bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conductive thin films and membranes their scientific foundations and industrial applications (pt. 2)
Authors: Bahador Sardar Khan 
Published: March 2011

AbstractBeside the fundamental studies on polymerization processes, conduction mechanism and chemical stability of conductive polymers, attention was focused on the application feasibilities of these materials. Although the major application of conducting polymers was suggested in several types of advanced energy conversion and storage devices, their specific features such as plasticity, thin film fabrication with ease, chromatic contrast and the like offers ample possibilities for the utilization of such materials in many instances of modern technology. Consequently, among several conductive polymers investigated, in this communication, as part of a project work, perfluorosulfonate ionomer (e.g. Nafion) and polyaniline modified electrodes were taken into account. Typical examples of application, such as in fuel cells and chlor‐alkali membrane cells etc., are provided. Characterization and performances of the material as well as the kinetics and mechanism of the corresponding reactions are briefly considered. In the case of polyaniline, the electropolymerization process, characterization of the product film, its application in high energy density Li‐batteries together with the kinetics and mechanism of polymer doping, the charge‐discharge reactions, including the parameters affecting the cell efficiencies, are discussed in some details. Merits and problem of the process and corresponding devices are pointed out. A cell having the configuration Pb/PbO2/H2SO4/PAN/Pt was constructed, accordingly various characteristics of the electrode materials and cell system are extensively discussed.
Matrix polymerization and polyelectrolyte complex formation
Authors: Rätzsch Manfred , Fanghänel Egon 
Published: March 2011

AbstractWe developed a model of the formation of symplexes by photoinitiated matrix polymerization. Symplexes are insoluble in water and all known solvents. They result from contrarily charged polyelectrolytes. In our model a polyelectrolyte is matrix and binder simultaneously. At the matrix a contrarily charged monomer is polymerized radically to the second polyelectrolyte. Different mechanisms are discussed for the matrix polymerization. As polymerizable monomers acrylic compounds with terminal tertiary amino group were used. Modified styrene/maleic acid copolymers served as polyanion. The influence of the composition of the components in this layers on the polymerization rate was investigated. The sensitivity of the developed photo‐material is compared with other photo‐polymerization systems and the conventional photographic materials basing on silver halogenides. A high resolution and an easy fixation result.
Holographic recording on poly(vinylcarbazole)
Authors: Kuwae Yoko , Sugawa Etsuko , Taniguchi Naosato , Kuwayama Tetsuro , Kushibiki Nobuo 
Published: March 2011

AbstractA reflection type volume‐phase hologram was recorded on poly(vinylcarbazole) (PVCz) in the presence of CI4. The grating with a half‐height width of 19nm was made with an argon ion laser at 488nm or 514. 5nm. The sections of PVCz and a dichromated gelatin (DCG) hologram, responsible for the diffraction efficiency, were observed by scanning electron micrography (SEM) and transmission electron micrography (TEM). Those micrographs showed that the amplitude of the index modulation in the hologram is formed bý voids. The diffraction efficiency was simulated with the parameters observed by TEM and showed that a thin PVCz hologram film attains the same diffraction efficiency as the thick DCG sample, because of the large refractive index of PVCz.
Synthesis and electrophysical properties of doped copolymers of functional derivatives of acetylene
Authors: Zalisnaya N. F. , Davydov B. E. , Mavrenkova G. V. , Zhuravleva T. S. 
Published: March 2011

AbstractWCL‐catalyzed bulk copolymerization of phenyl‐acetylene (PhA) with 3‐bromo‐1‐propyne was carried out. Soluble, colored products with different comonomer content were obtained. The copolymer structure was estimated by IR spectroscopy and elemental analysis; their molecular weight being 2000–3000. These copolymers were used to study the ability of doping with such acceptors as FeCL3, Sn(Ph)4, tetracyanobenzoquinone (TCNQ). The conductivity of the copolymers was found to increase from 10−13 to 10−3/cm with doping. Substitution of the lithium derivative of the polymer with SnCL3 for Li leads to an increase of conductivity as well.
Tailoring of polymer blends with copolymers
Authors: Hellmann G. P. , Kohl P. R. , Herth J. , Neumann H. J. , Andradi L. N. , Löwenhaupt B. 
Published: March 2011

AbstractMiscibility can particularly easily be “tailored” with blends P (AxB1‐x)/P (AyB1‐y) of random copolymers and with blends P (Ax‐b‐B1‐x)/P (Ay‐b‐B1‐y) of diblock copolymers, where the blend components differ only in composition. The former class of blends is discussed in some generality, the latter only in one special example, where the components are a homopolymer (x=0) and a symmetric copolymer (y=0.5). Phase diagrams and phase morphologies are shown.
Toughening behavior of polyamide‐rubber blends
Authors: Gaymans R. J. , Borggreve R. J. M. , Oostenbrink A. J. 
Published: March 2011

AbstractThe impact behavior of nylon 6‐ rubber blends is studied by varying the rubber concentration (0–26 vol. %), rubber particle size (0.1 ‐ 2.0 μm) and rubber properties.The brittle to tough transition shifts to lower temperatures by increasing the rubber concentration, decreasing the particle size and by lowering the modulus of the elastomer. With very small particle sizes, however, the transition temperature increases again.The toughness of the blends above their transition temperature increases with the rubber concentration, but the particle size has only some effect. Very small particle sizes decrease the impact behavior.The postulated deformation mechanism is cavitation of the rubber followed by shear deformation of the matrix.
Soluble LC polyesters and their blend behavior
Authors: Heitz Walter , Schmidt Hans‐Werner 
Published: March 2011

AbstractPoly(p‐phenylene terephthalate) with substituents on the hydroquinone or on both monomer units were synthesized with the aim to obtain soluble LC polyesters. Focus was given to phenylalkyl substitution. With one phenylalkyl group in the repeating unit the polyesters are crystalline with melting points > 300°C. With two substituents the crystallinity is very low or the polymers are amorphous. These polyesters are soluble in chloroform forming isotropic solutions. Isotropic films of polyesters obtained from these solutions either crystallize or become anisotropic if heated above the glass transition temperature. The exponent in the Kuhn‐Mark‐Houwink equation is 0.95. Some of the polyesters form homogenous ternary solutions with polycarbonate. Films of the blends show additivity of modulus with respect to both components.
Rheology and morphology of polymer blends in melt and solid state
Authors: Kulichikhin V. G. , Vasil'eva O. V. , Litvinov I. A. , Parsamyan I. L. , Platá N. A. 
Published: March 2011

AbstractThe rheological properties of polymer mixture melts containing polysulfone and LC‐polyester have been investigated in this work in terms of the morphology and physical‐mechanical characteristics of extrudates. The perculiarities of rheological behaviour are accounted for by morphology of stream which is maintained also in solid extrudates. The reinforcement of an isotropic mixture by LC‐polymers as well as formation of an anisotropic surface layer lead to a specific change in the strength properties of compositions. An increase in strength and initial modulus was observed for blends containing not more than 10% LC‐polymer.
Formation of crazes in polymer blends
Authors: Michler Goerg H. 
Published: March 2011

AbstractHigh‐voltage electron microscopy was used to study the micromechanical processes of deformation directly on thin deformed samples of rubber‐modified, high‐impact polymers. In these polymers the microprocesses are closely connected with the initiation and formation of crazes. Craze formation with its effects on the fracture toughness are discussed in dependence on several important morphological factors, particularly on the rubber volume content, particle diameter, and particle diameter distribution.
Zero shear viscosity in miscible polymer blends of polystyrene and poly(2,6‐dimethylphenylene ether)
Authors: Stadler Reimund , de Araujo Marco Aurelio 
Published: March 2011

AbstractThe dynamic viscosities of blends of high molecular weight, narrowmolecular‐weight distributed polystyrene and poly(2, 6‐dimethylphenylene ether) are studied. The zero shear viscosity ηo depends on the weight average molecular weight M̄w and on the average entanglement molecular weight M̄e in the blend according to ηo ≈︁ M̄3.4 w(blend)/M̄2.4e(blend).
The industrial interest in blends
Authors: Capaccio G. , Gardner A. J. , Hope P. S. , Wilkinson K. 
Published: March 2011

AbstractSelected examples of industrial blends have been reviewed. In each case specific reference has been made to their functional/economic justification. The area of incompatible blends is identified as the one with significant growth potential and providing the greatest scientific and technological challenge. Key to meeting this challenge is a concerted effort in three distinct areas, i.e. thermodynamics, processing and new compatibilisers.
Rigidity of segments of poly (ethyl methacrylate) in CCl14 solutions
Authors: Huyskens P. L. , Vael C. , Vandevyvere P. 
Published: March 2011

AbstractCollegial dispersion forces originate from a coordination of the temporary electronic dipoles of a series of molecules. To insure this coordination the nuclei on a row have to replace their individual vibrations by coupled ones. Such row is then rigid. For polymers collegial forces can already be temporarily active in given parts of a solution but are regularly annihilated by intrusion of the solvent. However the regular passage through the rigid state modifies the distribution of the dipole moments during the interval that solvent or ligand molecules are in contact with the segment. In a rigid domain the correlation parameter of Kirkwood g is zero. The existence of such rigidity in solution is demonstrated by the low experimental value of gmA for the dipoles of the complexes between poly(ethyl methacrylate) and phenols. Due to the large number of segments that separate the complexes the classical explanation of stiffness of the chain due to individual interactions between neighbours does not hold.
Structures in polystyrene solutions: Their origins and their implications on physical gelation
Authors: Guenet Jean‐Michel , Klein Marc 
Published: March 2011

AbstractFrom studies on dilute and semi‐dilute solutions it will be shown that gelation in atactic polystyrene proceeds via the creation of a nematic‐like order (formation of a polymer‐solvent intercalate with the highly syndiotactic sequences). A similar mechanism holds for isotactic polystyrene (intercalate wherein the chain adopts a near‐31 helical form). It will be emphasized that the gelation phenomenon depends upon both the solvent size and the volume of the cavities created by the phenyl groups along the chain. Finally, diffraction experiments on well‐organized structures (giant spherolites of 150–200/μm diameter) grown from isotactic polystyrene solutions and possessing the same melting point as the gel show the absence of 121 helices. Therefore, gel formation is not due to the growth of this helical form.
A definition of the concepts “gelation temperature” and “gelation curve” by means of relaxation time spectra
Authors: Visscher K. , Mijnlieff P. F. 
Published: March 2011

AbstractWith the aid of the Boltzmann superposition principle, the infinitesimal flow behaviour of a substance can be described in terms of a memory integral. The memory function in this integral can be expanded in a set of relaxation times and relaxation strengths: the relaxation spectrum. On basis of a specific form of the fluctuation‐dissipation theorem, a physical meaning is proposed for the relaxation spectrum. The theory of complex functions enables one to show that the relaxation spectrum, determined from dynamic mechanical measurements, has a unique meaning. The infinitesimal flow behaviour, expressed in terms of the relaxation spectrum, is used to develop a general description of the phenomenon of thermoreversible gelation. This description method was applied to a styrene‐isoprene‐styrene triblock copolymer solution.
Formation and properties of physical gels from saturated poly(ester‐urethane) in styrene
Authors: Wang Fu‐Cai , Fève Michel , Pascault Jean‐Pierre 
Published: March 2011

AbstractA gel was obtained from reacting a α, ω–hydroxy‐terminated polyester oligomer and a diisocyanate in styrene. Two types of morphologies were possible which are dependent on the quantity of catalyst. The rheological experiments led to the discovery that the “gel point” was not well defined and that the gel formation was a gradual process. A certain chain length was necessary for the appearance of the gel properties. The physical cross‐links could be destroyed and re‐formed.
Structure formation and gelation phenomena in solutions of ternary interpolyelectrolyte complexes
Authors: Kabanov V. A. , Zezin A. B. , Izumrudov V. A. , Bronitch T. K. , Kabanov N. M. , Listova O. V. 
Published: March 2011

AbstractThe representative of the new family of mechanically reversible gels is described. The gel is formed by mixing of an aqueous solution of non‐stoichiometric interpolyelectrolyte complex of poly (sodium methacrylate) and poly(N‐ethyl‐4‐vinylpyridinium bromide) containing a certain amount of covalent links between oppositely charged polyions, with aqueous solution of poly(potassium vinylsulfate). The gelation mechanism arises to the partial replacement of the electrostatic contacts between the polycation and poly(methacrylate) anion in the original polycomplex with those between the polycation and poly(vinylsulfate) polyanion. The network of the gel is most probably formed by the nodes consisting of covalent links and interpolyelectrolyte double‐strand electrostatic clusters, united by poly(sodium methacrylate) tie‐chains.
Light scattering from reacting polymer systems. Associating polymers in a good solvent
Authors: Burchard Walther 
Published: March 2011

AbstractThe forward scattering of light allows determination of the osmotic modulus (=inverse osmotic compressibility), which in good solvents is a measure of repulsive forces among the particles in solution but also depends on the molar mass of the particle. The osmotic modulus increases with concentration if the particle weight remains constant. The increase differs for particles of different architecture and can for c < 3c* be described by structure specific g‐factors, where g is defined through A3=gA22 Mw with A2 and A3 being the 2nd and 3rd virial coefficients. For associating systems in a good solvent also the particle weight increases with c. A procedure is suggested which allows within limits a correction of the measured apparent molar mass M̄app (c) for the true molar mass M̄w (c) at the concentration c. Three examples are discussed in detail.
A novel molecular association of poly (acrylic acid) in dilute solution under high shear flow
Authors: Kim Oh‐Kil , Choi Ling‐Siu 
Published: March 2011

AbstractA novel association of poly(acrylic acid) in dilute solution is induced by high shear flow, producing a rigid chain morphology via interchain H‐bonding; the association is destroyed upon adding salt to the shearing solution. Such macromolecular changes in conformation are reflected in drag reduction changes as a result of flow‐polymer interaction.
Elasticity and flow properties of actin gels
Authors: Hvidt Søren , Janmey Paul A. 
Published: March 2011

AbstractActin gels formed by polymerizing monomeric actin have been studied by use of small amplitude oscillatory deformations and steady shear flow. The length of actin filaments within the gel was varied by copolymerization in the presence of the filament‐capping protein gelsolin. The results for short filaments are in qualitative agreement with a model for semi‐dilute solutions of inter‐penetrating rods. Long filaments give rise to additional motions, believed to be flexing of rods. Steady shear viscosities, at high shear rates, are independent of initial filament length. Results are explained as due to breaking of filaments in shear flows.
Diffusion and phase separation in polymer solution during asymmetric membrane formation
Authors: van Den Boomgaard Th. , Boom R. M. , Smolders C. A. 
Published: March 2011

AbstractMost of the commercially available polymeric membranes are prepared by the phase inversion process. In this process a thermodynamically stable polymer solution is brought to phase separation by immersing the solution in a surplus of nonsolvent, followed by an exchange of solvent and nonsolvent. The ultimate membrane structure is the result of an interplay of mass transfer and phase separation. Asymmetric membranes as well as symmetrical porous membranes can be obtained. Two types of demixing processes (l‐l phase separation and formation of aggregates) can be distinguished by the kinetics of phase separation, as the formation of aggregates is supposed to be a slower process than l‐l demixing. Because it is impossible to measure the composition changes during the demixing processes experimentally, a theoretical analysis has to be applied. A suitable formalism to calculate the diffusion induced composition changes in the immersed casting solution, as a function of thermodynamic and hydrodynamic interaction parameters will be described. With this theory it can be shown that two distinctly different mechanisms of membrane formation may occur resulting in two different types of membranes. One type has a relatively thick toplayer and mostly exhibits reverse osmosis, gas separation and pervaporation properties; the other type results in a porous type of membrane, which will exhibit ultra‐ and microfiltration properties.Model calculations are in agreement with light transmission experiments on membrane forming systems. Therefore, it could be concluded that the elucidation of the diffusion behavior in the immersed polymer film is the key to better understanding of membrane formation by means of immersion precipitation.
Structure of single and double stranded dna solutions as studied by ultracentrifugation
Authors: Frisch H. L. , Trohalaki S. 
Published: March 2011

AbstractThe osmotic pressure of dense solutions of DNA fragments in aqueous 0.2‐2 M salt (NaCl, etc.) solutions were easily obtained from equilibrium ultracentrifugation data. Short, helical double stranded DNA fragment solutions showed a well defined ordering transition. The osmotic pressure of these helical solutions could be explained by the scaled particle theory of rigid sphero‐cylinders. On the other hand, dense solutions of (single stranded) etheno‐DNA derivatives (of about 100 nucleotides) showed no ordering phase transition. The osmotic pressure as a function of the ε‐DNA concentration verifies a scaling prediction for random coils in the semi‐dilute regime. Good fits to the reduced osmotic pressure are obtained by using the Kleintjens and Koningsveld modified mean field lattice gas equations of state. As inferred from the Zimm clustering function, essentially all intermolecular interactions at high ionic strength are purely repulsive.
Interaction between oppositely charged polyelectrolytes in aqueous solution
Authors: Oppermann W. , Schulz Th. 
Published: March 2011

AbstractOppositely charged polyelectrolytes interact in solution, forming polyelectrolyte complexes, which often appear as gel‐like precipitates. This kind of complex formation was studied by means of calorimetric and rheological measurements. The enthalpy effects, though being fairly small, give some information about the binding strength of counterions to the macroion. We studied the system poly(p‐styrene sulfonate)/poly(trimethylammonium‐2‐ethyl methacrylate) (PSS‐PTMA), varying systematically the low molar mass counterions of PSS. In every case, the maximum of enthalpy was found around a 1:1 (mol:mol monomer units) composition of the complexes, with the shape of enthalpy versus composition‐curve indicating a stoichiometric interaction. The maximum enthalpy decreased with increasing atomic mass of the counterion when the alkaline metal salts of PSS were used and no change was made on the side of the cationic polyelectrolyte. The salts of the alkaline earth metals gave a distinctly higher enthalpy.On the contrary, viscosity measurements showed a very broad minimum as a function of composition, indicating that the formation of non‐stoichiometric complexes is also occurring. The conclusion of these observations is that the complex formation is stoichiometric with respect to the monomeric units, but not necessarily stoichiometric with respect to the entire macromolecules.
Structure formation in systems involving poly(ethylene oxide) and small molecules
Authors: Point Jean‐Jacques , Damman Pascal 
Published: March 2011

AbstractThe structure of the intercalates in which poly(ethylene oxide), PEO, is the host component and para‐disubstituted benzenes are the guest molecules is completely elucidated by X‐ray diffractometry, polarized FTIR spectrography, and calorimetry. It is shown that the association of these molecules results from the adaptation of the shape of their external surfaces. On this basis the possibility of formation of structure involving PEO and small molecules is discussed.
Solvent‐induced crystallization of syndiotactic polystyrene in toluene
Authors: Vittoria V. , Russo R. , De Candia F. 
Published: March 2011

AbstractThe diffusion of toluene in glassy syndiotactic polystyrene was analyzed for films with different thickness. It was found that the reduced sorption curves superimpose, denoting that the diffusion follows a Fickian behaviour. The intensity of transmitted light in a polarizing microscope was followed during swelling, and it was found that there is development of order and it is strongly diffusion‐controlled.Films dried after immersion in toluene show a crystalline wide angle X‐ray pattern, while in the swollen state the possibility of a liquid‐crystalline‐like state can be suggested.
A kinetics approach to non‐linear polymerization
Authors: Galina Henryk 
Published: March 2011

AbstractThree formal equations are presented that describe the time dependence of the size distribution of polymer species in the tree‐like homopolymerization of f‐functional monomer, the copolymerization of 3‐ and 2‐functional monomers and the homo‐polymerization of 3‐functional monomer with cyclization taken into account. The equations have the form of the Smoluchowski coagulation equation extended to take into account substitution effects that may alter the reactivities of functional groups. Average degrees of polymerization up to gel point can relatively easily be extracted from the proposed equations. The results, illustrating applications of the kinetics approach, confirm that statistical theories are inadequate to model kinetically‐controlled polymerization reactions if substitution effects are present.