bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of polyesterification and models, 2. Kinetics and mechanism of 1,1,1‐trimethylolpropane esterification by long‐chain carboxylic acids at technological conditions
Authors: Bacaloglu Radu , Mǎtieş Marius , Csunderlik Carol , Cotarcǎ Livius , Moraru Ariana , Gros Josif , Marcu Nicolae
Published: April 2003

Kinetics of 1,1,1‐trimethylolpropane esterification by long‐chain (C4 —C18) carboxylic acids has been followed by GLC, HPLC, 1H‐NMR, and potentiometric titrimetry. The system composition evolution was established at technological conditions, i.e. molar ratio between 1/1 and 1/3 and temperatures between 160 and 205°C. The rate constants of the three involved consecutive reactions were determined according to the kinetic law which assumes a partial order of 1.5 with respect to the acid and 1.5 with respect to the alcohol.

Once the three rate constants k1, k2, and k3 are known by direct determination, a computer simulation for the esterification process has been carried out. The experimental variation of the component concentrations and the calculated values show a proper agreement, thus proving the selected kinetic model.
Synthesis of chiral polymers containing dimethylaminobornanol moieties
Authors: Liu Jui‐Hsiang
Published: April 2003

In order to investigate the influence of spacer on the stereoselectivity of the addition of n‐butyllithium to aldehydes, three kinds of chiral polymers containing dimethylaminobornanol moieties were synthesized. The polymerization of the chiral monomers was carried out under various conditions. Cross‐linked chiral polymers were prepared by copolymerization of the chiral monomers with commercial p‐divinyl benzene. The conversion was found to be affected by the kind of solvents. Asymmetric addition of n‐butyllithium to benzaldehyde was carried out in the presence of the chiral polymers having dimethylaminobornanol moieties, and it was found that all three kinds of chiral polymers are effective for the asymmetric addition. Advantages of insoluble chiral polymers such as the ease of separation from products and the ability to be recycled, are discussed.
Ein modell zur quantitativen beschreibung der morphogenesis von PVC‐S, II Modellierung der inneren morphologie — modellvorschlag
Authors: Weickert Günter , Platzer Bernd , Weißenborn Klaus‐Dieter , Klodt Rolf‐Dieter , Henschel Ines
Published: April 2003

In der vorliegenden Arbeit wird ein mathematisches Modell für die Berechnung der Morphogenesis von PVC‐S entwickelt, das die hierarchische Struktur von PVC‐S‐Körnern widerspiegelt. Die Bildung der Polymerketten wird auf der Basis eines selektierten kinetischen Modells beschrieben. Für den Prozeß der Aggregation der Teilchen innerhalb eines Subkornes wird ein Modellansatz aus dem Einstein‐Smoluchowski‐Gesetz abgeleitet. Die Modellparameter des Gesamtmodells sind physikalisch‐chemisch begründbar — lediglich ein Parameter dient als effektive Konstante zur integralen Erfassung von Prozessen, die einer genügend genauen und hinreichend einfachen Modellierung zur Zeit noch wenig zugänglich sind. Das aggregative Wachstum der Teilchen in den verschiedenen hierarchischen Ebenen wird mit Hilfe vereinfachter geometrischer Annahmen beschrieben. Auf diese Weise sind die Zahl und die Größe der Teilchen innerhalb der PVC‐Subkörner als Funktion der Reaktionszeit berechenbar.
In vitro blood compatibility of glow discharge‐grafted silicone rubber tubings
Authors: Jansen Bernd , Steinhauser Hermann , Prohaska Wolfgang
Published: April 2003

Small diameter silicone rubber tubings were grafted with vinyl methyl acetamide using a glow discharge treatment. Discharge conditions were chosen which allowed grafting exclusively on the inner surface of the tubings. Increasing the voltage as well as a posttreatment at increased monomer vapor pressures leads to higher conversions as a posttreatment at increased monomer vapor pressures leads to higher conversions as determined by contact angle measurement and gravimetry; no influence of the discharge pressure could be observed. Human blood plasma exposed to the grafted tubings showed some alterations in comparison to blood plasma exposed to ungrafted tubings. A prolongation of the activated partial thromboplastin time and lower levels of factor V and platelet factor 4 were measured, while almost no differences in the generation of fibrinopeptide A could be noticed. Platelet adhesion on grafted tubings was less than on unmodified tubings.
Natural graphite filled polyolefins — electrical and electrochemical behavior
Authors: Krohn Holger , Beck Fritz , Zahn Axel
Published: April 2003

Composite materials with 80 wt.‐% natural graphite and 20 wt.‐% polyolefins have been characterized for their application as positive electrodes in batteries. With respect to graphite, resistivity is enhanced by a factor of 104 (ρ = 1–10 Ωcm), and the anisotropy factor is lowered to 10. A thin polymer film barrier and/or a thin bilayer of graphite surface groups between the graphite flakes, crossed by electron tunneling, is responsible for this and for a pronounced field effect of resistivity.

The presence of a polymer binder is also indicated by a formation effect in the course of the first anion intercalation cycles performed by electrochemical experiments. Long term cycling of a model cell reveals a strong influence of the mechanical properties of the polyolefin binders. Those with high tensile strength lead to a much poorer cycle life than those with low tensile strength, where cycle numbers up to 5000 (one hour charge) have been obtained. The latter material has an improved compatibility to the periodical volume alterations in the course of electrochemical cycling.
Elektrische leitfähigkeit von rußgefüllten polyethylenen und polyethylenmischungen
Authors: Grigorova Marietta , Mladenov Ivan , Zlatkov Todor , Michailov Marin
Published: April 2003

Untersucht wurde die elektrische Leitfähigkeit von mit Acetylenruß gefüllten Systemen mit Ein‐ bzw. Zweikomponentenmatrix aus Polyethylenen verschiedener Dichte und unterschiedlicher Viskosität im Schmelzzustand.

Es wurde festgestellt, daß unter isothermen Bedingungen die elektrische Leitfähigkeit mit steigendem Kristallinitätsgrad und Schmelzindex der Polyethylenkomponenten steigt. Dabei übt das Fließverhalten der Polyethylenmatrix einen sehr wesentlichen Einfluß aus.

An ausgewählten Objekten wurde die Temperaturabhängigkeit der elektrischen Leitfähigkeit untersucht. Die wesentlichste Abnahme der Leitfähigkeit mit der Temperaturehöhung wurde bei den rußgefüllten Polyethylenen hoher Dichte festgestellt.

Die erhaltenen Resultate eröffnen die Möglichkeit einer geregelten Herabsetzung des elektrischen Volumenwiderstandes von rußgefüllten Polyethylensystemen durch die gezielte Änderung ihrer Matrix‐Komponenten‐Zusammensetzung.
Blends of chlorinated isotactic polypropylene with poly(ethylene‐co‐vinyl acetate) I. Effect of component polymers composition on the blend miscibility
Authors: Lee Seung Soo , Chung Ki‐Hyun , Kim Kwang Soo , Jung Jin Chul
Published: April 2003

Chlorinated isotactic polypropylenes (CPP) having various chlorine contents were blended with poly(ethylene‐co‐vinyl acetate)s (EVA) having various vinyl acetate (VA) contents. The blends were made by casting films from dilute THF solutions and miscibility of the blends was identified by single glass transition temperature, which was confirmed by DSC and dynamic mechanical measurements. Based on the miscibility data from a large number of CPP/EVA combinations, a miscibility map was depicted where CO equivalent weight (CO‐EQW) of EVA was plotted against chlorine equivalent weight (Cl‐EQW) of CPP.

Though an attractive interaction between CPP and EVA could be detected in all the miscible and immiscible blend pairs, miscibility of the CPP/EVA blends could solely be observed in a relatively narrow range of Cl‐EQW ca. 65–100 and CO‐EQW ca. 170–230.
Polymerization of diallyldimethylammonium chloride in inverse emulsion, II. Molecular weight and electrical conductivity of the polymer
Authors: Huang P. C. , Reichert K.‐H.
Published: April 2003

The dependence of molecular weight of poly(diallyldimethylammonium chloride) on conversion was studied and a model is proposed for the calculation of the conversion dependence of molecular weight under consideration of gel effect and chain transfer reactions to monomer and polymer. The influence of tetramethylammonium chloride concentration on the ionic conductivity of the solid polymer was studied. A maximum specific ionic conductivity of 2.2 · 10−4 S cm−1 was measured.
Kinetics of polyesterification and models, 3. Kinetics and mechanism of pentaerythritol esterification by long‐chain carboxylic acids at technological conditions
Authors: Bacaloglu Radu , Mǎtieş Marius , Cotarcǎ Livius , Gros Iosif , Moraru Ariana , Tǎrnǎveanu Alexandru
Published: April 2003

Kinetics of the esterification of pentaerythritol by long‐chain carboxylic acids (C7 – C18) has been followed by potentiometric titrimetry. A simplified approach for the estimation of the rate constant values and the rate constants of the consecutive processes was developed according to the previous established kinetic law for similar systems.

A computer simulation of the component concentrations variation has been carried out in order to prove the selected kinetic model.
Correlation between the production parameters and the mechanical properties of novolac resins reinforced with carbon fibers
Authors: Simitzis Johannis
Published: April 2003

Unidirectional composite materials of novolac resin with carbon fibers were fabricated according to the prepreg method. Novolac resin was prepared by polymerization of phenol with formaldehyde (mole ratio 1 : 0.82) in the presence of oxalic acid as catalyst (1.5 wt.‐% to phenol). The curing of novolac resin was performed with hexamethylenetetramine (hexa), while the appropriate proportion was determined by using the IR‐spectroscopy.

Specimens of novolac/hexa (weight ratio 14:1) reinforced with carbon fibers commercially available were fabricated under different conditions (e.g. different thermal programs and different proportions of novolac/carbon fibers). The mechanical properties of the fabricated specimens (like flexural strength, tensile strength, etc.) were determined and their structure was examined by scanning electron microscopy.

By increasing the volume proportion of carbon fibers, not only all mechanical properties of the composite material were increased, but also their degree of utilization was increased and also the production conditions had greater influence. Concerning the specimens produced by the same proportion of carbon fibers (e.g. 15 vol.‐%) their mechanical properties were improved by increasing the curing of novolac. The degree of curing of novolac during the initial phase (gel time) and during the ultimate phase (post‐curing) can be followed with the aid of IR‐spectra of the cured resin, while the degree of curing for the intermediate phase can be obtained only indirectly from the values of the mechanical properties of the corresponding specimens.

From the correlation between the production parameters and the mechanical properties of the samples the optimal conditions for processing of the thermopress for the manufacture of carbon fiber reinforced novolac were concluded (1. phase: T1 = 125–145°C, t1 = 20 min – 1 h, without pressure; 2. phase: T2 = 180–195°C, t2 = 40 min, P2 ≃ 1,5 kN/cm2).
Ein modell zur quantitativen beschreibung der morphogenesis von PVC‐S, III. Modellierung der inneren morphologie — parameterstudien
Authors: Weickert Günter , Henschel Ines , Platzer Bernd , Klodt Rolf‐Dieter , Weißenborn Klaus‐Dieter
Published: April 2003

In der vorliegenden Arbeit werden die Eigenschaften des früher1,2 entwickelten Modells untersucht und diskutiert. Die Variation der Modellparameter zeigt einen großen Einfluß der Aggregationsprozesse auf die Subkornmorphologie. Bei niedrigen Monomerumsätzen ist das Zeitintervall zwischen zwei aufeinanderfolgenden Aggregationsschritten sehr klein, so daß für das Teilchenwachstum die Geschwindigkeit der Aggregation der Unterstrukturen entscheidend ist. Im Bereich zwischen 5% und 20% Monomerumsatz sinkt die Aggregationsgeschwindigkeit sehr stark, so daß für das Teilchenwachstum zunehmend die Polymerisationsreaktion an Bedeutung gewinnt. Aggregative Stabilität wird nach dem Modell für einen Teilchengrößenbereich erhalten, der sich in Übereinstimmung mit experimentellen Daten aus der Fachliteratur befindet. Die berechneten Teilchengrößen entsprechen ebenfalls den in der Literatur publizierten experimentellen Werten, so daß das Modell eine gute Grundlage für die Beschreibung einiger morphologisch bestimmter Polymereigenschaften bildet.
Effect of concentration and temperature on the electrical conductivity of butyl rubber loaded with different types of carbon black
Authors: Eatah A. I. , Ghani A. A. , Hashem A. A.
Published: April 2003

In this study we are interested in the effect of concentration and temperature on the electrical resistivity of butyl rubber (IIR) loaded with two types of carbon black, (namely, high abrasion furnace black (HAF), and fast extrusion furnace black (FEF)). It was found that the conductivity at low carbon black concentrations is mainly achieved by thermal activation of carriers. Tunneling mechanism at low termperature followed by thermal activation at relatively high temperature is found to be predominant for moderate concentrations for both carbon blacks. The metal‐like behaviour which was observed in highly loaded compounds was attributed to both, the thermal expansion of the tunneling paths between carbon‐carbon agglomerates and the breakdown of carbon agglomerates with temperature.
Synthesis of halogenated phenyl glycidyl ethers and their use for flame retardancy of polymeric materials
Authors: Horák Oldřich , Eichler Josef , Dufek Jan , Melichárek Jan
Published: April 2003

This study deals with the synthesis of halogenated derivatives of phenyl glycidyl ether and with possibilities of their use as flame retardants and reactive diluents of epoxy resin.

The best reaction conditions optimized by Nelder‐Mead simplex method were found. The products of very high quality were prepared. They were mixed with a lowmolecular epoxy resin and cured by diamino diphenyl methane.

The viscosity of the resin mixtures and limiting oxygen index of cured systems were determined. It was found that a higher content of halogen, both chlorine and bromine, causes increasing viscosity and reduced flammability of the epoxides.
The characterisation of the polyethylene‐polystyrene‐divinylbenzene interpolymer cation‐exchange membranes in the electrolysis of borax solutions
Authors: Erbil H. Yildirim , Baysal Bahattin M.
Published: April 2003

The synthesis and the characterization of the PE‐PS‐DVB interpolymer cationexchange membranes in the electrolysis of borax solutions to produce boric acid and sodium hydroxide simultaneously was carried out. The characterization of the teflon based “Nafion 324” and polystyrene‐DVB based “Permaplex C‐20” membranes was also performed in the same system for comparison.

The DVB contents were varied between 3 – 12% (by wt. in total monomers) and the increase of the cross‐links resulted in the decrease of the water contents and ionexchange capacities of the membranes. The PE present in the membrane acted as a barrier for electroosmotic water transport. The membranes with high DVB contents showed better electrolysis performance due to their low water contents and low electroosmotic water transport properties. The use of the interpolymer membrane containing 11.6% DVB resulted in high current efficiency and high sodium cation dynamic transport number and worked satisfactorily at the process conditions of borax electrolysis.
Functional monomers and polymers, 163. Inclusion polymerization of cyclic diene monomers in deoxycholic acid canals
Authors: Tsutsumi Hiromori , Miyata Mikiji , Takemoto Kiichi
Published: April 2003

Inclusion polymerization of cyclic diene monomers, such as cyclopentadiene, 1,3‐cyclohexadiene, 1,3‐cycloheptadiene, 1,5‐cyclooctadiene, and 2,5‐norbornadiene, was studied, using deoxycholic acid (DCA) as the canal component.

The formation of monomer‐DCA adducts was observed, however, the polymerization occurred only in the case of cyclopentadiene, 1,3‐cyclohexadiene, or 1,3‐cycloheptadiene. The polymers obtained consisted preferably of 1,4‐units and almost 100% of 1,4‐units in the case of 1,3‐cyclohexadiene. ESR measurements revealed that inclusion polymerization of cyclopentadiene or 1,3‐cyclohexadiene in DCA canals proceeds by a free radical mechanism.
Interpenetrating polymer networks from castor oil and dibasic acids
Authors: Shah Tarulata B.
Published: April 2003

Prepolyesters were obtained from castor oil and dibasic acids, viz oxalic, malonic, succinic, glutaric, adipic, suberic and sebacic acid. These prepolyesters (PPE) were subsequently interpenetrated with methyl methacrylate containing 1% ethylene glycol dimethacrylate as crosslinker by radical polymerization initiated with benzoyl peroxide. The novel PPE poly(methyl methacrylate) PPE/PMMA interpenetrating polymer networks (IPNs) were obtained as powder. They were characterized by solubility behaviour, IR spectral study and thermal behaviour.
Studies of reactions with polymers, IV. Syntheses and properties of poly(vinyl alcohol) graft terpolymers containing imide side chains
Authors: Chiang Wen‐Yen , Hu Chun‐Min
Published: April 2003

A series of new poly(vinyl alcohol)‐g‐methyl methacrylate/N‐substituted maleimide graft terpolymers were prepared by reacting the residual anhydride groups on the poly(vinyl alcohol)‐g‐methyl methacrylate/maleic anhydride with the appropriate N‐substituted amines through the poly(vinyl alcohol)‐g‐methyl methacrylate/N‐substituted maleamic acid intermediate. Here, the N‐substituted amines were N‐benzyl, N‐butyl, N‐octyl, N‐dodecyl and N‐ethylol amines. The compositions and the proposed structure of the resultants were determined by elemental and infrared analyses. The water content, thermal and mechanical properties of the new poly(vinylalcohol) graft terpolymers were also investigated.
Synthèse de copolymères multiséquencés comportant des séquences cristallines organosiliciques
Authors: Schmitt D. , Beinert G. , Zilliox J. G. , Herz J.
Published: April 2003

Des copolymères multiséquencés comportant des séquences cristallisables de poly(diméthylsilyl‐1 diméthyléthylènesilyl‐4 benzène) et des séquences, soit de polystryrène (PS), soit de poly(oxyéthylène) (POE), ont été préparés par réaction d'hydrosilylation entre polymères précurseurs, α,ω‐difonctionnels. Le polymère organosilicique utilisé portait des fonctions diméthylsilane aux deux extrémités de sa chaîne. Les polymères précurseurs PS et POE étaient dotés aux deux extrémités de leur chaîne de fonctions silvinyliques portées par un motif chimique de même nature que celle de l'unité monomère de la séquence organosilicique. Dans des conditions expérimentales adéquates, la réaction d'hydrosilylation conduit alors à des copolymères multiséquencés comportant 6 à 10 séquences.
The cell‐plasma membranes as composite system of two‐dimensional liquid crystal and macromolecular network and how to mimick its physical properties
Authors: Duwe H.‐P. , Eggl P. , Sackmann E.
Published: April 2003

The evolution of the cell has become possible after nature had invented the composite membrane by combining two states of matter: the two‐dimensional liquid crystalline lipid/protein bilayer and the macromolecular network.

In the first part we introduce the essential structural features of the cell plasma membrane (case of erythrocyte) and describe their extraordinary mechanical properties. These are unmatched by the technical materials and allow migrating cells to squeeze through narrow gaps of the tissue or of the extracellular protein networks without loss of material or lysis. As an example, how nature manages to alter the structure and function of biomenbranes drastically by minor biochemical signals we consider chemically induced shape changes of cells.

In the second part we describe some efforts to mimick mechanical properties of cell membranes with composite membranes of monomeric and polymeric amphiphiles. These model systems exhibit promising new material properties for future applications in chemistry and biotechnology.
Polymerized model biomembranes
Authors: O'Brien David F. , Liman Ulrich
Published: April 2003

Over the past two decades lipid bilayer membranes have served as effective models for biomembranes. Pure lipid membranes allow investigators to probe the behavior of different classes of lipids in lamellar and nonlamellar phases. Nonlamellar phases are of current interest because of their considerable importance in cellular permeability, fusion, endo‐ and exocytosis. The reconstitution of biological membranes from purified protein and lipid components has proven to be a convenient method for the study of protein‐lipid interactions and membrane protein functionality. The introduction of methods to polymerize lipid bilayers in the early 1980s, now provides researchers with new ways to prepare and characterize model biomembranes. This report summarizes three areas of research on polymerized model membranes: 1) the enhancement of chemical stability and reduction in bilayer permeability by polymerization of single component membranes; 2) the polymerization induced domain formation in two‐component membranes, which is accompanied by membrane destabilization when one of the lipid components prefers a nonlamellar structure; and 3) the successful reconstitution of a purified delipidated membrane protein, rhodopsin, into partially polymerized bilayer membranes with retention of both protein functionality and phospholipid surface biocompatibility.
Ordering and organization in ionic solutions and emulsions
Authors: Ise Norio , Matsuoka Hideki , Ito Kensaku
Published: April 2003

Recent studies on ionic distribution in solutions and in suspensions were reviewed. Suspensions of latex particles, which were large enough to be seen under an ultramicroscope, were investigated by the 2‐D Fourier transformation. The micrograph showing ordered structures gave discrete scattering spots, whereas those of disordered arrangements displayed no spots or halos. The two‐state structure gave a limited number of halo, confirming our previous conclusion that the very frequently observed single, broad scattering peak was reminiscent of some kind of ordering of solute species. By using an image data analyser, the crystallization process was shown to follow the Ostwald ripening mechanism. The concurrent study by the quasi elastic light scattering method and by the Fourier analysis gave consistent scattering profiles, which indicated that the ordering phenomena took place in the entire volume of suspensions. The scattering intensity (correctly the lattice factor) was calculated for cubic systems with paracrystalline distortion. The peak intensity was lowered by enhanced distortion, while the peak position itself was not affected. This justifies our previous treatment of the single, broad peak in terms of the Bragg equation. The experimentally found scattering curve was compared with this theoretical calculation; the degree of distortion was evaluated.
Übermolekulare flüssigkristalline strukturen von hochkonzentrierten cellulosederivatlösungen
Authors: Siekmeyer Maria , Steinmeier Hans , Zugenmaier Peter
Published: April 2003

Lyotropic liquid crystalline phases of cellulose derivatives were explored as an analytical tool. Molar mass dependent measurements of the helicoidal cholesteric pitch of a cellulose tricarbanilate/solvent system may be used to determine the molar mass of this derivative by optical means. The compatibility of a ternary liquid crystalline system can be adequately investigated by a study of the supermolecular structure with spectroscopic measurements.
Phospholipid polymers & new haemocompatible materials
Authors: Hall Brenda , Bird Richard Le R. , Chapman Dennis
Published: April 2003

When blood comes into contact with an artificial surface, a number of events occur which include protein adsorption, platelet activation and the activation of the intrinsic pathway of blood coagulation. With the increased application of blood containing artificial devices, there is a great demand to develop new biomaterials which retard thrombus formation. Our new approach to solving this problem is to mimic the non‐thrombogenic surface of natural biological membranes at least in a simple form. We have developed a polymerisable phospholipid and polyesters based on the major phospholipid polar head group present on the erythrocyte outer membrane surface. The coagulation of blood exposed to these polymers was examined by the technique of Material Thrombelastography, a relatively simple test for the in vitro screening of polymer thrombogenicity. We present results which indicate that the polymerised phospholipid and polyesters show reduced thrombogenicity, and may therefore have potential for future biomaterials.
Modifizierung von polymeroberflächen zur erhöhung der zelladhäusion
Authors: Klee D. , Breuers W. , Bilo‐Jung M. , Mittermayer C. , Höcker H.
Published: April 2003

After implantation a stable bond between the implant and the surrounding tissue is required. Therefore a high cell adhesion of the polymer surface of the implant must be achieved. Depending on the treatment time of a polydimethylsiloxane foil with oxygen plasma, the cell adhesion can be improved. FT‐IR spectroscopy and ESCA analysis were used to characterize the surface modification. The cell spreading and cell adhesion increase with increasing hydrophilic character of the polymer surface after plasma treatment. A pronounced correlation was found between the efficiency of DNA and protein content, characterizing cell growth, and the spreading of the cells.

Polydimethylsiloxane, Glow‐Discharge, Surface Modification, Cell Adhesion, Cell Proliferation.
Explorations in cell biology and pharmacology using synthetic polymers
Authors: Lloyd J. B.
Published: April 2003

We have used synthetic polymers as tools to probe endocytosis and lysosome function. Their particular value lies in their well‐defined chemical constitution and in the possibility to custom‐synthesize molecules with desired characteristics. Polyvinylpyrrolidone, Percoll and polystyrene beads have been 125I‐labelled and used to explore the borderland of pinocytosis and phagocytosis. Derivatized poly(aspartamide), poly(hydroxypropylmethacrylamide) and a polylysine‐poly(ethylene oxide) block copolymer have been used to investigate the effects of hydrophobic moieties and sugar residues on substrate‐selection in pinocytosis. The effect of cationic moieties has been studied using vinylpyrrolidone‐vinylamine copolymers.

Poly(hydroxypropylmethacrylamide) with certain oligopeptide side‐‐‐chains have been shown to be susceptible to lysosomal peptidases. Ethylene glycol oligomers are being used to study the basal permeability of the lysosome membrane.

Soluble macromolecules have considerable potential in targeted drug‐delivery. Drugs attached to appropriate polymers by covalent links that are susceptible to lysosomal enzymes can deliver drug to target cells and avoid unwanted sideeffects. Synthetic macromolecules have several advantages over their natural counterparts: they are chemically more robust, less immunogenic, and easier and cheaper to prepare in bulk.
Preparation, properties and uses of polymer‐enzyme conjugates
Authors: Katchalski‐Katzir Ephraim
Published: April 2003

Enzymes can be immobilized by gel entrapment, by microencapsulation, by physical or ionic adsorption, by covalent binding to inorganic or organic carriers, or by whole cell immobilization. Of particular interest is the large number of chemical reactions developed for the covalent binding of enzymes via their nonessential functional groups to inorganic carriers such as glass, ceramics and iron, to natural polymers such as cellulose and Sepharose, and to synthetic polymers such as nylon, polyacrylamide, and other vinyl polymers and copolymers possessing reactive chemical groups. The stability of certain enzymes is markedly increased on their immobilization. It was thus possible to transform the biologically active polymer derivatives into active enzyme beads, enzyme capsules, enzyme columns and enzyme membranes and these enabled the construction of enzyme reactors such as the batch‐stirred tank reactors, the continuous packed bed reactors, and fluidized bed reactors. So far mainly immobilized hydralases and isomerases are being used in industry on a large scale. It seems likely, however, that once adequate techniques become available for cofactor recycling, the use of immobilized enzymes will be extended to other organic reactions, particularly those involving stereospecific synthesis of simple or complex organic molecules. Among the industrial processes in which immobilized enzymes are being used, it is worth mentioning the industrial‐scale continuous production of fructose enriched syrup from glucose by immobilized glucose‐isomerase, the batch process for the production of 6‐aminopenicillanic acid (6‐APA) from penicillin G with the aid of immobilized penicillin amidase; the production of aspartame from aspartic acid and phenylalanine by immobilized thermoase; the large scale production of optically active amino acids with immobilized amino acid acylase; and the large scale production and application of immobilized lactase for the hydrolysis of lactose. The recently developed process for acrylamide production using immobilized nitrilase containing microbial cells should also be referred to. The successful use of an NAD‐polyethylene glycol conjugate (NAD‐PEG) as a nondialyzable water‐soluble coenzyme derivative in the enzymic synthesis of leucine from α‐ketoisocaproic acid and ammonia, in a membrane‐enclosed reactor containing L‐leucine dehydrogenase, NAD‐PEG, formate and formate dehydrogenase, illustrates the new possibilities opened up by making use of cofactor‐polymer conjugates. The use of enzyme‐polymer conjugates in analytical and clinical is also illustrated.
Makromolekulare schalter für doppelschichtmembranen
Authors: Schröder Ulrich K. O. , Tirrell David A.
Published: April 2003

Kontrollierte Adsorption von Polyelektrolyten kann ein wirksames Werkzeug im Design von dünnen molekularen Filmen sein. Man kann erwarten, daß die Adsorption von Polyelektrolytketten das empfindliche Kräftegleichgewicht erheblich beeinflußt, das die strukturellen und funktionellen Eigenschaften von geordneten Strukturen wie Einzel‐, Doppel‐ und Mehrfachschichten bestimmt. Andererseits ist die Adsorption von Polyelektrolyten außerordentlich sensitiv auf Umgebungsparameter, z.B. pH, Temperatur oder lonenstärke. Kontrollierte Adsorption kann daher zu Sensitivität auf bestimmte chemische oder physikalische Stimuli führen, sodaß auf diese Weise ein molekularer Schaltmechanismus entworfen werden kann. Durch Umsetzen dieser ldee in reale Systeme gelang es uns, molekulares Schalten in Mischungen von Poly(2‐ethylacrylsäre) mit natürlichen oder synthetischen Phosphatidylcholinen zu bewirken. Insbesondere haben wir Phosphatidylcholinvesikel hergestellt, die ihren lnhalt nach einer Änderung von pH, Temperatur, Glukosekonzentration oder nach Bestrahlung mit Licht schnell und quantitativ freisetzen. Die Entwicklung und die Herstellung von Doppelschichtmembranen, die auf solche Änderungen reagieren, sowie die Kinetik und der Mechanismus des damit verbundenen molekularen Schaltprozesses werden im vorliegenden Artikel diskutiert.
Die nutzung gentechnischer methoden zur produktion wertvoller proteine in mikroorganismen
Authors: Heilmann Hans‐Jürgen , Strauß Michael , Stollwerk Jürgen , Appelhans Heribert , Weiler Hartmut , Gassen Hans Günter
Published: April 2003

The genetic make‐up of living systems especially of isolated cells can be altered by a variety of methods including chemical or light‐induced mutation. More modern procedures are the in vitro recombination of nucleic acids and the cell‐cell fusion.

The new methods are especially useful to reprogram microorganisms to produce valuable proteins or other natural products in excess quantties. In the following we will elucidate the importance of the new techniques by describing the bacterial production of glucose dehydrogenase, of the proteinase inhibitor stefin A and by outlining the methods and promisses of substractive cloning. Although the economic value of genetic engineering techniques still awaits justification, the importance of the methodology for basic biological research is well documented.
Synthesis and evaluation of pyridazines in natural rubber
Authors: Yehia A. A. , Doss N. L. , Ismail M. N.
Published: April 2003

Four pyridazine derivatives were synthesized and evaluated as accelerators in natural rubber (NR) mixes. The rheological characteristics were determined by a Monsanto Rheometer 100. The kinetic constants for the vulcanization reaction in the presence of the synthetic compounds were calculated using the rheometric data. The compounds showed a good accelerating efficiency compared with mercaptobenzothiazole (MBT), which is widely used in rubber industry.
N‐substituted maleimides as thermal stabilizers for rigid polyvinylchloride
Authors: Sabaa M. W. , Mikhael M. G. , Mohamed N. A. , Yassin A. A.
Published: April 2003

N‐substituted maleimides have been investigated as thermal stabilizers for rigid polyvinylchloride (PVC) at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration of the polymer. The results reveal the higher stabilizing efficiency of these products relative to basic lead carbonate, dibutyl tin maleate, and cadmium‐barium stearate stabilizers commonly used in industry. The induction period (Ts) increases as a function of the positive resonance effect of the substituents (+R). Moreover, the investigated stabilizers impart better color stability for the degraded samples as compared with the stearate stabilizer. The stabilizer efficiencies are attributed to their radical trapping potency which intervenes with the radical degradation process of PVC, while the good color stability is due to the ability of the stabilizer to interact with the conjugated double bonds formed on the PVC chains as a result of degradation. A mechanism illustrating the stabilizer's action is proposed.
Reaction of diimide compounds with diglycidyl ether of 4,4′‐dihydroxybiphenyl
Authors: Bertrán Manel , Mantecón Ana , Cádiz Virginia
Published: April 2003

New esterimide and ketoimide polymers containing a biphenyl group have been synthesized and characterized by spectral techniques. Their thermal properties have been studied by thermogravimetric (TGA) measurements, showing a different stability with regard to the imide structure. The analogous amide imide compounds have been tested as monomers, but their polymerization has not taken place as we expected and side reactions have been detected by 13C‐NMR spectroscopy.
Thermal and dyeing properties of acrylonitrile‐glycidyl methacrylate copolymers
Authors: Elsabee Maher Z. , Sabaa Magdy W. , Mikhael Michael G. , El Hamouly Sabrnal H.
Published: April 2003

The copolymerization of acrylonitrile (AN) with glycidyl methacrylate (GMA) has been investigated in tetrahydrofuran (THF). The reactivity ratios were estimated and the thermal behaviour of the homo‐ as well as the copolymers, both in air, and under nitrogen atmosphere was investigated using differential thermal analysis (DTA) and thermogravimetry (TG) techniques. GMA was found to initiate the nitrile oligomerization reaction in the copolymers upon heating. The dyeing ability, as well as the colour fastness towards UV light have also been investigated. It was found that the copolymers showed better affinity towards basic dyes compared to homopolyacrylonitrile. This affinity increases with increasing the GMA content in the copolymer.
Thermal stability of polyurethanes with carbon‐carbon crosslinks
Authors: Kościelecka Alicja
Published: April 2003

Thermal properties of polyurethanes based on 4,4′‐diphenylmethane diisocyanate and poly(ethylene adipate) crosslinked only by CC linkages were studied by isothermal and non‐isothermal thermogravimetry carried out in nitrogen atmosphere. Previously studied polyurethanes crosslinked only with allophanate groups were used for comparison.

It was found that the structure of crosslinks determines the initial stage of degradation process.
Copolymer of cyclohexanone‐formaldehyde resin and polystyrene
Authors: Akar Ahmet , Acuner Ayşegül , Hizal Gürkan , Öztürk Turan
Published: April 2003

The reaction product of cyclohexanone‐formaldehyde resin with an acid chloride of a radical initiator, 4,4′‐azo‐bis(4‐cyano pentanoic acid) was used as initiator for styrene polymerization to form a cyclohexanone‐formaldehyde resin/polystyrene copolymer. The copolymer showed similar solubility as polystyrene.
Photoabbau von styrol‐acrylnitril‐1‐vinylnaphthalin‐copolymeren
Authors: Bratschkov C. , Braun D.
Published: April 2003

Terpolymere aus Styrol, Acrylnitril und steigenden Gehalten an 1‐Vinylnaphthalin wurden photooxidative abgebaut, um den Einfluß des Comonomeren mit Naphthalinresten zu untersuchen. Es wurde festgestellt, daß bis zu 10 Gew.‐% 1‐Vinylnaphthalin‐Bausteine im Copolymeren keine Änderung des Abbauverhaltens gegenüber Styrol‐Acrylnitril‐Copolymeren bewirken. Bei 1‐Vinylnaphthalin‐Gehalten ab 20 Gew.‐% wird der Photoabbau deutlich unterdrückt.
Effect of charge groups in polyurethane and polystyrene interpenetrating polymer networks
Authors: Hsieh K. H. , Chou L. M. , Wong S. S.
Published: April 2003

Opposite charges, namely tertiary amine and carboxyl groups, were introduced into polyurethane (PU) and polystyrene (PS), respectively, to prepare PU/PS interpenetrating polymer networks (IPNs) by means of simultaneous bulk polymerization. Four IPNs were synthesized: a full‐IPN, two semi‐IPNs and a linear blend. The effect of charge groups on the mechanical properties and morphology of the four polymer alloys was investigated.

It is found that the PU/PS IPN which was incorporated with charge groups is free of any phase‐separation, and sufficiently uniformly distributed, as can be seen from the corresponding scanning electron microscopy (SEM) photographs. Dynamic mechanical analysis indicates that the transition peak of the loss modulus E″ will move towards the centre between the two transition peaks of both components in the absence of charge groups, as a function of an increase in the contents of the opposite charge groups. Meanwhile the storage modulus E′ will decrease in a single‐stage way from the previous two‐stage mode.

The tensile strength in all the four polymer alloys increased markedly along with an increase in the contents of acrylic acid (AA) in the poly(styrene‐acrylic acid) (PSAA), which clearly can be seen for the PU/PSAA full‐IPN.
Thermal degradation of partially carboxymethylated cellulose grafted with 4‐vinylpyridine
Authors: Leza M. Lourdes , Cortazar Milagros , Casinos Ismael , Guzmán Gonzalo Martin
Published: April 2003

Partially carboxymethylated cellulose (PCMC) was grafted with 4‐vinylpyridine (4‐VP) using ceric ammonium nitrate (CAN) as initiator and the thermal behaviour of the grafted samples having different grafting yields was studied by means of thermogravimetric dynamic analysis (TGA). For comparison, the thermal behaviour of poly(4‐vinylpyridine), P(4‐VP), and the ungrafted cellulosic substrate were also examined. The activation energies were determined according to the Broido method.

From the thermogravimetric curves the temperature range at which the main decomposition occurred was determined and showed that the thermal degradation of grafted samples was initiated at lower temperature than both PCMC and P(4‐VP).
Chemical dehydrofluorination and electrical conductivity of poly(vinylidene fluoride) films
Authors: Kise Hideo , Ogata Hiroshi , Nakata Masakazu
Published: April 2003

The dehydrofluorination of poly(vinylidene fluoride) (PVDF) powder and films was studied using several kinds of base solution. Especially the reactivity of 1,8‐diazabicyclo[5.4.0]‐7‐undecene (DBU) in ethanol, KOH in 2‐propanol and aqueous NaOH solution with tetrabutylammonium bromide was investigated by the change in infrared (IR) and ultraviolet‐visible (UV‐VI) absorptions of PVDF films. The elimination reactions by DBU or KOH were considered to be accompanied by substitution reaction. The electrical conductivity of dehydrofluorinated PVDF films increased markedly by doping with iodine, and the activation energies of conduction were found to be between 0.4 and 0.5 eV. When a drawn PVDF film was dehydrofluorinated and doped with iodine, anisotropy in conductivity was observed.
Mechanische eigenschaften von polyesterfasern bei kurzzeitiger zugbeanspruchung, 4. Strukturveränderungen durch kurzzeitverformung an polyester‐monofilamentgarn
Authors: Beier Manfred , Schollmeyer Eckhard
Published: April 2003

Interferenzmikroskopische Messungen eines PETP‐Monofilamentgarns zeigen, daß die Orientierung des schon hoch vororientierten Materials durch Dehnen und wieder Entspannen abnimmt, langsame Verformung wirkt dabei stärker desorientierend auf das Material als eine schnelle Verformung. Die Packungsdichte nimmt durch Dehnen ab. Die größte Dehngeschwindigkeit bewirkt die größte Abnahme.

Ein mit der Dehngeschwindigkeit ϵ = 104%/s gedehntes Monofilament zeigt interferenzmikroskopisch sichtbare „Crazes”︁. Diese „Crazes”︁ sind keine Risse, sondern nur rißförmige Orte verminderter Orientierung. Für kleinere Dehngeschwindigkeiten ist interferenzmikroskopisch Unsymmetrie der Orientierung sichtbar. DTA‐Kurven von PETP‐Fasern zeigen zwischen 30 und 80°C einen exothermen Peak, der spezifischen Strukturen der fehlgeordneten Bereiche zugeordnet werden kann. Bei niedrigen Dehngeschwindigkeiten verlagert sich dieser Peak zu niedrigeren Temperaturen. Durch Lagern des Materials kehrt er zur ursprünglichen Temperaturlage zurück. Für schnell deformiertes Material ändert dieser Peak seine Temperaturlage nicht.
Nylon 6/poly(ethylene terephthalate) polymer blends: Rheological properties of melts
Authors: Varma D. S. , Dhar V. K.
Published: April 2003

Melt rheological studies of nylon 6/polyethylene terephthalate (PETP) blends (PETP content varying from 10 to 50%) were carried out using capillary rheometer in the shear rate range of 58 s−1 to 1.15 · 103 s−1. With increasing PETP content in the blend a decrease of the melt viscosity as well as non‐Newtonian behaviour was observed. The model equation developed by Uemura and Takayanagi for viscoelastic melt blends has been used to understand the state of dispersion and morphology of a nylon 6/PETP blend system. Further, an inverse relationship between polymer melt viscosity (η) and elastic modulus (E') of fibres was observed.
Antioxidants and stabilizers, 109. The reaction between antioxidant N,N′‐diphenyl 1,4‐phenylene diamine and 1‐cyano‐1‐methylethyl
Authors: Taimr Luděk , Prusíková Miluše , Pospíšil Jan
Published: April 2003

The mechanism of action of an antioxidant, N,N′‐diphenyl‐1,4‐phenylene diamine (I, DPPD)

Decoding of abbreviations see p. 48.

, was investigated under model conditions. After oxidation to a semiquinone radical, phenyl (4‐phenylamino phenyl)aminyl (VIII), or to Wurster's cation phenyl (4‐phenylamino phenyl)ammoniumyl (IX), I reacts with 1‐cyano‐1‐methylethyl (model alkyl) by two routes, both of which are accelerated by weak acids. One of these routes results in alkyl being bound to nitrogen with formation of N,N′‐diphenyl N‐(1‐cyano‐1‐methylethyl)1,4‐phenylene diamine (III). The latter compound is labile, and particularly in the presence of acids readily splits off olefin with regeneration of DPPD. This behaviour is a model of the regeneration mechanism of the stabilizing effect of DPPD, which alternately with its oxidation product (VIII or IX) deactivates the alkylperoxyl and alkyl radicals during the ageing of hydrocarbon substrates under conditions of the relative deficiency of oxygen. The other route leads to binding of the alkyl in the benzene ring with formation of N,N′‐diphenyl 2‐(1‐cyano‐1‐methylethyl) 1,4‐phenylene diamine (IV) and N,N′‐diphenyl 2‐(1‐cyano‐1‐methylethyl) 1,4‐benzoquinone diimine (V), thus modelling the binding of DPPD in the polymer chain, and even the crosslinking of the chain during the ageing of a polymer inhibited with DPPD. Due to the presence of the nitrile group, IV undergoes some further changes, which give rise to the formation of 3,3‐dimethyl 2‐imino‐1‐phenyl 5‐phenylamino indoline (VI) and 2‐acetylimino 3,3‐dimethyl‐1‐phenyl 5‐phenylamino indoline (VII).
Organotin polymers XIV. Synthesis and copolymerization reactions of p‐acryloyloxy‐tri‐n‐butyltin benzoate with some vinyl monomers
Authors: Shaaban Abd‐El‐Fattah Fadel , Azab Mohamed Morsy , Messiha Nagi Naguib
Published: April 2003

p‐Acryloyloxy‐tri‐n‐butyltin benzoate (ABTB) was prepared by the reaction of p‐hydroxy‐tri‐n‐butyltin benzoate and acrylic acid in the presence of dicyclohexylcarbodiimide. The monomer reactivity ratios for the copolymerizations of ABTB (M1) with methyl acrylate (M2), ethyl acrylate (M2), n‐butyl acrylate (M2), methyl methacrylate (M2), styrene (M2) and acrylonitrile (M2) have been found to be r1 = 0.080, r2 = 1.046; r1 = 0.039, r2 = 1.585; r1 = 0.019, r2 = 2.076; r1 = 0.150, r2 = 1.710; r1 = 0.113, r2 = 1.339 and r1 = 0.007, r2 = 2.853, respectively. The Q and e values for the prepared organotin monomer were calculated. Copolymerization reactions were carried out in solution at 70°C using 1 mol‐% azobisisobutyronitrile. The structure of the ABTB monomer and the prepared copolymers was investigated by IR and 1H‐NMR spectroscopy.
Coordination polymers, 2. Effect of iodine doping on electrical properties of coordination polymers derived from terephthalaldehyde bis(S‐benzyldithiocarbazate)
Authors: Paliwal L. J. , Kharat R. B.
Published: April 2003

The electrical properties of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) chelate polymers of terephthalaldehyde bis(S‐benzyldithiocarbazate) (TBDTC) have been studied. Similarly, different concentrations of iodine were doped to these chelate polymers to increase their conductivity for producing a new class of electrical conductive material. The current interest in doping of iodine in chelate polymers is to a great extent due to their possible application in power sources and electrochemical devices. Electrical conductivity of chelate polymers and iodine doped chelate polymers have been studied over a wide range of temperature (∼ 300−450 K). From the electrical conductivity of these polymers activation energies of electrical conduction have been evaluated. A comparison of electrical conductivity and activation energy of electrical conduction of simple and iodine doped polymers has been made and conclusions about the role of iodine in chelate polymers regarding the electrical conductivity have been drawn.
Modification of polybutadienes by catalytic and photochemical decomposition of dimethyldiazomalonate
Authors: Yaǧi Yusuf , Anaç Olcay , Mazlumoǧlu Tülay
Published: April 2003

Modifications of polybutadienes via catalytic and photolytic decomposition of dimethyldiazomalonate (dmdm) are described. This method pertains to the generation of highly reactive carbenes which give rise to the formation of addition and insertion products. Chemical structures of the modified polymers were confirmed by NMR spectroscopy. It was found that carbene dimers were also formed in a significant extent depending on the molecular weight and microstructure of the initial polymers.