bluuebunny/crossref_metadata_2025 huggingface dataset:
Dilute solution properties of polyurethane
Authors: Ali S. I. , Ali S.
Published: April 2003

Low angle laser light scattering and viscosity studies were made on dilute solution of fractions of polyurethane prepared from butandiol and hexamethylene diisocyanate. The intrinsic viscosities were correlated to molecular weights by the MARK‐HOUWINK‐SAKURADA equation. The values of the constants Km and a have been determined. In spite of the low refractive index increment of polyurethane in benzene, molecular weights as low as 4300 could be measured.
Stromträgerrelaxationen in hochohmigen Polymerfestkörpern
Authors: Neumann W.
Published: April 2003

Neben relaxierenden Dipolen können auch Stromträger zeitabhängige Ströme nach Änderung des äußeren elektrischen Feldes bewirken. Als Kriterien dafür werden neben Intensität und Lage des Relaxationsgebietes die nichtlineare Abhängigkeit der gespeicherten Ladung von der äußeren Feldstärke angesehen. In Poly(chinoxalin) und Poly(ethylenterephthalat) werden Stromträgerrelaxationen durch blockierende Kontakte verursacht. Detaillierte Untersuchungen erlauben Aussagen über die Stromträgerdichte im Probenvolumen und Eigenschaften der Kontaktschicht. In Poly(chinoxalin) ist weiterhin Wechselstromhopping nachweisbar.
Block copoly(ether‐ester)s with oligo(1,2‐oxypropylene) soft segments
Authors: Słonecki J.
Published: April 2003

Random thermoplastic block copoly(ether‐ester)s were prepared by polycondensation in the melt. For the synthesis dimethyl terephthalate, butanediol‐1,4, and oxyethylated oligo(1,2‐oxypropylene)diol were used. The copoly(ether‐ester)s obtained contained tetramethylene terephthalate hard blocks and copolyether soft blocks. The copolymers were characterized by viscosimetry in solution, swelling, and determination of carboxyl end groups. The thermal properties were determined by DSC, dynamic mechanical testing, and melting temperature. Hardness and mechanical properties at tension were determined over a wide temperature range. Thermal and mechanical properties were discussed considering the influence of copoly(ether‐ester) composition on chain flexibility and some utility properties.
Polymerization of styrene with N,N′‐bis[(4‐t‐butylazo‐4‐cyano‐valeryl)‐oxyethyl]‐azo‐bis‐formamide
Authors: Simionescu C. I. , Popa A. A. , Comāniţā E. , Manolache S. , Comāniţā B.
Published: April 2003

The solution polymerization of styrene in benzene by using N,N′‐bis[(4‐t‐butylazo‐4‐cyanovaleryl]‐oxyethyl)‐azo‐bis‐formamide as a bifunctional initiator is studied. The reaction was proved to be influenced by some factors, namely, initiator and monomer concentrations, temperature, and duration. To correlate the polymer conversion and its molecular weight with these parameters, two regression equations were obtained by carrying out the experiments according to a centrated, rotatable, second order experimental design.
Infrared spectroscopic study of field‐induced band shifts and dipole orientation in poly(vinylidene fluoride)
Authors: Büchtemann A. , Müller I. , Stark W.
Published: April 2003

Infrared spectra of uniaxially drawn ß‐PVDF films under the influence of an electric field were registered. The direction and the strength of the applied field were changed in up to 13 cycles. The field‐induced frequency changes of the bands at 445 cm−1 (CF2‐rocking) and 510 cm−1 (CF2‐bending) were studied in detail. Model calculations concerning the influence of the field on band frequencies are presented revealing the possibility to discriminate by IR spectroscopy between opposite dipole directions. The experimental results suggest the formation of a remanent field in the samples during poling.
Cold drawing experiments with polyethylene gel fibres
Authors: Bauer A. , Hofmann D. , Schulz E.
Published: April 2003

High strength/high modulus fibres can be prepared by cold drawing of UHMW‐PE gel fibres. It is shown that the crystalline order in this fibres is not perfect. The supermolecular structure is characterized by a shish‐kebab morphology. Results of X‐ray and mechanical investigations permit to explain the drawing process by a three‐step mechanism of molecular orientation and stretching coupled with molecular and fibrillar sliding.
Synthese und charakterisierung der in anionischen systemen hergestellten polaren hybridmakromoleküle
Authors: Erussalimsky B. L. , Berger W. , Morgenstern U.
Published: April 2003

Pfropf‐ und Copolymere aus polaren Monomeren werden hinsichtlich ihrer Synthese und Charakterisierung näher beschrieben. Im Falle der Pfropfcopolymere sind aktivierte P2VP‐, P4VP, PVAC‐ und PMMA‐Ketten die Voraussetzung für die Monomeraddition. Dabei ablaufende mögliche Reaktionen werden diskutiert. Gut definierte Blockcopolymere sind zugänglich, wenn die kurze Lebensdauer der AN‐Ketten für die weitere Monomeranlagerung ausgenutzt wird. Die Untersuchung der chemischen Uneinheitlichkeit derartiger Systeme ist kompliziert.
Characterization of chloroacetylated/sulfonated cellulose membranes for hemodialysis by spectroscopical methods
Authors: Krämer S. , Dietel R. , Haupold G. , Lukas J. , Malsch G. , Paul D.
Published: April 2003

Surface characterization techniques (ATR‐IR, ESCA and SEM‐EDX) have been used to obtain information of the surface chemical composition of modified cellulosic dialysis membranes. Chemical modification of membranes can be defined and controlled correlations between surface chemistry and hemocompatibility of membranes can be made.
Morphology of poly(2,5‐thiophenediyl) prepared by electropolymerization of 2,2′;5′,2″‐terthienyl
Authors: Koßmehl G. , Fechler D. , Plieth W.
Published: April 2003

Poly(2,5‐thiophenediyl) (2) was prepared electrochemically from 2,2′;5′,2″‐terthienyl (1) on various metal electrodes (Pt, Au, Ni, Ni sputtered with Au) in acetonitrile, with tetrabutylammonium perchlorate as an electrolyte salt under application of varying temperatures (−5°C, room temperature) and current densities (0.05 to 1 mA/cm2). Coatings with a rough surface structure were formed by higher current densities, whereas low current densities built up a homogeneous, compact and smooth surface structure. Ni electrodes coated with Au formed such smooth surface structures even at higher current densities.
Template copolymerization of methacrylic acid and acrylic acid
Authors: Połowiński S.
Published: April 2003

The copolymerization of methacrylic acid and acrylic acid in toluene was investigated and the reactivity coefficients r1 and r2 have been determined. With dioxane as the solvent, deviations from the Mayo‐Lewis equation were observed. The copolymerization was further carried out in presence of poly(ethylene glycol) and the reactivity coefficients for the template copolymerization in toluene and benzene were determined. A slight increase of r1 and decrease of r2 have been established. The results are discussed.
Interpretation of the 13C‐NMR spectrum of poly(vinyl butyral) by low molecular weight model compounds
Authors: Lebek B. , Krause A. , Schlothauer K. , Marschner H.
Published: April 2003

The formation of Cyclic, open, and semiacetals on model substances with different numbers and arrangement of hydroxyl groups and the possibility to distinguish between them was shown by 13C‐NMR measurements. Informations on the course of acetalation were obtained from propanetriol‐1.2.3 and hexanetriol‐1.2.6 which had been converted with various quantities of butyraldehyde.
Effect of colour on the mechanical and chemical properties of naturally photooxidized high density polyethylene
Authors: Ogbobe O. , Ossai N. N.
Published: April 2003

The effect of colour on the mechanical and chemical properties of coloured high density polyethylene at photooxidation by natural sunlight is studied. The extent of polymer deterioration depends on the nature of the applied pigments.
Mechanical properties of binary mixtures of high molecular poly(ethylene oxide) and alkali metal salts
Authors: Bogdanov B. , Uzov Ch. , Michailov M.
Published: April 2003

The mechanical properties of thin foils of binary systems of high molecular weight poly(ethylene oxide) and salts of alkali metals (NaSCN, KSCN, NaI, KI) have been investigated as a function of composition. The yield strength, tensile strength, elongation at break and Shore hardness of the foils change nonlinearly with the increase of alkali salt content. It was established that the systems PEO‐NaI, PEO‐KSCN and PEO‐KI are noncrystalline in a concentration range of alkali salts corresponding to 9 mol PEO per 1 mol alkali salt and they are in a rubbery or plastic state at room temperature.
A comparison of X‐ray methods for structure refinement of Langmuir‐Blodgett multilayers
Authors: Reiche J. , Pietsch U. , Fink H.‐P. , Lemmetyinen H.
Published: April 2003

The possibilities and limits of structure refinement of Langmuir‐Blodgett films by means of symmetrical reflection of X‐rays are described using the example of a stearic acid multilayer. Three different techniques for the determination of the electron density profile from reflectivity data are compared: a Fourier method, a Patterson method, and model calculations. The important role of the a priori information for finding the best structure model is outlined.
Untersuchungen zur radikalischen Copolymerisation von Dimethyl‐diallyl‐ammoniumchlorid mit Vinylacetat und Funktionalisierungsreaktionen der Copolymere
Authors: Janietz S. , Hahn M. , Jaeger W.
Published: April 2003

Die radikalische Polymerisation von Dimethyl‐diallyl‐ammoniumchlorid mit Vinylacetat in methanolischer Lösung verläuft als nichtideale, nichtazeotrope Copolymerisation. Die nach der Kelen‐Tüdös‐Gleichung berechneten Reaktivitätsverhältnisse wurden zur r1 = 1,95 und r2 = 0,35 bestimmt. Die resultierenden Polymere sind relativ niedermolekular und im gesamten Zusammensetzungsbereich in Wasser löslich. An ausgewählten Copolymeren wurden Modifizierungsreaktionen wie Hydrolyse, Acetalisierung und Acylierung durchgeführt, die Produkte mit veränderten Eigenschaften ergaben.
Einfluß der scherbedingungen auf das koagulationsverhalten von lösungen aus polyacrylnitril unterschiedlicher molmasse
Authors: Fritzsche P. , Makschin W. , Hartig S. , Abel Ch. , Lehmann I. , Leonhardt H.‐W.
Published: April 2003

Bei der Bildung von Fäden aus Acrylnitrilpolymeren nach dem Naßspinnprinzip bewirkt eine Erhöhung der Molmasse der Polymere eine Herabsetzung des maximal erreichbaren Düsenabzuges bei gleichzeitig geringerem Düsenverzugsverhältnis. Der maximale Reckgrad der ersponnenen Fäden sinkt mit steigender Molmasse und nimmt darüber hinaus mit steigendem Düsenverzug ab. Unter vergleichbaren Bedingungen hergestellte Fäden besitzen bei höherer Molmasse trotz gleicher erzielter Festigkeiten einen geringeren Orientierungsgrad. Die Erzielung von Hochleistungseigenschaften an naßgesponnenen Fäden erfordert daher ein neues Koagulationskonzept, das sowohl polymer‐als auch prozeßimmanente Faktoren einschließt.
Principles of polymerization. 3rd edition. By Georg Odian. A Wiley‐Interscience Publication. ISBN 0‐471‐61020‐8. John Wiley & Sons, New York/Chichester/Brisbane/Toronto/Singapore 1991.768 p., cloth cover, £ 47,50
Authors: Tauer K.
Published: April 2003

No Abastract.
SAXS and WAXS investigations of mass coloured polyamide fibres
Authors: Wlochowicz A. , Broda J.
Published: April 2003

The supermolecular structure of uncoloured and mass coloured polyamide‐6 fibres has been investigated by means of SAXS and WAXS methods. Three different kinds of organic pigments have been used for the study. During fibre formation a crystalline lamellar structure is formed. The crystalline phase contains the α and γ modification. The pigment Copper Phthalocyanine Blue causes an increase of the content of the α‐form. During drawing of the fibres a recrystallization process occurs leading to changes of the structural parameters. These changes are independent of the presence of pigments.
Investigations on the cold crystallization of pure and filled PETP by dielectric measurements
Authors: Nowak H. , Kalinka G. , Hinrichsen G.
Published: April 2003

The cold crystallization of pure and filled poly(ethylene terephthalate) (PETP) after quenching from the melt has been investigated by dielectric measurements in two different modes: The first one using constant heating‐rate (in the temperature range from 320 to 480 K) and the second one under isothermal conditions (at 378 K). The complex dielectric constant (ϵ′, tan δ) is influenced by crystallization. Two α‐relaxation regions are identified: The αa‐relaxation region from the pure amorphous phase and the α′‐relaxation region from the spherulitic phase. The investigations on the filled systems (PETP + 10% aramid puple, PETP + 30% short glass fibres) prove that an influence of the fillers on the time delay and rate of crystallization and on the geometry of the growing spherulites exists.
Ring‐opening polymerization of 2‐phenyl‐1,3,2‐dioxaphosphorinane initiated with new catalyst system using a halobenzene and nickel(II) bromide
Authors: Kobayashi S. , Kadokawa J.
Published: April 2003

Ring‐opening polymerization of 2‐phenyl‐1,3,2‐dioxaphosphorinane (a six‐membered cyclic phosphonite, 4) has been initiated with a new catalyst system of a halobenzene and NiBr2. The polymerization proceeded in a living nature to produce poly(phosphinate) consisting exclusively of a “normal” unit. The kinetic analysis of the polymerization of 4 initiated with the catalyst system was successfully carried out. The rate constant of propagation (kp) was much lower than that initiated with MeI. Linear and star‐shaped telechelic polymers were synthesized using di‐, tri‐, tetra‐, and hexa‐ halobenzenes as a catalyst component.
XPS investigations on adsorption of polyurethanes and chlorinated poly(vinylchloride) on chromium dioxide
Authors: Gähde J. , Loeschcke I. , Fischer Th.
Published: April 2003

The adsorption behaviour of a polyurethane‐elastomer (PUR) and a chlorinated poly(vinylchloride) (CPVC) on unstabilized magnetic chromium dioxide is described. The polymers were adsorbed on chromium dioxide from a solution of tetrahydrofuran individually or as a mixture. The polyurethane is preferably adsorbed, and it is able for displacing CPVC in the adsorption layer. An enriching of CPVC in the phase boundary layer to chromium dioxide by process engineering parameters is not succeeded. Partial cross‐linking of the adsorption layer was registered during storage under the effect of temperature and humidity.
High temperature superconducting ceramics from polymer metal precursors
Authors: Lampe I.v. , Lorkowski H.‐J. , Wäsche M.
Published: April 2003

We report on the preparation of polymer metal precursors, their thermoanalytical degradation and their transformation to high temperature superconducting (HTS) Y‐Ba‐Cu‐O or Bi‐Sr‐Ca‐Cu‐O compounds. The thin precursor film was patterned by electron beam lithography and subsequently transformed to HTS phases.
Ziegler‐Natta polymerization of ethylene with Ti‐Mg catalysts anchored on polymeric supports
Authors: Fuhrmann H. , Pohl M.‐M.
Published: April 2003

The immobilization of Ti‐Mg catalysts via polymeric Grignards on crosslinked polystyrenes has been achieved in the presence of methylene spacers of varying length. The resulting catalysts are tested in the homopolymerization of ethylene in a suspension process at 85°C and a total pressure of 6 bar. Hydrogen has been used as molecular weight controlling agent. The polymerization activity of the catalysts is significantly enhanced when a MgCl2 phase is generated in the course of catalyst preparation. The results are supported by SEM and TEM techniques.
Synthesis and investigation of α,ω‐methacryloyl poly (epoxide‐carboxylic acid) and α,ω‐methacryloyl poly (epoxide‐phenol) macromonomers
Authors: Klee J. E. , Claußen F. , Hörhold H.‐H.
Published: April 2003

α,ω‐methacryloyl terminated macromonomers containing epoxide‐carboxylic acid and epoxide‐phenolic repetitive units were synthesised. They were prepared in the molecular range from 600 to 2000 g/mol by a two‐step reaction. At first prepolymers were formed from bisphenol‐A diglycidyl ether and carboxylic acids or phenols and then reacted in a second step with methacrylic acid to the macromonomers. Their structure is proved by elemental analysis, Mn (vpo) values, IR and NMR spectroscopy. By using HPLC and GPC analysis it was shown that the macromonomers consist of oligomer homologous series. The distribution of the oligomers agrees with the calculated ones. Furthermore HPLC analysis and NMR spectra show that the epoxide rings were opened by SN1‐ and SN2‐type reactions.
New developments in synthesis of star polymers with poly(ethylene oxide) arms
Authors: Rein D. , Lamps J. P. , Rempp P. , Lutz P. , Papanagopoulos D. , Tsitsilianis C.
Published: April 2003

The synthesis of star molecules consisting of small polydivinylbenzene (DVB) cores carrying a number of hydrophilic poly(ethylene oxide) branches has been investigated. Two different methods are discussed:

The “core‐first” technique, in which living poly(DVB) cores are used to initiate the polymerization of oxirane. This method is flexible and efficient, but the samples obtained exhibit broad molecular weight distributions, arising from large fluctuations of the core functionalities (and core sizes). The same method has been applied successfully to the synthesis of star‐block copolymers, in which each branch consists of a polystyrene (PS) block and a poly(ethylene oxide) (PEO) block.

The “three‐step” method (“In‐Out”) involves the use of living polystyrene “seed‐star” molecules as initiators for the polymerization of oxirane. The “seed‐stars” themselves arise from a classical “arm‐first” process. This method allows a better control of the functionality of the cores. The number of branches of either kind attached to a given core is equal. Hetero‐star PS‐PEO copolymers are obtained, but the length of the branches of either kind can be chosen at will within broad limits.
The interaction of acrylic diblock‐copolymers with aluminum oxide surfaces and their application for ceramic powder processing
Authors: Rudolph J. , Patzsch J. , Meyer W. H. , Wegner G.
Published: April 2003

Amphiphilic diblock copolymers were prepared by anionic copolymerization of t.‐butylmethacrylate (TBMA) with methylmethacrylate (MMA) and n‐butylmethacrylate (NBMA) respectively, followed by polymer analogous conversion of the TBMA‐into methacrylic acid‐ (MAA) blocks. These materials are highly efficient dispersants for oxide and nitride ceramic powders. A series of samples with Mn ranging from 4.000 to 135.000, and with block length ratios from 0.5 to 14 (MMA/MAA) with polydispersities close to 1.0 were obtained.

The influence of total molecular weight and block length distribution of the copolymers and quality of the solvent system on their interaction with α‐Al2O3 were studied by sedimentation, adsorption experiments and surface plasmon resonance (SPR). The acrylic diblock copolymers are adsorbed irreversibly at the alumina surface. The conformation of the adsorbed macromolecules depends on the “quality” of the solvent. With respect to powder dispersing efficiency, an optimum is found when the polymers consist of short anchoring and stabilizing blocks.
Carbohydrate modified polysiloxanes II. Synthesis via hydrosilation of mono‐, di‐and oligosaccharide allylglycosides
Authors: Jonas G. , Stadler R.
Published: April 2003

The synthesis of linear carbohydrate modified polysiloxanes has been successfully performed by hydrosilation of functionalized and protected carbohydrate derivates. The functionalization (allyl glycosilation) may be applied to a wide variety of reducing carbohydrates. In this study, mono‐, di‐ and oligosaccharides were converted by a simple two‐step reaction (β‐acetylation and allyl glycosilation) into active compounds, allowing the polymer analogous addition to random poly[dimethyl‐co‐hydromethyl]siloxanes (hydrosilation). By variation of the Si–H amount in the starting polymers, polysiloxanes with 1.5% to 56% (by weight) carbohydrate content were prepared.

At small degrees of substitution the modified polysiloxanes remain soluble in non‐polar media. With increasing carbohydrate content the polymers become more and more soluble in polar solvents like isopropanol or methanol. A polysiloxane with 29% maltose modified comonomeric units (56 wt.‐% carbohydrate content) was fully water soluble.
Synthesis and examination of chiral liquid crystalline side chain polymers
Authors: Kossmehl G. , Nagel H.‐I. , Haase W. , Meyer J.
Published: April 2003

Substituted poly(methylsiloxane)s connected by a spacer with a biphenyl system that is esterificated with a chiral α‐chlorocarboxylic acid have been synthesized and characterized. Their liquid crystalline properties have been studied by differential scanning calorimetry (DSC), polarization microscopy, electro‐optical methods and X‐ray diffraction. Most of the synthesized compounds and polymers have liquid crystalline phases, mainly smectic phases.
Effects of pH, ionic strength, and type of anion on the rheological properties of chitosan solutions
Authors: Chen R. H. , Lin W. C. , Lin J. H.
Published: April 2003

Changes in the rheological properties of chitosan solutions with pH, ionic strength, and type of anion were studied. Between pH 2.0 and 5.0, apparent viscosities increased with the decrease of pH in chitosan–organic acid solutions, while in chitosan–HCl solutions they behaved oppositely. In chitosan–NaOH solutions, they decreased with the increase of pH between pH 5.0 and 6.0, then increased as pH further increased to pH 6.0–6.4. The difference may be due to different interactions of counterions with macroions and also the third electroviscous effect. Relative viscosity increased with a decrease in chitosan concentrations at concentrations below 1.5 × 10−3 M. Intrinsic viscosities changed with media pH and ionic strength.
Telechelic prepolymers and macromonomers by step growth processes
Authors: Klee J.E.
Published: April 2003

The article describes recent achievements in the field of telechelic epoxide‐amine and epoxide‐dithiol prepolymers and of macromonomers which can be obtained by step growth processes of epoxides with amines, carboxylic acids or phenols. The distribution of the oligomers is investigated with the help of HPLC and GPC. Furthermore the reaction of epoxideamine prepolymers with cyclic carboxylic acid anhydrides is described as well as their polymerization to new hybrid networks. The prepolymers with their β‐hydroxypropyl structural units are able to form complexes with metal ions. We have used this property for the extraction of Cu2+ ions from water solutions.
Rheological study of polymer‐surfactant interactions in cellulose derivatives and gelatin aqueous solution
Authors: Pisárčik M. , Bakoš D.
Published: April 2003

The rheological properties of water soluble cellulose derivatives (hydroxypropylcellulose, modified hydroxyethylcellulose) and gelatin aqueous solutions in a system with ionic surfactant were studied. The viscosity maximum was found in the region of critical micellar concentration (CMC) of the surfactant as a result of micelle formation. An increase of the CMC value with increasing molecular weight was observed and a decrease of this value for the hydrophobically modified polymer solution was found compared to the CMC value of the surfactant aqueous solution. A slight viscosity maximum was also found in gelatin systems with cationic and anionic surfactant. The viscosity increase (cross bonding) of gelatin aqueous solutions is more affected by a cationic surfactant than by an anionic one. pH measurements on gelatin systems indicate that the minimal viscosity is reached in the region of the isoelectric point.
Some experimental and theoretical data on the dielectric relaxation in dilute polystyrene suspensions
Authors: Carrique F. , Zurita L. , Delgado A.V.
Published: April 2003

The study of the conductivity and dielectric response of colloidal suspensions when subjected to an alternating electric field can give a great deal of information on the characteristics of the solid‐liquid interface, as well as on the dynamic processes taking place in such systems. In fact, measurements of the dielectric relaxation spectra on colloids are more sensitive to the nature of the surfaces than any other electrokinetic technique. This work deals with this problem in dilute polystyrene suspensions. Their complex conductivity and dielectric constant are experimentally measured as a function of both the frequency of the applied field and the latex volume fraction, in KCl solutions. From these data, certain quantities have been obtained that can be compared to the predictions of advanced theoretical models. The agreement between theoretical and experimental data is qualitatively excellent, although the latter are significantly larger that the former. Reasons for such discrepancies are discussed in the light of recent experimental results and double layer models.
Mn(II) coordination and ionic conductivity in ionene glasses
Authors: Rietz R.‐R. , Hölz G. , Meyer W.H. , Spiess H.W. , Wegner G.
Published: April 2003

Glasses from cationic polyelectrolytes of the type “ionenes” are considered as being a new class of materials. Below their glass transition the quaternized ammonium groups in the polymer backbone are essentially static, due to their strong Coulomb interactions. At the glass transition temperature (Tg) the N+ cations become mobile. However, both the low molecular weight counterions and the organic chain segments linking the cations are already mobile below Tg. Therefore, in contrast to other polymers, the glass transition in ionenes is characterized by the relaxation of the cationic centers. Ionic conductivity in the glassy state is based on thermally activated anion transport. In this paper, the influence of the coordination of Mn2+ in the [MnBr4]2− ‐anions on the solid state properties is investigated by electron paramagnetic resonance (EPR) and by dielectric spectroscopy. The local structure of the magnetically active Mn2+ centers in the ionene glass is found to have a tetragonally distorted symmetry at low temperatures, which is transferred into Td symmetry of [MnBr4]2− via a distorted octahedral transition state [MnBr42−‐Br22−] gives rise to an additional dielectric relaxation and to an unusually high activation energy for the anion transport.
Prediction of deformative and thermal properties of hybrid fiber composites with polymer matrix
Authors: Kochetkov V. A. , Maximov R. D.
Published: April 2003

A theoretical and experimental investigation was carried out to examine the possibilities of a structural approach for prediction of elastic constants, creep functions and thermal characteristics of hybrid polymer composites reinforced with anisotropic fibers of several types. The theoretical solutions were obtained by generalizing the self‐consistent method for the case of a three‐phase model. The effects of brittle fiber breakdown under tension in the direction of reinforcement of a unidirectional hybrid composite were studied under conditions of short‐term loading and long‐term creep. A variant of the solution is proposed for predicting the thermal deformation of a hybrid composite containing not only elastic, but also viscoelastic thermorheologically simple components with different temperature–time shift factors. The experimental confirmation of the predicted results was done on specimens of organic/glass, organic/carbon, glass/carbon and organic/boron polymer composites with different ratios of volume contents of fibers.
Wetting behavior in three‐component polymer blends
Authors: Desai R. C. , Yeung C. , Noolandi J.
Published: April 2003

We determine the interfacial properties of a three‐component polymer blend in three‐phase coexistence. We discuss how the presence of the third component affects the behavior of the interface between two phases. We demonstrate the existence of a wetting transition in which one of the minority phases wets the other. Our results indicate that both first‐ and second‐order wetting transitions occur.
Characterization of linear low density polyethylene by temperature rising elution fractionation and by differential scanning calorimetry
Authors: Mara J. J. , Menard K. P.
Published: April 2003

In this study, solution crystallized samples of LLDPE were characterized by differential scanning calorimetry (DSC) to ascertain the feasibility of utilizing the DSC technique as an alternative to analytical temperature rising elution fractionation (TREF). All steps, from dissolving the polymers to crystallizing by controlled cooling to analysis were performed in the DSC. The DSC results were compared with analytical TREF runs using two commercial LLDPEs (designated Resins A and B). Both techniques provided similar compositional distribution information with the calorimetric results being obtained in considerably less time. In particular, resins evaluated via both techniques showed distinct bimodal distributions, although the shapes of the curves were not identical. For example, as measured calorimetrically, Resins A and B contained approximately 69% and 59%, respectively, of the lower melting, more branched species. These results compared favorably with analytical TREF runs which indicated that Resins A and B contained about 68% and 58%, respectively, of the lower melting, more branched species.
Preparation of light emitting diodes on flexible substrates: Elimination reaction of poly(p‐phenylene vinylene) at moderate temperatures
Authors: Herold M. , Gmeiner J. , Schwoerer M.
Published: April 2003

We report on detailed measurements of the elimination reaction of poly(p‐phenylene vinylene) (PPV) prepared by the precursor route. The influence of the temperature on the conversion was investigated by optical absorption measurements. Compared to the elimination reaction in vacuum we find that the temperature necessary for the elimination reaction is remarkably reduced if carried out in a proper exchange gas. As a result, we have prepared the first flexible light emitting diodes (LEDs) of PPV on polymer foil substrates.
Statistical mechanical theory for liquid‐crystalline polymer solutions
Authors: Sato T. , Teramoto A.
Published: April 2003

A statistical mechanical theory is presented for liquid‐crystalline polymer solutions, where the liquid‐crystalline polymer is regarded as a wormlike spherocylinder interacting by the hard‐core repulsion and a soft (attractive or electrostatic) interaction with other spherocylinders. The theory is based on the following two assumptions: (1) the intramolecular excluded volume effect is not effective and (2) the interaction between pair of spherocylinders can be treated by the “single contact approximation”. These assumptions are relevant to a polymer with a stiff backbone and not very long contour length. The theory is used to predict thermodynamic and spatial properties of isotropic solutions and also isotropic‐liquid crystal phase equilibrium behavior. The predicted solution properties and phase behavior are favorably compared with experimental results for some selected stiff‐chain liquid‐crystalline polymers.
On the copolymer and cross‐linking contribution to the glass transition temperature of model networks
Authors: Reekmans B. J. , Shi Ji‐Feng , Pyati M. , MacKnight W. J. , Lillya C. P.
Published: April 2003

The effect of molecular structure on the glass transition temperature of end‐linked networks has been studied by examining a series of stoichiometrically imbalanced poly(propylene glycol)‐Desmodur RF (PPG‐DRF) and poly(isoprene)tristar‐hexamethylene diisocyanate (PIP‐HDI) networks. A range of different molecular weights of each prepolymer was used. The PPG‐DRF system shows a strong influence of the copolymer contribution on Tg. The modified copolymer approach (MCA) gives good theoretical correspondence with the experiments. This approach successfully predicts the Tg behavior of other cross‐linked systems with relatively high cross‐link densities. Other existing universal theories have been shown not to describe the Tg well for the PPG‐DRF system. Correction of the MCA is possible to account for a small plasticizing effect observed for highly stoichiometrically imbalanced samples. The PIB‐HDI system shows no strong contribution of the copolymer effect by virtue of its structure. The difference in cross‐link density can explain the changes in Tg. The MCA also yields reasonable results. For both systems it is necessary to consider all cross‐linkers for the purpose of determining the cross‐link density.
Polysilylenes with ethynylphenyl substituents
Authors: Frey H. , Schulenburg E.‐J. , Möller M. , Noorlander‐Bunt H. , Engbersen J. F. J. , Reinhoudt D. N.
Published: April 2003

Ethynylphenyl‐methyldichlorosilane (EPDMS) has been prepared as a new monomer for the synthesis of polysilylenes with triple bonds attached to the catenated Si chain. A series of copolymers with methylphenyldichlorosilane (MPDS) as well as the homopolymer, PEPMS, have been synthesized. The content of ethynylphenyl substituents was quantitatively analyzed by FTIR spectroscopy. The optical properties of the new polymers were studied with respect to potential π−σ interaction. No significant bathochromic shift of the UV‐absorption maximum could be detected. Unexpectedly, increasing content of incorporated EPMS units led to a decrease of the (σ−σ*) absorption. The ethynylphenyl‐substituted polysilylenes exhibited strong, temperature‐dependent fluorescence in solution as well as in films.
Anhydride‐cured epoxy resins toughened with diol‐ and bis(4‐hydroxybenzoate)‐terminated poly(tetrahydrofuran) liquid rubbers. Part I. Morphology and blend properties
Authors: Albert P. , Läuger J. , Kressler J. , Mülhaupt R.
Published: April 2003

A novel class of liquid rubber comprises bis(4‐hydroxybenzoate)‐terminated poly(tetrahydrofuran), which reacts with bisphenol A diglycidyl ether to form segmented liquid rubbers with poly(tetrahydrofuran) and poly(hydroxyether) segments. In anhydride‐cured epoxy resins such segmented liquid rubbers afford improved toughness. Diol‐ and bis(hydroxybenzoate)‐terminated poly(tetrahydrofuran)‐based liquid rubbers are compared. It is possible to control the polymer morphology by the variation of the molecular architecture of segmented poly(tetrahydrofuran)‐based liquid rubbers. The average size of the dispersed rubber phases depends on the molecular weight of the segmented liquid rubbers and correlates with impact strength and stiffness.
Anhydride‐cured epoxy resins toughened with diol‐ and bis(4‐hydroxybenzoate)‐terminated poly(tetrahydrofuran) liquid rubbers. Part II. Phase separation
Authors: Läuger J. , Albert P. , Kressler J. , Gronski W. , Mülhaupt R.
Published: April 2003

The structure formation via spinodal decomposition is monitored by transmission electron microscopy (TEM) and small angle light scattering (SALS) using hexahydrophthalic anhydride cured bisphenol A diglycidyl ether mixed with bis(4‐hydroxybenzoate)‐terminated poly(tetrahydrofuran) segmented poly(hydroxyether). The poly(tetrahydrofuran) (PTHF) segment has a number average molecular weight of 4500 g/mol. There is good agreement between the particle—particle spacing obtained from the maximum of SALS traces and the digital image analysis of TEM micrographs. Time‐resolved SALS measurements are used to study the phase separation kinetics in the epoxy/diol‐terminated PTHF system.
Scanning force microscopy of high modulus polyethylene fibers
Authors: Wawkuschewski A. , Cantow H. ‐J. , Magonov S. N. , Hewes J. D. , Kocur M. A.
Published: April 2003

Surfaces of commercial ultrastrong polymer fibers Spectra® 900 and Spectra® 1000, which are produced by gel‐spinning of ultrahigh molecular weight polyethylene (UHWM PE), were examined with scanning force microscopy (SFM). Measurements were conducted in water in order to minimize surface damage caused by the tip‐sample interactions. Different types of imperfections (arbitrarily oriented fibrils, ends of fibrils and discontinuities in surface layers) were found on the fiber surface. These features interfere with the dominating fibrillar structure aligned along the fiber direction. Within the fibrillar structure were found domains of ribbon‐like features with a width of 30‐–110 nm. These ribbons are oriented perpendicular to the fiber direction and were assigned to lamellar platelets overgrown on oriented nanofibrils. SFM images in the nanoscale (1‐–100 nm) showed that nanofibrils 5‐–7 nm wide are the elementary construction elements of polymer fibers. They are combined into larger fibrils of 40‐–50 nm width. Needle‐type crystallites 10‐–30 nm wide were also found on the fiber surface. An extended chain molecular order was detected on surfaces of nanofibrils, needle crystallites, and within the central part of lamellar ribbons. Local regions with long period features having a repeat distance of 15‐–25 nm were found on the fiber surface. Etching of the fiber surface by elemental fluorination damaged the surface fibrillar structure, and produced deep pores tens of nanometer in diameter in the surface layer.
Formation of colloidal PMMA particles via free radical and group transfer dispersion polymerization of methylmethacrylate and methylmethacrylate/ethyleneglycoldimethacrylate
Authors: Hölderle M. , Mülhaupt R.
Published: April 2003

Non‐aqueous dispersions of colloidal PMMA microparticles with average sizes ranging from 70 to 330 nm were prepared by living polymerization of methylmethacrylate (MMA) and methylmethacrylate/ethyleneglycoldimethacrylate (EDMA) in n‐heptane diluent using 2‐methyl‐1‐methoxy‐1‐trimethylsilyloxy‐prop‐1‐ene (MTS) as initiator in the presence of tetrabutylammonium fluoride (TBAF) or tetrabutylammonium cyanide (TBAC) as catalyst, and polystyrene‐block‐poly‐(ethene‐alt‐propene) (SEP) as dispersing agent. The influence of process parameters such as concentrations of MMA, EDMA crosslinking agent, TBAF, and SEP on conversion, molecular weight, particle size, and molecular weight and particle size distributions has been investigated. In contrast to GTP in solution, group transfer dispersion polymerization (GTDP) was markedly slower and accompanied by agglomeration and drastic broadening of both molecular weight and particle size distributions with increasing MMA conversion. In a new GTDP process colloidal PMMA microparticles, obtained by free radical dispersion polymerization, were added as seeds, thus affording much narrower particle size distribution and high MMA conversion.
Effects of water on the mechanical relaxation in polyamide 4
Authors: Bellinger M. A. , Ng C.‐W. A. , Macknight W. J.
Published: April 2003

The relaxation behavior of polyamide 4 was investigated as a function of absorbed moisture using dynamic mechanical measurements. Two relaxations, α at 81 °C and γ at — 111°C, were observed in the “dry” sample at a frequency of 1 Hz. The addition of water resulted in the depression of the α relaxation (αw) of the “wet” polyamide and the appearance of a second α relaxation (αd), slightly depressed from that of the “dry” specimen, reflecting the movements of the polymer chains after water has evaporated during the heating scan of the experiment. A second run was performed, resulting in the appearance of a single relaxation peak (α) at temperature very close to that of “dry” polyamide 4. Additionally, a β transition was observed whose temperature decreased with increasing water content. Similar results were obtained for specimens of polyamide 6. From plots of the depression of the glass transition temperature, ΔTg, as a function of the ratio of the number of water molecules to the number of accessible amide groups in the amorphous regions, R, one observes a sharp depression in the glass transition temperature with increasing water content up to some critical value, above which additional water molecules do not significantly change the glass transition temperature. Based on existing models for the sorption of water in polyamides, we propose a model whereby the environment of the polymer—water complex varies with the amount of water added to the system. At low water contents, both loosely and tightly bound water exist at the sorption centers, or amide groups. Above the critical water concentration, additional water molecules form clusters at these sorption centers. Additional aspects of the model explain the appearance of two α or primary relaxation peaks (αw and αd) due to the changing environments as a consequence of the heating scan of the dynamic mechanical measurements.
Linear viscoelastic behavior of branched polybutadiene: A fractional calculus approach
Authors: Friedrich C.
Published: April 2003

A rheological constitutive equation for complex polymeric materials is derived starting from a special formulation of the Laplace transformed relaxance. Material functions such as the complex modulus G*(ω), the relaxation modulus G(t) and the relaxation time spectrum H(λ) are derived. These material functions contain six material parameters, which divide these functions into three characteristic regions: the plateau region, which is in fact a power law region with a small slope, and, towards smaller frequencies, two additional power law regions with different slopes.

The comparison of the measured dynamic moduli of modified polybutadienes with the predictions of the proposed phenomenological model shows good agreement. Due to the fact that the mentioned material functions can easily be used, this model represents a tool for the quantitative description and discrimination of certain materials showing intermediate power law regions.
Time‐resolved small‐angle and wide‐angle X‐ray scattering apparatus using the imaging plate as a two‐dimensional detector
Authors: Hashimoto T. , Okamoto S. , Saijo K. , Kimishima K. , Kume T.
Published: April 2003

We report an application of the imaging plate, which contains phosphor crystals photostimulable by an X‐ray beam, as a two‐dimensional (2D) detector for time‐resolved small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray diffraction (WAXD) studies especially designed for use with a rotating anode X‐ray generator as an incident X‐ray beam source. The detector constructed has the shape of an octahedral cylinder, and to each face is attached an imaging plate of 200 mm width and 100 mm height. Each plate consists of 800 × 1600 pixels with an area of 125 × 125 μm2/pixel. Time‐resolved data acquisition of SAXS and WAXD patterns on the 2D detector is performed by changing the plate face with time either by a rotation of the drum or by shifting a face of the plate in the drum with respect to the incident beam. The detection (which consists of writing and reading) of scattered X‐ray intensity distributions with the plates as well as erasure of the scattering patterns stored on the plates can be continuously performed by rotating the drum. The reading rate for the scattering patterns recorded onto the plate is 25 μs/pixel or 300 s/plate. The time required for changing the plate face from one to another by rotating the drum is 2 s, which corresponds to a minimum dead time for the time‐resolved study with an effective area of 100 × 200 mm2. When necessary, especially to shorten the dead time for the measurements, each plate can be further divided into N sections by shifting the drum with respect to the incident beam, the time required for the shifting being 25 ms/mm. Thus when the plate of 200 × 100 mm2 is divided into sections of (200/N) × 100 mm2, the minimum dead time is reduced to 25 × (200/N) ms.
Influence of a brushed polyimide surface on photoinduced reorientation processes in dye‐containing liquid crystalline polymers
Authors: Pfaadt M. , Boeffel C. , Spiess H. W.
Published: April 2003

Infrared spectroscopy is used to study the influence of the polarization of the irradiating light and the substrate surface treated with polyimide on the reorientation process of dye‐containing liquid‐crystalline side‐group copolymers. The depolarization of the linearly polarized light on brushed polyimide surfaces affects the reorientation process and as a consequence the irradiation direction becomes the new order axis after irradiation. Relaxation processes are observed after short irradiation times, since a new stable equilibrium state has not been reached. In contrast, complete reorientation, achieving changes in order parameter of 0.9, is observed after long irradiation times. The system is then stabilized in the new orientational distribution and no relaxation processes occur. The relaxation processes can be explained by a combination of matrix response and thermal cis‐trans back relaxation of the azobenzene.
Crystallization of amorphous polyamides from the glassy state
Authors: Androsch R. , Stolp M. , Radusch H.‐J.
Published: April 2003

The general crystallization behavior of amorphous polyamides during heating treatment was measured by wide angle X‐ray scattering (WAXS) and differential scanning calorimetry (DSC) to get information on (1) the temperature range where the crystallization in an anisothermic process takes place and (2) the type of the crystalline phases (α or γ) considering the Brill transition and the state of order in the α‐crystal. Various polyamides (PA 6, 6.10 and 6.6) were quenched and cooled to 200 K and then heated until they melted. During heating from the glassy state the crystallization starts rapidly at the glass transition temperature and then the crystallinity slowly increases until the melting point. The crystallinity was calculated on the basis of the separation of the amorphous and crystalline scattering by profile fitting. The angular position of the amorphous halo and so the density of the amorphous phase is higher in the presence of the crystalline phase compared to the completely amorphous state. The crystalline structure (α or γ), which is difficult to distinguish at higher temperatures due to the Brill transition, was determined by quenching the samples from elevated temperatures to room temperature after heating. The perfection of the α‐crystal, i.e. the crystal perfection index, increases with temperature during continuous heating.
Synthesis and characterization of interpenetrating polymer networks based on polyacrylate and epoxy
Authors: Tan Su‐sheng , Zhang Dong‐hua
Published: April 2003

The synthesis and properties of simultaneously interpenetrating networks (SINs) based on poly(polyethylene glycol diacrylate) (PEGDA) and epoxy (diglycidyl ether of bisphenol A, DGEBA) were studied. The effect of compositional variation on the morphology and properties of products was investigated. The swelling coefficient, densities, glass transition behavior, and thermal stability of these interpenetrating networks (IPNs) are discussed. Microphase separation morphological structures were found in all PEGDA/DGEBA IPNs. Decreased swelling ratios compared to the calculated swelling coefficients based on the weight additivity of the components were obtained after the formation of IPNs. Increased density and thermal stability were also obtained in these IPNs, implying the existence of interpenetration (topological entanglements) among the component networks.
Silver nanocluster formation within microphase‐separated block copolymers
Authors: Sohn B. H. , Cohen R. E.
Published: April 2003

Silver cluster formation in bulk block copolymer films (static‐cast) and in thin films (microtomed or spin‐coated) was investigated by transmission electron microscopy. In all cases, the silver clusters were formed predominantly within the original silver‐containing microdomains. A greater degree of control of cluster formation and a narrower cluster size distribution were achieved in the thin films of block copolymers. The interfaces between domains of the heterogeneous copolymers and the free interfaces of the thin film specimens all played an important role in nucleation and growth of clusters.
Stabilization of colloidal palladium particles by a block copolymer of polystyrene and a block containing amide sidegroups
Authors: Roescher A. , Hempenius M. , Klok H.‐A. , Möller M.
Published: April 2003

A block copolymer of polystyrene and poly(tert‐butylmethacrylate) was prepared by anionic polymerization. The ester groups of the poly(tert‐butylmethacrylate) were hydrolyzed, after wich the remaining carboxyl groups were reacted with pyrrolidine. The resulting block copolymer with amide sidegroups was used for stabilization of a palladium colloid in toluene.