bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption and displacement of beta‐2‐microglobulin at solid/liquid interfaces
Authors: Werner Carsten , Pilz Martin , Eberth Grit , Menning Anke , Lemke Horst‐Dieter , Eichhorn Klaus‐Jochen 
Published: March 2011

AbstractAdsorption of beta‐2‐microglobulin from aqueous solution onto unmodified and methylated silicon wafers and subsequent displacement of the small globular protein by fibrinogen were studied by spectroscopic ellipsometry, immunosorbent assays and atomic force microscopy.The results provide evidence that hydrophobicity of the substrate increases the maximum adsorbed amount of beta‐2‐microglobulin and the resistance of the adsorbed protein to displacement from the interface by competing species, respectively. Further, the dynamics of beta‐2‐microglobulin adsorption was found to induce significant differences in the degree of displacement achieved at given conditions. The observed variations in displacement behavior of adsorbed beta‐2‐microglobulin were interpreted based on information on the layer structure gained by atomic force microscopy. More compact and relatively smooth protein layers were formed on the hydrophobic surface corresponding to lower displacement by fibrinogen.
Deposition and bioadhesion properties of polymer multilayers: An in‐situ‐ATR‐FTIR‐study
Authors: Müller Martin , Rieser Theresia , Köthe Marcello , Keßler Bernd , Brissova Marcela , Lunkwitz Klaus 
Published: March 2011

AbstractThe multilayer formation by consecutive deposition of oppositely charged polyelectrolytes and the protein adsorption at the outermost layer was investigated by in‐situ attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy. For the polyelectrolyte multilayer generation the polycation / polyanion pairs poly(diallyldimethylammonium chloride) (PDADMAC) / sodium poly(maleic acid‐co‐propylene) (PMAPP) and poly(ethyleneimine) (PEI) / poly(acrylic acid) (PAC) respectively, were used. The v(CO)‐ and the vas(COO)‐band due to COOH‐ und CO−‐groups of the polyacid/polyanion as well as the v(OH) band due to desorbed water were used for monitoring the multilayer build up.By the multilayer surface modification we were able to diminuish or enhance significantly the adsorption of the model plasma protein human serum albumine (HSA), as a measure for bioadhesion, in dependence on the character of the outermost layer. This protein resistence mainly was attributed to the repulsion between the like charges of the outermost adsorbed polyanion layer (e.g. PAC) und the acidic HSA (IEP=4.7). Vice versa it could be shown, that HSA was bound by an outermost polycation layer by a factor >10 stronger compared to an outermost polyanion layer. Furthermore studies on protein adsorption at multilayers built up by the reactive polymer pair poly(butadienepoxide) (PBDE) / poly(allylamine) (PAA) were introduced.
Sorption and swelling in ultra‐thin polymer films
Authors: Meier Frank , Schiewe Beate , Esker Alan , Wegner Gerhard 
Published: March 2011

AbstractDifferent polymers were investigated with respect to the sorption of solvents and gases. Depending on the chemical nature of the polymers this sorption leads to polymer swelling. The degree of swelling D/D0 was measured utilizing Small angle X‐ray scattering (SAXS) as well as Surface plasmon resonance (SPR). From the change in film thickness after swelling in different solvents Hildebrand parameters of the polymers were determined. By crosslinking of the polymer films the degree of swelling can be controlled. In the case of ultra‐thin polyimide films a higher degree of crosslinking led to a decreased selectivity of the transport of gases through the membrane. Reptation of macromolecules was also investigated and the influence of polymer swelling in different solvents has a great influence on the selectivity and diffusion coefficient.
Relaxation study of poly[(4‐oligodimethyl‐siloxanyl)styrene]s by solid state 29Si NMR
Authors: Kawakami Yusuke 
Published: March 2011

AbstractQuantitative evaluation of spin‐lattice relaxation time (T1) was made at each silicon atom of the side chains by solid‐state 29Si NMR. It was found that the closer the silicon atoms were to main chain, the more the motion was restricted. Such local mobility of side chains was correlated to the gas permeation behavior through the polymer membrane.
The superstructure of carbosilane dendrimers with perfluorinated end groups in bulk and in solution
Authors: Stark B. , Lach C. , Frey H. , Stühn B. 
Published: March 2011

AbstractCarbosilane dendrimers of generation 1 to 4 are functionalized with perfluorinated (‐C6F13) end groups. Extending the spacer between the central Si and the first layer of branching points allows the synthesis of the 4th generation. The superstructure of these systems in bulk observed with X‐ray scattering is the result of the microphase separation between the carbosilane scaffold and the end groups. It varies with generation from a layered to a columnar structure. In dilute solution only the second generation dendrimer shows a tendency for aggregation. The others form compact particles consisting of single molecules with a core shell structure.
New polymer electrolyte membranes for low temperature fuel cells
Authors: Ennari J. , Hietala S. , Paronen M. , Sundholm F. , Walsby N. , Karjalainen M. , Serimaa R. , Lehtinen T. , Sundholm G. 
Published: March 2011

AbstractPartially fluorinated proton exchange materials were synthesised by pre‐irradiation grafting of styrene into poly(vinylidene fluoride) films with subsequent sulfonation. The grafted and sulfonated membranes, PVDF‐g‐PSSA membranes, have been studied with respect to water uptake, ion and water clustering, ion conductivity and water diffusion coefficients. Water associates with the membranes in three different ways: bound non‐freezable water, freezable bound water and freezable free water. The proton conductivity of the membrane is strongly dependent on the hydration, it decreases more rapidly than the water self diffusion with decreasing water content. Ion clusters with a Bragg distance of 25 Å form the conducting channels in the membranes.
Rheo‐optical FT‐IR spectroscopy of solid poly(acrylic acid) films
Authors: Mavinkurve Amar A. 
Published: March 2011

AbstractThis paper describes experimental work where the mechanical behaviour of relatively dry, solid poly(acrylic acid) films at room temperature was correlated with changes in hydrogen‐bonding in the polymer. Hydrogen‐bonding between the carbonyl and the hydroxyl groups was followed by FT‐IR spectroscopy while the films were stretched uniaxially. Limited mobility of the polymer below its Tg led to small but detectable changes in bonding. A characteristic strain‐hardening behaviour was observed if no bound water was detected in the samples.
The role of intermolecular interactions in the viscoelastic properties of polymer melts
Authors: Fatkullin Nail , Kimmich Rainer 
Published: March 2011

AbstractThe exact microscopic expression for the stress tensor in polymer liquids contains a tensor product of the the segment position vector with the total, intra‐ plus inter‐chain, force acting on the segment. On the other hand, the widely accepted theory of viscoelasticity of polymer melts1) is based on the assumption, that contributions from interchain interactions to the viscosity of polymer melts is negligible relative to the effectively intrachain entropic interactions. Starting from the exact Green‐Kubo formula for the viscosity, the Rouse dynamic correlation functions, and Newton's second law, we show that the intrachain assumption is inadequate. Rather, the intrachain and interchain forces acting on polymer segments cancel each other largely. The intrachain contribution therefore cannot be dominant as anticipated in the usual treatment1), or, in other words, the interchain contribution cannot be ignored. The main contribution to viscoelastic properties of polymer melts can only arise from a part of the total stress tensor as already suggested by M. Fixman based on a different argument2). It is concluded that the viscosity is of a purely interchain nature, and is determined by the tensor product of the vector connecting the centers‐of‐mass of neighboring macromolecules on the one hand, and the total force by which macromolecules interact, on the other, just in the case of simple liquids.
Steady‐state properties and dynamic behavior of polymer chains in dilute solution under elongational flow
Authors: Cifre José Ginés Hernández , De La Torre José García 
Published: March 2011

AbstractThe behavior of polymer chains in dilute solution under a steady, homogeneous elongational flow has been studied employing Brownian dynamics simulation. We first consider the dependence of polymer properties in steady state on the elongational rate, ϵ. When this rate exceeds some critical value, ϵc, the properties show a dramatic change from the values typical of the coil state to those of a stretched conformation. We describe the dependence of ϵc on chain length for different polymer/solvent conditions. Following the trajectories of individual molecules, we have characterized dynamic aspects of the coil‐stretch transition. Each chain suffer the transition after some time, ttrans, has elapsed after the flow start‐up. The values of ttrans vary remarkably from one molecule to another, and we have characterized the statistical distribution of this quantity. We also determine the kinetics of the coil‐to‐stretch process, which seems to follow a first‐order kinetics after some induction time. The dependence of the statistical and kinetic parameters on chain length and elongational rate has been determined.
The effect of polyolefin's molecule and supermolecule structures on some industrial processes
Authors: Mamedov Sheval , Kovun Ahmet , Varol Selçuk , Alekperov Velayet , Lenger Yeşi M. , Öksüz Selcen 
Published: March 2011

AbstractIn this study, the raw materials and their structural properties were analyzed in synthetic polymer pipe production by the following events: 1) The effect of extruder processes to dynamic‐mechanical properties of polyethylene (PE) and polypropylene (PP) pipes in pipe production; 2) The effect of the fiber direction on dynamic‐mechanical properties and extruder materials; 3) The heat process on welding during the pipe production and the effect of polymer structure on welding duration; 4) Physical properties and structural changes of pigmented PE and PP raw materials. 5) The relationship between dynamic‐mechanical properties of polymers with thermodynamic and kinetic concepts and effect of temperature. The results (that were) derived after several measurements are as follows: 1) The best stability properties were observed on the pipe samples which have same fibre direction. In samples with opposite and vertical fiber directions the stability properties are 30% lower. 2) The maximum dynamic‐mechanical properties of the pipe samples were observed when the extruder temp. Is 463 k. These properties were lower in the pipe compared to the samples taken from the inner and outer part of the extruder. For the sample during this time the concentration of the oxygen groups are at the lowest and amorphous regions are at the highest level. These results prove that the temperature, the pressure and the cooling rate of the material taken from the extruder have too much effect on polymer structure. 3) Welding duration is investigated without changing the fibrillar structure. The best welding conditions have been obtained in case of deformation graphs with minimum areas. The results can be explained with the difference in polymer structures at different temperatures during pipe manufacturing process. 4) The σ, τ, γ values differ greatly in the samples taken from different companies (∼ 50%). The analyses of IR spectra and microphotographs show that this difference depends on the differences of the polymer structures and the initial data.
A study of the optical properties of polypropylene based polymer composite films
Authors: Boydag F. Senel , Mamedov Shaval V. , Alekperov Vilayet A. , Kandemir Gulcin 
Published: March 2011

AbstractThe optical clarity of the polymeric material can be influenced by changing the preparations parameters and thus the polymer structure. In this study, the transmittance, absorptance and reflectance of the polypropylene (PP) based polymer composites, synthesized by pressing method, changing the thickness between 8 — 29 μm, are investigated. Infrared and ultraviolet spectra of PP/diamond and PP/fiber composite in the wavelength range 200–25000 nm are examined. Optical absorption spectra recorded in the UV‐Visible range are presented; the determined values of energy gaps are listed. The results indicate that both mechanism, direct and indirect transitions may exist. The analysis of absorption peaks corresponding to oxygen groups, for PP/diamond (0.3–0.5 %) and PP/fiber (20–30 %) composites, show low optical densities which complies with our other studies.
Hydrogel composites of neutral and slightly charged poly (acrylamide) gels with incorporated bentonite. Interaction with salt, linear polyelectrolytes and ionic surfactants
Authors: Starodoubtsev Serguei G. , Churochkina Natalia A. , Dembo Alexander T. , Khokhlov Alexei R. 
Published: March 2011

AbstractThe swelling behavior in the solutions of sodium chloride, linear polyelectrolytes and ionic surfactants of the composites based on clay mineral bentonite (BENT) embedded in neutral and slightly charged poly(acrylamide) (PAAm) gels is studied. Negatively charged flat clay particles incorporated into polymer gel adsorb oppositely charged surfactant and linear polyelectrolyte and attract the charged chains of cationic polymer matrix. The results of SAXS study manifest the formation of lamella structure of the cationic surfactant adsorbed by the clay plates. The gels loaded with the clay show a strong response to changes in the nature and the composition of the ionic environment.
Polymer gel/organic dye complexes in aqueous salt solutions
Authors: Nasimova I. R. , Makhaeva E. E. , Khokhlov A. R. 
Published: March 2011

AbstractThe present work is devoted to the study of the complex formation of polymer gel with organic dye and their properties in the aqueous salt solutions. Two systems were studied: 1) polyelectrolyte gel based on poly(diallyldimethylammonium chloride) and water soluble oppositely charged organic dyes (alizarin red S and catechol violet) and 2) organogel based on poly(N‐vinylcaprolactam) and dithizone. The collapse of the polyelectrolyte gels in the presence of oppositely charged dyes together with the effective absorption of dyes was observed. The shrinking degree and the dye absorption by the gel depends on the dye concentration. In the case of PVCa gel in organic media the dye absorption takes place.The main attention has been concentrated on the study of the behaviour of gel/dye complex immersed in the salt solution if dye is the chelating ligand for metal ions. It was shown that polyelectrolyte gels generally form stable complexes with oppositely charged dyes.The behaviour of PVCa‐dithizone‐chloroform system was studied in AgNO3 aqueous solution. The release of dithizone to the external aqueous solution of AgNO3 reservoir is completely suppressed.Absorption spectra of gel/dye and gel/dye/metal ion systems were studied. It was shown that metal ions penetrate inside the gel phase and the dye/metal ion complexes form within the gel. The dependence of the optical density for the systems of gel/dye/metal ion on the salt concentration is observed.
Theory of supercrystalline structures in mixtures of ABC triblock and ab, bc, and ac diblock copolymers
Authors: Birshtein Tatiana M. , Polotsky Alexey A. , Amoskov Victor M. 
Published: March 2011

AbstractTheoretical analysis of the ability of forming mixed supercrystalline structures in the mixtures of ABC triblock copolymer with ab, bc, and ac diblock copolymers in the strong segregation limit is carried out. Effects of combined phase and microphase segregation are analysed. The possibility of changing the initial superstructure is demonstrated.
Polyelectrolyte gel elasticity in poor solvent
Authors: Johner A. , Vilgis T. A. , Joanny J. F. 
Published: March 2011

AbstractPolyelectrolytes in poor solvents are expected to show a necklace structure where collapsed polymer pearls are linked by stretched polymer strands. This prediction by Kantor and Kardar worked out by Dobrynin Rubinstein and Obukhov Macromol. 1996,29,2974 has mainly be confirmed by computer simulations of Dobrynin; Darinskii; Holm and Kremer. We study the unwinding of pearls under an external force. Polyelectrolyte gels in poor solvents are then discussed, mainly on the basis of single chain elasticity following Katchalsky.
Competition between liquid‐crystalline ordering and glassy freezing in melts of semiflexible polymers: A monte carlo simulation
Authors: Paul W. , Weber H. , Binder K. 
Published: March 2011

AbstractWe present results of a Monte Carlo simulation of dense melts of semi‐flexible polymers using the bond‐fluctuation model. The chosen Hamiltonian increases the chain stiffness upon cooling which in turn leads to glass‐transition like freezing of the polymer mobility. Employing an efficient simulation algorithm, which is able to equilibrate the simulated systems to lower temperature than the Rouse‐type algorithm showing the glassy freezing, we are able to observe an isotropic‐nematic phase transition. This transition lies above the glass transition temperature one would extrapolate from the observed freezing behavior.
Molecular dynamics studies of anchored polyelectrolytes
Authors: Csajka Félix S. , van Der Linden Catharina C. , Seidel Christian 
Published: March 2011

AbstractWe study polyelectrolytes end‐grafted to a surface in a model which includes counterions explicitly and treats the full long‐range Coulomb interaction. For strongly charged polyelectrolytes the counterions are localized inside the brush and electroneutrality is satisfied locally. Under these conditions, we find that the brush thickness is linearly proportional to the chain length and the grafting density. The counterion distribution is strongly inhomogeneous, and counterion condensation can be observed although the Bjerrum length is smaller than the average bond length. Varying the Bjerrum length we find a non‐monotonic behaviour of the brush height. Counterion diffusion is anisotropic, and is enhanced at higher grafting densities. For partially charged polyelectrolytes we obtain a crossover from quasi‐neutral behaviour to the strongly charged behaviour reported above.
Computer simulation of globules with microstructure
Authors: Ivanov Victor A. , Chertovich Alexander V. , Lazutin Alexei A. , Shusharina Nadezhda P. , Khalatur Pavel G. , Khokhlov Alexei R. 
Published: March 2011

AbstractWe present recent data of our Monte Carlo computer simulation study of properties of AB‐copolymer globules which depend strongly on the primary sequence of A and B monomeric units. Different primary sequences have been studied: random, random‐block, regular and designed ones by using some particular spatial conformation of a homopolymer chain (we have compared here three models: proteinlike copolymers, AB‐copolymers modeling membrane proteins and ABC‐copolymers modeling proteins with active enzymatic center). We have found several evidences for the fact that an AB‐copolymer chain with a primary sequence prepared on the basis of a particular conformation of a homopolymer chain by some “coloring” procedure preserves the “memory” about its “parent” spatial conformation. Analyzing the power spectra of AB‐sequences, we find the existence of long‐range power‐law correlations for the copolymers with specially designed primary sequences.
Collapse of diblock copolymer in poor solvent. Molecular dynamics study
Authors: Neelov Igor , Niemela Satu , Sundholm Franciska , Skrifvars Mikael 
Published: March 2011

AbstractThe modification of unsaturated polyesters (UPE) by poly (ethylene glycol) (PEG) end groups [1] and the computer simulation of the collapse of a single molecule of a diblock copolymer AB consisting of PEG (A) and UPE (B) blocks [2] were reported recently by us. In the present paper the static and dynamic characteristics of the final collapsed structure were investigated by a molecular dynamics simulation. The structure and the local dynamic of collapsed homopolymers (AA and BB) were studied also. The initial conformations in all cases were taken near completely extended ones. The final structures of the diblocks are similar to the structure of a core (UPE) and shell (PEG) model. The differences in torsion angle distributions between diblock and homopolymer are maximal for the CCOC dihedral angles (both in UPE and PEG blocks). The orientational order of the COC vectors (‘chords’ along backbone of polymer chain) inside both blocks is larger in the diblock than in the homopolymer. Local orientational mobility of the COC vector and the translational mobility of the monomers is larger in the diblock than in the homopolymers for both blocks.
Creep rate spectroscopy: High‐resolution analysis of relaxations and prediction of anomalies in mechanical behavior of solids
Authors: Bershtein Vladimir A. , Yakushev Pavel N. , Peschanskaya Nina N. 
Published: March 2011

AbstractAn original laser‐interferometric creep rate spectroscopy method was applied to analysis of molecular motion in some polymers, composites and interpenetrating polymer networks. Its potentials for study of nanoscale dynamic/compositional heterogeneity in complex systems, of a peculiar relaxation behavior of polymer binder in composites, and for prediction of temperature anomalies in strength are demonstrated.
Characterization of polymers in particulate systems
Authors: Glass H. J. , De Graaf M. J. M. 
Published: March 2011

AbstractSmall amounts of polymers (ca. 1 wt.‐%) are often used in the processing of ceramics to bond the particles. The purpose is to enhance mechanical properties, notably the strength, of intermediate or green products obtained after consolidation of the powder. In this paper, the influence of polymers on mechanical properties of green (Mn, Zn)‐ferrite products is investigated. Frequently used polymers are methyl methacrylate ‐ ethyl acrylate copolymer and poly(vinyl alcohol) (PVA). Because PVA generally produces low‐strength compacts and is sensitive to moisture, a blend of the copolymer and PVA was used. The glass transition temperatures (Tg) of the polymers and green products were determined. The good correspondence between the Tg's indicates that the polymers dominate the mechanical behaviour when tensile stresses are applied. In practice, compacts usually have an axisymmetric shape and are subject to diametral compression during handling. Therefore, ring‐shaped compacts were crushed at different velocities. The crushing velocity has a strong influence on the compact strength when the copolymer is used and only a small effect when the compact contains the PVA blend. This indicates that the copolymer can absorb a rapid buildup of stress through plastic deformation. By contrast, the rate of plastic deformation in the PVA blend is relatively slow. Further insight is obtained by subjecting rectangular compacts to three‐point bending. By interpreting the experimental data with a mechanical model, the deformation of compacts containing acrylic is found to be elasto‐plastic. With compacts containing the PVA blend, a yield point is observed. This indicates that elasto‐plastic deformation is preceded by elastic deformation.