bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experiences with interlaboratory GPC experiments
Authors: Bruessau Rudolf J. 
Published: March 2011

AbstractBased on some round robin experiments organized in the last years by a DIN working group and by the IUPAC working party IV.2.2, the paper discusses measures for getting a better interlaboratory reproducibility of GPC results. The most important points are:‐ selecting columns according to their separation selectivity and range‐ avoiding artifacts in the distribution curves, caused by gaps in the pore volume distribution‐ avoiding adsorption and memory effects‐ calibration: using calibration standards of high quality selecting suitable calibration points checking the influence of the injected concentration‐ selecting a common detector‐ data treatment, especially finding the correct baseline‐ preparing a detailed data report according to a uniform schedule.
Effects of electrostatic and hydrophobic interactions on the chromatographic behavior of biopolymers in HPLC columns
Authors: Corradini Danilo 
Published: March 2011

AbstractThe effect of electrostatic and hydrophobic interactions on the chromatographic behavior of biopolymers with the use of chemically bonded silica‐based HPLC columns and aqueous buffered mobile phases containing neutral salts in a wide range of concentration is discussed. Two columns packed with stationary phases appositely designed for biopolymer HPLC in size exclusion and anion exchange mode, respectively, are examined. Experimental data are evaluated by plotting the measured isocratic elution volumes of several standard proteins of different isoelectric point against the salt concentration in the mobile phase. Depending on the concentration and nature of salt, both columns exhibit different domains where either sieving effect or electrostatic or hydrophobic interactions are predominant. At sufficiently low salt concentrations electrostatic interactions are predominant leading to either increasing or decreasing elution volumes depending on the sign of the charges on the stationary phase and the protein, respectively. On the other hand, at high salt concentrations of a salt with sufficiently high molal surface tension increment proteins may be retained by hydrophobic interactions.
Catalytic chain transfer polymerisation (cctp) of methyl methacrylate: Effect of catalyst structure and reaction conditions on chain transfer coefficient
Authors: Haddleton David M. , Maloney Darren R. , Suddaby Kevin G. , Muir Andrew V. G. , Richards Stuart N. 
Published: March 2011

AbstractCatalytic chain transfer polymerisation of methyl methacrylate has been investigated by a range of cobalt(II) complexes. The effect of catalyst structure, reaction temperature and solvent has been examined. At 60°C in the absence of solvent, the chain transfer coefficient, Cs, for MMA and cobaloximes modified by bridging BF2 groups e.g. 3 is found to be 40,900, this is constant over a wide mass range. Cs is lowered when catalysts of larger cross sectional area are used supporting a diffusion controlled process. Co‐ordinating solvents suppress Cs by competing for coordination of the Co(II) effectively reducing the concentration of active species. No conclusions can be drawn regarding the effect of temperature and thus the activation energy of the process. CCTP lowers the observed rate of polymerisation.
Local monomer concentrations in emulsion polymerization
Authors: German Anton L. , Manders Bart G. , Zirkzee Hennie F. , Klumperman Bert , van Herk Alex M. 
Published: March 2011

AbstractKnowledge of local monomer concentrations in the case of heterogeneous polymerizations is extremely important, since these local concentrations determine the kinetics of the reactions. In this paper two techniques to determine the local concentrations are reported. The first technique makes use of the well known pulsed initiation method, which is frequently used nowadays for the experimental determination of the propagation rate constant (kρ). The second technique is applied for the determination of monomer concentrations in vesicle bilayer structures.
Propagation and termination processes in free radical copolymerization
Authors: Fukuda Takeshi , Ide Nobuhiro , Ma Yung‐Dae 
Published: March 2011

AbstractThe propagation and termination processes in free radical copolymerization were discussed on the basis of current experimental data. It was shown that the penultimate unit effect (PUE) in propagation is very general, affecting not only the absolute values of the rate constant but also the monomer reactivity ratios r1 and r2. The analysis suggests that the alternating index r1r2 originates in the PUE. An adequate description of the termination process also requires a penultimate model, which leads to a general, yet simple two‐parameter rate‐of‐copolymerization equation with PUEs in both propagation and termination.
Inversion of phase continuity during polymer‐polymer blending: Effect of processing parameters
Authors: Sundararaj Uttandaraman 
Published: March 2011

AbstractThe melting order of polymer blend components influences the morphology development during extrusion. An inversion in phase continuity occurs during processing if the minor component softens first. Additional power input is required to process the blend due to this inversion. The power input is intensified and the inversion is delayed when a reaction occurs during blending. Increasing the concentration of the minor phase or decreasing the mixer shear rate delays the inversion.
Metastable mesophases
Authors: Wunderlich Bernhard 
Published: March 2011

AbstractMesophases are briefly summarized and defined on a uniform basis, making use of order and mobility parameters. A schematic one‐component phase diagram is then reviewed that includes equilibrium as well as nonequilibrium phases. Assuming only five condensed phases (crystal, melt, glass, mesophase, and mesophase glass), fifteen different phase areas exist with simultaneous presence of up to three phases. Examples of all phase areas are documented with results from our laboratory. This scheme can be extended to more components and more than these five phases and produces then many more possible phase areas than can be handled experimentally at the present.
Conformational transitions in macromolecules of complex chemical structure during liquid crystalline ordering
Authors: Volchek Boris , Shilov Sergej , Purkina Alla , Medvedeva Darja 
Published: March 2011

AbstractConformational transitions in thermotropic main‐chain polymers of complex chemical structure including homopolymers with possibility of conformational transformations in mesogens and random copolymers (CPLs) containing mesogens of the same type and spacers of different lengths were investigated. It was demonstrated that liquid crystalline (LC) state influences conformational transformations in fragments of chain restraining them in comparison with an isotropic melt. It was found that CPLs studied form LC order of smectic type. Peculiarities in spacers behaviour during transition to LC state ensure formation of such type of LC order. Conclusion about dependence of mechanism of smectic LC order formation on chemical structure of rigid components of CPLs is made.
Ground‐state description of the adsorption of homodisperse and polydisperse polymers
Authors: Fleer G.J. 
Published: March 2011

AbstractA ground‐state approximation (GSA) is employed to model the structure of an adsorbed layer of homodisperse and polydisperse polymer. The model uses the basic assumption that the volume fraction at a distance z from the surface of a component with chain length N can be written as the product of the square of an eigenfunction g(z) and the N‐th power of an eigenvalue eϵ. This approximation implies the neglect of end effects (tails): only loops are considered. For a homodisperse polymer, the eigenvalue is defined through ϵN = In(1/ϕb), where ϕb is the bulk solution concentration. The eigenfuction can be written in terms of two parameters: a “proximal” length D which through the boundary condition may be related to the adsorption energy, and a “distal” length which is inversely proportional to √ε. For a polydisperse polymer, D is the same as for a homodisperse polymer, but ε has to be computed from an implicit equation which involves a summation over all chain lengths present. The contribution of each chain length N in a mixed adsorbed layer is obtained by weighting with eεN.This approximate analytical model gives results which are in good agreement with numerical self‐consistent‐field calculations. Examples are given to illustrate the applicability of the model to polydisperse systems. These include adsorption preference of long chains in polymer mixtures and the difference between adsorption and desorption isotherms in polydisperse systems. Simple expressions are obtained for the chain length characterising the transition between (long) adsorbed and (short) non‐adsorbed chains and for the width of the transition zone.
Polymerization of the 12‐methacryloyloxydodecanoic acid and a corresponding phospholipid in monolayers at the liquid/gas interfaces
Authors: Zaitsev S.Yu. , Baryshnikova E.A. , Vereschetin V.P. , Zubov V.P. 
Published: March 2011

AbstractThe following surface‐active monomers with methacrylic group at the end of hydrophobic tail: 12‐methacryloyloxydodecanoic acid (12‐MAODA) and 12‐(methacryloyloxydodecanoyl)‐glycerophosphatidylcholine 12‐MAODPC) were synthesized and investigated. Both monomers are forming monolayers at the liquid/gas interfaces with liquid‐expanded and liquid‐condensed states at low and high surface pressures, respectively. These monomers have been polymerized in the monolayers just by soft UV‐irradiation (254 nm). Dependences of polymerization rate vs. surface pressure for both monomers have maxima (3.33*10−4 s−1 for 12‐MAODPC and 4.89*10−4 s−1 for 12‐MAODA) at about 8–10 mN/m. The higher polymerization rate of 12‐MAODA polymerization as compared to 12‐MAODPC is due to the more dense packing of the acid molecules in monolayers as compared to the lipid. Areas per monomer unit in the obtained polymeric monolayers are much smaller than those for the monomer one. The collapse pressures increase after monomer polymerization that evidences the increase of the monolayer stability in case of polymer as compared to monomer.
Diblock copolymer nanostructures
Authors: Liu Guojun 
Published: March 2011

AbstractPolystyrene‐block‐poly(2‐cinnamoylethyl methacrylate) (PS‐b‐PCEMA) and poly(acrylic acid)‐block‐poly(2‐cinnamoylethyl methacrylate) (PAA‐b‐PCEMA) were synthesized. These polymers formed micelles with PCEMA as the core in solvents poor for the PCEMA block but good for the other blocks. When the PS block was much longer than the PCEMA block, star micelles were prepared. The PCEMA cores of these micelles were then photo‐crosslinked to yield PS star polymers. Nanospheres of PCEMA were obtained by photolyzing crew‐cut micelles of PAA‐b‐PCEMA, in which the water‐soluble PAA block was much shorter than the water‐insoluble PCEMA block.PS‐b‐PCEMA self‐assembled at silica and their THF/cyclopentane micellar solution interfaces to form diblock monolayers called polymer brushes, in which the insoluble PCEMA block spread like a melt on the silica surface and the chains of the soluble PS block stretched into the solution phase like bristles of a brush. By tuning the relative composition, PCEMA in bulk formed cylindrical micro‐domains dispersed in the continuous PS matrix. Irradiation of the PS‐b‐PCEMA brushes enabled our preparation of crosslinked PS‐b‐PCEMA monolayers. Nanofibers were prepared by dissolving in THF the irradiated PS‐b‐PCEMA films with crosslinked cylindrical PCEMA micro‐domains.
Polymer‐solvent complexes in thermoreversible gels and in solids as studied by NMR and other methods
Authors: Spêváček Jiří , Suchopárek Miloš 
Published: March 2011

AbstractThe existence of polymer‐solvent complexes, very probably of the inclusion type, was proved in gels and solids of syndiotactic poly(methyl methacrylate) (PMMA), in gels of isotactic PMMA, and in poly(vinyl chloride) gels by NMR spectroscopy combined with DSC and infrared measurements. For PMMA‐solvent complexes, the stoichiometry was estimated. NMR was also used to characterize the dynamic structure of the crystalline intercalate complexes of poly(ethylene oxide) with p‐nitrophenol and other hydroxybenzenes.
Polymers for electrochemical devices
Authors: Sanchez Jean‐Yves , Alloin Fannie , Benrabah Djamila , Roux Christcl 
Published: March 2011

AbstractPolymeric materials are already present in electrochemical storage devices such as batteries and PEM fuel cells. The polymer is an electro‐active material in lithium polymer batteries. Several network based polymer electrolytes provide thermal, mechanical and redox stabilities, while insuring a high conductivity level. Linear unsaturated polyether precursors may be obtained either by step‐growth polymerization from oligomeric polyethers, or by ring‐opening polymerization from oxirane mixtures. Some prototype performances, performed on a 10 Wh lithium polymer cell, are presented and discussed.
The role of polymer‐solvent compounds in thermoreversible gelation
Authors: Guenet J.M. 
Published: March 2011

AbstractThe definition of a thermoreversible gel is first discussed through the use of two criteria dealing with topology and with thermodynamics. According to this definition only fibrillar systems, as opposed to spherulitic packings, ought to be considered gels. A simple mechanical test is presented that helps recognize such gels. The gelation mechanisms are briefly reviewed and the importance of the role of the polymer‐solvent compound in preventing chain from folding, which favours fibrillar structures, is stressed. Also, the role of such compounds in gel ageing, particularly in the case of PVC, is highlighted.
Ciliation and lamellae in crystalline polymers
Authors: Bassett DC 
Published: March 2011

AbstractMolecular cilia, the uncrystallized portions of chains already partly attached to polymer crystals, exert a profound influence on the course of polymeric crystallization with ultimate responsibility for the divergence of adjacent lamellae which leads to spherulitic growth. Their effective size and pressure have been measured, in α‐polypropylene, from electron microscopic measurements of the separation and maximum curvature of lamellae in row structures. That cilia exist and extend the effective region occupied by a lamella beyond the geometrical confines of its fold surfaces is important for crystallization theory and may well have implications for the connection of lamellae into networks and for gelation.
The salt effect over the physical interactions occurring for schizophyllan in the presence of borate ions
Authors: Grisel Michel , Muller Guy 
Published: March 2011

AbstractSchizophyllan solutions in the presence of borate ions were studied in order to evidence physical interactions occurring in aqueous media. The experiments were conducted using viscometric measurements. Changing the added salt was found to have a dramatic effect on the properties of the solutions, and the results were interpreted in terms of water structure variations.
Solvent‐polymer interactions in associative polymer/aqueous media systems
Authors: Picton Luc , Muller Guy 
Published: March 2011

AbstractLight scattering measurements in the dilute regime (C<C*) of the amphiphilic hydrophobically modified hydroxyethyl cellulose (HMHEC) have shown a metastable equilibrium of solubility in pure water. As a consequence such ageing solutions present a great instability and in severe conditions of added NaCl or temperature, a demixion has been evidenced. In a more concentrated range of concentration, aqueous solutions of HMHEC possess higher viscosity than HEC precursor due to intermolecular hydrophobic associations. But in a 1M NaCl/ethanol mixture this effect is greatly weakened.
Ternary complexes in agarose gels prepared from binary solvents
Authors: Ramzi Mohamed , Guenet Jean‐Michel , Rochas Cyrille 
Published: March 2011

AbstractThe thermoreversible gelation of agarose has been investigated in four different aqueous binary solvents: Water/dimethyl sulfoxide, water/N,N‐dimethylformamide, water/N‐methylformamide, and water/formamide. The phase diagrams have been subsequently established as a function of agarose concentration and solvent composition. These diagrams suggest the formation of ternary complexes agarose/water/cosolvent.
Study of metal clusters intercalation into cellulose by waxs, spectroscopic, and microscopic methods
Authors: Kotelnikova N.E. , Paakkari T. , Serimaa R. , Wegener G. , Kotelnikov V.P. , Demidov V.N. , Schukarev A.V. , Windeisen E. , Knozinger H. , Kudryashov V.I. , Serebryakov A.S. 
Published: March 2011

AbstractCellulose substrates are increasingly used as supports and fillers in medicine, as membranes and components of organic sensors. In the present paper the WAXS as well as SEM, TEM, XRF, EDXA, ESCA, FTIR, Raman, and 13C NMR were used to study methods of metal clusters intercalation (taking as an example silver clusters) into the cellulose matrix and changes of cellulose structure in the resulting samples in bulk after this intercalation. Clusters in matrix can be formed simultaneously with the appearance of the metal phase proper on the cellulose surface. Some paths for intercalation of regularly distributed highly dispersed metal particles are shown.
Crystalline structure of PEO‐hydroquinone and PEO‐2‐methylresorcinol molecular complexes
Authors: Paternostre L. , Damman P. , Dosière M. 
Published: March 2011

AbstractThis paper deals with the calorimetric study of PEO‐hydroquinone and PEO‐2‐methylresorcinol complexes. The phase diagrams determination and the evaluation of the exact stoichiometry of both binary systems has been carried out. For the PEO‐2‐methylresorcinol system, WAXS experiments have been used to clarify the phase diagram.
Synthesis of poly(oxypropylene)‐lithium bis(trifluoromethyl‐sulfonylimide) polymer electrolytes. Diffusion study by NMR techniques
Authors: Roux Christel , Gorecki Wladimir , Sanchez Jean‐Yves , Belorizky Elie 
Published: March 2011

AbstractHigh molecular weight polymers have been prepared by ring‐opening polymerization of propylene oxide PO using a Vandenberg initiator. Polymer electrolytes based on this polymer and an imide salt LiTFSI have been investigated. We present the results concerning the synthesis of the polymer and the glass transition temperatures evolution of the complexes with respect to salt composition. Diffusion constants of 19F and 7Li nuclei are determined by NMR techniques and a value of the cationic transport number t+ = 0.1 is obtained.
On the clathrate forms of syndiotactic poly(p‐methylstyrene)
Authors: Dell'Isola Annamaria , Floridi Giovanni , Rizzo Paola , de Ballesteros Odda Ruiz , Petraccone Vittorio 
Published: March 2011

AbstractA classification for clathrate structures of syndiotactic poly(p‐methylstyrene) in two classes (α and β), on the basis of X‐ray diffraction analyses as well as of the different observed behavior with respect to the thermal and acetone treatment, is presented. A structural correlation between α and β class clathrates and forms I and II, respectively, is evidenced. It is also suggested that form I and form II could be the “emptied forms” of the α and β class clathrates, respectively. Similar steric hindrance of the molecules inducing clathrate structures, within each class has been observed.
On the gelation rate of thermoreversible poly(vinylidene fluoride) gels in glyceryl tributyrate
Authors: Mal Sukumar , Nandi Aran K. 
Published: March 2011

AbstractThe gelation rate of poly(vinylidene fluoride) (PVF2)/glyceryl tributyrate (GTB) system has been measured. It has been analysed with the help of an equation which contains φn and f(T) term where φ is a reduced overlapping concentration and n is analogous to the percolation exponent β in a three‐dimensional lattice. f(T) is related to the temperature function of the coil‐to‐helix transition. Analysis of the gelation rates supports that the three‐dimensional percolation is a suitable mechanism in this gelation process and it also indicates that the gelation is caused by coil‐to‐helix transition followed by their association.
NMR determination of the ordering of the molecules in cholesteryl esters liquid crystal phases
Authors: Andreev Vladimir A. , Oleynikova Irina V. 
Published: March 2011

AbstractA procedure based on the method of moments of NMR line is applied to determine the order parameter tensor for cholesteryl esters. The order parameter dependence on the length of alkyl chain is obtained. The proposed method can be used to estimate the concentration of two independent conformations.
Etude rheologique de gels mixtes de poly(alcool vinylique) et d'alginate de sodium
Authors: Christelle Desmarquet , Eliane Fabrègue , Geneviève Cassanas , Michel Vert 
Published: March 2011

AbstractSnake‐cage hydrogels were prepared by the association of poly(vinyl alcohol) (PVA) and sodium alginate. The aim of this work is to study the viscoelastic properties of PVA networks having different molecular weights and trapping alginates of various mannuronate/guluronate ratios, molecular weights and aqueous concentration. The elastic and viscous moduli, G′ and G″, were found to depend on alginate concentration. With the sodium alginate (mannuronate/guluronate =1.78, M̄w=380 000), the elasticity was observed to be independent of the PVA molecular weight in the 7.5% to 10% (w/w) concentration range. Hydrogels elasticity was found to be sodium alginate nature‐dependent only in the case of PVA with M̄w =22 000. Moreover, it seems that the viscoelastic parameters G′ and G″ become increasingly insensitive to the nature of sodium alginate as the molecular weight of PVA increases.
Photooxidation of copolymers of fluorinated olefins and allyl or vinyl ethers
Authors: Gardette Jean‐Luc , Posada Fabrice , Philippart Jean‐Louis , Kappler Patrick 
Published: March 2011

AbstractThis article reports the results on the photooxidation mechanisms of two copolymers of fluorinated olefins and allyl or vinyl ethers. It is shown that the presence of the fluorine atoms influences strongly both the orientation of the reaction and the photooxidation kinetics. Due to the neighbouring fluorine atoms, the methylene groups in α‐position of the oxygen of the ether groups are not equivalent regarding oxidation and the secondary carbon becomes more oxidable than the tertiary one. Because these unexpected results were obtained, the study has been extended to non fluorinated polyethers. On the basis of the results obtained, a general mechanism of the primary oxidation of polyethers is given, and the role played by the fluorine atoms on the orientation of the reactions is discussed.
Review and kinetic analysis of the photodegradation of UV absorbers
Authors: Pickett James E. 
Published: March 2011

AbstractUltraviolet absorbers (UVA's) undergo photodegradation with quantum yields on the order of 10−6 even in glassy, unreactive matrices such as poly(methyl methacrylate) (PMMA). The kinetics of UVA loss in a film or coating can be described by the equation: A = log10[(1‐To)10 + 1] where A is the absorbance at time t, To is the initial transmission, Ao is the initial absorbance, and k is an “infinite absorption” zero order rate constant. The derivation and implications of this equation and a general review of UVA degradation chemistry are discussed.