bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase behaviour of poly(vinyl methyl ether)‐cross‐polystyrene semi‐interpenetrating networks
Authors: Felisberti Maria Isabel , Krieger Volker , Stadler Reimund 
Published: March 2011

AbstractSemi‐interpenetrating polymer networks of varying composition are prepared by crosslinking polystyrene containing a small number of maleic anhydride groups (4.8 mol% of MA units) with hexamethylene‐diamine (HMDA) in the presence of linear poly(vinyl methyl ether) (PVME). Lightly crosslinked samples are homogeneous at room temperature and show a phase behaviour similar to uncrosslinked blends, i.e. lower critical solution temperature (LCST) behaviour. The influence of crosslinking on the phase behaviour has been studied by small angle light scattering (SALS) and turbidity measurements. The cloud point strongly depends on the heating rate. The presence of the network reduces the stable single phase region in agreement to theory. In systems showing spinodal decomposition, it is expected that some concentration fluctuations will grow more rapidly than others resulting in a separated phase system which shows high degree of connectivity with characteristic dimensions. Using temperature jump experiments, SALS can be used to estimate parameters of the phase separation kinetics and the characteristic dimensions of the phases. In temperature jump experiments into the spinodal region a maximum in the scattered light intensity is observed with time at a certain scattering vector. However, the semi‐IPN's develop no scattering maximum. This is explained by a damping of the thermodynamical dominant wavelength in spinodal decomposition in the network.
Fracto‐emission accompanying adhesive failure in a model fiber pull‐out system
Authors: Dickinson J. T. , Zhen‐Yi Ma 
Published: March 2011

AbstractFracto‐emission (FE) is the emission of particles and photons during and after fracture of materials. The observed emission includes electrons, negative and positive ions, neutral species in both ground states and in excited states, and visible photons. This emission can often serve as a sensitive probe of crack growth and may prove to be a useful tool for investigating molecular and microscopic events accompanying crack growth and for studying the details of failure modes in a variety of materials. Here, we examine photon and electron emission during failure of axially loaded stainless steel fixtures (e.g., rods) embedded in epoxy. These experimental data provide time resolved information on the sequence of events leading to interfacial fracture proceeding pullout. In addition, we examine the emissions during frictional pullout which over a large range of strain rates exhibits stick‐slip behavior. Relations of these emissions to the fracture and pullout processes are discussed.
Electron emission during deformation of polymers
Authors: Zakrevskii V. A. 
Published: March 2011

AbstractElectron emission was detected during deformation of both carbochain and heterochain polymers in vacuum. It was found that the features of emission are similar to those observed in molecular scissions under drawing of unoriented and oriented polymers. This fact indicates that there is a relationship between the fracture process and electron emission under deformation of polymers. This relationship is also obvious from the experiments with interruption of loading when electron emission during the repeated loading does not begin immediately at the moment of load application, but can be recorded only at the degree of deformation which is higher than that reached during the first loading. The interconnection between deformational electron emission and molecular scissions allowed visualization of the fracture process in the subsurface layers of polymers using an electron‐optical convertor which gives a mechanoemission image of a stretched sample. It is supposed that the deformation‐induced electron emission of polymers is caused by ionization of stressed macromolecules resulting from tunnel transitions of electrons into deep traps. During deformation, the traps are destroyed and a part of electrons escapes in vacuum.
Crazing and shear deformation of polymer alloys
Authors: Narisawa Ikuo , Kuriyama Takashi , Ojima Kennichiro 
Published: March 2011

AbstractCrazing and/or shear yielding mechanisms in multiphase polymer alloys play a critical role in toughening. The present paper describes the use of finite element models (FEM) to simulate the crazing and shear deformation behaviour around the particles embedded in brittle or ductile matrices. The FEM simulation results on the stress distribution reveal that the dilatational stress within the rubber particles is high enough to cavitate. The stability of craze growth can be reached when the compliant particle is incorporated in a brittle matrix. On the other hand, shear yielding around the particle occurs in the equator of the particle/matrix interface when the stress locally exceeds the yield stress of the matrix. This yield‐initiation stress increases with the increase in the elastic modulus and Poisson's ratio of the particles. The toughening mechanism, that cavitation occurs first followed by shear yielding to form a neck between the particles, is discussed based on the simulation results for the two‐particle model.
Some aspects of the control of physico‐mechanical properties of polymer compositions with elastomeric inclusions
Authors: Rozenberg B. A. 
Published: March 2011

AbstractThe paper reviews the author's works on the regulation of physico‐mechanical properties of polymer compositions with elastomeric inclusions. The factors, determining the modification efficiency of elastomeric inclusions in epoxy matrices, are analyzed. The regularities of the phase separation in curing system and the control of the interface interaction and morphology of epoxy polymers with elastomeric inclusions are considered.
Some monomers, oligomers and polymers with conjugated triple bonds
Authors: Giesa Reiner , Klapper Markus , Schulz Rolf C. 
Published: March 2011

AbstractIn the first part new monoaminodiacetylenes with different numbers of CH2‐groups, the formation of Perowskit‐type Mn complexes and their polymerizability are described. Symmetrical diaminodiacetylenes and some derivatives therefrom have also been prepared. The second part deals with different types of polymers with diacetylene units in the backbone. Under irradiation color formation and crosslinking take place. Well‐defined low molecular weight model compounds of polydiacetylenes is the subject of the third part. Finally rod‐like but soluble polymers with alternating p‐phenylene and acetylene units are described.
Molecular dynamics in low‐molar and polymeric ferroelectric liquid crystals
Authors: Kremer Friedrich , Vallerien Sven Uwe , Zentel Rudolf , Kapitza Heinrich 
Published: March 2011

AbstractBroadband dielectric spectroscopy covering the frequency range from 10−1 Hz to 109 Hz was employed to study the molecular dynamics in low‐molar and polymeric ferrroelectric liquid crystals. At frequencies below 106 Hz the ferroelectric modes, soft and Goldstone mode are observed. In the frequency regime from 106 Hz to 109 Hz a fast relaxation process is found, which is assigned to the hindered rotation of the mesogens around their long molecular axis. It turns out that the molecular dynamics is not principally different between low‐molar and polymeric systems.
High‐resolution optical spectroscopy of polymers: Molecular potentials and internal fields
Authors: Haarer D. , Kador L. 
Published: March 2011

AbstractPhotochemical hole burning is a spectroscopic method which creates, via laser irradiation at low temperatures, narrow persistent dips in the inhomogeneous absorption bands of solids which are doped with appropriate dye molecules. Especially in amorphous samples, the spectral width of these dips can be several orders of magnitude smaller than that of the total inhomogeneous bands. This does not only provide an enormous increase in spectral resolution, but in addition it allows to select very small subsets of absorbers in the sample with accidentally degenerate transition frequencies. It can be shown that by applying external fields, material parameters and molecular potentials can be probed.
ON peculiarities of the influence of oxyaromatic compounds on physico‐mechanical properties of nylons
Authors: Arzhakov M. S. , Volkov A. V. , Volynskii A. L. , Bakeyev N.Ph. 
Published: March 2011

AbstractThe physico‐mechanical properties of nylons modified by oxyaromatic compounds (OAC) have been studied. It has been shown that such modification results in an increase of the Young's modulus and glass transition temperature and in a decrease of water sorption. A noticeable improvement of the elastic properties of the modified nylons in a humid atmosphere is assigned to a shift of glass transition temperature towards higher values of humidity and moisture content. Mechanism of the OAC reinforcing action on polymers involves an increase of energy of intermolecular interaction and a decrease of kinetic mobility of macromolecules in the modified polymer system due to the formation of the strong hydrogen bonds between phenol hydroxyls of OACs and Ny‐6 amide groups in the amorphous polymer regions.
The preparation of poly(aryl ether ketones) by the use of trifluoromethanesulfonic acid
Authors: Risse Wilhelm , Sogah Dotsevi Y. , Boettcher F. Peter 
Published: March 2011

AbstractTwo synthetic routes were used for the preparation of aromatic poly(ether ketones): Friedel‐Crafts acylation and aromatic nucleophilic substitution. The first route involved the reaction of diphenyl ether and terephthalic acid dichloride in trifluoromethane‐sulfonic acid. The addition of trifluoromethanesulfonic anhydride or phosphorus pentoxide resulted in increased molecular weights. The second synthetic route involved the synthesis of an amorphous tert ‐butyl‐substituted poly(ether ketone) prepolymer. Subsequently, the tert ‐butyl groups were removed by a reversed Friedel‐Crafts alkylation reaction yielding the crystalline polymer PEEK. The dealkylation reaction was performed in trifluoromethanesulfonic acid. The addition of a tert ‐butyl group acceptor resulted in high dealkylation conversions.
Synthesis and properties of alternating copolymers of acrylics and olefins
Authors: Eisenbach Claus D. , Bülow Ulrich , Lieberth Wolfgang 
Published: March 2011

AbstractThe free radical copolymerization and terpolymerization of acrylic monomers with olefins in the presence of Lewis acid complexing agent for the acrylic monomer has been investigated. The course of the polyreaction is in agreement with the features of a radical chain growth reaction, and the polymer properties can be varied by changing the composition of the reaction mixture and the reaction conditions. The alternating copolymers are usually amorphous materials, and only the alternating ethylene/acrylonitrile copolymer can be obtained as a material of relatively high crystallinity. The degree of crystallinity can be varied through terpolymerization of complexed acrylonitrile with ethylene/propylene comonomers. The basic features of the polyreaction and the polymer structures as well as some of the physical and material properties of the copolymers have been studied.
Kinetics of curing reaction and properties of polymeric materials based on epoxy resins
Authors: Privalko V. P. , Kramarenko V.Yu. , Feinleib A. M. 
Published: March 2011

AbstractBase epoxy oligomers of Bisphenol A type were cured by aliphatic and aromatic amines, as well as by anhydride and isocyanate hardeners. The glassy networks obtained were characterized by scanning calorimetry, linear dilatometry, IR spectroscopy and electron microscopy.
Reversed micelles as matrix microreactors for chemical processing of macromolecules
Authors: Alexander V.Kabanov 
Published: March 2011

AbstractBeing solubilized in the systems of the surfactant reversed micelles (RM), the macromolecules incorporate into the inner cavity of RM, whose size can be changed by varying the surfactant hydration degree Wo, i.e. [H2O]/[Surfactant] molar ratio. The conjugates of macromolecules (protein‐protein, protein‐linear polyelectrolyte) are synthesized in RM of AOT (Aerosol OT, sodium bis[2‐ethylhexyl]sulfosuccinate) in octane. The yield critically depends on the hydration degree: the reaction does not proceed at low Wo, but at Wo exceeding threshold value (which differs for various macromolecules) the yield increases sharply and reaches 100%. Using the ultracentrifugation it was demonstrated that at Wo lower than threshold the polyelectrolyte represents a compact globule compressed by the micellar matrix in the RM inner cavity. Under these conditions there is no space for the protein in the RM, containing polyelectrolyte, and therefore reaction does not proceed. At Wo higher than threshold RM become large enough to entrap the conjugated macromolecules simultaneously. The possibility of regulation of the conjugate composition by variation of Wo (size of micellar matrix) was demonstrated. The RM are applied as universal matrix microreactors, for modification of macromolecules with water insoluble reagents and for regulation of supramacromolecular composition of oligomeric enzymes.
Synthesis and characterization of molecular ribbons
Authors: Blatter K. , Godt A. , Vogel T. , Schlüter A.‐D. 
Published: March 2011

AbstractThis paper describes a recently developed route to obtain soluble, fully characterizable and high‐molecular‐weight ladder polymers with perfect molecular structures. It is based on Poly‐Diels‐Alder ‐Additions of suitable bifunctional building blocks.
Concentration fluctuation effects for dynamics of polymer solutions
Authors: Semenov A. N. 
Published: March 2011

AbstractDynamics of concentration fluctuation in a semidilute polymer theta‐solution in the regime of entanglements is studied theoretically. A number of relaxation modes is predicted, the largest amplitude corresponding to a reptation mode with the time , where q is the wave vector, the static correlation length, R the size of a polymer coil. A mode with a “superlong” time N2q−2 is predicted for . It is shown also that fluctuations of molecular field result in a substantial decrease of macromolecular curvilinear diffusion constant. The same effect gives rise to an increase of zero‐shear viscosity of the solution; the dependence of viscosity on number of links per chain, N, is much stronger than N3 in the regime of high N.
Sol ‐ gel transition in biopolymers
Authors: Axelos M. A. V. , Kolb M. 
Published: March 2011

AbstractRheological measurements have been performed on pectin biopolymers close to the sol‐gel transition. From these measurements scaling exponents were determined independently for the viscosity, s = 0.82(5), for the elastic modulus, t = 1.93(8), for the frequency‐dependent modulus, Δ = 0.71(2), and for the relaxation times below and above the transition, vz = 2.67(12) and vz' = 2.65(9). The exponents satisfy the scaling relations predicted by the theory and their numerical values agree with those from scalar elasticity percolation.
Gelation and vitrification of epoxy resins monitored by ultrasonic measurements
Authors: Lairez D. , Durand D. , Emery J. R. 
Published: March 2011

AbstractUltrasonics measurements were performed during the cure of epoxy resins. The results show some different comportments if there is only the gelation process which passes through the frequency window of the study or if there is also a vitrification phenomenon. The last case occurs with a high glass transition temperature epoxy resin like DGEBA‐DDS. with which the increasing glass transition temperature of the resin is rapidly higher than the study temperature. The former case happens for low Tg epoxy resin like BDGE‐HMDA. But in any case the method is very sensitive to the mechanical properties evolution of the material.
Anhydride curing of epoxy resins via chain reaction
Authors: Trappe V. , Burchard W. , Steinmann B. 
Published: March 2011

AbstractIn contrast to common curing reactions, the anhydride curing of epoxies follows a living anionic chain growth. The resulting consequences of this mechanism, i.e. (1) DPn = a[Mo]/[Io], (2) first‐order kinetics and (3) Poisson chain‐length distribution were tested with the phenyl glycidyl ether/phthalic acid anhydride system, using l‐methyl imidazole. Overall agreement was found and the observed deviations could be explained with a modified Poisson process.Conformational properties of the resins were measured by static and dynamic light scattering and by viscometry. These were compared with the quantities of a corresponding branched system prepared with a mixture of phenyl glycidyl ether and bisphenol‐A diglycidyl ether. Typical deviations to smaller dimensions were observed at high molar masses as a result of increasing branching.
Relaxation of entangled polymers in melts
Authors: des Cloizeaux J. 
Published: March 2011

AbstractThe stress relaxation function of a monodisperse or polydisperse melt, and the corresponding viscosity, have been calculated in the entanglement domain by applying the Doi‐Edwards theory which relies on the reptation concept introduced by P. G. de Gennes. Though the theory has been considered as successful, the agreement with precise experiments is only qualitative, and strong anomalies remained to be explained. A new theory is presented here: it is obtained by introducing simple approximations derived from elementary but novel considerations. This theory is shown to be in good agreement with experiments on monodisperse and polydisperse melts. In particular, it explains the well‐known fact that the viscosity of a monodisperse polymer melt of molecular mass M seems to increase proportionally to M3,4 when M is large.
Continuous time simulation of transient polymer networks: Rheological properties
Authors: Biller Peter , Petruccione Francesco 
Published: March 2011

AbstractIn this work the rheological properties of a concentrated polymer solution or melt are investigated. The polymeric material is described as a transient network and the specific model is of the Yamamoto type with configuration dependent creation and loss rates. For the solution of the model a continuous time simulation approach is used which is based on the stochastic interpretation of the fundamental equations of the theory. The qualitative predictions for the rheological behaviour turn out to be very good. For a quantitative test the unknown configuration dependence of the loss rate function is extracted from experimental data as the solution of an inverse problem. The comparison of experimental data for planar elongational flow with the simulation results using the fitted loss rate function shows that the agreement is satisfactory, but not yet perfect. A possible reason for this finding is given.
Dynamic uniaxiality in strained networks: A deuterium NMR investigation
Authors: Sotta Paul , Deloche Bertrand , Herz Jean 
Published: March 2011

AbstractThe 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

AbstractAn 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

AbstractPhosphatidylcholines (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

AbstractIn 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

AbstractLigand‐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

AbstractWe 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.