bluuebunny/crossref_metadata_2025_split huggingface dataset:
CPF: Continuous polymer fractionation
Authors: Wolf B.A. 
Published: March 2011

AbstractA method is presented by means of which it is possible to fractionate polymers according to their solubility on a technical scale. The CPF consists of a continuous counter‐current extraction process in which a homogeneous mixture of a molecularly or/and chemically non‐uniform high molecular weight product is divided into two portions of considerably lower non‐uniformity. The principle of the CPF is described in general terms and examples are given for the fractionation of homopolymers.
The application of the size exclusion chromatography/ viscometry technique to the determination of molar‐mass and long‐chain branching in polychloroprene
Authors: Krämer‐Lucas Helga , Ramthun Jürgen , Lucas Heinz W. 
Published: March 2011

AbstractThe coupling of a low‐pressure size exclusion chromatography (SEC) with a modified Ubbelohde capillary viscometer is described. This SEC/viscometry system measures the flow time of aliquot fractions (5ml) of the SEC effluent along with the refractive index change. This dual detection leads to the determination of the intrinsic viscosity as a function of the elution volume, thus allowing a precise use of Benoit's universal calibration. Moreover information of the branching factors (degree of long‐chain branching, long‐chain branching frequency) can be calculated under certain assumptions.As an example the changes in molar‐mass distribution and branching factors during mechanical shear degradation (mastication) of special polychloroprene samples were investigated. It is shown that the SEC/viscometry system is especially suitable for the characterization of polymers with broad molar‐mass distribution and extremely high molecular tails. The data provided by this method are useful for the investigation of the viscoelastic behaviour of concentated polychloroprene solutions and for quality control of polymers in the rubber and adhesives industries.
Influence of mechanical stress on the molar mass distribution and the rheological behavior of polysaccharides
Authors: Windhab E. , Zu Höne T. 
Published: March 2011

AbstractThe mechanical stress acting on hydrocolloid macromolecules in flow processes may change the molecular structure, the rheological properties, affecting the technical function and thereby the properties.This paper introduces a newly developed method for definite “mechanical stress treatment” of xanthan and guar gum. Rheological measurements (intrinsic viscosity) and chromatography (GPC) allowed the resulting rheological and structural changes to be quantified.
Characterization of polymer molecular mass distribution from rheological measurements
Authors: Fleissner M. 
Published: March 2011

AbstractVarious methods for the determination of molecular mass distribution from rheological measurements of polymer melts are introduced. Shear viscosity, entrance pressure loss, recoverable shear, and in particular the dynamic viscoelasticity data G' and G” are discussed as analytical tools to evaluate the molecular mass distribution. Well characterized samples and homologous series of the polymers PS, PE‐HD, PP, and PTFE were measured to check the methods. Precise and reliable results can be obtained by calculating the molecular mass distribution from the frequency dependence of the storage modulus.
Determination of molecular parameters from polymer solutions in shear flow
Authors: Link Alfred , Zisenis Mathias , Prötzl Brigitte , Springer Jürgen 
Published: March 2011

AbstractA light scattering photometer with a double cylinder shear cell has been developed which allows detection not only in one plane as usual, but in a half‐spherical range around the scattering volume. The anisotropic scattering behavior of oriented and deformed polymer molecules in dilute solution was investigated. All measurements were performed on polystyrene in several viscous solvents. From measurements in the plane of flow the average orientation angle was determined. By variation of detector position and wavelength of the primary beam, the determination of all three axes of the molecular gyration space of polymer coils was possible. Compared to predictions of the well‐known dynamic theories by Kuhn, Rouse and Zimm, corresponding orientation data were found while the molecular deformation ratio shows much lower values than expected.
Determination of molar mass distribution of poly(tetrafluoroethylene)
Authors: Wu Chi 
Published: March 2011

AbstractHigh‐temperature static and dynamic laser light scattering characterization of polytetrafluoroethylene in perfluorotetracosane has been accomplished after solving the following experimental difficulties: (1) constructing a high‐temperature laser light scattering spectrometer which can be operated at a temperature as high as 340 °C, (2) developing a new all‐glass apparatus for dissolving and filtering, (3) measuring the refractive index increment of polytetrafluoroethylene in perfluorotetracosane at 325 °C, and (4) establishing a scaling relation between the molecular weight (M) and the translational diffusion coefficient at both infinite dilution and the zero scattering angle from only two broadly distributed polytetrafluoroethylene samples so that we can convert the translational diffusion coefficient distribution to the molecular weight distribution. This paper presents a summary of our published results of the characterization of poly(tetrafluoroethylene), which emphasizes the experimental details of high‐temperature laser light scattering and the principle of the transformation from a translational diffusion coefficient distribution to a molecular weight distribution.
Molecular mass determination in the liquid crystalline state ‐ lyotropic cholesteric phase of a cellulose derivative
Authors: Zugenmaier Peter , Siekmeyer Maria 
Published: March 2011

AbstractLyotropic cholesteric phases of cellulose derivative/solvent systems exhibit a reflection wavelength or supermolecular helicoidal pitch dependency on molecular mass besides the well known variation of the pitch by temperature and concentration. This observation allows a molecular mass determination by spectroscopic means (UV/VIS‐, ORD‐, CD‐spectra) or by an evaluation of the colours seen in a polarizing microscope or by a direct measurement of the pitch with the Cano‐Grandjean technique.
Beyond the born approximation. The case of very long polymer chains adsorbed at an interface
Authors: Guiselin O. , Jannink G. , des Cloizeaux J. 
Published: March 2011

AbstractTwo experimental evidences are discussed of the reflectance discontinuity associated with very long adsorbed polymer chains.The anomalous low reflectivity is compared to the Ramsauer‐Townsend effect in the scattering of slow electrons by rare‐gas atoms.
Adsorption of polymer solutions on heterogeneous surfaces
Authors: Joanny J. F. , Andelman D. 
Published: March 2011

AbstractWe discuss the adsorption of polymer solutions on chemically heterogeneous surfaces. Two types of heterogeneities are considered, annealed and quenched. In both cases, the disorder increases the adsorption. For a same adsorption strength, the adsorbed amount of polymer is higher on an annealed surface than on a quenched surface. The adsorption on an annealed surface can induce a two‐dimensional phase transition on the surface.
Nonlinear kinetics of spinodal decomposition, and dissolution of inhomogeneities formed by spinodal decomposition in polymer blends
Authors: Akcasu A. Ziya , Erman B. , Bahar I. 
Published: March 2011

AbstractNonlinear kinetics of both spinodal decomposition at early stages, and the dissolution of homogeneities formed during spinodal decomposition, is studied. Variation of the scattering intensity during a complete cycle consisting of a step temperature change from T1 in the one‐phase region to T2 in the two‐phase region, a period of spinodal decomposition followed by a temperature drop from T2 back to T1, and the subsequent relaxation to the original equilibrium state, is investigated at various wavenumbers. Step temperature changes within one‐phase region are also investigated.
Ordered structure of block polymer/homopolymer mixtures, 4. Vesicle formation and macrophase separation
Authors: Koizumi Satoshi , Hasegawa Hirokazu , Hashimoto Takeji 
Published: March 2011

AbstractSelf‐assembled structures in solvent‐cast films of binary mixtures of poly(styrene‐block‐isoprene) (SI) and homo‐polystyrenes (HS) were studied as a function of rs, the ratio of molecular weights of HS and polystyrene block (PS) in SI and of wHS, the weight fraction of HS. For rS<1 (a criterion for “wet brush”), HS tends to be solubilized into the microdomain of PS and to swell the PS chains, causing a change in microdomain morphology with long‐range order. Spherical microdomains composed of polyisoprene block (PI) dispersed randomly in the matrix of HS and PS (“spherical micelles”) are formed at the limit of high wHS (wHS→1). For rS≳1 (a criterion for “dry brush”), HS tends either to be segregated from SI, forming a macrophase‐separated morphology (at rS>>1), or to be solubilized into the PS microdomains without swelling PS or without a significant change of a degree of swelling with wHS, if any, (at rS≌1). In the latter case, HS does not significantly affect the lamellar domains of PI for the particular SI studied here, which by itself gives alternating lamellar microdomains of PS and PI, but increases the mean distance between them. AS wHS→1, the long‐range spatial order of the PI lamellae is lost, while keeping their thicknesses constant and uniform, resulting in morphologies of lamellar, cylindrical, and spherical vesicles. The vesicular morphology was analyzed by small‐angle X‐ray scattering and transmission electron microscopy. At rS>>1 (still in the criterion of dry brush), SI and HS undergo macrophase separation, forming SI domains composed of alternating lamellae in the matrix of HS.
Static and dynamic light scattering studies of the critical behaviour of polymer mixtures
Authors: Fischer E. W. , Meier G. , Momper B. 
Published: March 2011

AbstractCritical fluctuations were studied in polymer mixtures of poly(dimethylsiloxane) and poly(ethylmethylsiloxane), which exhibit an upper critical temperature at Tc ⋍ 57 °C. The measurements were performed in a broad temperature range at three compositions in the miscible region close to the coexistence line. The temperature dependence of the static structure factor S(q=0) can be described by a mean field behaviour except for temperatures in the range of 6 K above Tc. There, a turnover to an Ising behaviour is observed according to a modified Landau‐Ginzburg criterion. The mean field spinodal temperature Ts was determined by extrapolation of S(0)−1 to zero. From the Ornstein‐Zernike representation of the angular dependence of S(q), the correlation length ζ of the concentration fluctuations can be determined and leads to a critical amplitude ζ0 = lim ζ(T→∞) = 20.5 Å.The interdiffusion dynamics described by the mutual diffusion constant D has been measured by quasielastic light scattering. It shows for the critical composition ϕc a critical slowing down as T approaches the critical temperature Tc. Furthermore, the q2 scaling of the relaxation rate of the interdiffusion dynamics changes to q3 behaviour close to Tc according to the mode coupling theory by Kawasaki.
Investigation of polymer surfaces using scanning force microscopy (SFM) “a new direct look on old polymer problems”
Authors: Grim P.C.M. , Brouwer H. J. , Seyger R. M. , Oostergetel G. T. , Schutter W.G. Bergsma , Arnberg A. C. , Güthner P. , Dransfeld K. , Hadziioannou G. 
Published: March 2011

AbstractIn this contribution, the general concepts of force microscopy will be presented together with its application to polymer surfaces (Ref.1). Several examples will be presented to illustrate that force microscopy is a powerful and promising tool for investigation of (polymer) surfaces, such as the imaging of polymer single crystals and the surface structure of thin films of piezo‐ and pyroelectric block copolymers. Individual molecules were resolved in the case of polytetrafluoroethylene and double‐stranded circular DNA, without any particular surface treatment.
Interfacial dynamic properties of polymer films
Authors: Yu Hyuk 
Published: March 2011

AbstractMany vinyl homopolymers are surface active by virtue of their side chains being hydrophilic while backbone hydrocarbon structure being hydrophobic, thus they form remarkably stable monolayers. We report here the studies of collective dynamics of these monolayers and thin films with the technique of surface light scattering by the spontaneous capillary waves on the air/water and oil/water interfaces. The dynamics are represented by the viscoelastic parameters of the lateral dilational mode, which couples efficiently with the transverse mode in the case of air/water interface.
Dynamic light scattering by weakly ionized gels: Effects of inhomogeneities and non‐ergodicity
Authors: Candau Sauveur Jean , Moussaid Abdellatif , Munch Jean‐Pierre , Schosseler François 
Published: March 2011

AbstractSmall angle neutron scattering and light scattering experiments have been performed on partially neutralized poly(acrylic acid) solutions and gels. The structure factor obtained from small angle scattering and static light scattering reveals the absence of significant contribution from large scale inhomogeneities in the gels as soon as the ionization degree exceeds 9·10−3. The comparison of the time and ensemble averages of the autocorrelation function of scattered light intensity shows that the gels behave with respect to that experiment as ergodic media.
Mesomorphic ordering of polymers
Authors: Skoulios Antoine 
Published: March 2011

AbstractDepending upon their chemical architecture, polymers may give rise to well ‐ ordered mesomorphic phases. A few typical examples of mesomorphic polymers (block copolymers, polysoaps and side‐chain liquid ‐ crystalline polymers, rigid‐chain polymers) will be considered. Their structure will be described as determined by x‐ray diffraction.
Biosynthesis of new polymers of controlled molecular structure
Authors: Dougherty Michael J. , Kothakota Srinivas , Krejchi Mark T. , Zhang Guanghui , Mason Thomas L. , Tirrell David A. , Fournier Maurille J. 
Published: March 2011

AbstractThis paper describes the use of artificial genes to direct bacterial synthesis of new polypeptides of precisely defined molecular structure. This approach has been applied to three problems in polymer chemistry and physics: i) control of chain folding in crystalline polymers, ii) biosynthesis of polypeptides containing unnatural amino acids, and iii) preparation of monodisperse helical polymers.
The role of amine in vinyl radical polymerization
Authors: Feng Xin‐De 
Published: March 2011

AbstractAdvances of radical initiation systems and their initiation mechanisms in vinyl polymerization through peroxycompound and amine systems as well as photo‐induced charge transfer initiation in the presence of amine are briefly reviewed which is concerned with some generalization regarding to the role of amine in the form of aminium radical in such vinyl radical polymerization.
The role of ceric ion in vinyl polymerization and graft copolymerization
Authors: Qiu Kun‐Yuan 
Published: March 2011

AbstractSix kinds of new ceric ion redox initiation systems for vinyl radical polymerization and two kinds of macromolecule graft copolymerization by ceric ion have been briefly reviewed in this paper. The initiators include ceric ion/acetanilide, ceric ion/alkyl phenylcarbamate, ceric ion/4‐methoxysuccinyltoluidine, ceric ion/aliphatic aldehyde, ceric ion/aromatic aldehyde, ceric ion/diketone systems. Macromolecules such as poly(ether‐urethane) and macromolecules having active pendant groups were selected for graft copolymerization with acrylamide initiated by ceric ion.
Synthesis and characterization of polymers from itaconic acid derivatives
Authors: Otsu Takayuki , Watanabe Hiroyuki , Yang Jian‐Zhong , Yoshioka Masahiro , Matsumoto Akikazu 
Published: March 2011

AbstractSome itaconic acid derivatives were prepared and polymerized, in which itaconic acid (IA), β‐monoalkyl itaconates (mRI), dialkyl itaconates (DRI), N‐substituted itaconamates (IAE), itaconamides (IAm), itaconic anhydride (IAn), N‐alkylitaconimides (RII), and N‐(alkyl‐substituted phenyl)itaconimides (RPhII) are included. The polymerization reactivity was examined, and discussed in relation to the structure of the monomers. The structure and some properties of the resulting polymers were investigated. Some citraconic acid (CA) and mesaconic acid (MA) derivatives were also polymerized, and their reactivities were compared with the corresponding IA derivatives.
The kinetics and compartmentalization of seeded emulsion polymerization of styrene with a series of seeds of different size
Authors: Fu Shoukuan , Qian Yu , Bai Feng , Yu Tao 
Published: March 2011

AbstractThe Interval II kinetics and compartmentalization effect of emulsion polymerization of styrene with the seeds of five radii (r=40.2, 51.3, 76.5, 99.7 and 252.0 nm) have been studied. The kinetic parameters, i.e., the rate coefficients ρ, K and C which refer, respectively, to the entry of free radicals into latex particles, the exit of free radicals from the particles and the bimolecular termination of free radicals within the particles; nss and nss(thermal), the average number of free radicals per particle in the steady state and in the thermally induced background polymerization, respectively, are obtained. The propagating rate coefficient kp, the termination rate coefficient kt, as far as possible, are calculated in the runs.From this work, it can be concluded that the kinetic behavior, the kinetic parameters and the compartmentalization effect of emulsion polymerization are greatly influenced by the latex particle size.
Kinetics of polymeric network synthesis via free‐radical mechanisms ‐ polymerization and polymer modification
Authors: Zhu Shiping , Hamielec Archie 
Published: March 2011

AbstractThe kinetics of polymeric network formation via free radical mechanisms is an attractive research area because there are many phenomena which are not well understood and in addition, the commercial potential for crosslinked systems is great. Recently, a large research/development program was initiated at the McMaster Institute for Polymer Production Technology (MIPPT) to investigate the fundamentals and applications of polymeric network, in particular, the kinetics of synthesis via free‐radical mechanisms and network characterization. The research on crosslinking involved both theoretical developments and experimentation. Herein is provided a comprehensive summary of this work.In the experimental polymerization, two comonomers, methyl methacrylate (MMA) / ethylene glycol dimethacrylate (EGDMA) and acrylamide (AAm) / N,N‐methylene bisacrylamide (Bis), as model systems were studied in considerable detail. Measurements included: monomer conversions, radical concentrations, sol/gel fractions, crosslink densities (equilibrium swelling and swollen‐state 13C‐NMR) over the entire range of divinyl monomer levels as a function of polymerization time. In the polymer modification, high density polyethylenes were crosslinked using peroxides and γ‐radiation. For this system, crosslinking and chain scission occur simultaneously.In the theoretical studies, it was shown that in general, network formation by free‐radical mechanisms is highly irreversible requiring that the classical equilibrium gelation theories after Flory/Stockmayer be generalized. The general model which was developed using the pseudo‐kinetic rate constant method predicts the existence of a crosslink density distribution (crosslink density of a primary polymer chain depends on its birth time) with a variance which can vary widely depending on network synthesis conditions.
Studies on molecular weight of poly ((vinylidene chloride)‐co‐(vinyl chloride)) in the suspension process
Authors: Liu Long‐Xiao , Weng Zhi‐Xue , Huang Zhi‐Ming , Han Dong‐Lin , Pan Zu‐Ren 
Published: March 2011

AbstractVarious factors affecting the molecular weight of poly ((vinylidene chloride)‐co‐(vinyl chloride)) were studied in the paper. Mathematical models correlating intrinsic viscosity of the copolymer with concentrations of 1,2‐dichloroethane and initiators, and temperature were proposed and may be used to control the molecular weight of the copolymer.
Non‐steady state model for free radical polymerization
Authors: Yan Deyue , Feng Jing 
Published: March 2011

AbstractThe non‐steady state theory for the kinetics of free radical polymerization taking no account of gel‐effect is reviewed. Considering the facts that the monomer consumption in chain propagation is much higher than that in chain initiation and the rate constant of chain termination is much larger than that of chain propagation or transfer, a few very close approximations are introduced to solve the set of kinetical differential equations of free radical polymerization. The expressions for various molecular parameters, such as the molecular size function, the number‐ and weight‐average degrees of polymerization and the dispersity, are derived. In accord with the non‐steady state theory, the curves of free radical decay with reaction time or monomer conversion and the molecular parameters mentioned can be predicted from the reaction conditions. Several numerical examples are given.
Stereochemical control in homogeneous Ziegler‐Natta catalysts
Authors: Chien James C. W. 
Published: March 2011

AbstractRacemic ethylenebis(η5‐indenyl)zirconium dichloride (Et[Ind]2ZrCl2) activated with methylaluminoxane (MAO) catalyzed propylene polymerization with varying degree of stereochemical control which decreases greatly with the increase of Tp (temperature of polymerization). The PP&s are characterized by low melting temperature (Tm), high solubility, and prefers to crystallize in the γ‐modification. The catalytic activity of Et[Ind]2ZrCl2/MAO becomes very small with the lowering of Tp. Very active and highly stereoselective cationic metallocene alkyl, Et[Ind]2Zr+(CH3), was produced by the reaction of Et[Ind]2Zr(CH3)2 with Ph3C+B(C6F5)4−. Comparison of this system with the Et[Ind]2ZrCl2/MAO catalyst showed that in the latter case a quarter of the Et[Ind]2ZrCl2 was converted by MAO to Et[Ind]2Zr+CH3 at room temperature but less than 0.14% of the Zr was so activated at −20°C. The Et[IndH4]ZrCl2/MAO catalyst was shown to have two kinds of catalytic species one with high propagation rate constant (kp) and stereoselectivity and another with low kp and poor stereoselectivity. The very narrow molecular weight distribution of the PP produced may be attributed to the fact that the different types of active species have comparable kp/ktrA, the latter is the rate constant of transfer. Non‐symmetric, rac‐[anti‐ethylidene(1‐η5‐indenyl)(1‐η5‐tetramethylcyclopentadienyl)‐Ti‐Cl2 and ‐(CH3)2 have been synthesized and structures determined. The complexes provide dissimilar steric environment to propagating chains to produce crystalline‐amorphous multiblock thermoplastic elastomeric PP. The polymerization process here involves a two‐state propagation mechanism.
Copolymerization of propene with high‐1‐olefin using a MgCl2/TiCl4 catalyst
Authors: Yang Shi‐Ling , Xu Zhi‐Kang , Feng Ling‐Xian 
Published: March 2011

AbstractCopolymerization of propene and 1‐olefins including 1‐octene, 1‐decene, 1‐dodecene, 1‐tetradecene, and 1‐hexadecene were studied with the catalyst system MgCl2/TiCl4‐Al(i‐Bu)3. It was found that the polymerization productivity and the consumption rate of propene are improved significantly in the presence of the comonomer. The total productivity of propene/1‐olefin copolymerizations decreases as follows: 1‐octene> 1‐decene>1‐dodecene>1‐hexadecene>1‐tetradecene. The reactivity ratios were estimated from the copolymerization results. 13C NMR was used to characterize the microstructures of propene/1‐octene copolymer. Finally, the oxygen enrichment behavior of propene/1‐octene copolymer was investigated.