bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectroscopic studies on modified wood
Authors: Lindberg J. Johan , Laanterä Matti , Soljamo Kari
Published: March 2011

The FTIR spectra of solid resin‐free samples of chemically modified Norway spruce wood were recorded. Correlations were noted between spectral and hydrogen bond structure, chemical modification, fibre crystallinity and macroscopic softening point.
Conformational ordering of chain molecules in liquid crystals
Authors: Abe Akihiro
Published: March 2011

Deuterium NMR studies have been performed to elucidate orientational characteristics of some ether‐type main‐chain liquid crystals. Spacers used are of the type ‐O(CH2)nO‐ with n = 9 and 10. Dimers, homopolymers as well as copolymers in which spacers n = 9 and 10 are arranged in an alternative fashion were investigated. The quadrupolar splitting data obtained from the deuterium‐labeled mesogenic core and spacer have been studied within the rotational isomeric state (RIS) approximation. The ordering characteristics thus estimated were found to be consistent with the magnetic susceptibility data obtained by using superconducting quantum interference device (SQUID) for the same polymers.
Modelling copolymerization kinetics
Authors: O'Driscoll Kenneth
Published: March 2011

The composition and rate behavior of free radical copolymerizations is usually described by the Mayo‐Lewis (ML) model and the associated reactivity ratios, r1 and r2. Particularly with respect to rate, a number of systems have been found to be poorly described by the simple ML model and the penultimate unit effect (PUE) model has been suggested as an explanation. A small but significant amount of work has been done with small model analogues of polymer chains and with ESR which has established the chemical feasibility of a PUE. This paper reviews recent work with pulsed laser polymerization kinetic measurements which are successfully described in terms of a modified PUE. It is concluded that the strength of the PUE correlates inversely with the monomer reactivity ratio product, r1r2. The effect is important for rate, but not for composition.
Competition between dopants on redox reaction of polypyrrole
Authors: Ko J. M. , Rhee H. W. , Kim C. Y.
Published: March 2011

The surface of PPy prepared in a multiple electrolyte solution such as NaDS‐NaClO4 in H2O shows a coarser structure than that of the polymer prepared in a single electrolyte system. DS− with a large aliphatic chain is used as a dopant in preparation of PPy. The dopant is trapped in PPy when the polymer is reduced in an aqueous system. A cation Na+ or K+ is inserted into the polymer to balance the free DS− liberated form and remained in it on reduction. PPy doped with DS− shows a high degree of redox reactivity in the system of TBADS‐AN but a poor stability in repeated redox process. The degree and rate of redox reactivity enhance when an aqueous solution of NaClO4 is used as an electrolyte system. Both Na+ and ClO4−take part in the redox reaction and the reduction process is intense at only one current potential.
Room‐temperature curing epoxies and their elevated‐temperature properties
Authors: Dodiuk H. , Kenig S.
Published: March 2011

Low‐temperature curing epoxy formulations for elevated‐temperature service were developed and characterized for adhesive repair and composite matrix. Balanced lap‐shear and peel strengths for adhesive applications and flexural and interlaminar shear strengths for composites were obtained when a blend of tetra‐functional and tri‐functional epoxies was used. For low‐temperature curing triethylenetetraamine (TETA) was proven to be effective combined with an amine terminated elastomer. The latter component served also as a toughener. Lower‐functional epoxies and curing agents resulted in a peel strength increase and a simultaneous decrease in shear strength. Furthermore, the incorporation of the lower‐functional constituents or silanes, resulted in development of a three‐phase morphology compared to a conventional two‐phase elastomer‐epoxy morphology. Thermal analysis carried out by Differential Scanning Calorimetry (DSC) and Dielectric Loss Factor (DLF) indicated that the reduced temperature‐curing formulations have relatively low activation energy and that the main cross‐linking reaction takes place close to 50°C and is completed at 120°C with a maximum glass transition temperature at 180°C. Mechanical properties of the adhesive formulation were comparable or better than existing commercial products. Flexural and interlaminar shear strengths, for glass‐epoxy composites incorporating a selected low‐curing‐temperature formulation, exhibited enhanced properties compared to commercially 120°C epoxy‐glass prepreg composites.
Reactive‐ion etch resistant polysulfones for microlithography
Authors: Bowden Murrae J. , Gozdz Antoni S. , DeSimone Joseph M. , McGrath James E. , Ito Seiki , Matsuda Minoru
Published: March 2011

The various chemical approaches aimed at improving the reactive‐ion etch resistance of poly(olefin sulfone)s are described. Resist systems based on incorporation of RIE‐resistant moieties via random copolymerization, blending and block copolymer formation are described and lithographic properties noted.
Design and characterization of polymers and polymer blends for high temperature structural applications
Authors: Jaffe Michael , Chenevey Edward , Cooper William , Glick Morton , Haider M. Ishaq , Rafalko Joseph
Published: March 2011

Reviewing the development of new polymeric materials for high temperature structural applications (T > 200°C) over the past several decades, reveals a paradox which, to date, has not been completely resolved. Polymers which exhibit very high temperature stability tend to be either intractable or brittle, whereas, easily processible polymers tend to fall short of property targets. Approaches to resolving this paradox include modification of the chain backbone chemistry and polymer blending (especially to form miscible systems). Recent research has shown that, in contrast to low temperature flexible polymers, many high temperature aromatic heterocyclic polymers form miscible systems which permit the design of the desired processibility and performance into the blend. An example of such a system is the blend of Poly(2,2′‐(meta‐phenylene‐5,5′‐bibenzimidazole) (PBI) with a series of polyamides, including commercially available polyether imide (PEI) and imide copolymers containing sulfone and fluorinated isopropylidene (6F) units. Other examples include all polyimide blends and blends of polyimides with polyethersulfone.
Interfacial behaviour of block polyelectrolytes, III. Formation of surface micelles
Authors: Zhu J. , Hanley S. , Eisenberg A. , Lennox R. B.
Published: March 2011

The aggregation of (poly)styrene/quaternized (poly)‐4‐vinylpyridine diblocks into regular circular structures has been observed in Langmuir‐Blodgett films removed from a pure water surface. These novel aggregates, termed surface micelles, form at low surface pressures (< 2 mN/m) and exhibit rich isotherm behaviour as Langmuir films. A distinct first order phase transition is observed for the decylated derivatives of a series of diblocks (i.e. (PS)260(C10PVP+I−)n; n = 70, 120, 240) which has been interpreted as a transition from an entirely surface‐adsorbed micelle to a surface micelle whose polyelectrolyte chains have been forced into the aqueous subphase. Transmission electron and atomic force micrographs of LB films provide for direct visualization of these surface micelles as well as the means to estimate their aggregation numbers, N.
Molecular coils and their deformation
Authors: Kausch H. H. , Nguyen T. Q.
Published: March 2011

The study of stress‐effects on chain conformation has always been a fruitful ‐ and sometimes highly controversial ‐ issue in macromolecular science. In this paper chain scission in transient elongational flow is investigated. Particular attention is given to the possible nature of stress transfer from the deforming highly dilute polymer solution to the embedded molecular (PS) chain. The dependencies of the measured degradation efficiency on molecular weight, solvent viscosity, nozzle geometry and flow rate exclude the classical mechanism of chain loading through strain‐rate dependent viscous friction. On the basis of their findings the authors propose a model where the loading of hairpin‐like segments in almost static friction works against the internal relaxation of these structures.
Band texture formation of sheared polymeric liquid crystalline state
Authors: Qian Renyuan , Chen Shouxi
Published: March 2011

The phenomenon of band texture formation of sheared main chain liquid crystalline polymers is reviewed. The bands seen in a polarizing microscope are optical effects. The macromolecular chains are aggregated into zig‐zag bent fibrils perpendicular to the bands. The band texture is formed during shear relaxation. The induction period depends on the shear rate applied, the shearing time, solution concentration (lyotropic), solution layer thickness, temperature and the nature of the polymer. There exists a critical shear deformation to bring a multi‐domain nematic or cholesteric phase into a monodomain continuous phase, from which the band texture is formed. These two phases show quite different rheological behavior. In certain cases randomly oriented regions of bands can also be formed during quenching of a thermotropic nematic polymer melt or during standing of a lyotropic nematic polymer solution, where the nematic domains in the melt or in the solution have grown to a sufficient size.
Reactions of atomic oxygen [O(3P)] with polymer films
Authors: Golub Morton A.
Published: March 2011

The reactions of polymer films with oxygen atoms are reviewed. Emphasis is on work from this laboratory on polybutadienes having different amounts of 1,4 or 1,2 double bonds and their polyalkenamer homologues, on a polyimide (Kapton), and on a series of polyolefins with increasing fluorine content ranging from polyethylene (PE) to polytetrafluoroethylene (PTFE). Interest in this topic stems from a need to understand the mechanism(s) of surface erosion, or etching, that occurs in organic polymers when exposed to the low Earth orbital (LEO) environment, where ground‐state atomic oxygen [O(3P)] is the most abundant constituent. The major findings for O atom reactions with the polyalkenamers were: (1) etch rates increase with decrease in ‐CH=CH‐unsaturation, starting with 1,4‐polybutadiene and reaching the maximum rate with PE or ethylene‐propylene rubber; (2) in polybutadienes having both 1,4 and 1,2 double bonds, the rate of O(3P)‐induced etching is lower the higher the 1,2 content; and (3) the reactions are confined to the polymer surface. Relative etch rates for various commercial polymer films (e.g., Kapton, Teflon, PE) exposed to O(3P) downstream from a low‐pressure, radio‐frequency O2 plasma were compared with corresponding literature data for films exposed to O(3P) either during a Space Shuttle flight or in the plasma glow (where many species besides O(3P) are present). The use of O2 discharge reactors – whether exposures are conducted “out of the glow” or “in the glow” – cannot serve as a routine, ground‐based simulation of exposures of a polymer to the LEO environment. ESCA analysis of the surfaces of Kapton and other polymers, before and after reaction with O(3P), showed that there is a steady‐state competition between surface recession and oxidation. In a series of fluorine‐containing polyolefins exposed to O(3P), the maximum oxygen uptake increased regularly with decrease in fluorine content, ranging from a minimum in PTFE to a maximum in PE.
Universality in polymer viscoelasticity
Authors: Lin Y.‐H.
Published: March 2011

This paper brings together seven aspects of universality in viscoelasticity of linear flexible polymers: (1) the stress relaxation modulus G(t) being a universal function of the normalized molecular weight (MW), M/Me; (2) the MW dependence of the zero shear viscosity; (3) the MW dependence of the steady state compliance; (4) the MW dependence of the diffusion constant; (5) the damping functions; (6) slip‐stick melt fracture being a universal phenomenon; and (7) the number of entanglement strands per cubed entanglement distance being a universal constant. As presented in the text, the consistency, agreement and relation among these different aspects of universality can be properly brought to light.
The slip‐link model: A constitutive equation for general biaxial extension of polymer melts
Authors: Wagner M. H.
Published: March 2011

Starting from a slip‐link model, we derive a general strain measure for polymer melts. Predictions are compared to experimental data of uniaxial, planar, ellipsoidal, and equibiaxial extensions of a polyisobutylene (PIB) melt. The data do not support Doi's assumption that the tube diameter remains unchanged by deformation. The relative tube diameter and its inverse, the molecular stress function, can be extracted directly from the data. At small strains, the relative cross section of the tube is inversely proportional to the average stretch of the tube.
Rheometry towards complex flows: Squeeze flow technique
Authors: Laun Hans Martin
Published: March 2011

Disk‐like samples are submitted to controlled squeezing forces between parallel plates and the time‐dependent sample height is measured. Isothermal tests at constant force enable the determination of viscosity functions of melts. Experiments using a constant disk radius and a constant disk volume are compared. Creep and creep recovery tests are made possible by a height‐dependent control of the force. The evaluation of a pressure‐dependent yield stress is demonstrated for wax powder. The squeeze flow technique is of advantage for systems with a layer structure or matrices containing long fibres or mats. In non‐isothermal experiments on solidifying materials, either by crystallization or polymerization, the total deformation and the speed of solidification in processes like stamp moulding can be determined.
Rheology of heterophase polymer systems
Authors: Kotaka Tadao , Shikata Toshiyuki
Published: March 2011

This lecture attempts to elucidate rheological behavior of multiphase polymer systems through a comparison with our studies on much simpler systems such as suspensions of (a) non‐aggregating and (b) aggregating monodisperse spheres in viscoelastic media, (c) polymer latex in the same polymer liquids, and (d) emulsions or blends of two polymers with or without an emulsifying block copolymer. For the system (a) not only the viscosity η but also the modulus obey the known simple dependence on volume fraction ϕ of hard‐sphere suspensions, while for the system (b) the flow induced‐aggregation and dissociation of the particles govern the rheology. In the system (c), relaxations of entanglements of the adsorbed chains as well as the spatial distribution of the latexes are essential. For the emulsion (d) of a biased composition range (e.g., ϕ1 > ϕ2) the matrix phase 1 dominates, unless η1 << η2. When η1 ≥ η2, deformation and/or bursting of the dispersed phase 2 take place. For those of an even composition, the viscosity is additive of those of the components and is enhanced by adding the emulsifying block copolymer component.
Mathematical tools for solving new, more realistic models of polymer melts
Authors: Öttinger Hans Christian
Published: March 2011

Stochastic processes play an important role in the kinetic theory of polymeric liquids. Various concepts, such as “configurational distribution functions”, “diffusion equations”, “Brownian motion”, “white noise”, “generalized Langevin equations”..., are indispensable in the theory of polymer dynamics. We review the mathematical description of various types of stochastic processes in order to provide (i) a sound basis for the formulation of new kinetic theory models, (ii) recipes for the development of computer simulation algorithms, and (iii) a feeling for the possible pitfalls in the naïve use of stochastic calculus. Various possible applications of the mathematical background presented here are discussed in connection with particular models of polymer melts.
Molecular tube models of branched polymer melts
Authors: McLeish T.C.B. , O'Connor K. P.
Published: March 2011

We apply the tube model to a specific problem in polymer melt dynamics ‐ the rheology of star polymers as an additive to a monodisperse linear matrix. We find that the tube dilation picture of constraint release may be applied to the relaxation of the star fraction. There are four qualitatively different cases depending on the relative concentrations and relaxation times of the two fractions. Terminal relaxation times and relaxation spectra are calculated for each case and compared with available experimental data. The existence of a modified Rouse relaxation such that G(t)∼t−3/2 is argued.
Processing/morphology/rheology relationships in polymer blends
Authors: Favis Basil D.
Published: March 2011

In this paper certain aspects concerning the influence of rheological parameters on the morphology of immiscible polymer blends are considered. The author reviews his own work with reference to other key studies carried out in the field. The influence of the viscosity ratio on morphology for compatibilized and non‐compatibilized systems are treated, as well as the influence of shear stress. The role of viscosity and viscosity ratio in controlling co‐continuous and complex composite droplet morphologies are also discussed.
Prerequisites for successful recycling of polymer waste
Authors: Brandrup Johannes
Published: March 2011

An increasing awareness of ecological problems will enhance all activities towards recycling of polymers. In other words, we have to expect a fast increasing amount of recycled polymers. Today, most activities concentrate on the economical feasible part of recycling ‐ waste of higher prized plastics, only slightly contaminated plastic waste.

Public pressure and legislation request solutions for heavily contaminated commodity plastics from household waste as well. The strategy to produce thick walled, profiles out of comingled plastics will be a contribution towards, but not the solution of the problem. We have to make the serious attempt to separate specific polymers like PE, PS, PET from the waste and to introduce these recyclates into the plastic market. In other words, we have to establish closed loops for all our products. Tremendous problems lay ahead of us in order to accomplish it. We need markets for recyclate, we have to change specifications accordingly, we have to improve existing technologies for work up, we have to develop “raw material” specifications when we turn waste in an economic good, we have to develop scenarios for unsufficient economics.

The paper will deal with all these aspects in detail and will discuss the present situation in Germany.
Separation of poly(vinyl chloride) from poly(ethylene terephthalate) by micronyl process
Authors: Famechon René
Published: March 2011

Mixed Poly(vinyl chloride) (PVC) and Poly(ethylene terephthalate)(PET) scraps can be separated by various methods based on the difference in their physical or chemical properties. A short review of the presently known methods is made. The presentation is focused on a method developed by MICRONYL WEDCO and based on the difference in impact strength resistance of the two polymers at room temperature.
Liquefaction of plastics
Authors: Hirota T. , Fagan F. N.
Published: March 2011

A plastic liquefaction process which features a combination of thermal and catalytic cracking has been developed. The process can charge polyethylene, poly(propylene) or polystyrene and produces relatively low pour and highly aromatic liquid at a yield of about 85 %. Based on laboratory development a 500 ton per year prototype unit has been constructed and operated successfully both for testing and further development. An additional 1000 ton per year prototype unit is in the design phase and is scheduled for operation in 1992. The salient aspects of the process are described.
Recycling concepts for polyurethanes and polycarbonate
Authors: Müller Peter , Riess Reinhard
Published: March 2011

The opinion is that all thermoplastics are infinitely recyclable, while crosslinked polyurethanes (PUR) and thermosets are not recyclable. The present paper uses comparative data to show that the waste management problem associated with crosslinked PUR materials has been largely overcome on a pilot‐plant scale. Direct and indirect material recycling as well as thermal recycling are discussed. A direct recycling method in which granulated PUR‐RIM scrap is made to “flow” under heat and pressure to re‐mould it, is quoted as evidence that crosslinked polyurethane elastomers can be reclaimed and reused in a similar manner to thermoplastics. This process is called “compression molding”. Recycling methods for thermoplastics under consideration from an early stage, as well as entirely new possibilities that are emerging, are demonstrated, using polycarbonate Makrolon® as an example.
Glycolytic recycle of poly(ethylene terephthalate) (PET)
Authors: Gintis Daniel
Published: March 2011

In a comparison of PET waste recovery methods, glycolysis to monomer (DHET + low MW oligomers) represents a compromise between regeneration of starting ingredients by methanolysis or hydrolysis and direct remelt extrusion. It is less costly than the former and more versatile than the latter. The resultant easily filtered, low viscosity monomer is repolymerized to a useful molecular weight (MW), used as an ingredient for copolymers and used with additives for controlling luster, color, etc. Glycolytic recycle can be a batch or continuous process, the rate being dependent on temperature, catalyst, state of subdivision of the feedstock and the 2G/T ratio. In addition, the final monomer composition is controlled by the time of reaction and hold‐up time after depolymerization. Low 2G/T ratios permit higher temperatures and faster reactions but result in higher MW oligomers. Side reactions occurring in the depolymerization are minimized by addition of a buffer as sodium acetate and limiting storage time at high temperatures. PET scrap suitable for glycolytic recycle includes production waste, fibers, film, flake, bottles, etc., but ingredients leading to side reactions, copolymers, end caps or color must be minimized for critical products and satisfactory rates of polymerization.
Catalytic degradation of polyolefins
Authors: Audisio Guido , Bertini Fabio , Beltrame Pier Luigi , Carniti Paolo
Published: March 2011

Silica, alumina, silica‐aluminas and zeolites were screened as catalysts for polyolefins degradation. The degradations were carried out at temperatures from 200°C till to 600°C under vacuum. The degradation products were analyzed using gas chromatography‐mass spectrometry (GC‐MS). The comparison between these products and those obtained by thermal degradation in the absence of catalyst gives us many informations about the different mechanisms of the two degradation reactions. Kinetic measurements and thermogravimetry provided further useful data for screening the catalysts, finding the best operating conditions.
Watergas from plastic waste and its possible uses
Authors: Kessler Birgit , Semel Joachim
Published: March 2011

Coal gasification technology should also be applicable to plastic waste. The resulting product is watergas or in general terms syngas which is used as a feedstock for several large chemical products. Based on theoretical considerations the study evaluates the costs related to syngas production from plastic waste and subsequent conversion to chemical raw products. Net waste disposal costs of 275 – 690 DM/ton are calculated depending upon the end product(s).
Chemical recycling of polyurethanes and separation of the components by supercritical ammonia
Authors: Lentz H. , Mormann W.
Published: March 2011

Chemical recycling of a polyurethane elastomer and a flexible foam based on methylenebis(phenyl isocyanate) (MDI) and a polyetherpolyol was performed by ammonolytic cleavage of urethane and urea bonds under supercritical conditions. Resulting products were the polyols, the amines corresponding to the isocyanates used, and unsubstituted urea. Under suitable conditions the polyetherpolyol was completely separated from the other ammonolysis products which in turn can be further separated and used for the manufacture of polyurethanes or for the synthesis of diisocyanates.
Compatibilization strategies for upgrading recycled plastics performance: Use of reactive rubbery polymers
Authors: Scobbo J. J.
Published: March 2011

One of the inherent problems in the recycling of polymers involves the wide variety of immiscible and incompatible polymer resins. For this reason, it is important to keep scrap from different sources separate, especially if it is known beforehand that the compositions are significantly different. Approaches to upgrading the performance of the scrap streams can then be tailored to each stream. Our work has been based, in part, upon one such approach. Reactive rubbery polymers have been used to modify several recycle streams. These models represent household scrap, business machine housings, and automobile bumpers. Dramatic property improvements can be obtained if specific reactive rubbery polymers are matched to certain recycle streams. Also, it was found that variability in the source and the composition of a given stream over time can dramatically affect results. These findings underscore the inherent difficulty in developing a universal approach to the recycling of mixed plastics.
Variations in the mechanical properties of end products from mixed plastics
Authors: Breant P.
Published: March 2011

From well selected polymers, using an experimental plan methodology, we show the different influences (nature, processing conditions, composition) on the properties of end products from mixed plastics such as strain and stress at rupture, flexural modulus, impact strength and extrusion flow rate. From models, it is possible to adjust necessary formulations to obtain a good quality level and, eventually, an improvement of poor properties. Mixed plastics can be considered as a polyethylene matrix containing other polymers such as polypropylene (PP), polystyrene (PS) or poly(vinyl chloride) (PVC). Poly(ethylene terephthalate) (PET) is neglected in this study. Properties such as strain at rupture or impact strength are drasticly affected by the level of polypropylene, polystyrene or poly(vinyl chloride): 5 or 10% nullify these properties. Other properties such as stress at rupture, flexural modulus or extrusion flow rate highly depend on the relative ratio of polymers. To improve the poor properties or to obtain a good level in a property, it is necessary to add well adapted compatibilizers or to dope the mixed plastics material by one of the polymers.
Interaction of segmented polyurethanes and polyurethane‐ureas with water
Authors: Bohdanecký Miloslav , Petřík Stanislav , Hadobaš František , Šimek Lubomír
Published: March 2011

Sorption of water vapor by oligomeric homopolymers and triblock copolymers of ethylene oxide and propylene oxide, and by polyurethanes and polyurethane ‐ ureas derived from them is discussed. While the sorption isotherms (plots of ψ1 vs a1, where ψ is he volume fraction of sorbed water and a1 is activity) for most polymers investigated here are smooth and convex towards the abscissa, those found with polyurethane‐ureas containing long hard blocks have a “toe” at low activities. The plots of a1/ψ1 vs a1 are shown to facilitate the analysis of data and the interpretation in terms of the D'Arcy‐Watt theory.

Smooth isotherms are fitted by a simple equation with two parameters. The first is related to the limiting value, χ0, (at ψ1 → 0) of the χ parameter characterizing the polymer‐water interaction. The dependences of χ0 on the polymer composition (content of hard segments or oxyethylene units) can provide information on the interaction between hard and soft segments.

The second parameter is used in the computation of parameters characterizing the clustering tendency of water molecules. This tendency depends mainly on the content of oxypropylene units but is also raised by urethane or urea groups, though not so much as by oxypropylene groups.
Critical association and thermoreversible gelation of some selected polymers
Authors: Burchard Walther , Lang Peter , Schulz Liane , Coviello Tommasina
Published: March 2011

The study of associating polymers is complicated by the fact that at a finite concentration only an apparent molar mass is directly measured. This apparent molar mass deviates from the true one because of thermodynamic interaction. In a good solvent the repulsive interaction can be fully described in terms of the second virial coefficient, which can be measured at very low concentrations, and a correction can be made for the true molar mass. The technique has been successively applied to β‐galactosidase in a phosphate buffer and to cellulose 2,5‐acetate in acetone.

The gel point could be determined, and critical behavior was found in very good agreement with percolation prediction. Two other methods were employed and tested. One is based on the condition that the longest relaxation time must diverge at the gel point, and correspondingly the translational diffusion coefficient should go to zero. The second criterion consists of the prediction that power law behavior should be observed for the time correlation function of dynamic light scattering as well as for the frequency dependent storage and loss moduli.

These predictions were indeed found to hold for two polysaccharides which form thermoreversible gels in water at a fairly low salt concentration. The two polysaccharides are the Tamarind seeds polysaccharide in 1M Na2SO4 and an exopolysaccharide from Rhizobium leguminosarum, strain 8002 in 0.1M NaCl solutions respectively.
Classical light scattering studies on structure formation in polymer solutions
Authors: Gohlke Ulrich , Rother Gudrun , Otto Andreas , Hartmann Juergen
Published: March 2011

The scattered light is very sensitive to the presence of supermolecular structures in polymer solutions, offering the possibility to study structure formation in situ by classical light scattering and to characterize the generated particles. An improved analysis of light scattering data yields information on the structure type, polydispersity of the systems, particle mass and size as well as the degree of swelling. The flocculation process of ampholytic modified poly(acrylonitrile) was investigated in dependence on the pH‐value and the content of different salts in the solvent. Results obtained give a deeper insight into the flocculation mechanism.
Structure rheological investigations of segment interaction in polymer solutions of the network type
Authors: Schurz Josef
Published: March 2011

The solution structure of flexible chain polymers is described in terms of an equivalent entanglement network characterized by its apparent chain element A'. Such networks can exhibit free penetration of polymer segments, hindered penetration or no penetration at all. The segment interaction effects a hindrance to penetration. It can be characterized by the concentration dependence of the mass of network strand Me resp. the entanglement density ν. Another parameter is the entanglement fraction ß, which describes the ratio of the entanglements actually formed to that possible in case of free penetration. Experimental results with different polymers illustrate these ideas.
Determination of microscopic interaction parameters of ternary polymer solutions with light scattering data
Authors: Kappeler Ch. , Schäfer L.
Published: March 2011

Using a renormalized form of the Random Phase Approximation (or Tree Graph Approximation) we analysed data on the zero angle scattering intensity and the apparent radius of gyration for the system polystyrene‐poly(methyl methacrylate)‐bromobenzene. Since the microscopic parameters of this system are known from the analysis of the zero‐angle scattering data, the theory yields a parameterfree prediction of the apparent radius of gyration which fits the data very well. To show the influence of renormalization we also analyse the data by an unrenormalized version of RPA.
Studies on main ‐ chain liquid ‐ crystalline model oligomers of defined length and structure
Authors: Seliger H. , Eppel M. , Göldner E. , Kittel I. , Ludwig A. , Schorr R.
Published: March 2011

Oligomers of defined sequence and structure modelling main chain LC polymers were prepared a) by solution synthesis; b) by a novel liquid phase synthesis using two monomethoxy‐poly (ethylene glycol) supports. Benzyl‐ and tert.butyl‐groups were used as orthogonal pair of protecting groups for route a), and also as compatible anchor groups for carriers in route b). Depending on chain structure and end groups, at least ca. 3 mesogenic elements are required to allow for LC phase transitions. The phase behaviour of oligomers with free carboxylic ends can be explained by their association tendency.
Poly(methyl methacrylate) dispersions in decane stabilized by a diblock copolymer
Authors: Stejskal Jaroslav , Kratochvíl Pavel
Published: March 2011

In a dispersion polymerization, the monomer is miscible with the reaction medium, while the resulting polymer is insoluble under the same conditions. The macroscopic precipitation of the polymer is prevented by a steric stabilizer. Methyl methacrylate was polymerized in decane in presence of polystyrene‐block‐poly(ethylene‐co‐propylene) and spherical dispersion particles of poly(methyl methacrylate) (PMMA) were obtained. The static light scattering yielded molar masses of particles in the range 4 × 107 to 7 × 109 g mol−1. Dynamic light scattering provided the hydrodynamic radii from 60 to 190 nm and also information on the non‐uniformity of the particles. The relations between the characteristics of the dispersion particles (concentration of components, particle mass and dimensions, molar mass of PMMA chains, surface density of stabilizing chains, etc.) were looked for. The kinetics of polymerization seems to be only little affected by the colloidal character of the system.
Solution properties of complexes between oxygen‐ and nitrogen‐containing polymers and alkali metal salts
Authors: Bekturov Esen A. , Dzhumadilov Talkybek K.
Published: March 2011

The results of investigations of the complexation of polymer ethers and polybases with alkali metal salts in organic solvents are discussed. The influence of different factors as nature of polymers, salts and solvents on the complexation process is considered.
Lanthanide metal polymer complexes. Synthesis, characterization and application
Authors: Okamoto Yoshi
Published: March 2011

Our recent results on the investigation of lanthanide metal polymer complexes were presented. Luminescence properties of Tb3+ or Eu3+ ‐polycarboxylate complexes in aqueous solution were investigated. The excitation band near 300 nm for Tb or Eu(polyacrylate) solutions were drastically enhanced by the addition of hydroxy radical generating reagents as well as ultrasonic irradiation. These spectral changes were attributed to the energy transfer from chromophore molecules formed by generated hydroxy radicals in both systems. Since the increase in the luminescence intensity was proportional to the hydroxy radical concentration, the Eu3+ or Tb3+ (PAA) system can provide a convenient method for the determination of hydroxy radical concentration in aqueous solution. We have also utilized lanthanide metal ion complexes as a luminescent emitter in electroluminescence (EL) devices. The configuration of the EL cell and experimental results were discussed.
Synthesis of new conducting poly(2,5‐thienylene)s containing alkylhydroxy and alkylester side chains
Authors: Delia Casa C. , Salatelli E. , Andreani F. , Costa Bizzarri P.
Published: March 2011

The chemical synthesis of new electroconducting poly(2,5‐thienylene)s containing alkylhydroxy and alkylester side‐chains in the β‐position of the thiophene rings is reported. The polymers were obtained by oxidative homopolymerization or copolymerization of 2‐(3‐thienyl)ethanol and 2‐(3‐thienyl)ethyl hexanoate by FeCl3 in nitromethane. Structural characterization using elemental analysis, FT‐IR and NMR spectroscopy shows that a partial nucleophilic substitution of the hydroxy group by chlorine and a partial cleavage of the ester function take place during polymerization. The presence of the ester function with a long aliphatic chain makes the polymers soluble and allows them to be processed into films. The polymers can be doped using a solution of FeCl3 to the maximum electrical conductivity of 10−3 Ω−1 cm−1.
Voltammetric study of some macromolecule ‐ metal complexes
Authors: Esteban M. , Díaz‐Cruz J. M. , Ariño C. , Casassas E.
Published: March 2011

The usefulness of a voltammetric model for studying macromolecule ‐ metal complex systems is verified. Complexes formed by a metal ion (Zn(II), Cd(II), Pb(II) or Cu(II)) and a macromolecule (polymethacrylic (PMA), polyacrylic (PAA), alginic (AA) or polygalacturonic (PGA) acids) are investigated. Several voltammetric techniques have been used: sampled direct current polarography (DCP), normal pulse polarography (NPP), differential pulse polarography (DPP), reverse pulse polarography (RPP), cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). Results confirm the validity of the model, in determining not only formation constants but also diffusion coefficients of the complexes. The behaviour of some systems agrees with that predicted by the model. Nonetheless, other systems only partially fulfil the predictions for different reasons, which are discussed.
Amidoxime polymers ‐ copper complexes
Authors: Boudakgi Amer , Jezierska Julia , Kolarz Bozena N.
Published: March 2011

The aminolysis of nitrile groups in macroporous acrylonitrile‐divinylbenzene copolymers leads to amphoteric ion exchange resins with 1.0 ‐ 3.3 mmol/g amidoxime groups content. The starting copolymers were synthesized from the same monomer mixture, but the composition of diluents used were different. The resulting polymers with amidoxime groups have different sorption of Cu(II) ions, the highest values between 1.3 and 3.5 mmol/g at pH 5. EPR and IR spectra were used to indicate the formation of the complexes between Cu(II) ions and amidoxime polymers. On the basis of the EPR parameters structure of complexes formed at different pH and Cu(II) concentration was postulated.
Structural macromolecular parameters determining electroconductivity of oxidized poly‐n‐vinylpyrrole
Authors: Ciardelli Francesco , Mori Stefano , Ruggeri Giacomo , Colligiani Arturo , Cagnolati Roberto , Campani Enzo , Rolla Pier Angelo , Lucchesi Mauro
Published: March 2011

The dependence of electroconductivity on conjugation length as well as the related basic mechanism was investigated by chemical (FeCl3) oxidation of insulating polymers from N‐vinylpyrrole (NVP) starting with different Fe/NVP ratios and different molecular weights. The results allow to establish that oxidation occurs mainly intrachain and that electroconductivity has a sharp increase for a conjugation length higher than ∼15 NVP‐units.
Structural features of 4‐methyl‐1‐pentene polymers prepared with different transition metal catalysts
Authors: Altomare Angelina , Solaro Roberto , Ciardelli Francesco , Barazzoni Lia , Menconi Francesco , Masi Francesco
Published: March 2011

Homopolymerization of 4‐methyl‐1‐pentene carried out in the presence of catalysts containing variable relative amounts of Ti, Hf and Mg indicates that molecular weight and stereoregularity can be varied to an appreciable extent depending on catalyst nature and composition. A distinct behaviour of the various catalytic systems is also observed during the copolymerization of 4‐methyl‐1‐pentene with monoalkenes such as propylene, 1‐butene and 1‐hexene. These data are discussed by underlining the important role of the transition metal in determining the features of polyolefins materials.
Effect of the mixture t ‐ BuCl/SnCl4 on the cationic polymerization of isobutylene
Authors: Lukáš Rudolf , Toman Ludêk
Published: March 2011

The polymerizations of isobutylene initiated with the system tert‐butyl chloride (t‐BuCl)/SnCl4 and carried out in CH2Cl2 at −20°C and −78°C were investigated. The results obtained demonstrate that the presence of t‐BuCl in the polymerizing system gives rise to a PIB product with a distinctly bimodal MWD. The higher‐molecular weight (HMW) PIB, M̄n = 20000, I=M̄w/M̄n ∼ 2.5, is the result of existence of the protogenic initiation with residual water in the reaction system. The lower‐molecular weight (LMW) PIB, M̄n < 600, M̄w/M̄n ≤ 1.4, is the product of polymerization initiated presumably with a complex t‐BuCl‐SnCl4‐H2O. To elucidate the reaction mechanism of the polymerization initiated with the complex, a series of similar isobutylene polymerizations using the initiation system 2,5‐dichloro‐2,5‐dimethylhexane (DDH)/SnCl4 was run and the oily LMW PIB samples were investigated by 1H‐NMR. A new polymerization mechanism describing the role of DDH and t‐BuCl is suggested.
Living cationic polymerization of vinyl ethers and styrene derivatives: Design of initiating systems based on added salts with halogen anions
Authors: Sawamoto Mitsuo , Higashimura Toshinobu
Published: March 2011

This paper overviews three living cationic polymerization systems (for styrene, p‐methoxystyrene, and isobutyl vinyl ether) that are, in common, featured by:

(i) specifically in nonpolar solvents, the use of the hydrogen halide/metal halide initiating systems (HX/MXn; X: I, Br, Cl; MXn: ZnX2, SnCl4), which generate a living growing carbocation stabilized by a nucleophilic counteranion (X−…MXn);

(ii) specifically in polar solvents, the use of externally added ammonium salts (nBu4N+Y−; Y−: I−, Br−, Cl−), which permit the generation of living species from HX/MXn by providing nucleophilic halogen anions Y−, either the same as or different from the halogen X− in HX.
Direct observation and stability of active species in cationic polymerization: A reexamination of the polymerization of styrene initiated by triflic acid
Authors: Vairon J.‐P. , Rives A. , Bunel C.
Published: March 2011

Polymerization of styrene initiated by triflic acid in CH2Cl2 solution was reexamined, using a new stopped‐flow device working in high purity conditions over a wide temperature range. Monomer and styryl cation were followed simultaneously through their respective absorbances at 290 and 340 nm. Initiation is very rapid, and cations concentration reaches a plateau the duration of which is depending on temperature. In our conditions (I0 = 0.5 − 9.10−3M, M0/I0 = 1 to 20), cations concentration is so low at room temperature that it is almost unmeasurable. At −65°C, it is 100 times higher, remains constant for several seconds and complete termination takes place within a minute or more. Such a profile of cation evolution agrees with an equilibrium situation between initiation and a much more temperature‐dependent backward deprotonation. Apparent initial rate of initiation is first order with respect to monomer, but the order with respect to initiator was found very high and variable with temperature (from 4.5 at −65°C to 3 at −20°C). This supports the presence, even if they are in low concentration, of acid high agregates, the reactivity of which increases with size. A first order monomer consumption is observed during the plateau, which leads to kp values ranging from 103 at −65°C to 9.104 M−1.s−1 at −10°C (Ep# = 43 kJ.mol−1). The disappearance of cations, which follows the plateau, slows down and becomes unimolecular when monomer consumption is complete, and kt values range from 6.10−2s−1 at −65°C to 1.2s−1 at −23°C (Et# = 33 kJ.mol−1).
Recent advances in macromolecular engineering via ionic methods
Authors: Rempp Paul
Published: March 2011

Selected recent developments in the field of macromolecular engineering via ionic methods are presented: ω‐functional polymers and macromonomers, ampholytic block copolymers and novel thermoplastic block copolymers, star shaped macromolecules of several kinds. Attention is called upon the absolute necessity of adequately characterizing the samples obtained, in order to check wether their structure meets with expectation.
A comparison of group transfer and anionic polymerization of acrylic monomers
Authors: Webster Owen W.
Published: March 2011

The living polymerization of acrylic monomers by a repeated silyl Michael addition reaction (GTP)a operates at temperatures as high as 100° C. The resulting polymers are, however, nearly identical to those produced by anionic polymerization at low temperatures. Is GTP merely a special form of anionic polymerization? A proposal is made that GTP catalyzed by weak nucleophiles proceeds by insertion of monomer in silylated chain ends and that GTP catalyzed by strong nucleophiles proceeds by reversible generation of free enolate.
Solvation effects in anionic polymerization of polar vinyl monomers
Authors: Tsvetanov Ch.B. , Dimov D.K. , Petrova E.B. , Dotcheva D.T.
Published: March 2011

The anionic polymerization (AP) of polar vinyl monomers (PVM) is strongly affected by additives with electron donor and electron acceptor properties. For the purpose of estimating the interactions of the active centers (AC) of chain growth with different ligands, the approach of studying a reference system was adopted, viz. lithium picrate (LiPi) in dioxane (DO). Three types of interaction were distinguished: with electron pair donors (EPD), with Li salts and alkoxides, and with Lewis acids. Spectral evidence was found of charge transfer complexation with Li alkoxides and enolates, leading to modified dianionic Meisenheimer adducts. The experimental procedure was employed in studies of competitive solvation of LiPi by two ligands. The results were related to reviewed literature data on the kinetics and stereochemistry of methyl methacrylate (MMA) and 2‐vinylpyridine (2VP) polymerizations by lithium initiators.
Determination of the microstructure of the fermentation polymer xanthan
Authors: Kulicke W:‐M. , van Eikeren A.
Published: March 2011

Although xanthan has long been the subject of wide‐ranging investigations, it has not yet been possible to establish any clear link between the solution properties and the chemical and steric microstructure. This is due to the fact that large variations in the properties may occur between samples of different manufacturers. Hence more than fifty different samples in liquid and powder form were investigated. This involved the determination of pyruvate and acetate content for all the samples by means of enzymatic analysis and Comparison with results from 1H NMR spectroscopy. In addition, the contents of the side groups are for the first time given in mass and molar percentages.

Low angle and multi‐angle laser light scattering as well as viscometry were employed for the determination of the steric microstructure. Here it was ascertained that preliminary treatment of the sample has a crucial influence on the results of light scattering. A method of sample preparation was therefore devised which is aimed at avoiding the formation of microgels and preserving the structure of the native. xanthan. In addition, xanthan is used to illustrate a novel procedure which enables very readily interpretable Zimm plots to be obtained from one individual reading over a few minutes. In a comparison of the scattering curve extrapolated to c=0 with calculated model curves for semiflexible rods, the structure of native xanthan was determined to be more rigid than corresponds with the exponents of previously published [η]‐Mw relationships.
Supermolecular structures in polymer solutions interpretation of static light scattering data
Authors: Dautzenberg Herbert , Rother Gudrun
Published: March 2011

The characterization of supermolecular structures in polymer solutions by static light scattering requires an improved analysis of the scattering curves. A comparison of the experimental curves with model calculations for various basic structure types in a scaled plot offers the possibility to extend the range of a reliable determination of the structural parameters to particle sizes up to 500 nm. The influence of the polydispersity and problems of an unambiguous interpretation are discussed. Especially, a closed analytical expression for the scattering function of polydisperse systems of spheres with a Schulz‐Zimm distribution of radii was derived.