bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composite dextran gels as size exclusion chromatography stationary phases
Authors: Spychaj Tadeusz , Bartkowiak Artur 
Published: March 2011

AbstractComposite dextran gels have been prepared using epichlorohydrin as the covalent cross‐linker and a modifying agent, typically a polyvalent metal compound creating complexes with the residual OH groups of the polymer matrix. Two series of gels were prepared and investigated by a comparison of their swellabilities in water as well as the separation characteristics when used as size exclusion chromatography (SEC) stationary phases. The gels were in situ modified with sulfates of Mg(II), Zn(II), Co(II), Ni(II), Cu(II), Mn(II), Al(III), Fe(III) and tetraethylorthotitanate or with the oxides: MgO, ZnO, Al2O3, TiO2 and SiO2. Large differences in the swellabilities and SEC calibration dependences for poly(ethylene glycol) standards in an aqueous eluent have been found and discussed.
Molded separation media: An inexpensive, efficient, and versatile alternative to packed columns for the fast HPLC separation of peptides, proteins, and synthetic oligomers and polymers
Authors: Svec Frantisek , Fréchet Jean M. J. 
Published: March 2011

AbstractA simple molding process carried out within the confines of a chromatographic column has been used for the preparation of macroporous poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) and poly(styrene‐co‐divinylbenzene) rods. The novel monolithic separation media that are obtained are useful for the HPLC separation of biological and synthetic polymers. The presence of large pores with a diameter of about 1 μm makes the molded rod columns easily permeable to eluents. Therefore, the back pressure of these columns is modest even at high flow rates. In contrast to the conventional HPLC columns packed with beads, all of the mobile phase flows through the continuous monolithic medium. As a result of this total convection, the efficiency of the molded media is almost independent of the flow rate. This improves significantly the separation ability of the rod columns and very fast separations of macromolecules such as peptides, proteins, and synthetic polymers have been demonstrated.
Chemical composition distribution of graft copolymer prepared by macromonomer technique: Determination by gradient HPLC
Authors: Teramachi Shinya 
Published: March 2011

AbstractThe chemical composition distributions (CCDs) of poly(methyl methacrylate)‐graft‐polystyrene samples prepared from the polystyrene macromonomers having methacryloyl and p‐vinylbenzyl end‐groups were determined by high‐performance liquid chromatography (HPLC) based on reversed‐phase and normal‐phase adsorption modes. The CCDs determined by both modes were in good agreement with one another, indicating that the effect of the molecular weight distribution on the CCD is negligible. The results demonstrated the features of the CCDs in agreement with the theoretical predictions and the strong effect of the intrinsic reactivity of the end‐group on the copolymerization reactivity of the macromonomer.
Investigation of statistical, block and graft copolymerizations using nmr‐sensitive initiators and macroinitiators
Authors: Harwood H. James , Christov Latchezar , Guo Mingming , Holland Troy V. , Huckstep April Y. , Jones Daniel H. , Medsker Robert E. , Rinaldi Peter L. , Saito Takeshi , Tung Deborah S. 
Published: March 2011

Abstract13C‐ and 31P‐NMR studies on polymers and copolymers derived from 13C‐enriched AIBN, 13C‐enriched dibenzyl ketone and diphenyl‐2,4,6‐trimethylbenzoylphosphine oxide (Lucrin TPO) are reported. They provide information about the influence of solvent on the initiation step in copolymerization reactions, the selectivity of diphenylphosphinyl radicals and the chemical behavior of radicals derived from dibenzyl ketone. In addition, NMR, molecular weight and molecular weight distribution measurements on polymers obtained from polymerizations of methyl methacrylate conducted in the presence of stilbene indicate that stilbene or radicals derived from it may be able to moderate MMA polymerizations.
New aspects of pseudostationary polymerization and their application
Authors: Olaj Oskar Friedrich , Zifferer Gerhard 
Published: March 2011

AbstractContrary to the stationary state little thought has been given so far to the general principles of the pseudostationary state. In this discourse an attempt is made to demonstrate that — within wide limits — arbitrary initiation profiles may be used to determine kp/kt (kp = rate constant of chain propagation, kt = rate constant of chain termination) from the frequency dependence of rate of polymerization (in analogy to the rotating‐sector technique) as well as to evaluate kp from the chain‐length distribution (CLD) of samples prepared under pseudostationary conditions. Adverse factors like nonspontaneous transformation of absorbed photons into primary radicals do not invalidate this result. The existence of a universal relationship (independent of the initiation profile) is proved to exist for the second moment of the CLD of samples prepared under pseudostationary initiation conditions for constant (chain‐length independent) kt. Pseudostationarity, however, might be also achieved if not the initiation but the termination is periodically varied. In this case the CLD has a completely different shape but allows determination of kp likewise. Finally, the case of chain‐length dependent kt is shortly discussed in connection with pulsed‐laser initiation. Although the general equation for the second moment of the CLD does not apply any longer for this case some generality appears to exist under these conditions, too.
The Correlation between segment interaction parameter and interface width of polymer blends
Authors: Stamm Manfred 
Published: March 2011

AbstractThe correlation between the segment interaction parameter and the interface width of incompatible polymer blends can be used to obtain information on the segment interaction of incompatible polymers via an accurate measurement of the narrow interface width by neutron reflectometry. Several model systems are discussed including polystyrene/poly(cyclohexyl acrylate‐stat‐n‐butyl methacrylate), polystyrene/ poly (styrene‐ stat‐p‐bromo styrene) and poly styrene/poly(methyl methacrylate).
In‐situ deformation studies of rubber toughened PMMA: A SAXS analysis of the response of core‐shell particles to deformation
Authors: He Chaobin , Donald Athene M. , Butler Michael F. , Diat Olivier 
Published: March 2011

AbstractThe deformation behaviour of core‐shell rubber particles in a polymer matrix under tensile strain was studied using small‐angle X‐ray scattering (SAXS) combined with computer simulation of the scattering. The core‐shell rubber particles first undergo inhomogeneous deformation, followed by a progressive debonding at the rubber/poly(methyl methacrylate) (PMMA) interfaces beyond the yield point. A dilatation band of cavitated rubber particles, with a tilt angle of 46–48°, is also observed in samples with a high rubber particle concentration.
Limitations of short‐term ageing tests in assessing polyethylene blends for wire and cable applications
Authors: Tran Conchita 
Published: March 2011

AbstractMedium‐density PE (MDPE) and high‐density PE (HDPE) compounds are commonly used in telecom wire insulation. Many of these compounds are blends of low‐density PE (LDPE) with HDPE in a ratio in which the two PE are immiscible. These blends feature very low mechanical properties that are often interpreted erroneously as being thermal degradation of the compound.
Controlled architectures and property synergisms of polypropene/polyamide 6 blends prepared via reactive processing
Authors: Rösch Joachim , Mülhaupt Rolf , Michler G. H. 
Published: March 2011

AbstractVariation of molecular architectures of blend compatibilizers and reactive processing reaction conditions gave excellent control on morphology development and toughness/stiffness balance of polypropene/polyamide 6 blends. Basic structure/property relationships of blends containing discrete PA6 phases, PA6 nanoparticle cores encapsulated in a rubber shell, dispersed PA6 particles with rubber subinclusions, and percolation structures of agglomerated core/shell particles were investigated. Deformation behavior of percolation structures were analyzed by means of high‐voltage transmission electron microscopy.
Chemical modification of polyolefin blends
Authors: Chodak Ivan , Repin Hans , Bruls Willie , Janigova Ivica 
Published: March 2011

AbstractThe effect of crosslinking on the properties of low density polyethylene / polypropylene blends was investigated. It was found that crosslinking results in much higher deformability of the blends compared to uncrosslinked materials. A decrease in crystalline portion determined by DSC leads to lower modulus in crosslinked samples. High drawability of crosslinked samples is mainly attributed to peculiar behaviour of PE part of the crosslinked blend where thicker lamellae are formed during drawing.
Encapsulation: A new concept to control alloys morphology
Authors: Patrice Perret , Alain Bouilloux , Marius Hert , Igor Leclere 
Published: March 2011

AbstractA new concept for tailoring polyamide or polyester / polyamide alloys containing core shell particles has been developed. This alloy technology is based on the combination of one polyester and one polyamide (or two polyamides) of different melting points and a rubbery ethylene ‐ acrylic ester ‐ glycidyl methacrylate terpolymer. Optimum properties are a function of compounding temperature profile. Resulting alloys offer a good balance of flexibility, toughness and dispersed phase morphology stability.
Microphase separation in correlated random copolymers
Authors: Angerman Henk , Brinke Gerrit Ten , Erukhimovich Igor 
Published: March 2011

AbstractIn this paper we present the results of a calculation of the phase diagram of a highly polydisperse multiblock copolymer in the weak segregation limit. The theory for polydisperse systems developed by Erukhimovich and Dobrynin [Erukhimovich, I.; Dobrynin, A. V. Macromol. Symp. 81, 253 (1994)] has been used. The model of the copolymer has the following characteristics: the blocklengths, as well as the molecule lengths are highly polydisperse (Mw/Mn = 2). The average number of blocks per molecule is very large and the effects of the finiteness of the blocklengths (the fluctuation corrections) are ignored. The resulting phase diagram shows some remarkable differences with the phase diagram of a regular monodisperse multiblock. Known differences are e.g. the order of the transition from the homogeneous state, and the variation of the period of the microstructure with the X‐parameter. In addition, we found a peculiar feature at the critical point: the phase boundaries have discontinuous derivatives.
Artificial muscles based on nematic gels
Authors: De Gennes Pierre‐Gilles , Hébert Matthieu , Kant Rama 
Published: March 2011

AbstractMechano‐chemical conversion through the swelling of polymer gels suffers from several limitations, as far as the artificial muscles applications are concerned: mechanical response is too slow and strong local stress damages the sample. We propose a different approach to bypass these difficulties: artificial muscles based on nematic gels. When the temperature is lowered below the nematic clearing point, strong uniaxial deformations occur. The estimated shape relaxation time is well within actual muscle contraction times.
Thermal relaxation in poled non‐linear optical sidechain polymers: Influence of annealing
Authors: van Der Vorst Cornelis P.J.M. , van Gassel Rob A.P. 
Published: March 2011

AbstractThe influence of different annealing treatments has been investigated on the stability of the Electro‐Optic coefficient in a poled DANS (4‐dimethylamino‐4′‐nitrostilbene) sidechain polymer, which was poled near its Tg‐onset of 140°C. The annealing treatments and the EO relaxation experiments were performed at 120°C. The EO stability can be significantly increased both by an annealing treatment after poling and by annealing before poling. This latter effect is concluded from the reduction of the EO relaxation rates in successive relaxation cycles performed in the same polymer sample ‐ completely depoled and repoled in between the cycles. The effect from the different annealing treatments on the time‐dependence of the EO relaxation process is different and is analyzed in terms of a Debye‐like model with a single, time‐dependent Debye relaxation time r(t)=ri+C. t3. The time‐dependence of r and the observed effects from annealing are attributed to the parallel relaxation process of physical ageing.
Neutron scattering studies of syndiotactic polystyrene crystals
Authors: Moyses Stéphane , Sonntag Philippe , Spells Stephen J. 
Published: March 2011

AbstractNeutron scattering experiments are reported on solution grown crystals of syndiotactic polystyrene (sPS) at small and large q, in order to investigate the chain conformation within the lamellar crystals. From the results in both the Guinier and the intermediate ranges, we come to the following conclusions: The chain folds in one or several sheet depending on the molecular weight, comparison between measured and calculated intensity plots give strong indication that a is the fold direction. The statistical model recently built for the spatial arrangement of stems in a sheet‐like structure is successful again, and demonstrate a strong statistical preference for adjacent re‐entry.
Anisotropic agarose gels
Authors: Rochas C. , Hecht A.M. , Horkay F. , Geissler E. 
Published: March 2011

AbstractAgarose hydrogels deswell reversibly over a wide range of concentration. Two types of deswelling measurements are considered here, isotropic and uniaxial. We describe some of the properties of the gels observed in the deswollen state. In both the isotropic and uniaxial geometry, the swelling pressure varies approximately as the square of the concentration.
Molecular recognition effects in polyaniline
Authors: Ikkala O. T. , Pietilä L.‐O. , Vikki T. , Österholm H. , Passiniemi P. J. , Ahjopalo L. , Österholm J.‐E. 
Published: March 2011

AbstractPolyaniline (PANI) is known to dissolve in strong acids, such as sulphonic acids. PANI, in its electrically conductive form, is generally regarded to be poorly soluble in low‐acidic solvents and to be infusible, closely resembling fully aromatic rigid rod polymers. We show that “less” acidic solvents and plasticizers can be found based on phenyl‐phenyl interactions in combination with hydrogen bonding. The requirement is that the interactions are strong enough and, importantly, sterically match the complementary moieties of the sulphonic acid doped PANI. Dihydroxybenzenes and bisphenols are examples of such low‐acidic compounds. This type of molecular recognition allows solution and melt processibility of PANI doped by generic sulphonic acid, such as methanesulphonic acid or alkylbenzenesulphonic acid. Molecular recognition is also offered as an explanation for the previously observed high solubility of camphorsulphonic acid (CSA) doped PANI in phenols.
Structural changes of the molecular complexes and consolute phenomena in binary liquid mixtures
Authors: Brovchenko Ivan V. , Oleinikova Alia V. 
Published: March 2011

AbstractConsolute phenomena in the aqueous solutions of the polymers are considered In view of the temperature induced structural changes of the hydrogen bonds between water and functional groups of polymer. The lower and upper critical consolute points are attributed to the appearance of the “critical” concentration of the complexes with one hydrogen bond between single water molecule and functional group of polymer. Namely such kind of the hydrogen bonds are responsible for the formation of the strongly associated water clusters, that may be followed by phase separation. Experimentally observed dependences of the critical consolute temperatures for the aqueous solutions of polyethylene glycol on the molecular weight of polymer and adding of salts are well reproduced in the framework of the proposed model.
Polymorphism of the poly(ethylene oxide)/Li triflate complexes
Authors: Moulin Jean‐François , Damman Pascal , Dosière Marcel 
Published: March 2011

AbstractWe hereafter present the study of the high concentration zone of the PEO/Li triflate phase diagram. This system was found to form three different molecular complexes. Their thermal behaviour was elucidated by use of three complementary techniques: Calorimetry, X‐ray diffraction and optical microscopy.
Effect of absorption of low‐molecular‐weight compounds by some polymer flocculants
Authors: Zheltonozhskaya Tatyana B. , Romankevich Olga O. , Syromyatnikov Vladimir G. , Bulavin Leonid A. , Kudrya Vladislav Yu. , Ogul'chansky Tymish Yu. , Yashchuk Valeriy M. 
Published: March 2011

AbstractThe sorption properties of the intramolecular complex ‐ poly(acrylamide) to poly(vinyl alcohol) grafted copolymer (PVA‐PAAN) in block state were investigated with respect to a number of compounds. The relatively small molecules of phenol, phenylalanine in water solution as well as nitrobenzene in hexane are strongly absorbed by PVA‐PAAN films. The large humine acid molecules (sizes are larger by more than ≈ 10 times) are absorbed by PVA‐PAAN very weakly. It was determined the absorption influence on the character of polymer film solution. In a number of cases the oscillation of the dilution and sorption were observed when determining the critical concentrations of guest molecules in the upper layer of polymer films were achieved. The possible mechanisms of absorption were discussed.
Polymer‐solvent interaction in physical networks
Authors: Solovyov M.Ye. , Ivashkovskaya T.K. , Irzhak V.I. , Galushko A.G. 
Published: March 2011

AbstractThe theoretical model of thermodynamical properties of swollen polymer network with physical junctions is proposed. Temperature transitions in network depending on solvent volume fraction and strain are investigated. As is shown, phase transition and collapse — decollapse processes are obtained in dependence on thermodynamical parameters and concentration of physical junctions.
Microstructure of poly(ethylene oxide) gels dispersed in various organic solvents
Authors: Kobayashi Masamichi , Kitagawa Kenji 
Published: March 2011

AbstractOrdered structure formed in gels of poly(ethylene oxide) (PEO) dispersed in various organic solvents has been investigated by means of infrared spectroscopy. In a cooled gel (below −35 °C) of PEO dispersed in a 1:1 mol/mol mixture of chloroform and carbon disulfide, a uniform (7/2) helical conformation is formed, in contrast to the distorted helix present in the monoclinic crystal modification. In a low‐temperature range below −65 °C formation of a rigid polymer‐solvent complex is suggested. The structure of the resultant gels as well as the gelation behavior are strongly dependent on solvent, reflecting the difference in the strength of polymer‐solvent interactions.
Complex formation of boric acids with DI‐ and TRI‐ carboxylic acids and poly(vinyl alcohol) in aqueous solutions
Authors: Kobayashi Mitsue , Kitaoka Yoshinori , Kobayashi Masamichi 
Published: March 2011

AbstractComplexation of dihydroxyboryl compounds such as dihydroxyboryl phenylalanine and boric acid with polycarboxylic acids as well as polyols was studied by infrared spectroscopy and zone electrophoresis. By consulting the results obtained, gel formation of poly(vinyl alcohol) (PVA) in aqueous solutions of boric acids (BA) and borax was studied. The IR spectra of aqueous PVA‐BA gels indicate that BA mainly assumes a planar triangle form, while the local conformation of PVA in the gel is different from that in aqueous solutions.
A small‐angle neutron scattering study of the helical form involved in the thermoreversible gelation of syndiotactic poly(methyl methacrylate)
Authors: Saiani A. , Guenet J.M. 
Published: March 2011

AbstractThe chain trajectory in syndiotactic poly(methyl methacrylate) thermoreversible gels has been studied by neutron scattering. Theoretical fits of the scattering curves are consistent with a double‐stranded helix in which the inner helix adopts a structure proposed by Kusuyama et al. The solvent is thought to be intercalated between the two strands of the double helix.
Role of the polymer microstructure in the thermoreversible gelation of poly(vinyl chloride)
Authors: López Daniel , Mijangos Carmen , Guenet Jean‐Michel , Santamaría Antxon , Eugenia Muñoz María 
Published: March 2011

AbstractGels of polyvinylchloride (PVC) and PVC copolymers of different microstructure and molar composition, were prepared in a series of diester‐like solvents. The viscoelastic properties of these gels were evaluated as a function of temperature and the molecular structure was studied by small‐angle neutron scattering. The degrees of proton association in the polymer solutions were determined by 1H NMR spectroscopy by measuring the intensity of proton bands of CH2 monomeric units. The body of experimental data shows clearly that there is a straight relation between molecular structure, viscoelastic properties of the gel, degree of polymer‐solvent interaction and polymer microstructure.
A spreading model for the oxidation of polypropylene
Authors: George Graeme A. , Celina Mathias , Lerf Claude , Cash Gregory , Weddell David 
Published: March 2011

AbstractA model for the heterogeneous oxidation of polypropylene (PP) is proposed in which it is considered that there is a small initial fraction, po, of oxidizing centres which have a high local rate of oxidation. Within these zones there is a free radical chain reaction producing secondary oxidation products, volatiles and chemiluminescence (CL) from peroxy radical termination reactions. These zones progressively spread (rate coefficient b/s−1) and the free radical reactions die away within the volume of the original zones, producing a measurable concentration of oxidation products (rate coefficient α/s−1). Analysis of the CL‐time curve as representing the instantaneous infectious, fraction, pi, in the spreading model enables the parameters po, b and α to be determined and profiles of the remaining fraction (pr) and dead or oxidized fraction (pd) constructed. Analysis of CL curves from 120°C to 150°C gives an activation energy for spreading in PP particles of 96kJ/mol. Both single particles and groups of particles of different types of PP have been examined and evidence is presented of rapid surface spreading of oxidation from particle to particle.
LCP polyesters vs thermosetting polyesters: A paradigm for research in the 21st century
Authors: Economy James , Frich Dan , Schneggenburger Lizabeth A. 
Published: March 2011

AbstractIn this paper we attempt to trace the course of development of our work on aromatic copolyesters starting in 1963 with the successful polymerization of p‐hydroxybenzoic acid and its aromatic copolyesters and continuing up to the present. In so doing a number of interesting issues are identified which provide us with important insights into the rapidly changing research environment of the past 30 years. Perhaps more importantly, some of the key requirements for successfully carrying out research into the 21st Century within a University framework begin to emerge. As part of the overview, a brief retrospective of work over the last 40 years in the field of high temperature polymers is given to provide a suitable background to the motivation for our research.
Amalgamation of ziegler‐natta and metallocene catalysts
Authors: Soga K. , Jin J. , Kaji E. , Uozumi T. , Suzuki Y. 
Published: March 2011

AbstractThe MgCl2 supported half titanocenes and Ti(4, 4, 4‐trifluoro‐1‐phenyl‐1, 3‐butanedionato)2Cl2 catalysts were synthesized and applied to propene polymerization. Without supporting on MgCl2, those complexes displayed almost no activity even using methylaluminoxane (MAO) as cocatalyst. When supported on MgCl2, on the other hand, the resulting catalysts could be activated by ordinary alkylaluminums to yield polypropene in fairly high yields. The catalyst isospecificity was markedly improved by the addition of a suitable Lewis base.