bluuebunny/crossref_metadata_2025_split huggingface dataset:
The synthesis and cationic polymerization of novel monomers from renewable sources
Authors: Crivello James V. , Narayan Ramesh , Bratslavsky Svetlana A. , Yang Bo 
Published: March 2011

AbstractThis communication describes recent developments in this laboratory directed towards the design of cationically polymerizable monomers from biorenewable sources. Three classes of ubiquitous biorenewable substrates were explored, namely: lipids, carbohydrates and terpenes. Considered in the synthesis and design were the cost and availability of the substrates, and the practicality and environmental acceptability of the chemical methodology. The polymerizations of the monomers were carried out using photoinitiated cationic polymerization.
Modelling carbocationic polymerizations: Kinetics of the reactions of carbocations with alkenes
Authors: Mayr Herbert , Patz Matthias 
Published: March 2011

AbstractReactions of carbocations with olefins and related π‐nucleophiles follow second order kinetics, first order with respect to carbocation and first order with respect to olefin. The rate constants are equal for paired and non‐paired ions and independent of the nature of the negative counter‐ions. Rate constants k < 107‐108 L mol−1 s−1 can be calculated by lg k(20 °C) = s (N+E), where E represents the strengths of the electrophiles, while nucleophiles are characterized by the slope parameter s and the nucleophilicity parameter N. These parameters can be used for selecting initiators for carbocationic polymerizations and for designing copolymers.
Design of latent catalysts and their application to polymer synthesis
Authors: Endo Takeshi , Sanda Fumio 
Published: March 2011

AbstractDesign of latent catalysts such as benzyl sulfonium, benzyl ammonium, benzyl pyridinium, benzyl phosphonium, and hydrazinium salts, and their application to polymer synthesis have been described. They have been demonstrated as excellent thermal or photolatent catalysts for polymerizations of cyclic monomers such as epoxides, bicyclo orthoesters, spiro orthocarbonates, and vinyl monomers such as styrene and vinyl ethers.
Well defined polymer structures by ionic ring‐opening polymerization of cyclic monomers comprising the respective structure
Authors: Keul Helmut , Melchiors Martin , Neffgen Stephan , Gotsche Michael , Höcker Hartwig 
Published: March 2011

AbstractRing‐opening polymerization of cyclic monomers is the method of choice when tailor‐made polymers and copolymers with heteroatoms in the main chain are to be prepared. Triblock copolymers comprising a poly(ethylene oxide) block [poly(EO)] and two poly(2,2‐dimethyltrimethylene carbonate) blocks [poly(DTC)] were prepared using a telechelic poly(EO) as initiator for the DTC polymerization. These block copolymers dissolve suitable salts leading to solid polymeric electrolytes. The thermal properties and the ionic conductivity of these materials are presented. Block copolymers comprising a poly(tetrahydrofuran) block [poly(THF)] and a poly(trimethylene urethane) block [poly(TU)] were obtained by sequential cationic polymerization of THF and TU with methyl trifluoromethane‐sulfonate as initiator. Mechanistic and kinetic aspects of the TU polymerization are discussed. To achieve the synthesis of block copolymers with a poly(L‐lactide) block [poly(LLA)] and a poly(α‐amino acid) block [poly(AA)] amino‐terminated poly(LLA) was prepared which served as initiator for the polymerization of α‐amino acid N‐carboxyanhydrides.
Use of polyiminophosphazene bases for ring‐opening polymerizations
Authors: Eßwein Beate , Molenberg Aart , Möller Martin 
Published: March 2011

AbstractThe polyiminophosphazene bases Et‐P2 and t‐Bu‐P4 were used as a promoter for ethylene oxide and siloxane polymerizations. Initiation by an alcohol in combination with t‐Bu‐P4 lead to an extremely rapid polymerization reaction of octamethylcyclotetrasiloxane. In the case of ethylene oxide, well‐defined polymers were obtained, however the rate of polymerization decreased during the polymerization reaction due to decomposition of the counterion. In combination with organolithium compounds, the phosphazene bases lead to well‐defined polymers in the case of cyclotrisiloxanes as well as in the case of ethylene oxide.
Polymers and european union research funding
Authors: Quivoron Claude 
Published: March 2011

AbstractThe 4th Framework Programme for Research and Technological Development (4th FPRTD) of the European Union was adopted in April 1994. It has a duration of five years (1994‐1998) and a global budget of at least 12,300 MECU. The 4th FPRTD contains 15 sectorialized specific programmes (First Activity) and 3 interdisciplinary ones (Second, Third and Fourth Activities). Polymer Science has no specific programme but can be partially found in some of them. It will be given, in this paper, the main lines of the specific programmes where polymers are involved.
Some peculiarities of the surface chemical modification of the high‐dispersed silica fillers
Authors: Tertykh Valentin A. 
Published: March 2011

AbstractAdvantageous routes of preparation of dense hydrophobic coverings on the silica surface are discussed. An analysis of the experimental data allows to realize the optimum choice of modifying reagents and catalysts for the surface reactions. Possibilities of the use of solid‐phase hydrosilylation reactions for this purpose are examined.
Rheology of highly filled polypropylene compounds: Measurement and applications
Authors: Gahleitner Markus , Bernreitner Klaus , Knogler Bernhard , Neißl Wolfgang 
Published: March 2011

AbstractIt is common knowledge among rheologists as well as polymer engineers that compounds of thermoplastics with a high volume content of mineral fillers show a viscoelastic behaviour which is significantly different from homogeneous systems. A strong nonlinearity is combined with the development of a second plateau region of the dynamic moduli at lower frequencies. This for one makes the rheological characterization of these materials more complicated, as could be shown in a round robin test, including a PP‐compound with talc. The linearity criterion has to be handled carefully to achieve comparable and representative results. However, the viscoelasticity gives access to a quick characterization method regarding dispersion quality in compounds. This can be shown for the case of PP‐talc‐compounds, where correlations between relaxation spectrum and impact strength could be developed.
Particle filled polyolefins with high stiffness and toughness, as used for load bearing components
Authors: Savadori Aurelio , Scapin Marco , Walter Rolf 
Published: March 2011

AbstractMineral fillers have been used very often in the past for improving elastic modulus and temperature resistance of polyolefines, also to the detriment of impact resistance. Very recently it has been pointed out that good fracture toughness can be achieved if an appropriate mechanism is stimulated and a good bonding of the filler particles to the matrix is guarantied.This work shows some interesting results obtained in this field with HDPE (high density polyethylene) and kaolin. In particular the effect of filler content and of adhesion between matrix and filler is considered. A comparison is also made with literature data concerning filled polyolefines (HDPE and PP).
Comparison of electrically conductive fillers in polymer systems
Authors: Kozlowski Marek , Kozlowska Anna 
Published: March 2011

AbstractA comparative evaluation of different carbon black grades was performed for polymer composites whose matrices were composed of a single polymer, or polymer blend. The electrical resistivity, rheological properties, tensile strength and morphology were evaluated. The highest conductivity level was measured for the composites with Ketjenblack EC 600 JD from Akzo Nobel.
A qualitative study to the influence of molar mass on retention in gradient polymer elution chromatography (GPEC)
Authors: Klumperman Bert , Cools Paul , Philipsen Harry , Staal Wim 
Published: March 2011

AbstractGradient Polymer Elution Chromatography (GPEC) appears to be a powerful method for the determination of chemical composition distributions (CCD) of high molar mass copolymers. In order to perform these experiments, molar mass dependence of the retention time must be minimized. It is shown that variation in solvent and non‐solvent strength is a powerful method for adjusting the molar mass dependence. There appears to be a relation between molar mass dependence of retention behavior in GPEC on one hand and solubility under critical solvent conditions on the other hand. This phenomenon can be explained qualitatively from the important precipitation/redissolution mechanism in GPEC.
Crystaf: Crystallization analysis fractionation. A new approach to the composition analysis of semicrystalline polymers
Authors: Monrabal Benjamin 
Published: March 2011

AbstractCrystallization Analysis Fractionation is a new technique for the analysis of composition distribution in semicrystalline polymers; more specifically for the analysis of branching distribution in Polyethylene and tacticity in Polypropylene type resins. CRYSTAF as well as TREF (Temperature Rising Elution Fractionation) are separation techniques which fractionate species of differing crystallizability by slow cooling of a polymer solution. TREF however, demands in addition to the crystallization step a second temperature cycle, elution step, to obtain the polymer composition. CRYSTAF, on the other hand, extracts the information in the crystallization cycle by monitoring the solution concentration depression as temperature goes down; thus reducing significantly the analysis time and simplifying the hardware needs. CRYSTAF principles are discussed and various applications are described.
Inverse size exclusion chromatography and universal calibration
Authors: Potschka Martin 
Published: March 2011

AbstractThe mechanism of size‐exclusion chromatography (SEC) is reciprocal in respect to the properties of the porous material and of the solutes immersed. The porosimetric interpretation (inverse SEC) yields information about the morphology of porous solids. It depends on a number of assumptions and in particular on the steric properties of the probing macromolecules whose ‘Universal Calibration’ remains disputed to this day. The central question concerns the equilibrium distribution of molecules in confined spaces of complex geometry, and is, as such, not limited to the particulars of chromatographic technique. This survey hopes to help focus future research activities in this field of analytical chemistry and material science.
New aspects of determination of polymer heterogeneity by 2‐Dimensional orthogonal liquid chromatography and maldi‐tof‐ MS
Authors: Krüger Ralph‐Peter , Much Helmut , Schulz Günter , Wachsen Olaf 
Published: March 2011

AbstractLiquid Adsorption Chromatography at Critical Conditions (LACCC) of polymers in combination with Matrix‐Assisted Laser Desorption / Ionization Time‐Of‐Flight Mass Spectrometry (MALDI‐TOF‐MS) and different types of detectors is a very convenient method for the characterization of polymer heterogeneities. A pathway for working out these methods is given. Additionally to the coupling of different chromatographic modes a device for post‐column reaction detection is described and applied. Examples of applications are given for aliphatic and aromatic polyesters. MALDI‐TOF‐MS, reaction detection and relations between “critical” solvent composition and structure of polyesters are discussed. Conclusions concerning the mechanism of thermal degradation of polylactides are shown.
Characterization of polyethers using different methods: SFC, LAC and SEC with different detectors, and MALDI‐TOF‐MS
Authors: Trathnigg Bernd , Maier Bernhard , Schulz Günther , Krüger Ralph‐Peter , Just Ulrich 
Published: March 2011

AbstractPolyethylene glycol 300 (PEG 300) and polypropylene glycol 425 (PPG 425) were analyzed using size exclusion chromatography (SEC) in different solvents, normal and reversed phase liquid chromatography (NPLC and RPLC), supercritical fluid chromatography (SFC), and matrix‐assisted laserdesorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). In liquid chromatography, different detectors were used: density, refractive index (RI) and evaporative light scattering detector (ELSD).
First‐principles prediction and interpretation of propagation and transfer rate coefficients
Authors: Heuts Johan P. A. , Sudarko  , Gilbert Robert G. 
Published: March 2011

AbstractPropagation and transfer rate coefficients in free‐radical polymerizations are calculated from first principles, using quantum calculations (both ab initio and semi‐empirical) to determine geometries, frequencies, torsional potentials and energies of reactants and transition state, after which transition state theory yields the Arrhenius parameters. While activation energies can only be calculated for small species and with large computational resources, acceptable frequency factors (A) are obtained with relative ease provided that lower frequencies corresponding to torsions are treated as hindered rotors, not harmonic oscillators; this entails finding the torsional potential and exact evaluation of the corresponding partition function. Simple theory can be used to find A because this involves a ratio of partition functions of reactant and transition state, and because torsions (which are dominated by geometrical considerations) dominate A. A is determined by three modes in the transition state: rotation of the monomer about the forming bond, rotation of a “propylene”‐group about the terminal C–C bond in the radical, and simultaneous bending of the two angles associated with the forming bond. Calculations on ethylene and acrolein give agreement with experiment. These studies explain some experimental observations. (i) Changing the penultimate unit gives a small but significant change in the torsion of two of the three modes dominating A, leading to a penultimate‐unit effect of ca. a factor of 1–10. (ii) Deuteration affects the moments of inertia of the torsions, leading to changes in A in accord with experiment. (iii) A, but not the activation energy, changes predictably along a homologous series (e.g., methyl, butyl methacrylate). (iv) For a given monomer, A's for transfer to monomer and propagation are similar.
Applications of esr techniques to the study of free radical processes and kinetics in acrylic polymerizations
Authors: Chang Hsiu‐Rong , Lau Willie , Parker Hsing‐Yeh , Westmoreland David G. 
Published: March 2011

AbstractElectron spin resonance (ESR) techniques have been applied to a detailed study of batch and semicontinuous emulsion polymerization of methyl methacrylate; butyl acrylate and styrene have been briefly studied. Quenching of samples from the polymerization reactor followed by ESR analysis are useful, but we have developed continuous flow techniques which are preferable in many cases. ESR techniques can provide valuable information relating to the nature of free radical reactions, the concentration of propagating free radicals, and the kinetic processes in these reactions. Direct ESR analysis is most valuable but is not applicable to all systems. Spin trapping techniques can be useful for systems not accessible by direct analysis.
Studies in free radical initiation
Authors: García‐Rubio L. H. 
Published: March 2011

AbstractIn this paper, the consequences of the standard assumptions made in free radical initiation are explored to explain effects that could be attributed to the kinetics of initiation. Experimental results based on end‐group analysis through the course of bulk and suspension polymerizations demonstrate the importance of reactions involving initiator molecules. Studies on the combined effects of mixing and initiator decomposition, and oxidation reduction systems further demonstrate the importance of an adequate description of free radical initiation mechanisms.
Estimating interactions in blends of polyamides, polyesters and polycarbonate using copolymers
Authors: Ellis Thomas S. 
Published: March 2011

AbstractA binary interaction model (BIM), formulated in terms of elementary chemical species, e.g., ‐ CH2 ‐, ‐COO‐, is applied to blends of homopolymers and copolymers composed of polyamides, polyesters and polycarbonate. By establishing interactional “null” points it is shown how estimates of the interactions, both favorable and unfavorable, between the blend constituents can be obtained. The predictive potential of the parameters derived is examined in various situations, such as blends of PA‐66/PET.
Morphology resulting from coupling of phase separation and glass transition in polymer blends
Authors: Danchinov S. K. , Shibanov Yu. D. , Godovsky Yu. K. 
Published: March 2011

AbstractAt temperatures near glass transition temperature, off‐critical binary polystyrene/polybutadiene (PS/PB) mixtures were found to experience phase separation through the mechanism of slow hydrodynamic coarsening. A bicontinuous phase structure was produced on quenching the PS/PB‐blends under cloud point curve. Different coarsening regimes of this percolation structure depending on degrees of supersaturation were found. At late stages of coarsening, secondary phase separation was observed.
Studies on the compatibilization between polyamide and poly(arylether sulfone)
Authors: Mäder Dietmar , Kressler Jörg , Weber Martin 
Published: March 2011

AbstractThe influence of functionalized poly(arylether sulfone)s on the adhesion of a poly(arylether sulfone) and a polyamide was studied using a fracture test of sandwich specimens. All reactive compatibilizers used improve the interfacial adhesion. The chemical reaction at the interface between a maleic anhydride grafted polysulfone and a polyamide was analyzed by X‐ray photoelectron spectroscopy. Differing crack propagation mechanisms at the interface were observed by optical microscopy during the fracture test for the reactive and non‐reactive systems. Furthermore, the fracture surfaces were studied by optical and atomic force microscopy. Using transmission electron microscopy on ultrathin sections taken across the interface, it could then be shown that the interface was reinforced by the chemical reaction of maleic anhydride grafted polysulfone with the polyamide. The non‐reactive system fails at the weak interface, whereas strongly reinforced samples show cohesive failure in the polyamide bulk phase.
Small‐angle X‐ray scattering studies on plastically deformed rubber‐modified polystyrene
Authors: Magalhães Arminda M. L. , Borggreve Rein J. M. 
Published: March 2011

AbstractThe deformation process of blends of polystyrene (PS) and rubbery block copolymers based on polystyrene and hydrogenated polybutadiene (SEBS, Shell Kraton G1651)was studied by Transmission Electron Microscopy (TEM) and Small‐angle X‐ray Scattering (SAXS) on deformed tensile samples, under loaded conditions. When the rubber concentration is increased the impact toughness as well as the elongation at break Increases while the SAXS studies show that the amount of crazing decreases. TEM studies suggest that the main deformation mechanism in these materials is cavitation‐induced shearing. When a crazing agent is incorporated in the disperse phase of rubber‐modified PS the amount of crazing increases more than four times, but the toughness decreases dramatically.
In‐situ preparation of graft copolymers
Authors: Hellmann G. P. , Walter M. , Dietz M. , Steurer A. 
Published: March 2011

AbstractGraft copolymers are closer to supermolecular structures than any other class of polymers. Most grafting reactions proceed in demixed blends or lead in situ to such blends The competition of chemical chain coupling and physical phase separation generates complex phase morphologies that cannot (or not so directly) be produced otherwise. To demonstrate potential and problems of graft copolymer systems, high‐impact thermoplastics, block‐graft copolymers and reactive blending are discussed.
Roles of polymer‐solvent complexes in conformational ordering of polymer molecules dispersed in gels
Authors: Kobayashi Masamichi 
Published: March 2011

AbstractOn gelation of crystallizable stereoregular polystyrenes (isotactic IPS and syndiotactic SPS), highly ordered skeletal conformations of particular types characteristic of the respective polymer are formed. The conformational orderliness is evaluated in the absolute scale through quantitative analysis of infrared absorption bands due to the respective ordered conformation. The kinetic and/or thermodynamic behaviors of gelation process and the accompanied conformational ordering are strongly influenced by solvent. Solvent effect on the aggregation state formed in SPS gels has been investigated by means of small angle neutron scattering and discussed in relation to the gelation rate. In some solvents, two different ordering processes, gelation and crystallization, proceed in a competitive way. On the basis of these experimental facts, the roles of specific polymer‐solvent interactions in gels are considered from the viewpoint of molecular‐level structure.
Multi‐functional coordination crosslinks in poly(vinylamine) complexes with cobalt chloride
Authors: Belfiore Laurence A. , Indra Erik , Das Pronab 
Published: March 2011

AbstractPoly(vinylamme) complexes with cobalt chloride hexahydrate exhibit the largest glass transition temperature enhancements that have been measured in this laboratory. Tg increases from 56°C in the undiluted polymer to 193°C when the molar concentration of cobalt is only 3%, based on the moles of polymeric repeat units. This translates to a 45°C enhancement in Tg per mol% cobalt. Higher glass transition temperatures have been measured for other polymeric complexes with d‐block salts, but this study reports the largest ΔTg=Tg(complex)‐Tg(undiluted polymer) when transition‐metal catalyzed chemical crosslinking reactions do not occur. A plausible explanation for this effect is based on the fact that cobalt chloride hexahydrate maintains pseudo‐octahedral symmetry in the undiluted crystalline state and in an amorphous glassy complex with the polymer. The lone pair on nitrogen in the amino sidegroup is a strong base and, most likely, displaces all four waters of hydration that coordinate directly to the metal center. In fact, estimates of the ligand field splitting and the ligand field stabilization energy for octahedral cobalt complexes that contain methyl amine (CH3NH2) model ligands suggest that five or six amino sidegroups from several different chains might coordinate to each metal center, drastically reducing the mobility of the polymer. Both chloride anions remain near each divalent Co2+ center, but either one or two Cl− might not reside in the first‐shell coordination sphere of the transition metal. This bonding picture suggests that octahedral cobalt acts as a multi‐functional bridge between five or six amino sidegroups. Empirical ligand field stabilization calculations support the concept that octahedral Co2+ is a multi‐functional coordination crosslinking agent, and the inorganic literature provides experimental verification that similar small‐molecule complexes (i.e., [Co(NH3)6]2+) exist. It is proposed that the onset of Tg occurs when sufficient thermal energy is supplied to remove either x or (x‐1) amino sidegroup ligands from the coordination sphere of cobalt, where x is either 5 or 6. This is an endothermic process based on bond energies, as well as calculations which focus on the relative energies of the metal d‐electrons.