bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and mechanism of epoxy oligomers curing
Authors: Rosenberg B. A. 
Published: March 2011

AbstractA review of new results concerning kinetics, thermodynamics and mechanism of epoxy oligomers curing with various nucleophilic agents (amines, phenols, carboxylic acids) has been made. The concept of the mechanism of such reactions is formulated on the basis of this study. Kinetic data obtained are interpreted within the framework of cyclic transition state. The addition of nucleophilic agent to epoxy ring is rather complicated. It results from preliminary formation of homo‐ and heteroassociates of reaction system components which finally form reactive cyclic heteroassociates. Reaction products are formed as a result of monomolecular rearrangement with synchronous transfer of electrons in the reactive cyclic heteroassociates.
Conformational properties of polyhydroxyethers
Authors: Burchard W. , Bantle S. , Wachenfeld‐Eisele E. 
Published: March 2011

AbstractThe conformation of four types of polyhydroxyethers and one amine‐cured triglycidyl isocyanurate resin were studied. Static and dynamic light scattering as well as small angle neutron scattering revealed a scarcely detectable influence of branching on the overall dimensions. The branching density has, however, a very pronounced effect on the intrinsic viscosity. The behavior of the latter results from the inverse proportionality of the intrinsic viscosity to the segment density. Estimation of this apparent density gave swelling ratios of only 2 to 5. The cured epoxy resins showed no swelling up to molecular weights of 10 000; in the higher molecular weight region the swelling ratios increase continuously up to a factor of 9.
The characterization and structure‐property relations of epoxies
Authors: Morgan Roger J. 
Published: March 2011

AbstractThe structure‐deformation/failure process‐mechanical property relations of epoxies used as matrices in high performance fibrous composites are presented. Such composites are fabricated either from fiber‐epoxy prepregs or by filament winding. The parameters that affect the processing, cure reactions and the resultant chemical and physical structure of the epoxies are discussed. The deformation and failure processes of these glasses are described. The structural parameters that control the deformation and failure processes, the mechanical response and aging of epoxies are addressed and means of improving their processing and performance are described.
Intrinsically conductive organic polymers as electrode material for functional ceramics in electronics
Authors: Schnöller M. , Wersing W. , Naarman H. 
Published: March 2011

AbstractLayers of intrinsically conductive organic polymers were chemically or electrochemically applied to ferroelectric ceramics. Using chemically deposited polypyrrole layers as an example, the applicability of these layers for electrodes was demonstrated and compared with metal electrodes. Practically the same, almost square hysteresis loops were observed with these polymer electrodes. In addition, equivalently high permittivity and piezoelectric constants were found. Conductive polymer layers can be used to an advantage in all applications where only relatively low operating frequencies are used, i.e. especially for all types of piezoelectric transducers which function quasistatically. Due to their elastic properties they are also interesting for piezoelectric composites. Furthermore, because of their optical absorption they appear to be interesting for pyrodetectors. They can also be considered for electrical screening and protective layers as well as for further applications.
Electrodeposition and cycling of polypyrrole
Authors: Beck Fritz , Oberst Manfred 
Published: March 2011

AbstractPolypyrrole has been electrodeposited at a constant current density of 4 mA cm−2 onto Pt from 0.1 M pyrrole, 0.1 M NBu4 BF4 in dry CH3CN. The thickness of the polypyrrole has been varied over a wide range of 0.02 to 50 μm. Elemental analysis reveals an excess of hydrogen in the polymer. The electrochemical equivalent corresponds to an insertion of 25–35 mole % BF4‐anions and a current efficiency of 80–100% for the electrodeposition process. SEM technique shows a highly textured material at a thickness larger than 1 μm. Reversible water vapour adsorption of this material has been detected. The potential/time curve during galvanostatic electrodeposition is without special features. The start potential, USSCE = 0.9 V, is relatively negative. A slight decay of potential in the course of the electrodeposition of thick layers is explained in terms of increasing surface roughness. Cyclic voltammetry has been used for a systematic investigation into the role of the positive and negative endpotentials. The importance of a total primary discharge after electrodeposition has been clarified. At a film thickness d exceeding 1 μm, the cyclovoltammetric curve degenerates, and the anodic peak flattens and shifts to more positive potentials. Active mass utilization decreases with increasing d and with increasing voltage scan rate vs. The plot of anodic peak current density vs. vs is linear for layers below 1 μm thickness. For thick layers and at high vs, deviations occur, indicating a transport limitation in the film. As the film is not homogeneous, a quantitative evaluation is not possible.
Formation and electronic conductivity of polyaniline
Authors: Thyssen A. , Borgerding A. , W. Schultze J. 
Published: March 2011

AbstractPotentiostatic measurements of polyaniline (PANI) formation show the growth of a metallic conducting phase, probably growing after instantaneous nucleation by a semisphere mechanism. The double layer capacity proves the formation of a metallic phase at first, but in a later stage the surface is covered by any dielectric reaction product forming an interface of a few nm thickness. Various measurements of electron transfer reactions show the very good conductivity of the PANI film within a potential range of 0 to 1 V. A large nucleation overvoltage hinders the cathodic metal deposition. Oxidation at higher potentials causes an overoxidation with the formation of an insulating film.
Possibilities of formation or modification of polymers by means of chemical reactions during processing (polymer processing)
Authors: Rätzsch Manfred 
Published: March 2011

AbstractThe trends for polymeric engineering materials are marked by the search for defined thermomechanical, plastic‐elastic stability of dimension, and surface properties. This trend is caused by the demands for higher usage values of the polymers and more efficient processing technologies. The greatest chances are granted to the chemical modification and reactive compounding of known polymers to reach the aims of this development. Thermodynamically, most of the polymers are incompatible with each other and no sufficient disperse distribution is reached by only physical mixing. During the last 10 years a good compatibility at the interfaces has been found as one supposition and the influence of the viscosity of the polymer components and of the shear rate in the mixing machine as a further supposition to reach a fine‐dispersed distribution. Polymer composites with fibres and fillers are a further importent group of materials. The properties of composites are also determined by the interactions in the interfaces, by the dispersity of the fibres and fillers, and by the physical properties of the interfaces. Polymer‐analogous reactions, polymer blends, and polymer composites with and without low molecular reactants in the melt are decisively influenced by the parameters of the compounding machine. The quality of mixing, distribution of the residence time and of the shear rate, and the temperature profile of the reaction mixture are essential criterions for the course of the reaction. Continuous and quasi continuous technologies as, e. g., extruders and internal mixers are preferred. The lecture will deal with the present state and technical possibilities. Polymer syntheses in screw extruders are a new trend for the future. All these possibilities offer prospective chances of development.
Specific features of the field‐induced effects in comb‐like liquid‐crystalline polymers
Authors: Platé N. A. , Talroze R. V. , Shibaev V. P. 
Published: March 2011

AbstractThe main problems concerning the liquid crystalline polymers and their behaviour in outer fields are discussed. The influence of the mesophase structure type of the side‐chain LC polymers on the orientation processes in mechanical, electrical and magnetical fields is shown. The field effects in polymers permit to evaluate the specific peculiarities of the polymeric state of liquid crystals.During the last 10 years the field of Liquid‐Crystalline (LC) polymers has been developed and is going to expand so intensively that one could not predict this at the time when first lyotropic and thermotropic LC‐systems were discovered.Not only thousand of new LC polymers were synthesized and our Symposium gives a good example of very interesting papers devoted to this area, but it became clear that LC‐state of polymers should be considered as normal, thermodynamically stable, widespread state of macromolecular substances ‐ the idea which you hardly could find in textbooks a decade ago.First applications of thermotropic LC‐polymers start to be described (memory devices, optical filters, ferroelectric polymers) while lyotropic systems continue its victorial march in the field of high tenacity fibers and films.It is absolutely impossible to give in one lecture an overall review of what is going on in this area because this would need at least 5–6 lectures of two hours each. That is why on preparing this talk we decided to concentrate ourself onto only one side of this rich picture ‐ the field induced effects in comb‐like LC thermotropic polymers.
Poly(phenylenevinylene)s ‐ synthesis and redoxchemistry of electroactive polymers
Authors: Hörhold H.‐H. , Helbig M. 
Published: March 2011

AbstractThe development of PPV‐systems has moved from intractable powders to solution processible film‐forming materials by introducing solubilizing phenyl groups. This opens new uses ranging from thin‐film insulators, over photoconductive electrophotographic recording materials, to novel electroactive battery electrodes. In addition, the phenylated PPV may be utilized as a promising thin‐film precursor for microstructured carbon patterns with a stable electrical conductivity (σ = 40 S/cm).PPV is not a metal‐like conductor, but rather a high‐ohmic photoconductor with a band gap of 2.4 eV. It can be made highly conducting upon appropriate chemical or electrochemical treatment (σ= 10−4 − 103 S/cm).The formation of coexisting polymeric ion radicals (polarons) and diions (bipolarons) is well understood in terms of the concept of chain segment redox reactions (ECS concept).A wide variety of PPV derivatives has been synthesized and characterized by their electrochemical oxidation and reduction potentials. Substituents like phenyl, methoxy and cyano groups have a significant influence on the redox potentials of PPV as the standard polymer (EOx = 0.8 V, ERed = −1.7 V).Thus, for poly(1,4‐phenylene‐1,2‐diphenylvinylene) a broadening of the band gap up to 2.9 eV along with an increase of the oxidation potential up to 1.2 V is estimated.The knowledge of the redox potentials which reflect fundamental properties of conjugated polymers is essential for theoretical and practical reasons.
Synthetic polymers today and in the future of pharmacy
Authors: Kálal Jaroslav 
Published: March 2011

AbstractSynthetic polymers have since a long time played a relatively important role in present‐day medicinal practice. Many devices in medicine and even some artificial organs are constructed with success from synthetic polymers. It is possible that synthetic polymers may play an important role in future pharmacy, too. This lecture should but scratch the surface of several directions in this particular field.
Polymers for medical applications
Authors: Frommelt H. 
Published: March 2011

AbstractThe paper starts with some general introductory comments on properties and influence factors such as biocompatibility, surface structure, processibility and purity. Hence it is derived that polyurethanes deserve special attention as biomaterials, which is explained by the variability of the structure. A number of examples with new types of polyurethane elastomers are described, their advantages and disadvantages are pointed out, and conclusions are drawn for further research.
Direct methods in small‐angle scattering
Authors: Svergun D. I. 
Published: March 2011

AbstractDirect methods of small‐angle scattering data treatment and interpretation are reviewed. The possibilities of Tikhonov's regularization method for solving ill‐posed experimental data processing problems (desmearing, size distribution functions evaluation) are shown; comparison with other data treatment methods is made. Methods for direct reconstruction of the structure of particles in isotropic monodisperse objects are presented. The cases of particles described by one‐ and two‐dimensional density distributions and the possibilities of application of the multipole expansion theory are considered.
Applications and limitations of deuterium labeling methods to neutron scattering studies of polymers
Authors: Wignall G. D. , Bates F. S. 
Published: March 2011

AbstractDeuterium labeling techniques have been widely used to study polymer chain configuration and motion, based on the assumption that the H‐ and D‐ chains are thermodynamically identical and that the interaction parameter between them, XHD is zero. By an appropriate choice of the degree of polymerization and temperature, both critical scattering and phase separation can be made to occur, due solely to the small but finite thermodynamic differences between protonated and deuterated molecules. These experiments helped delineate the range of validity of the assumptions which had been used hitherto in neutron scattering studies of polymers. The majority of previous experiments, carried out at modest molecular weights, have been shown to be in large part unaffected by such effects.
A review of some recent applications of small‐angle scattering in studies of polydisperse systems and porous materials
Authors: Schmidt Paul W. 
Published: March 2011

AbstractRecent progress in two fields of small‐angle scattering is reviewed: (a) New procedures have been developed by Kotlarchyk and Chen and by Triolo, Griffith, and Compere for calculating the intensity of the small‐angle scattering from polydisperse systems of interacting particles of different sizes. These techniques have significantly increased the quantitative information that can be obtained from the scattering data. (b) The pore boundaries in many porous solids have been found to be fractal surfaces. In a porous solid in which the pores have an average diameter ϵ and the pore boundary surfaces have a fractal dimension D, the scattered intensity for qϵ, >> 1 is proportional to q−(6‐D), where q = πλ−1sin(θ/2), θ is the scattering angle, and λ is the wavelength. Some small‐angle scattering studies of fractal porosity are outlined.
A new approach in small‐angle neutron scattering: A method of triple isotopic substitutions
Authors: Serdyuk Igor N. , Yu. Pavlov Michail 
Published: March 2011

AbstractA new method is proposed for studying the structure and mutual arrangement of selected components in multicomponent particles. Here the difference between the scattering curve of a solution containing two types of structurally identical particles (differing only in the degree of deuteration) and the scattering curve of a solution containing particles of a third type (deuterated to an intermediate degree) is considered. This difference scattering curve differs only by a numerical multiplier from the “vacuum” scattering curve of the particle in which the scattering density is equal to the difference between the scattering densities of the particles of the first and second types. This means that any particle component which is deuterated (protonated) to the same degree in the particles of three different types does not contribute to the difference scattering curve and, consequently, is “invisible” for neutrons. The difference scattering curve depends neither on the isotopic content of the solvent nor on the inter‐particle interference and particle association. Possible applications of this method are discussed.
The determination of the lamellar thickness in semi‐crystalline polymers by small‐angle scattering
Authors: Vonk C.G. 
Published: March 2011

AbstractThree small‐angle scattering methods for determining the thickness of the crystalline lamellae in polymers are described. These are based on 1. observation of the identity period, 2. determination of the specific surface of the phase boundary, and 3. analysis of the shape of the peak at the origin. The conditions for application of these methods and the types of average obtained are discussed, and some results are presented.
Liquid crystal polymers: Studies of labelled parts by Neutron scattering
Authors: Pépy G. , Cotton J.P. , Hardouin F. , Keller P. , Lambert M. , Moussa F. , Noirez L. , Lapp A. , Strazielle C. 
Published: March 2011

AbstractThe studies of the conformation of comb‐like liquid crystal polymers have been made by Small Angle Neutron Scattering (SANS) with samples containing mixtures of totally protonated polymers and homologous polymers with deuterated backbones. For a polymethacrylate the conformation of a chain is determined in the isotropic nematic and smectic phases. Theoretical predictions of Renz and Warner (similar to the hairpin model of de Gennes) are verified from the temperature dependence of the radius, parallel to the director, of one chain in the smectic phase. When the terminal groups of the pendant part of the monomer are deuterated a segregation seems to occur. The problem of the generalization of results is raised.
Emulsifying effects of block copolymers in incompatible polymer blends
Authors: Leibler Ludwik 
Published: March 2011

AbstractWe discuss some theoretical aspects of interfacial and emulsifying activity of block copolymers A‐B in incompatible blends of homopolymers A and B. We predict the reduction in interfacial tension due to equilibrium adsorption of copolymers at the interface. It is shown that for an appropriate choice of block copolymer composition and molecular weight a very low interfacial tension can be achieved. This suggests a possible existence of a thermodynamically controlled stable droplet phase in which minority homopolymer particles protected by an interfacial film are suspended in a majority homopolymer matrix. The size distribution of the droplets depends on the rigidity and spontaneous radius of curvature of the interfacial film which, as we show, can be controlled by molecular parameters of copolymers.
Miscibility mapping in some blends involving poly(styrene‐co‐acrylonitrile)
Authors: Cowie John M. G. , Lath Dieter 
Published: March 2011

AbstractBinary interaction parameters, Xij have been determined for the monomer pairs, styrene‐acrylonitrile and methyl methacrylate‐acrylonitrile from phase separation measurements in homopolymer‐copolymer blends. These have been used to predict regions of miscibility in different blends of statistical copolymers where the components were (a) poly(styrene‐co‐acrylonitrile), (b) poly(styrene‐co‐methylmethacrylate) and (c) poly(methylmethacrylate‐co‐acrylonitrile). Agreement between prediction and experiment was good in all cases. Extensive miscibility ranges were obtained for blends of (a) with (b), and (a) with (c), but combinations of (b) with (c) are immiscible.
Structured polymer blends
Authors: Meijer H. E. H. , Lemstra P. J. , Elemans P. H. M. 
Published: March 2011

AbstractVarious morphologies can be realized via processing of incompatible polymer blends such as droplets or fibers in a matrix and stratified or cocontinuous structures as is shown for the model system polyethylene/polystyrene The structures induced are usually intrinsically unstable. Modelling of extrusion processes and continuous mixers yields expressions for the shear rate and shear stress but also for the limited residence time and the number of reorientations. These results could be combined with detailed knowledge of respectively distributive and dispersive mixing processes to predict the development of various morphologies as a function of time. Control of morphology is of utmost importance. In the case of droplets in a matrix, usually encountered in toughening of glassy polymers, the use of compatibilizers and/or reactions at the interphases is utilized. However, in designing specific morphologies i.e. structured polymer blends, fixation of intermediate morphologies before final processing is a prerequisite. Some preliminary results will be presented.
Automotive industry and polymer blends
Authors: Moro A. , Chiolle A. , Credali L. , Foschini G. 
Published: March 2011

AbstractA key to the success of plastics in the automotive industry is the use of alloying technology which, relatively quickly leads to tailor‐made materials at interesting cost‐performance ratios. In this paper an overview of the various criteria used in the laboratory in testing alloys for auto parts is given and an attempt is made to point out the most significant determinations. The results obtained comparing the materials indicate how inadequate the standard methods are in describing the real behaviour of the items under operating conditions. Nonetheless, just making some modifications in test geometry leads to a sufficiently realistic correspondance between laboratory test data and item performance.
Examples of “intrinsically” and “extrinsically” determined phase morphologies in polymer alloys
Authors: Lohmar J. , Meyer K. , Ag Hüls 
Published: March 2011

AbstractThe properties of polymer alloys are strongly dependent on their phase morphologies. Usually, the phase dispersion and domain sizes are affected by the process and can be influenced and stabilized only “extrinsically” by dispersants and emulsifiers. But, there are some examples of alloys with phase morphologies which are “intrinsically” determined and thus independently of the processing conditions. This aspect of phase determining factors is discussed using four principally different examples of polymer alloys.
Investigations of blends containing coil polymers and thermotropic main‐chain polymers
Authors: Friedrich Klaus , Hess Michael , Kosfeld Robert 
Published: March 2011

AbstractBlends containing main‐chain thermotropic, semiflexible polyesters and flexible‐chain polymers (PC and PET) are investigated by calorimetry and microscopy. First results of studies about the mechanical behaviour by torsional pendulum are presented.
Prediction of phase separation behaviour from thermodynamic measurements in the one phase region
Authors: Higgins J. S. , Fruitwala H. , Tomlins P. E. 
Published: March 2011

AbstractWhen a polymer blend is heated to within the unstable region of the temperature ‐ composition diagram spinodal decomposition may be observed using small angle neutron scattering. In the one phase region scattering has been used to obtain the temperature and composition dependence of the second derivative with respect to composition of the Gibbs free energy of mixing. Correlation of these two types of measurement not only tests the current theories of spinodal decomposition, but provides insight into the molecular parameters controlling domain morphology in phase separation blends.