical viewpoint. However, PC/PAr is homogenized by transesterification between PC and PAr at high temperatures. There is observed a competition between phase separation due to thermodynamical factor and phase dissolution due to transesterification. The pattern of the phase separation was spinodal decomposition type and the structure was successfully analysed by DIA.
Polyurethane IPN membranes
Authors: Kim Sung Chul
Published: March 2011

Hydrophilic/hydrophobic, cationic/anionic polyurethane membranes were prepared and the effect of the synthesis pressure and temperature on the morphology were evaluated. The pervaporation characteristics of the membranes for the separation of ethanol/water mixture as well as the gas separation performances in the separation of nitrogen/oxygen mixture were measured and the effect of the IPN synthesis parameters were analyzed.
Structure of valinomycin/fatty acid langmuir‐blodgett films
Authors: Howarth V. A. , Petty M. C. , Lvov Y.
Published: March 2011

We report on the structure of monolayer and multilayer Langmuir‐Blodgett films of mixtures of arachidic acid and the ionophore valinomycin. Compressibility measurements on the floating layers and low angle x‐ray diffraction experiments with multilayers indicate the possible miscibility of the two components at low concentrations of the ionophore. However, it would appear that the arachidic acid and valinomycin are insoluble in one another over most of the composition range.
Mechanisms of polymerization of methacrylate copolymers of biological interest
Authors: Carswell Trudy G. , Hill David J.T. , Kellman Raymond , Londero Daniel I. , O'Donnell James H. , Pomery Peter J. , Winzor Catherine L.
Published: March 2011

The kinetics of the free radical copolymerization of HEMA, EGDMA and TEGDA with MMA have been studied using NIR spectroscopy to follow the reduction in the total C=C concentration with time and 1H NMR to distinguish between the monofunctional and difunctional monomers. ESR measurements of the concentrations of propagating radicals during polymerization have been combined with the conversion results to derive values for the rate constants kp (propagation) and kt (termination). HEMA decreases the gel time of MMA, but the initial rate is unchanged, whereas EGDMA and TEGDA decrease the gel‐time and increase the initial rate of polymerization.
ESR applications to photochemical polymer reactions
Authors: Rånby Bengt
Published: March 2011

ESR spectroscopy combined with spin‐trapping technique is a selective and powerful method for studies of reaction mechanisms and intermediates in free radical reactions of polymer systems. The method has been applied to several problems in our research program of which three are presented in this paper. ‐ The mechanism of photo‐initiation with aromatic ketone/tert. amine and subsequent photocuring of acrylic coatings has been largely resolved. ‐ The mechanism of photocrosslinking of ethylene‐propylenediene copolymers (EPDM elastomers) studied by model compounds has been shown to involve formation of allyl radicals in the diene groups and crosslinking by allyl radical combination. ‐ The photoinitiated crosslinking of polyethylenes (LD, LLD and HD) has been studied using model compounds. It involves formation of primary alkyl and allyl radicals which crosslink the polymer by radical combination. ‐ The mechanism of photocrosslinking indicates a second order reaction, i.e. rate of crosslinking depends of the square of irradiation intensity which has been verified experimentally. This result is the basis for development of rapid crosslinking processes of technical and industrial interest.
Vibrational characterization of langmuir‐blodgett monolayers of tetra(p‐methoxyphenyl) porphine
Authors: Guhathakurta‐Ghosh U. , Aroca R.
Published: March 2011

Langmuir–Blodgett (LB) monolayers of tetra(p–methoxyphenyl)porphine (H2TMPP) have been prepared, transferred to glass slides and metal surfaces, and characterized using surface–enhanced Raman scattering (SERS). The technique of mixed monolayers (H2TMPP in a lipid matrix of arachidic acid) was used to obtain maximum enhancement in the SERS experiments.
Pyrolysis‐gas chromatography/fourier‐transform infrared spectrometry of poly(ester urethane) elastomers
Authors: Weber Daniela , Fülöp Gábor , Hummel Dieter O.
Published: March 2011

Three types of industrial poly (ester urethane) elastomers were studied by Curie–point pyrolysis–gas chromatography/Fourier–Transform infrared spectrometry (Py–GC/FTIR) with a maximum pyrolysis temperature of 973 K. The samples chosen were the Urepans 600 and 641 from Bayer and Elastollan C 78 A from BASF/Elastogran. The poly(ester urethane) elastomers are composed of three units: a polyesterdiol, a short chain diol and a diisocyanate. Py–GC/FTIR allows a rapid and unambiguous identification of the polymer chains by key fragments.
A route to quantitative 13C NMR analysis of multicomponent polyesters
Authors: Hvilsted Søren
Published: March 2011

A protocol for quantitative sequential 13C NMR analysis is developed for polyesters composed of trimethylol propane (TMP), neopentyl glycol (NPG), and adipic and isophthalic acids. TMP centred, structural models with methyl adipate and isophthalate branches in all possible combinations are synthesized and purified. A detailed 13C NMR investigation of the models unequivocally allows the identification of the TMP polyester structural sequences through the quaternary TMP carbon multiplicity. Spin‐lattice relaxation times, T1, of model quaternary TMP carbons are in the 2.3–5.2 s range, depending on the size of the specific model. This relaxation behaviour defines the experimental conditions for obtaining the quantitative assessment of all polyester polyol structural sequences based on quaternary TMP and NPG carbons. The special case dealt with here additionally centers all acid moieties between poyols in triads and thus makes quantitative determinations of all polyester constituents possible.
Segment orientation in topologically constrained networks
Authors: Sommer Jens‐Uwe , Straube Ekkehard
Published: March 2011

Using the continous Edwards–chain model the simultaneous influence of harmonic–like constraints and of a stochastic order parameter field on the segment orientation in polymer networks is investigated. The harmonic potential reduces the orientation order parameter in comparison to the value for an unconstrained freely jointed chain. This reference value is approached from below in the case of strong topological constraints. The introduction of a stochastic order parameter field enlarges the orientation but the reference value remains the upper boundary.
MC‐determination in elastomers by 1H‐NMR relaxation and 2H‐NMR spectroscopy
Authors: Simon G. , Schneider H.
Published: March 2011

We show how 1H–NMR transversal relaxation and 2H–NMR spectroscopy can be used for the determination of the number average molecular mass MC in typical elastomers at temperatures well above the glass transition temperature. MC‐results of the different NMR methods are compared among one another and with MC‐results of other common independent methods. Moreover, the NMR measurements provide a number of additional useful parameters: correlation times, portions of dangling chain ends and of sol molecules, molecular order.
Melting of isotactic polypropene in blends with atactic polypropene and isotactic poly(1‐ethylethylene)
Authors: Tampier Monika , Trafara Gundolf
Published: March 2011

The melting behaviour of isotactic polypropene (it–PP) in blends with atactic polypropene (at–PP) and isotactic poly(1–ethylethylene) (it–PB) was examined by thermal analysis. It is shown that the double melting endotherm obtained under certain experimental conditions is caused by new crystallization. In the examined blends the tendency of new crystallization depends on the composition.
The interactions of macrocyclic ethers by 13C dipole‐dipole relaxation time measurements
Authors: Erk Cakil
Published: March 2011

13C dipole–dipole relaxation time measurement studies of free and cation complexed cyclic polyethers in solution are reviewed briefly. The 13C dipole–dipole relaxation time of the macrocyclic ether backbone has been recognized to be a function of a motion of the molecular segment acting as a macrocyclic ligand site. This has been particularly investigated by NMR under extreme narrowing conditions.