bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resonance raman spectroscopy of conjugated polymers what can we learn?
Authors: Kuzmany H. 
Published: March 2011

AbstractThis paper gives a review on the use of resonance Raman spectroscopy to analyse electronic and molecular structures of π‐conjugated and σ‐conjugated polymers. It starts with a short introduction into the present state of research in the field of conducting polymers and with a very short introduction into the principles of resonance Raman spectroscopy. Then the potentialities of the technique are demonstrated for the examples of the analysis of conjugation length in polyacetylene, for studying the thermochromic phase transition in polysilanes and in polyalkylthiophenes, for a sudy of the doping processes in polyaniline and finally for an analysis of the ground state in the narrow gap system polyisothianaphthene. Advantages and pitfalls for such analyses are outlined.
Photoconducting composite, polyester polymer‐cds powder
Authors: Kuczkowski Andrzej 
Published: March 2011

AbstractThe relation between electrical, photoelectrical and electrophotographical properties of polyester polymer–CdS composites as a function of component weight ratio, electric field strength and light intensity were investigated. Cl and Cu activated CdSa powder as well as unactivated CdS powder were added to polyester polymer. It has been shown that the composite containing from 60 to 70 wt‐% of CdSa has the best photoelectric properties. The electrophotographical layers of this composite exhibited a photosensitivity as high as 1.25 (Lx · s)−1. The results have been explained in terms of the reduction in interparticle barrier height assisted by the localized trapping of photoexcited or field‐excited holes.
New mechanism of the formation of superconductive ferromagnetic structures in elastomers without conjugation in the backbones
Authors: Grigorov L. N. , Andrejev V. M. , Smirnova S. G. 
Published: March 2011

AbstractA quantum‐mechanical model of charge condensation is proposed for non‐conjugated polar elastomers It was found that the stability of the bi‐ and multi‐polaron state may be achieved if the dielectrical permeability of the matrix is high enough. It is shown that the multi‐electron unit, called as superplaron, should have a linear structure and possess ferromagnetic properties. The one‐dimensional character of the conductivity of a superpolaron leads to the formation of electron pairs and to the appearance of high temperature superconductivity of superpolarons. A lot of experimental data confirms the real existance of superconductivity at some polar elastomers at 300 K.
Nonlinear optical properties of thin organic films
Authors: Bubeck Christoph , Neher Dieter , Kaltbeitzel Anke 
Published: March 2011

AbstractA brief survey is given on our recent work on the linear and nonlinear optical properties of thin films of polymers with a conjugated π–electron system. Third harmonic generation and degenerate four wave mixing experiments are used to study magnitude and response time of the third order nonlinear optical susceptibility of poly(p‐phenylenevinylene) and poly(phenyl acetylene). Phthalocyanine derivatives show a strong influence of the intermolecular electronic coupling on the response time of transient gratings. The influence of energy transfer on the relaxation process is discussed.
Nonlinear optical properties of poly(arylenevinylene) polymers
Authors: Bradley D. D. C. 
Published: March 2011

AbstractThis paper concerns investigations of the third order nonlinear optical response of poly(arylene vinylene) polymers and in particular precursor route poly(p‐phenylene vinylene) [PPV]. Results for photoexcitation measurements provide information on the response time and the nature of the nonlinearity in the single‐photon resonant excitation regime. Transmission third harmonic generation [THG] measurements yield complimentary information on the single‐photon non‐resonant regime.
Fracture resistance in rubber‐toughened polymers
Authors: Bucknall C. B. 
Published: March 2011

AbstractThe effects of rubber content, particle size and interparticle spacing on the fracture behaviour of toughened polymers over a range of strain rates and temperatures are discussed with particular reference to high‐impact polystyrene and rubber‐toughened nylons. It is concluded that the limiting factor in determining fracture resistance is a kinetic one: the rate at which the matrix polymer can respond to stress by forming oriented fibrils. Fibrillation can occur either by multiple crazing, in which case the preferred particle diameter D is about 1 μm; or as a result of cavitation within the rubber particles followed by shear yielding, which requires smaller inter‐particle spacings. An extension of the Argon‐Salama model for crazing is proposed to explain the interparticle spacing effect. Morphology is less critical in controlling fracture at low strain rates or higher temperatures.
Lyophilic polymer‐polymer emulsions in vicinity of the phase separation point
Authors: Kuleznev Valerü N. , Klykova Valentina D. 
Published: March 2011

AbstractExperimental and theoretical results of the investigation of the laws governing the lamination process in polymer‐polymer systems in the transient region between binodal and spinodal have been systematized. The causes of the viscosity decrease in the phase separation region have been explained. An assumption has been made that the laws observed result from differences in the conditions of segregation of macromolecules of polymers forming a mixture and segments of the same molecules in interphase layer.
A comparison of theoretical predictions and experimental evidences of miscibility for poly(ethylene oxide)‐based blends
Authors: Cimmino S. , Martuscelli E. , Saviano M. , Silvestre C. 
Published: March 2011

AbstractMixtures of poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/At‐PMMA) blends and poly(ethylene oxide)/poly(ethylene‐co‐vinylacetate) (PEO/EVAc‐1) blends were prepared by casting from a common solvent and were found miscible. The applications of the Solubility Parameter Theory, Patterson Theory and the Equation of State Theory of Flory are reported. The miscibility predictions obtained are discussed and compared to experimental miscibility evidence.
Interactions between polymers
Authors: Rätzsch Manfred , Haudel Gottfried 
Published: March 2011

AbstractThe main part of this report deals with the thermodynamic fundamentals of one‐ and multi‐phase polymer blends and the presently reached state of a theoretical prediction is estimated. Potentialities and limits of the thermodynamic theories are discussed. Furthermore, a theoretical conception, basing on interfacial tensions between polymers and successfully used for the theoretical description of polymer alloys, is considered. The second topic of this report is the development of highly impact resistant thermoplastics and thermoplastic elastomers. In connection with it, the technological parameters necessary for the realization of multi‐phase polymer blends by mechanical mixing in the melt, are discussed. The experimental methods for the determination of the distribution are presented. The practical importance of multi‐phase blends is substantiated, the role of the interfacial energies revealed and discussed. In the third part the possibilities of the increase of compatibility are given forth and in further part demonstrated by examples.
Thermodynamics of miscible polymer blends studied by inverse gas chromatography
Authors: Munk P. , Hattam P. , Abdel‐Azim A‐A. A. , Du Qiangguo 
Published: March 2011

AbstractUse of inverse gas chromatography for the investigation of polymer‐polymer interactions is compromised by a dependence of the measured polymer‐polymer interaction coefficient, B23, on the chemical nature of the probe in contradiction to theory currently used. We have developed a procedure whereby the “true” B23, may be extracted from the probe dependent data. Additionally a theory of mixing based on a multidimensional solubility parameter approach has been developed. The new theory has been used to predict the polymer‐polymer interaction coefficients and these are compared with experimentally determined values on several miscible blends.
Miscibility and mechanical properties of polymer blends
Authors: Pukánszky Béla , Tüdõs Ferenc 
Published: March 2011

AbstractThe tensile properties of 16 blends prepared from 12 different polymers were investigated in the whole composition range. The composition dependence of Young's modulus has shown less, while that of the yield and ultimate properties exhibited more significant variations with miscibility. The quantitative evaluation of the yield stress and tensile strength data resulted in a parameter, which could be related to the interfacial tension and miscibility.
Compatibility and thermodynamic interaction in random copolymer blends
Authors: Shiomi Tomoo , Imai Kiyokazu 
Published: March 2011

AbstractSome random copolymer blends have been found to be miscible in a certain range of copolymer composition even though any combinations of their corresponding homopolymers are not miscible. The opposite case may exist. These two types of miscibility behaviors have been called miscibility and immiscibility windows, respectively. Such two miscibility behaviors were discussed by application of the equation‐of‐state theory to copolymer systems. The equation‐of‐state theory gives two kinds of temperature dependences of the interaction parameter X: (a) a U‐shaped curve which is always positive regardless of temperature and (b) a function increasing monotonically from negative to positive values. Infinite molecular weight polymer blends are immiscible over all the temperature in the case (a), while in the case (b) two polymers are miscible below a temperature at which X=0. Applying the equation‐of‐state theory to random copolymer blends in which miscibility changes with the copolymer composition at a certain temperature to be immiscible → miscible → immiscible, two types of dependences of the temperature‐X curve can be obtained: (1) (a) → (b) → (a) dependent on the copolymer composition and (2) (b) regardless of the copolymer composition. For the blends in which miscibility changes with the copolymer composition to be miscible → immiscible → miscible, there can be two types: (3) (b) → (a) → (b) and (4) (b) regardless of the copolymer composition. It may be concluded that socalled miscibility and immiscibility windows should be defined by the types (1) and (3), respectively. The equation‐of‐state theory for random copolymer systems was applied to the real systems. The blends of poly(vinyl acetate‐co‐vinyl chloride) and poly(ethylene‐co‐vinyl acetate) were of the type (1), while it was suggested that the blends of poly(vinyl acetate‐co‐vinyl chloride) and poly(isobutyl methacrylate‐co‐ butyl methacrylate) may be of the type (4) though this system behaved like an immiscibility window at a certain temperature.
Condis‐crystal structure of flexible‐chain polymers in polymer blends
Authors: Antipov E. M. , Borisenkova E. K. , Kulichikhin V. G. , Platé N. A. 
Published: March 2011

AbstractWhen heated above the melting point, a thermodynamic equilibrium mesophase of conformationally disordered crystal type (so‐called condis state) has been found in some flexible‐chain polymers (not containing mesogenic groups) dispersed in a matrix of another polymer. Typical organic and inorganic polymers such as polyethylene (PE) and poly[bis (2, 2, 2‐trifluoroethoxy) phosphazene] (PPh) were taken as main components of the polymer blends under investigation. The most interesting situation is realized if two mesophase polymers are used in the same binary blend.
Gelation mechanism of ionic polysaccharides
Authors: Gamini A. , Civitarese G. , Cesàro A. , Delben F. , Paoletti S. 
Published: March 2011

AbstractExperimental results obtained by membrane equilibria, osmotic pressure, viscosity and circular dichroism measurements on alginate and pectate solutions in the presence of Ca2+ ions are presented. From equilibrium dialysis data both electrostatic and cooperative interactions seem to describe the binding process of Ca2+ ions onto polymer chains. An increase of the number‐average molecular weight M̄n for both poly‐saccharides with calcium ion concentration is observed. An increase of polymer dimensions can well account for the observed increase of the intrinsic viscosity [η] with bound Ca2+ ion concentration at several ionic strengths.
Amylose gelation in low‐concentration conditions
Authors: Doublier J. L. , Llamas G. , Choplin L. 
Published: March 2011

AbstractAmylose gels of low concentration (1–2 wt.‐%) were studied by means of a rheological method and turbidity measurements. The effects of temperature and concentration were investigated. The kinetics of turbidity evolution and of the storage modulus G' variations were strongly dependent of both parameters. The overall gelation process could be described in three steps: first, an induction period, followed by a sharp variation of G' and turbidity, and finally a slow variation of G'. These observations confirm that amylose gelation proceeds through a phase separation process.
Thermodynamic properties of gels of lithium poly(alkyl borates)
Authors: Dmitrieva Z. T. , Tikhonova L. D. 
Published: March 2011

AbstractThe temperature‐viscosity dependence of structured solution (gel) of [t‐C4H9OB(OR)3]Li · mROH and [B(OR)4]Li in heptane, where R = n‐C4H9, n‐C7H15, n‐C10H21; m = 0, 1, 2, has been studied in the range of threshold shear stress. Energy, heat and entropy of activation values have been obtained for the elasto‐viscous flow of gels of complexes. The energies of activation determined for the flow of gels of complexes are unaffected by the temperature in a temperature range of 293–343 K, while the heat of activation increases with temperature.
State diagrams of perfluorocarbon/solvent systems
Authors: Dobnik E. , Borchard W. 
Published: March 2011

AbstractThe phase behaviour of perfluorocarbons in various solvents has been investigated. In case of perfluorohexadecane the state diagrams with trichlorotrifluoroethylene (CF2Cl‐CFCl2) known also as Freon F113 and hexafluorobenzene (C6F6) as solvents could be determined in the total concentration range and also at temperatures far below the melting temperatures of the pure components. Beside the normal melt transitions in this binary systems some not yet known intramolecular phase transitions were found. From the course of the liquidus curve the Flory‐Huggins interaction parameter of these systems could be determined. So statements about the quality of these solvents can be made. The investigated substances are suitable solvents for all perfluorocarbons which are actually available. The high molecular polytetrafluoroethylene (PTFE) cannot entirely be dissolved by these solvents, although traces are soluble. The reason is that the boiling points and critical temperatures of the solvents lie below the temperatures of the liquidus curve of the polymer of the considered system.
Relaxation phenomena near the sol‐gel transition
Authors: Martin James E. , Adolf Douglas , Odinek Judy 
Published: March 2011

AbstractNear the sol‐gel transition, relaxation phenomena exhibit a form of critical slowing down that is manifest in a variety of microscopic and macroscopic dynamical phenomena. For example, quasielastic light scattering studies (QELS) of the relaxation of thermally induced density fluctuations in critical silica sol‐gels reveal a self‐similar dynamics wherein decay processes occur on all time scales (fractal time), and average decay times diverge. Likewise, time‐ and frequency‐dependent viscoelastic phenomena of critical gels are described by power laws and both the viscosity and recoverable equilibrium creep compliance diverge. These unusual relaxation phenomena appear to be associated with the connectivity divergence that occurs at the sol‐gel transition. Light scattering studies of this sol‐gel transition reveal fractal clusters whose size diverges as a power law, in reasonable accord with the predictions of percolation theory. Based on these structural observations, we have developed a scaling description of the dynamics that relies on a length‐scale‐dependent viscosity and the geometrical self‐similarity of the sol‐gel transition. When percolation exponents are used in these expressions, a good description of the viscoelastic phenomena and the relaxation of density fluctuations near the gel point is obtained. Finally, it is shown that the dynamic scaling treatment of the viscoelastic properties can be summarized in a Time‐Cure Superposition principle, which predicts certain universal axes for frequency‐ or time‐dependent properties near the gel point.
Frequency dependence of viscoelastic properties of some physical gels near the gel point
Authors: Cuvelier Gérard , Launay Bernard 
Published: March 2011

AbstractThe sol‐gel and gel‐sol transitions of three biopolymer gelling systems (gelatin, iota‐carrageenan and xanthan‐carob) have been studied by dynamic measurements. At the gel point a power law dependence of the storage (G') and loss (G”) moduli on frequency is observed, with an exponent varying from 0.5 to 0.65. The variation of log(tgδ = G”/G') versus the gelation (or melting) parameter (time or temperature) at different frequencies leads to a precise determination of the gel point.
Network formation and properties: Rate theory description of effects of ring formation on elastic shear modulus of RA2 + RB3 networks
Authors: Rolfes Heidi , Stepto Robert F. T. 
Published: March 2011

AbstractThe rate theory of RA2+RB3 polymerization has been developed to enable the concentrations of the smallest inelastic loops and the resulting reductions in elastic shear modulus at complete reaction to be evaluated. Reduction in modulus is expressed as Mc/M°c, the effective molar mass of chains between elastically active junction points (Mc) relative to that for the perfect network for given reactants (M°c). Calculations have been carried out for stoichiometric reaction mixtures and the concentration of loops is characterized by λ, a ring‐forming parameter. λ = Pab/CAo, where CAo is the initial concentration of A‐groups and Pab = (3/(2πvb2))3/2/NAv, with v the number of bonds in the chain forming the smallest loop, b the effective bond length of the chain, and NAv Avogadro's number. Pab is equal to the mutual concentration, assuming Gaussian statistics, of the A‐ and B‐groups at the two ends of the linear sub‐chain of v bonds. Loop formation increases as λ increases, that is, as the initial concentration of reactive groups (CAo) decreases, or, at constant CAo, as the molar mass of reactants (v) or their chain stiffness (b) decreases. Comparison with existing experimental data on two series of polyurethane networks formed from hexamethylene diisocyanate and two polyoxypropylene triols at different initial dilutions shows that the values of Pab decrease with increases in initial dilution and molar mass of triol. The decrease with molar mass is entirely accounted for by changes in v and the variation with dilution shows that the approximation of counting only smallest loops improves as dilution increases.
Molecular aspects of polymer network deformation ‐ small angle neutron scattering and NMR studies
Authors: Gronski W. , Forster F. , Pyckhout‐Hintzen W. , Springer T. 
Published: March 2011

AbstractPoly(1,4‐butadiene) networks obtained by a 4‐functional random cross‐linking reaction over a broad range of polymer concentration were studied by small angle neutron scattering(SANS), 2H NMR and Monte Carlo(MC) simulation in the isotropic and uniaxially deformed state. The defect structure of the networks has been characterized by MC simulation of the cross‐linking reaction. The anisotropy of the radius of gyration in deformed networks determined from SANS has been analyzed by the theory of Ullman. It was found that the number of active cross‐links per chain is in agreement with MC and that the chain deformation follows phantom behaviour. The local orientation as measured by 2H NMR is related to the global anisotropy of the network by a MC calculation of oriented chains. The 2H NMR line shape of the deformed network is analyzed in terms of two relaxation processes arising from interior parts of the chains and from segments at chain ends. The mobility of both decrease with strain. It was found that the orientation connected to the first process shows the classical strain dependence of rubber elasticity, whereas the second exhibits a weaker dependence on strain.
Direct evidence of crosslinks by metathesis degradation
Authors: Hummel Klaus , Hubmann Ewald 
Published: March 2011

AbstractThe degradation of unsaturated polymers by olefin metathesis has already been applied to the investigation of crosslink structures. In the present paper, crosslinks in poly(butadiene‐alt‐propene), obtained by partial bromination with N‐bromosuccinimide and reaction with 1,4‐bis(bromomagnesium)butane, were investigated by this method. Metathesis degradation was carried out with (E)‐4‐octene using the catalyst WCl6‐Sn(CH3)4. The low‐molecular‐weight products were identified by combination of gas chromatography (GC) and mass spectrometry (MS).
Study of structure and dynamics of gelatin gels by temperature ramped holographic relaxation spectroscopy
Authors: Wu Chi , Schrof Wolfgang , Lilge Dieter , Lüddecke Erik , Horn Dieter 
Published: March 2011

AbstractA technique combined temperature ramp with holographic relaxation spectroscopy (HRS) is used to investigate on the structure and dynamics of gelatin gels. Two kinds of photochromic probes are used. The first is the gelatin molecule covalently labeled with fluorescein‐isothiocyanate. After gelation, some of the labeled gelatin molecules will form the gel and the rest will still be in the sol. Therefore, the mobility of labeled gelatin molecules in the sol and the gel are probed. The translational diffusion coefficient of gelatin molecules in the sol, the gel content and the gel melting temperature at different gelatin concentrations ranging from 1 to 15 weight‐% are measured. The second probe is the small fluorescein molecule in the gelatin gel as a tracer. The mobilities of the tracer in the “gel” are probed. An HRS curve with double peaks is observed. It is experimentally proven that this “anomalous” HRS curve is related to the structure of the gelatin gels. During a normal cooling process (2 C/min), two kinds of networks are found. A “coarse” one is formed through the aggregation of collagen‐like triple‐stranded helices and a “fine” one is formed simply by entanglements between gelatin molecules.