bluuebunny/crossref_metadata_2025_split huggingface dataset:
X‐ray study of LB multilayers of cadmium soaps in the vicinity of the break up point
Authors: Merle H. J. , Lvov Y. M. , Peterson I. R. 
Published: March 2011

AbstractTemperature dependent SAXS measurements were carried out on multilayers of two different salts, cadmium palmitate (hexadecanoate) and behenate (docosanoate). The pattern characteristic of layer structure disappears at a transition temperature well below the bulk melting point in both cases. Examination by means of optical microscopy shows that the LB films break up at a temperature close to this transition. Measurements in its vicinity demonstrate that over a certain temperature range just below the transition a second set of peaks arises in the diffraction pattern. During this transition region of about 3 °C width two d‐spacings for both salts were found, suggesting the simultaneous existence of two different structures for each component at the same temperature.
New amphiphilic terphenyl liquid crystals for the preparation of highly ordered ultrathin films
Authors: Decher G. , Maclennan J. , Straus M. , Sohling U. 
Published: March 2011

AbstractFour new amphiphilic liquid crystals have been synthesized, in which terphenyl was used as the mesogenic unit. In order to enable the formation of Langmuir Monolayers at the air/water‐interface, the molecules were equipped with slightly polar headgroups such as esters or a carboxylic acid group. All compounds can be transferred onto solid substrates. In addition, it is possible to prepare freely suspended films of at least one compound in the temperature range of the smectic phases. The phases of the different states, bulk, monolayer, freely suspended film, and Langmuir‐Blodgett multilayers have been investigated by means of monolayer isotherms, optical textures, differential scanning calorimetry (DSC) and small angle X‐ray scattering.
Stereocomplexation of poly(methylmethacrylates) in monolayers at the air water interface
Authors: Brinkhuis R. H. G. , Schouten A. J. 
Published: March 2011

AbstractWhen mixtures of isotactic and syndiotactic PMMA are spread on the air water interface from a non‐complexing solvent, a pressure induced transition can be observed, that is identified as a stereocomplexation between the two stereoregular components in the mixture, similar to bulk or solution processes. Analogous to the monolayer crystallization of isotactic PMMA, double helical structures are formed that can be transferred to solid substrates forming oriented thin films.
Formation and x‐ray and electron diffraction study of Cds and Pbs particles inside fatty acid matrix
Authors: Erokhin V. , Feigin L. , Ivakin G. , Klechkovskaya V. , Lvov Yu. , Stiopina N. 
Published: March 2011

AbstractLangmuir‐Blodgett films of lead and cadmium stearate were treated by exposure to H2S atmosphere. Such treatment lead to formation of CdS and PbS particles and protonation of stearic acid head‐groups. The process was studied by small‐angle X‐ray scattering. The reaction was shown to be completed after 5 hours of treatment.
Langmuir trough with enhanced performance
Authors: Ivanov G. R. , Todorov A. T. , Petrov A. G. 
Published: March 2011

AbstractHere is presented the general design and performance of a new Langmuir‐Blodgett trough. It is designed as a very precise flexible research instrument. It has a velocity dynamic speed range in excess of 1:10 000, stick‐slip free movement at velocities below 0.5×10−6 m/s, special antivibration construction, Wilhelmy type surface pressure sensor connected to a Lock‐in amplifier, micrometer precision position sensors, analogue feed back loops for the surface pressure and velocity control. It is a fully computerized instrument with a productivity of 18 measurements per second with an IBM PC/AT computer. The software has a lot of new features. For the first time we have measured such perturbational parameters for the film quality as the unevenness of the velocity and the acceleration spectra of vibrations of the barrier and the substrate holder. Unevenness as high as 48% can be measured while the amplitude of the vibrations were in the range of 10−4 m/s2 at medium speeds. These values are several times higher than the background ones.
Studies of monolayer/substrate adhesion as function of the monolayer headgroup charge: DMPE and DMPA
Authors: Engel Maria , Riegler Hans 
Published: March 2011

AbstractThe variation of the work of adhesion between lipid monolayers and a plane silicon oxide surface in a typical LB‐configuration is measured as function of the subphase pH. The adhesion energy is deduced via fluorescence microscopy from the equilibrium meniscus height. With increasing pH the negative headgroup charge of both, dimyristoylphosphatidylethanolamine (DMPE) and dimyristoylphosphatidic acid (DMPA) monolayers increases. The increasing charge of DMPE is reflected in a measured decrease of the work of adhesion at higher pH. The DMPA/SiO2 interaction is not affected by increasing headgroup charges. These results are qualitatively understood in terms of an electrostatic double layer interaction between charged surfaces. It predicts decreasing adhesion for increasing, but low surface charge densities (DMPE). whereas the adhesion is constant for high surface charge densities (DMPA).
Epifluorescence microscopy studies of fatty acid monolayers: Domain formation induced by polymeric gegenions
Authors: Chi L. F. , Johnston R. R. , Ringsdorf H. 
Published: March 2011

AbstractThe 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.
Surface‐plasmon optical characterisation of asymmetric soap films
Authors: Lawall R. , Knobloch H. , Knoll W. 
Published: March 2011

AbstractStable water films covered by arachidic acid monolayers were prepared on vertically arranged glass/Ag/SiO2‐substrates, which were partially pulled out of a film balance trough. The thickness profiles were recorded by on‐line‐measurement, using the thickness dependence of the dispersion of surface plasmon polaritons. The surface plasmon imaging technique allows for a thickness resolution of 0.2 nm and a height resolution of ca. 20 μm. Variations of these profiles as a function of the lateral pressure of the horizontal arachidate layer on the film balance were observed.For the first time Raman studies were made on asymmetric soap films. The intensity ratio of the Δηa = 2800 cm−1 to the Δηs = 2850 cm−1 line in the CH‐stretching vibration range shows a dependence on the lateral pressure in the monolayer.
The role of the hydrophobic force in bilayer adhesion and fusion
Authors: Helm C. A. , Israelachvili J. N. 
Published: March 2011

AbstractThe Surface Forces Apparatus technique was used for measuring the adhesion, deformation, and fusion of bilayers supported on mica. The technique allows the molecular rearrangements to be followed in real time during the fusion process, and the most important forces involved to be identified. The adhesion between two bilayers can be increased by two orders of magnitude if they are thinned so as to expose more hydrophobic groups. For all the bilayer systems studied a single basic fusion mechanism was found in which the bilayers do not “overcome” the short‐range repulsive steric‐hydration forces; instead, local bilayer deformations allow these repulsive forces to be “bypassed”. The results further indicate that the most important force leading to the direct fusion of bilayers is the hydrophobic attraction acting between the hydrophobic interiors of bilayers (1, 2).
Structure analysis of discotic, sanidic and ferroelectric crystals and liquid crystals using electron microscopy
Authors: Voigt‐Martin I. G. , Schumacher M. , Simon P. , Honig M. 
Published: March 2011

AbstractThree types of liquid‐crystalline materials with specific molecular structures were investigated using electron diffraction and high resolution imaging. Discotic and smectic liquid crystals were compared with the crystalline state. The superstructure of the sanidic liquid crystals showed effects in the line profiles and contour plots of the electron diffraction patterns.
Anionic vinyl polymerization and polycombination reactions induced by electron transfer reactions
Authors: Höcker Hartwig 
Published: March 2011

Abstract1, 1‐Diphenylethylene is not capable of being homopolymerized, neither by radical nor by anionic mechanism. This is due to both electronical and sterical reasons. 1, 1‐Diphenylethylene, however, is eligible to electron transfer reactions to yield the radical anion which subsequently upon combination reaction forms the dimeric dianion. On the other hand, 1, 1‐diphenylethylene may be subjected to the nucleophilic addition of strong nucleophiles such as carbanions, e.g., butyllithium or polystyryllithium. Upon this reaction, a carbanion is formed the nucleophilicity of which is significantly reduced as compared with that of the starting carbanion. Molecules containing the characteristic group of 1, 1‐diphenylethylene twice, in analogous reactions, may be subjected to polycombination reactions upon electron transfer. The polymers exhibit cyclic or linear structure depending on the molecular structure of the starting divinylidene compound. Upon reaction with carbanionic species, biscarbanions are formed which may be used as initiators for the anionic polymerization of suitable monomers. A variety of divinylidene compounds and their specific features are presented.
Living cationic polymerization of vinyl monomers: New initiators and functional polymer synthesis
Authors: Sawamoto Mitsuo , Higashimura Toshinobu 
Published: March 2011

AbstractThis paper focuses on two recent topics in living cationic polymerization of vinyl monomers, i.e.,(a) Development of new initiating systems: RCOOH/Lewis acid for vinyl ethers; CH3CH(C6H5)Cl/SnCl4/nBu4NCl for styrene.(b) Synthesis of shape‐controlled poly(vinyl ethers): Tri‐armed star polymers; Multi‐armed spherical polymers.For the RCOOH‐based systems, a generalized concept of living cationic polymerization was discussed on the basis of the effects of the counteranions (or R) and Lewis acids (ZnCl2 and EtAlCl2). The CH3CH(C6H5)Cl‐based system permitted a truly living cationic polymerization of styrene. The tri‐ and multi‐armed poly(vinyl ethers) included new amphiphilic polymers of unique topology, solubility, etc., all of which were prepared by living cationic polymerization.
Some special aspects of the copolymer synthesis with Ziegler‐Natta catalysts
Authors: Spitz R. , Pasquet V. , Joly J.‐F. 
Published: March 2011

AbstractAn approach of the special problems observed in copolymerization with Ziegler‐Natta heterogeneous catalysts is given on the basis of linear low‐density polyethylene synthesis in gas phase reaction. The reaction is controlled by chemistry and not by diffusion. The ethylene‐l‐butene copolymerization reactivity computed from the kinetic study varies with the copolymer composition, and this is due to the fact that the comonomer acts as a ligand of the active centers. The reactivities computed from NMR analysis are also not really reliable as the copolymer is a mixture of copolymers with different compositions.
Synthesis of soluble LC‐polyesters
Authors: Heitz W. 
Published: March 2011

AbstractSoluble LC polymers were synthesized with the aim to approach molecular reinforcement. Chemical modification results in a decrease of the crystallinity and an increase of the solubility. Substitution of the amide hydrogen in poly(4‐aminobenzoic acid) by a methyl group reduces the stiffness of the polymer very much, and as a result no lyotropic solutions are obtained. Poly(p‐phenylene terephthalate) with substituents on the hydroquinone or on both monomer units were synthesized. With one phenylalkyl group in the repeating unit the polyesters are crystalline with melting points > 300°C. With two substituents the polymers form in many cases amorphous anisotropic glasses at room temperature. 2‐Biphenyl is the most effective substituent with regard to increase of solubility. These polyesters form isotropic solutions in chloroform. Isotropic films obtained from these solutions become anisotropic on heating above the glass transition temperature. Films of polyester/polycarbonate blends show additivity of E‐modulus with respect to both compounds.
Kinetics of ε‐caprolactone polymerization on dialkylaluminum alkoxides
Authors: Duda Andrzej , Penczek Stanislaw 
Published: March 2011

AbstractPolymerization of ε‐caprolactone initiated with dialkylaluminum alkoxides is a living system; formation of macrocyclics is fully depressed. Polymerization initiated with diethylaluminum alkoxide and diisobutylaluminum alkoxide proceeds on monomeric (deaggregated) active species, reversibly aggregating into trimers for the former and into dimers for the latter initiator. Kinetic treatment of this system allowed to determine simultaneously the aggregation‐deaggregation equilibrium constant and the rate constant of propagation. Propagation most probably proceeds with insertion (pseudoanionically). Application of amines, complexing the growing species, allowed to break down the aggregates; polymerization became firstorder in initiator. Only secondary amines complexed strongly enough with growing species, the tertiary ones did not affect polymerization, at least up to the ratio 2:1 ([amine]/[initiator]o). Rate constants of propagation in all of the studiedo systems, whether aggregated or not, have been found to be the same and equal to 0, 04 1·mol−1·s−1 at 25° in THF solvent. This value is approx. 102 times lower than for ion‐pairs at these conditions. Moreover, rate constants are almost the same for the growing species …‐OAl(C2H5)2 and …‐OAl(i‐C4H9)2, although aggregation is very much influenced by the size of the alkyl groups.
Synthesis and reactions of telechelic polyacetals
Authors: Goethals Eric J. , De Clercq Ronny R. , De Clercq Hilde C. , Hartmann Patrick J. 
Published: March 2011

AbstractTelechelic polyacetals have been synthesized by endcapping of bifunctionally living polyacetals with tertiary amines. Bifunctionally living poly‐(1, 3‐dioxolane) (poly‐DXL) was obtained by polymerization of the cyclic acetal initiated with terephthaloyl‐bis‐triflate. Attempts to prepare well defined bifunctionally growing poly‐DXL with trifluoro‐methane sulfonic acid anhydride failed. Low molecular weight dialkyl formals containing functional groups were used as transfer agents for the polymerization of cyclic acetals to control the molecular weight of the polymer and to introduce functional endgroups. Polytelechelic hydroxy‐terminated poly‐DXL was synthesized by copolymerization of DXL and glycidol. The latter monomer reacts as comonomer through its epoxy ring and as transfer agent by its hydroxyl group.
Polymerization chemistry of the family of cyclic imino ethers
Authors: Saegusa Takeo , Aoi Keigo , Miyamoto Masatoshi , Chujo Yoshiki 
Published: March 2011

AbstractCharacteristics of the polymerization mechanisms of the family of cyclic imino ethers are described. The variety of the mechanism of propagation has been systematized on the basis of the nature of propagating species, i.e., cationic or electrophilic covalent (dipole) species. In the polymerizations of 2‐alkyl cyclic imino ethers (5‐ and 6‐membered), propagation mechanism via one of these two different species has been established, which is dependent upon the relative nucleophilic reactivities of the monomer and the counter anion derived from initiator.The polymerization of cyclic pseudoureas having a cyclic amine substituent at 2‐position proceeds in two different ways. Ionic propagation leads to the single isomerization/ring‐opening polymerization involving only the cyclic imino ether ring. On the other hand, covalent propagation gives rise to the double isomerization ring‐opening polymerization involving the two rings of cyclic imino ether and cyclic amine.Polymerization of 5‐membered cyclic iminocarbonate with a sulfonate initiator proceeds through the isomerization/ring‐opening of 2‐oxazoline ring. The same monomer was isomerized to the corresponding cyclic urethane when it was treated with benzyl bromide.
13C‐13C NMR coupling constants in substituted allylic ion‐pairs of the type occurring in anionic diene polymerization
Authors: Bywater Stanley , James Worsfold D. , Black Paul E. 
Published: March 2011

Abstract13C‐13C NMR coupling constants have been measured on the 1:1 adduct of tert‐butyllithium and butadiene, a model for the active centres in the anionic polymerization of butadiene. Solutions in three solvents in which solvation and aggregation properties differ were studied, tetrahydrofuran, diethyl ether and benzene. The 2‐methyl‐ substituted analogue, more appropriate for isoprene type systems was also converted to the potassium salt and a comparison was made of the effect of counter ion. Ion‐pair structure is discussed in terms of these measurements.
Anionic copolymerization of α‐methylstyrene and styrene: Kinetics and mechanism
Authors: Chen Fei , Ying Shengkang 
Published: March 2011

AbstractA kinetic study of copolymerization of styrene and α‐methylstyrene accompanied with depropagation, initiated by n‐butyilithium in cyclohexane with tetrahydrofuran as an additive polar solvent, has been performed. The various propagation rate constants of active species and the complexation equilibrium constants between different kinds of active species were determined. Furthermore, the reactivity ratios of two monomers with regard to monomeric, monoetherated and dietherated active species were obtained.
Synthesis of new, functionalized poly(butyl vinyl ether) oligomers and novel copolymers containing these materials
Authors: Verma A. , Nielsen A. , Bronk J. M. , McGrath J. E. , Riffle J. S. 
Published: March 2011

AbstractThis paper reports the synthesis and characterization of new, functionalized poly(alkyl vinyl ether) oligomers, and block copolymers containing poly(alkyl vinyl ether) and poly(methyl methacrylate). Using the HI/ZnI2 initiating system in nonpolar solvents (hexane, toluene) at −20°C, both monofunctional and difunctional poly(alkyl vinyl ether) oligomers of predicted molecular weights precisely terminated with aldehyde, primary hydroxyl and ester endgroups have been prepared. Novel diblock copolymers comprised of poly(methyl methacrylate) and poly(butyl vinyl ether) have also been synthesized using a combination of living cationic and living group transfer polymerization.
Cationic polymerization of isobutyl vinyl ether initiated with the system aluminium trichloride/ethyl acetate, in toluene solution
Authors: Leleu J.‐M. , Tardi M. , Polton A. , Sigwalt P. 
Published: March 2011

AbstractThe cationic polymerization of isobutyl vinyl ether initiated with the title system apparently has some features of a living polymerization (linear increase of number average molecular weight M̄n with conversion). However, evidence is given for the occurrence of a transfer reaction resulting in the increase of the number of macromolecules, and this even for relatively low molecular weights.
Cationic oligomerization of isoprene and structure of its oligomers
Authors: Audisio Guido , Priola Aldo , Rossini Alessio 
Published: March 2011

AbstractThe results obtained in a study of isoprene cationic oligomerization in the presence of some oxyacids (H2SO4, CH3SO3H, Nafion® H) are reported. Oligomers up to pentamers are obtained which were examined through gas chromatography/mass spectrometry analysis either of the reaction products or of the hydrogenated products. The structure of the dimer fraction was investigated and revealed the prevalent presence of α‐pinene and p‐cymene together with different cyclic unsaturated hydrocarbons. Only small quantities of linear dimers were found. Possible reaction mechanisms are presented.
Inverse‐microsuspension polymerization: Mechanism, kinetics and modelling
Authors: Hunkeler David 
Published: March 2011

AbstractA mechanism has been developed for the inverse‐ microsuspension polymerization of acrylic water soluble monomers. This free‐radical reaction scheme includes elementary reactions for polymerization in the aqueous and organic phases, nucleation in the monomer droplets and heterophase oligoradical precipitation. The latter being the dominant initiation process. A unimolecular termination reaction with interfacial species has also been elucidated and has been found to compete with and often dominate over the conventional biomolecular reaction. A kinetic model is developed which includes the influence of ionogenic monomers and polyelectrolytes and is able to predict the rate, molecular weight and composition data well for polymerizations of acrylamide and copolymerizations with quaternary ammonium cationic monomers. A categorization and systematic nomenclature for heterophase water‐in‐oil and oil‐in‐water polymerizations is also developed based on physical, chemical and colloidal criteria.
Thermal polymerization of arylacetylenes: A stepwise activated monomer mechanism
Authors: Sekiguchi Hikaru , Kang Hee‐Cheol , Tersac Gilles , Sillion Bernard 
Published: March 2011

AbstractKinetics of the thermal polymerization of ATR(acetylene‐terminated resin) model compounds, bisphenol A monobenzyl mono(ethynylaryl) ethers, was studied by means of GPC and the resulting oligomers were characterized by FTiR, UV, and H1 NMR techniques. It was found that monomer was consumed rapidly at first, and later slowly, yielding a mixture of dimer, low oligomers (DP ⩽ 6) and higher ones. The concentrations of every lower species remained nearly constant throughout the polymerization (except first ten minutes). In order to account for these results, a new mechanism involving the activation of monomer and its attack on the end unit of the polymer chain was proposed. This is the first example of activated monomer mechanism (a. m. mechanism) for non‐catalyzed polymerization of unsaturated monomers and, at the same time, the first example of stepwise a. m. mechanism. The structure of the resulting polymer will be discussed on the basis of this mechanism.
Copolymerization of methyl vinyl ketone with styrene in the presence of cobalt(II) nitrate
Authors: Masuda Seizo , Minagawa Keiji , Tanaka Masami , Asahi Yutaka 
Published: March 2011

AbstractCopolymerization of methyl vinyl ketone (MVK) with styrene was carried out at 50°C in the presence of cobalt(II) nitrate. The resulting monomer reactivity ratios decreased with an increasing concentration of the cobalt salt. This finding suggests that the metal salt participates in the propagation step of the copolymerization. Absolute copolymerization parameters were determined by assuming a three‐component system as free MVK (M1), MVK complexed with cobalt(II) nitrate (M2), and styrene (M3): k11/k12 = 0.184, k11/k13 = 0.235, k22/k21 = 7.18 × 10−2, k22/k23 = 6.79 × 10−4, k33/k31 = 0.380, and k33/k32 = 2.77 × 10−3, and Q2 = 19.65 and e2 = 2.83. The complexed MVK monomer is more reactive to the polymer radical with the terminal styrene unit than the free MVK. Very small values for the monomer reactivity ratios, k22/k23 and k33/k32, show the marked alternating tendency for the copolymerization of the complexed monomer with styrene. In practice, however, alternating copolymer could not be obtained because of the poor solubility of cobalt(II) nitrate.