bluuebunny/crossref_metadata_2025 huggingface dataset:
PH‐induced structure change of poly(vinyl alcohol) hydrogel crosslinked with poly(acrylic acid)
Authors: Hirai Toshihiro , Okinaka Toshihiro , Hayashi Sadao , Amemiya Yoshiyuki , Kobayashi Katsumi , Hirai Mitsuhiro
Published: April 2003

The structure of the hydrogel of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was investigated by small angle X‐ray scattering (SAXS) of synchrotron radiation. A physically crosslinked blend gel, which was prepared by repetitive freezing and thawing of an aqueous solution of PVA and PAA, could be chemically crosslinked by esterfication of PVA with PAA even in the hydrogel state. The chemical crosslinking induced the destruction of physical crosslinks into a folded structure, indicating that the chemical crosslinking proceeds at the sites around the physical crosslinks that contain PVA and PAA in much higher concentration than other portion of the gel. The pH‐induced structure changes of the PVA hydrogels, chemically crosslinked with poly(acrylic acid) (PAA) were investigated by SAXS on the samples of various chemical crosslinking time. The gels were shrunk at pH4, and swollen at pH8. The results of SAXS showed, that the Porod slope changed with chemical crosslinking time from ‐3.5 to −2.9 at pH4, and from −2.9 to −2.4 at pH8. The results suggest that a folded structure as a structural domain, which is characterized by fractally rough interface, tends to change into the structure that corresponds to percolation cluster, particularly at pH8. The gels immersed in pH8 showed a remarkable structure change accompanying swelling. The results revealed that a conformational change of PAA chains, induced by the pH change, can be explained by the presence of a structural domain in the gel network, where both PVA chains and PAA chains get entangled and partially form a interpenetrating polymer network(IPN).
Polyurethane‐elastomer‐actuator
Authors: Hirai Toshihiro , Sadatoh Hiroki , Ueda Tsutomu , Kasazaki Toshiaki , Kurita Yasushi , Hirai Mitsuhiro , Hayashi Sadao
Published: April 2003

Polyurethane elastomers were investigated as electrically active materials for actuators. Components in hard segment and soft segment in the elastomers were varied. The elastomers with excellent electrostrictive properties were limited to those which had soft segments of polyesters and polylactones. It turned out, that the elastomers, whose soft segments are polyethers are electrically inert under the experimental conditions. The chemical structure of the hard segment seems not to influence to the electrostrictive property. The charging and discharging process was investigated. The charging process was found to proceed simultaneously with the contracting process caused by the electric field, suggesting that the orientation of the soft segment in the elastomer plays critical rolls in the electrostrictive action. In the elastomer, which has a soft polyether segment and was inactive to the electric field, could be actuated very efficiently when the elastomer was swollen with dimethyl sulfoxide. We conclude that the polyurethane elastomer, whose soft segment has chemical bonds with a relatively large dipole moment, can be actuated by the electric field application, and that even the elastomer, whose soft segment is inactive, could be actuated in the presence of a solvent with a large dipole moment. Thus, the concept found with the gel, could be applied to an elastomer, the soft segment of which plays partly the roll of the solvent in the gel.
Chemical reactions on polysaccharides, 5. Reaction of mesyl chloride with pullulan
Authors: Mocanu Georgeta , Constantin Marieta , Carpov Adrian
Published: April 2003

The reaction of mesyl chloride with crosslinked pullulan microparticles was investigated, in particular the influence of the reaction conditions on the ratio between the two possible products chlorodeoxy or O‐mesyl pullulan. It was found that in N,N‐dimethylformamide the preponderent reaction product is chlorodeoxy pullulan, while in pyridine at low temperatures the main product is the mesyl ester of pullulan. In N,N‐dimethylacetamide, the substituent groups are both chlorodeoxy and mesyl ones, in about 2:1 ratio. By the introduction of either chlorodeoxy or mesyl groups, the pullulan‐crosslinked microparticles become hydrophobic.
Friedel‐crafts polyketones: Synthesis, characterization and antimicrobial properties
Authors: Patel R. K. , Patel R. T. , Patel R. M. , Sinha T. J. M.
Published: April 2003

A series of seven polyketones was prepared by Friedel‐Crafts reaction using 2‐chloroanisole, choroacetyl chloride, 1,2‐dichloroethane and dichloromethane with anhydrous aluminium chloride as catalyst and carbon disulfide as a solvent under different experimental conditions. The polyketones thus obtained were characterized by determination of the chlorine content (Carius method), IR spectroscopy, vapour‐pressure osmometry, thermogravimetry and differential scanning calorimetry. All these polyketones were tested for their antimicrobial properties against selected microorganisms. The results indicate that some of these resins show fair to good antimicrobial properties towards tested microorganisms and may be used as commercial biocides.
Structural analysis of poly(4‐hydroxybutyl acrylate)‐grafted silk fibres
Authors: Tsukada Masuhiro , Freddi Giuliano , Shiozaki Hideki , Kasai Nobutami , Kobayashi Masao
Published: April 2003

Poly(4‐hydroxybutyl acrylate) poly(4‐HBA) was graft‐copolymerized onto silk fibres (bombyx mori) in aqueous medium with ammonium persulfate as initiator. The weight gain increased with increasing concentration of monomer in the grafting system. The grafting efficiency ranged from 45 to 65%. Equilibrium moisture regain decreased sharply beyond 10% weight gain. The tensile properties of the silk fibres did not change significantly as a function of the increasing weight gain. Birefringence and isotropic refractive index decreased until 35% weight gain and then remained unchanged. The X‐ray diffraction patterns showed that the crystalline structure was not affected by grafting. Differential scanning calorimetry (DSC), thermomechanical (TMA), and thermogravimetric (TG) measurements showed that poly(4‐HBA)‐grafted silk fibres underwent only slight changes in the thermal behaviour. The dynamic mechanical measurements (DMA) exhibited a downward shift of both the storage (E′) and loss modulus peak (E″) with increasing weight gain. Scanning electron microscopy (SEM) observations showed the presence of some deposits adhering to the surface of silk fibres grafted at high monomer/silk ratio (>50%).
Partial hydrolysis of cellulose acetate in toluene/acetic acid/water system
Authors: Olaru Niculae , Olaru Liliana , Andriescu Adrian , Tudorachi Niţǎ
Published: April 2003

The partial hydrolysis of cellulose acetate was studied in homogeneous toluene/acetic acid/water media of different compositions using sulfuric acid as a catalyst. The presence of toluene considerably increases the hydrolysis rate. Products with a degree of substitution (DS) of about 1.70, useful for further derivatization, were obtained at 60°C with 15–34 wt.‐% toluene in the reaction medium and without addition of water during the process in shorter times than in the conventional procedure free of toluene. The kinetic behaviour of toluene‐containing systems is dependent on the composition of the reaction medium, as well as on the temperature. The reaction systems with 15 wt.‐% and 20 wt.‐% toluene, respectively, were found to obey a linear relationship of ‐ln(DS/DS0) versus time. The behaviour of the studied reaction systems is tentatively explained by an enrichment of the solvation shell in water and sulfuric acid, since the acidity function of the sulfuric acid was not influenced by the presence of toluene. The hydrolysed products obtained by the described procedure are soluble in some common organic solvents used for derivatization, such as dimethylformamide, acetic acid and dimethyl sulfoxide.
Characterization and application of poly(vinyl alcohol)/starch composite as a sizing agent
Authors: Hashem Mohamed M. , Kesting Wolfgang , Hebeish Ali A. , Abou‐Zeid Nabil Y. , Schollmeyer Eckhard
Published: April 2003

A macromolecular sizing agent based on the copolymerization of poly(vinyl alcohol) (PVA) with hydrolysed starch was prepared using the chemically reactive bifunctional compound N‐methylolacrylamide. Detailed characteristics of the resultant PVA/N‐methylolcarbamoylethylated starch copolymer were studied where emphasis has been placed on solubility, rheological properties, molecular weight distribution, adhesive power and stability. Elucidation of the nature of the macromolecular segments of both N‐methylolcarbamoylethylated PVA as well as PVA/N‐methylolcarbamoylethylated starch copolymer fulfilled the prerequisite to tailor PVA/starch copolymer which is appropriate for application as a water‐soluble recyclable sizing agent by ultrafiltration.
Properties of mixed aqueous solutions of perfluorooctanoate with poly(N‐vinylpyrrolidone)
Authors: Iijima Toshiro , Sugiyama Chisato
Published: April 2003

Aqueous mixtures of ammonium perfluorooctanoate (C8FN) and poly(N‐vinylpyrrolidone) (PVP) were characterized by measuring the surface tension, conductivity and solubilization. Sodium perfluorooctanoate was also used for comparison. The critical micelle concentration (c. m. c.) of C8FN was found to be 30 mmol L‐1. The dependence of the surface tension on the surfactant concentration could be successfully described by the surface condensation based on the Langmuir‐type adsorption. The cross‐sectional molecular area of the C8FN oriented perpendicular on the surface is estimated at 19.8Å2. The addition of PVP increases the molecular area, suggesting an interaction between C8FN and PVP on the surface. The solubilization of p‐aminoazobenzene (PAAB) in these systems shows a synergetic effect in the low‐concentration range of C8FN and PVP. Changes in the absorption spectra of PAAB indicated the interaction between C8FN and PVP.
Beeinflussung der Fließeigenschaften von Polyamid 6 durch submikrone Additive
Authors: Koine Axel , Mennig Günter , Schütz Angelo , Haufe Andreas
Published: April 2003

Der Einfluß submikroner mineralischer Additive auf die rheologischen Eigenschaften von Polyamid 6 (PA 6) wurde untersucht. Üblicherweise steigt bei niedriger Schergeschwindigkeit die Viskosität nach der Einarbeitung zunehmender Mengen kommerzieller Füllstoffe (Mikronbereich der Korngrößen) stetig an, weil die Reibung in den Gleitschichten zunimmt.

Nach intensiver Dispergierung submikroner Additive in Ethylenglykol unter Zusatz von Polyethylenimin als kationaktivem Dispergierhilfsmittel wurde eine agglomeratfreie Dispergierung aller untersuchten Additive erreicht. Unter Standardbedingungen wurden die glykolischen Suspensionen mit Hilfe eines Doppelschneckenextruders in die PA 6‐Matrix eingearbeitet, dabei mittels einer Entgasungsstufe sofort der Glykolüberschuß entfernt. Die erwarteten Effekte verbesserten intramolekularen Gleitens zeigten sich in unterschiedlicher Höhe bei TiO2, Al2O3, SiO2, Kaolin und Talkum. CaCO3 dagegen schränkte auch im Submikronbereich das intramolekulare Gleiten schon in Konzentrationen unter 1 Gew.‐% deutlich ein. Bei der Einarbeitung pulverförmiger Additive mittels eines Doppelschneckenextruders direkt in die PA 6‐Matrix wurden analoge Effekte nicht erreicht.
Emulsion polymerization in the presence of colloidal silica particles. Application to the reinforcement of poly(ethyl acrylate) films
Authors: Bourgeat‐Lami E. , Espiard P. , Guyot A. , Gauthier C. , David L. , Vigier G.
Published: April 2003

Emulsion polymerization of ethyl acrylate was carried out in the presence of different kinds of functionalized and non‐functionalized silica particles. 3‐(Trimethoxysilyl)propyl methacrylate, 2‐hydroxyethyl methacrylate and 3‐(triethoxysilyl)‐propanethiol functionalization agents were examined. It is demonstrated that use of the first two coupling agents results latexes able to give films which display remarkable mechanical properties similar to those of vulcanized elastomers reinforced with solid particles. A qualitative model is then set up to give account for these properties. It is proposed that a part of the polymer is covalently bound to silica as tight loops, giving rise to a set of strong entanglements with the non‐grafted polymer during film formation. This model is supported by stress‐strain measurements. Some validation experiments are described using the third grafting agent of the series.
New results of the self‐initiation mechanism of SH/En addition polymerization
Authors: Kühne Gudrun , Diesen Jarle Sidney , Klemm Elisabeth
Published: April 2003

No radicals are formed in bis(mercaptopropionate)‐diene‐mixtures, as shown by means of ESR spectroscopic investigation. Radicals are produced spontaneously only in the presence of triethylene glycol dithiol. The hydrogen‐bonded structure of the dithiopropionates is obviously responsible for the inhibition of the charge transfer interaction with the diene compounds and prevents subsequent radical formation. The 13C NMR spectra confirm the anti‐Markownikow structure of the polymers formed with diallyl succinate and diallyl terephthalate.
Evaluation of terpolymers of 2‐hydroxyethyl methacrylate, dodecyl methacrylate and ethylene glycol dimethacrylate as matrices for hydrophobic interaction chromatography
Authors: Bryjak Marek , Trochimczuk Andrzej , Bryjak Jolanta
Published: April 2003

Polymer matrices were prepared by suspension polymerization of 2‐hydroxyethyl methacrylate, dodecyl methacrylate and ethylene glycol dimethacrylate. It was shown that porosity decreased with the addition of monomers with hydrophobic side chains. Trypsin, bovine serum albumin and lipase served as standard proteins in sorbent hydrophobicity evaluation. Isocratic chromatography at various ionic strengths revealed different elution behaviours. Some sorbents exhibited an ion‐exchange mode in the whole range of ionic strength variation. Some others showed a hydrophobic interaction character when the salt concentration exceeded a critical value. It is suggested to take this critical salt concentration as a relative measure of hydrophobicity for particular protein‐matrix‐salt systems. It was shown that the matrix containing 90 μmol/g of dodecyl methacrylate was enough hydrophobic to differentiate proteins and thus could be used effectively for hydrophobic interaction chromatography of proteins.
Fluorinated poly(1,3,4‐oxadiazole‐imide‐amide)s
Authors: Hamciuc Corneliu , Hamciuc Elena , Bruma Maria
Published: April 2003

A series of new fluorinated poly(1,3,4‐oxadiazole‐imide‐amide)s containing various ratios of amide/oxadiazole groups in the repeating unit have been prepared by cyclodehydration of the corresponding poly(hydrazide‐imide‐amide)s resulting from the reaction of diacid dichlorides incorporating both hexafluoroisopropylidene bridges and imide rings with p‐aminobenzhydrazide or with mixtures of certain aromatic diamines and p‐aminobenzhydrazide or terephthalic dihydrazide. The new polymers are soluble in polar amidic solvents and can be processed into flexible films by casting from solution. Their glass transition temperatures are in the range 254–325°C and they are thermally stable up to 415–450°C.
Macromonomers based on low‐molecular‐weight polyisobutenes
Authors: Maenz Karsten , Stadermann Dietmar
Published: April 2003

Radically polymerizable macromonomers were synthesized by alkylation, epoxidation and SH‐en addition of low‐molecular‐weight polyisobutenes followed by esterification with methacrylic acid derivatives. Highly functionalized products (≥ 95%) can be obtained from polyisobutenes with double bond content ≪ 1 by separation of non‐functionalized polymer by column chromatography.
Tensile and transformational behavior of poly(ether sulfone)/polycarbonate blends
Authors: An Lijia , Wang Zhigang , Yu Donghong , Jing Jiaokai , Jiang Zhenhua , Ma Rongtang , Kou Xichun
Published: April 2003

Blends of a poly(ether sulfone) (PES) and a polycarbonate (PC) were prepared by melt‐mixing and were studied by tensile tests, differential scanning calorimetry, dynamic mechanical analysis, density measurements and transmission electron microscopy (TEM). The blends were found to be two‐phase systems and an interfacial layer was presumed to be formed between two phases, which was verified by TEM. A synergism of elongation at break and tensile modulus was shown in PES/PC blends. The effects of the crosshead speed on the mechanical properties were discussed for blends with different PES/PC weight ratios.
Functionalization of isotactic poly(propylene) with maleic anhydride in the solid phase
Authors: Lazár Milan , Hrc̆ková L̆udmila , Fiedlerová Agnesa , Borsig Eberhard , Rätzsch Manfred , Hesse Achim
Published: April 2003

The influence of temperature and type of initiator on the grafting efficiency of maleic anhydride onto isotactic poly(propylene) powder under solid‐state reaction conditions was investigated. The level of bonded maleic anhydride was found to be about 20% higher using aliphatic peroxide, such as lauroyl peroxide, in contrast to dibenzoyl peroxide, dicumyl peroxide, 2,5‐dimethyl‐2,5‐di‐tert‐butylperoxyhexane or tert‐butyl perbenzoate as initiator.

The higher grafting efficiency of maleic anhydride onto polyethylene when compared with poly(propylene) is accounted for by a higher kinetic length of the addition‐transfer chain reactions.
Epoxidation of cis‐cyclooctene with molecular oxygen catalyzed by magnesium oxide supported polytitazane cobalt (III) complexes
Authors: Ma Zhao‐Hui , Wang Tie‐Jun , Yan Yuan‐Yong , Huang Mei‐Yu , Jiang Ying‐Yan
Published: April 2003

Magnesium oxide supported polytitazane cobalt (III) complex is demonstrated as an effective catalyst for the epoxidation of cis‐cyclooctene with molecular oxygen at atmospheric pressure in the presence of isobutyraldehyde as the sacrificial reductant. XPS data show that the high‐valent cobalt (III) is stabilized by the multidentate nitrogen ligand of polytitazane. The conversion of cis‐cyclooctene is as high as 95.2% with 100% selectivity to the cis‐cyclooctene oxide at 25°C within 5 h. The catalyst can be used at least nine times without loss of its activity.
Effects of morphological changes on the oxygen transport properties of poly[(ethylene terephthalate)‐co‐(1,4‐cyclohexylene dimethylene terephthalate)]
Authors: Testa Giovanni , Seves Alberto , Vicini Loredana , Pedrelli Turno , Marcandalli Bruno
Published: April 2003

To improve the physical picture of the polymeric glassy state, the influence of morphological changes achieved by different thermal treatments of an amorphous glassy poly(alkylene terephthalate) film on the oxygen transport properties has been studied. Annealing treatments were performed on films in constraint imposed giving samples of different crystallinity contents and morphology.

The dependence of the oxygen permeability and diffusion as the free volume from crystallinity content was investigated at sub‐Tg temperatures within the range of 303–348 K.

The investigations reveal that on crystallized samples, permeability and solubility coefficients decrease at higher crystallization temperature, while annealed samples showed an opposite trend despite higher crystallinities. Further, annealed films showed higher free volume content.

The trend of results suggests that different parameters are likely to play a significant role in determining apparent permeability coefficients. The presence of microvoids in annealed samples may be supposed.
Cellulose‐based polymer blend filaments spun from N‐methylmorpholine‐N‐oxide
Authors: Morgenstern Bernd , Leillinger Olaf , Maron Reinhard
Published: April 2003

The influence of a small addition (<15 wt.‐%) of an aromatic polyamide [poly(2,6‐dichloro‐1,4‐phenylene terephthalamide) (P26C1PTA)] as additive on the textile‐physical properties of cellulose filaments was investigated. The blend filaments were spun from homogeneous blend solutions prepared in the common solvent N‐methylmorpholine‐N‐oxide. Most of the estimated properties of blend filaments containing not more than 10 wt.‐% of P26C1PTA do not differ significantly from those of pure cellulose filaments. However, the wet abrasion resistance attains a maximum at a P26C1PTA content of 10 wt.‐%. At higher P26C1PTA content the fibrillation tendency of the blend filaments is increased. Coincidentally, a decrease of tenacity and wet abrasion resistance was obtained.
Synthesis and properties of powdery hydrogels based on acrylamide, methacrylamide, and their N‐substituted derivatives
Authors: Lopour Petr , Ševčík Stanislav , Labský Jiří , Lednický František
Published: April 2003

Lightly crosslinked hydrogels based on acrylamide, N‐(1,1‐dimethyl‐3‐oxobutyl)‐acrylamide, N,N‐dimethylacrylamide, methacrylamide, N‐(2‐hydroxypropyl)methacrylamide and N‐[tris(hydroxymethyl)methyl]methacrylamide were synthesized in form of fine powders, consisting of aggregates of very small (∼10−1 μm) particles. The powdery hydrogels were obtained by precipitation polymerization in acetone and diethyl ether, using N,N′‐methylenebisacrylamide and ethylene dimethacrylate as crosslinking agents. Dependences of water‐swellability, particle size, aggregation, specific surface and content of the uncrosslinked water‐soluble polymers and low‐molecular‐weight substances in the hydrogels on the conditions of their synthesis were studied. Suitability of particular powdery hydrogels synthesized for the preparation of silicone rubber‐hydrogel composites is discussed.
Phase diagram and crystallization of polycarbonate/poly‐ϵ‐caprolactone blends
Authors: Hatzius Knut , Li Yong , Werner Martin , Jungnickel Bernd‐J.
Published: April 2003

It is reported on the equilibrium melting point depression of polycarbonate from bisphenol A (PC) in its blend with poly‐ϵ‐caprolactone (PCL). To this end, a model which explains the bended course of the measured Hoffman‐Weeks plots is developed which takes into account the composition changes at the crystal growth front upon progressive crystallization. The occasional melting point depression of the PCL component is discussed. The calculated Flory‐Huggins parameter of χ12 ≈︁ −0.09 indicates only weak enthalpic interactions. The remarkable drop in the glass transition temperature of PC with blending allows PC degrees of crystallinity up to 25% upon crystallization from the melt.
PVC‐ein werkstoff im wandel
Authors: Engelmann Manfred
Published: April 2003

The consumption of PVC amounts to 5.3 Mio t in Western Europe with an annual increase of about 2%. The most important field of application is building and construction.

The main targets relating to the production process are less energy consumption, the reduction of emissions to air and water and the increase of the productivity of the plants.

In the field of processing a dramatic increase of the output of extrusion or calandering devices has been realized ‐ connected with an improvement of quality and economy.
Polycarbonat‐ein vielseitiger werkstoff mit zukunft
Authors: Zaby G. , Fengler G. , Genz J.
Published: April 2003

The market development of bisphenol‐A‐polycarbonate has shown higher growth than any other engineering thermoplastic. The reasons can be found in the permanent improvement of the cost/performance‐relationship and in the technical use of the variability of the basic structure. Incorporation of specific monomer units leads to tailor‐made properties for a wide range of applications, as for example medical devices, electronic parts and glazing.

This process has not yet slowed down, rather it is accelerated by new results from research and development. The improvement of flaw behavior and pit replication for new grades of materials for the next generation of compact discs, new grades that can be sterilized by γ‐radiation without degradation and the microstructuring by low‐energy laser systems are examples for the ongoing expansion of polycarbonate applications. Surface modification by hardcoatings with nanosized particles will allow to enter the fast growing market of glazing.
Polyethylen, polypropylen: Neue perspektiven für standardpolymere
Authors: Böhm L. L. , Enderle H.‐F. , Fleissner M. , Kloos F.
Published: April 2003

Polyolefins like polyethylene (PE), polypropylene (PP) and their copolymers inclusive elastomers (EPM, EPDM) are materials with wide ranges of properties and excellent environmental compatibility. Therefore use and production of these products increase steadily. By the development of new catalysts and advanced technologies tailor‐made products with new combinations of properties are available which open superior applications. To these products belong materials with Schúlz,Flory‐ or bimodal molecular mass distributions, new types of linear low density products with homogeneous comonomer distribution, multiphase polypropylene blends and long glass fibre reinforced polypropylene materials. With metallocenes new types of polyolefins can be synthesized like syndiotactic polypropylene and other polyolefins.
Funktionspolymere‐ein interdisziplinäres forschungsgebiet‐
Authors: Winkler Ekhard , Pielartzik Harald , Schneller Arnold
Published: April 2003

Functional polymers differ from structural polymers in various aspects. The most evident difference is their lack of visibility as they are mostly empolyed in surface applications, e.g. as crystal growth modifiers to inhibit encrustation in detergents, as hair setting agents, or as electro‐conductive films. Additional important differences concerning the motivation for new developments, market aspects, and customer relationships are the subject of this paper.

The development of technology and market competence in the field of functional polymers and the special problems of low‐volume, high‐performance chemicals are discussed in detail. The paper deals with examples of recent developments: Polyaramides for membranes, 3,4‐polyethylenedioxythiophene as an electroconductive polymer, polyaspartic acid as a biodegradable polycarboxylate in detergents, highly crosslinked, insoluble vinylpyrrolidone/vinylimidazole copolymers for the removal of heavy metals from wine, and finally an insoluble, crosslinked polyvinylpyrrolidone‐iodine complex for the sterile filtration of liquids. The outlook discusses the research challenges which remain before a full understanding of the structure/property relationships can be attained.
Polymeric prodrugs. Synthesis, release study and antimicrobial properties of polymer‐bound acriflavine
Authors: Patel H. , Raval D. A. , Madamwar D. , Sinha T. J. M.
Published: April 2003

A matrix of poly(methyl methacrylate‐co‐maleic anhydride) with surface containing functional anhydride groups of different percentage was prepared by solution polymerization and characterized. Acriflavine was bound on the surface of this matrix by chemical bonding in organic medium. The amount of acriflavine chemically bound to the matrix was spectroscopically characterized and the in vitro release rate of acriflavine in weakly basic medium was established along with the determination of its antimicrobial activity.
Block copolymerization of poly(ethylene glycol) with methyl methacrylate using redox macroinitiators
Authors: Nagarajan Soundappan , Sabdham Kalathur , Srinivasan Vangepuram
Published: April 2003

A series of block copolymers of poly(ethylene glycol) (PEG) with methyl methacrylate (MMA) were prepared using a redox system consisting of ceric ion and PEG of various molecular weights in aqueous medium. The block copolymerization experiments were carried out under such conditions in which there was no homopolymerization of MMA by Ce4+ alone. The intermediacy of the PEG macroradical in the redox process was substantiated by ESR spectroscopy and a polymerization proceeding through ‘blocking from’ mechanism was postulated. The formation of the block copolymers was confirmed by chemical test and fractional precipitation as well as by FT‐IR and FT‐NMR (1H and 13C‐(1H)) spectroscopy. The triblock nature of the block copolymers was ascertained through the cleavage of the ether linkage of the PEG segment. Simultaneous TG/DTA studies of the block copolymers revealed multiple stage decomposition patterns and their DSC curves exhibited two glass transition temperatures. GPC investigation of the block copolymers revealed unimodal molecular weight distribution with Mn values showing a smooth increase with ascending molecular weights of PEG. SEM studies indicated a fine dispersion of PEG in the continuous PMMA matrix.
Effect of metal ions on self reinforcement of metal/adhesive interphase by γ‐aminopropyltriethoxysilane
Authors: Gu Xiaohong , Xue Gi
Published: April 2003

When copper/epoxy joints are pretreated with 1 wt.‐% solution of γ‐aminopropyltriethoxysilane (γ‐APS) in ethanol, the coordination between the copper ions and the amino groups of γ‐APS and 4,4′‐diaminodiphenylmethane could bring about self‐reinforcement of the metal/adhesive interphase when the joints were exposed in 3% aqueous NaCl solutions for 160 d. This is also confirmed with a model experiment by pretreating the aluminium substrates with γ‐APS solution containing moderate amounts of copper salts and subsequent formation of the aluminium/epoxy joints.
Rigid‐chain polyesters grafted with flexible‐chain vinyl polymers
Authors: Braun Dietrich , Wilhelm Volker , Hellmann Götz P.
Published: April 2003

The concept of “molecular reinforcement” has been advanced, in the last decade, as an alternative to conventional fibre reinforcement of thermoplastics: In blends with normal (flexible‐chain) thermoplastics, rigid chains of main‐chain LC polymers (PLC) can act as strengthening fibres on the molecular scale. However, the rigid PLC chains must be well dispersed which is improbable since PLC and normal polymers are usually incompatible. A related concept is “micellar reinforcement”: Graft copolymers made of a rigid‐chain PLC backbone and flexible‐chain grafts can form a microphase morphology of cylinderic micelles where the PLC chains act as reinforcing fibres on a micellar scale. Such rigid‐flexible graft copolymers are discussed in this study. They were pepared from a polyester of terephthaloyl, dihexoxyterephthaloyl and phenylhydroquinone moieties with special comonomer units carrying a double bond onto which styrene was grafted via radical copolymerisation. Grafting occurred with high efficiency, leading to products with the desired morphology of cyclindric micelles.
Synthesis and characterization of polypyrrolepolyurethane cationomer composites
Authors: Buruiană T. , Diaconu I. , Buruiană E. C. , Han X. , Guo F.
Published: April 2003

Poly(ether urethane) cationomers based on poly(oxytetramethylene), 4,4′‐bibenzyldiisocyanate, N‐methyldiethanolamine as chain extender, and acrylic acid/poly(acrylic acid) as quaternization agent were synthesized. Pyrrole (15 wt.%%) was polymerized in films of the ionomer containing CuCl2. The films were characterized by dynamic mechanical analysis, thermogravimetry and differential scanning calorimetry. The electric conductivity of the film without polypyrrole is 7.5 · 10−12 Ω−1 cm−1, while incorporation of polypyrrole increases the conductivity to 4.5 · 10−6 Ω−1 cm−1.
Cationic polymerization using allyl sulfonium salt. 3. Allyl sulfonium salt/ascorbate redox couple
Authors: Önen A. , Denizligil S. , Yağci Y.
Published: April 2003

The cationic polymerization of cyclohexene oxide was initiated by reduction of allyl sulfonium salt in the presence of ascorbyl‐6 hexadecanoate and copper (II) benzoate. A redox reaction in which the copper compound serving as an electron carrier for the initiation step was proposed.
Synthesis, characterization and polymerization of waxy monomers
Authors: Moszner Norbert , Fischer Urs Karl , Völkel Thomas , Rheinberger Volker
Published: April 2003

Waxy monomers and crosslinkers, respectively, were synthesized from commercially available waxes by esterification with 2‐hydroxyethyl methacrylate, glycerol dimethacrylate, or glycidyl methacrylate or by functionalization with 2‐isocyanatoethyl methacrylate. The resulting opaque methacrylates with melting points between 45 and 80°C were polymerized in bulk and in toluene solution in presence of free radical initiators. The obtained polymers were characterized by a broad molecular weight distribution. Opposite to the bulk polymerization, the double bond conversion in solution polymerization is nearly quantitative. The observed volume shrinkage during polymerization is very low due to the high molecular weight of the monomers. Polymerizates containing crosslinking comonomers exhibit improved mechanical stability.
An investigation of the grafting of cellulose powder with acrylamide under a magnetic field
Authors: Chiriac Aurica P. , Neamtu Iordana , Cazacu Georgeta , Simionescu Cristofor I. , Rozmarin Gheorghe
Published: April 2003

Cellulose powder obtained from oak furfural lignocellulose by nitration reaction was grafted with acrylamide using a radical initiation. The grafting reactions were carried out and compared both in presence and in absence of a continuous external magnetic field with the intensity extended between 0.15–0.35 T. The effect of monomer and initiator concentration, time and temperature of reaction and magnetic field intensity onto the grafting process were examined. It was observed that the presence of a magnetic field leads to a significant increase of the graft conversion.
Application of molecularly imprinted polymer as a drug retaining matrix
Authors: Sreenivasan K.
Published: April 2003

Copolymerization by gamma irradiation of 2‐hydroxyethyl methacrylate with ethylene glycol dimethacrylate in the presence of hydrocortisone as model drug gave a molecular imprinted polymer (MIP). The hydrocortisone was removed from the matrix with chloroform and incorporated again from methanol solution. Release data show that 96% of the incorporated drug is retained after 30 days storage in a methanol/water (3 : 1 v/v) mixture. In comparison with hydrocortisone, only a small quantity of testosterone is absorbed by the matrix.
Surface modification and bonding of poly(p‐phenylene sulfide)
Authors: Piglowski Jacek , Coen Martine Collaud , Schäfer Rüdiger , Kressler Jörg , Mülhaupt Rolf
Published: April 2003

It is demonstrated that both chemical oxidation, e.g. by using acetic acid/hydrogen peroxide or chromosulfuric acid, and plasma treatment of poly(p‐phenylene sulfide) (PPS) surfaces introduce polar groups. The changes of the surface chemistry are detected by FTIR spectroscopy, X‐ray photoelectron spectroscopy, and contact angle measurements. The increased polarity is partially responsible for better adhesion as verified by lap shear measurements using acrylic adhesive. Another important contribution to the improved adhesion originates from increased surface roughness after surface modification as measured by atomic force microscopy. This effect is very pronounced for PPS surfaces treated with chromosulfuric acid.
Polyester composites reinforced with recycled FR‐4 epoxy laminates
Authors: Hong S. G. , Su S. H.
Published: April 2003

The feasibility of using recycled FR‐4 epoxy laminates as reinforcing fillers in manufacturing unsaturated polyester (UP) composites was studied using differential scanning calorimetry (DSC), and flexural tests. UP resins filled with recycled laminates had a higher flexural strength and modulus than the plain UP because of energy dissipation effects from glass fibers and rigid epoxy resins in the laminates. The size and loading of the laminates affected the flexural properties of the molded products. The addition of CaCO3 fillers and Cu decreased the flexural strength but promoted the flexural modulus of the UP. As revealed by DSC measurements the presence of laminates affected the free‐radical reaction of the UP resin and decreased the curing rate. The curing kinetics were also dependent on the size and relative content of the laminates added.
Charakterisierung von vernetzten Polymeren, 9a. Verfolgung der Nachvernetzung von Poly(styrol‐co‐divinylbenzol) zu feinporigen Adsorberpolymeren
Authors: Sommer Christian , Bürger Heidrun , Häusler Karl‐Georg , Popov Georgi
Published: April 2003

Die Nachvernetzung von chlormethyliertem Poly(styrol‐co‐divinylbenzol) zu hochvernetzten porösen Adsorberpolymeren wurde über einen weiten Temperatur‐(50–80°C) und Reaktionszeitbereich (bis zu 24,5 h) untersucht. Die vernetzten Materialien wurden durch Stickstoffadsorption/Desorption, Quecksilberporosimetrie, Bestimmung des Chlorgehalts, Quellungsmessungen, Pyrolyse‐Gaschromatographie und Fourier‐Transform‐Infrarotspektroskopie charakterisiert.

Die Oberfläche, die Porengrößenverteilung, das Porenvolumen, der Chlorgehalt, ausgewählte Peakverhältnisse in den Pyrogrammen und den FTIR‐Spektrogrammen sind eindeutige Funktionen der Nachvernetzungszeit. Der Nachvernetzungsprozeß kann somit sowohl mit physikalischen als auch mit chemischen Charakterisierungsmethoden verfolgt werden. Darüber hinaus ermöglichen Quellungsmessungen und pyrolysegaschromatographische Untersuchungen Aussagen zur Homogenität und Inhomogenität der chlormethylierten Copolymeren und porösen Adsorberpolymeren.

Der Einsatz verschiedener Lösungsmittel bei der Quellung erlaubt die Konstruktion von Quellungsdiagrammen, anhand derer das anomale Quellungsverhalten der Adsorberpolymeren während der Nachvernetzung erklärt werden kann.

Im Verlauf der Nachvernetzung werden die Oberfläche und das Porenvolumen stark vergrößert und eindeutige Korrelationen zwischen der Probentextur und den Pyrolyse‐ und FTIR‐Daten gefunden. Die Veränderung der physikalischen Eigenschaften im Verlauf der Vernetzung kann generell auf die chemische Modifikation des Materials zurückgeführt werden.
Die chemische Beständigkeit eines Steinschutzstoffes auf Polyurethanbasis in der künstlichen Bewitterung
Authors: Hagenauer Michael , Gerhard‐Abozari Eva , Höcker Hartwig
Published: April 2003

Die Dauerhaftigkeit eines Steinschutzstoffes auf Polyurethanbasis im Sander Schilfsandstein gegenüber chemischen Angriffen wurde nach verschieden langen Bewitterungszeiten in einer Versuchsanlage zur naturnahen Umweltsimulation untersucht. Dabei wurden sowohl die Gelpermeationschromatographie (GPC) als auch oberflächensensible Analysenmethoden (XPS und PAS‐FTIR) zur Untersuchung der Polyurethan‐Mikroschicht im Stein eingesetzt. Nur im Bereich der ersten vier Millimeter Gesteinstiefe konnten bewitterungsbedingte chemische Veränderungen des Polymeren festgestellt werden.
Influence of emulsifier and initiator concentration on the copolymerization of 1,4‐divinylbenzene with comonomers of different solubility in water
Authors: Kaczun J. , Funke W.
Published: April 2003

The influence of the concentration of sodium dodecylsulfate and 2,2′‐azoisobutyronitrile on the crosslinking emulsion copolymerization of 1,4‐divinylbenzene with hydrophobic cyclohexyl methacrylate and with hydrophilic methyl acrylate was studied. The emulsions were prepared by joint and by separate solubilization to study diffusion effects. Monomer conversion was measured and the microgels were characterized by molar mass, particle size diameter and intrinsic viscosity. The monomer conversion was maximal in the transition from a normal to a micellar emulsion. With the hydrophobic comonomer increasingly insoluble coagulates from polymerized monomer droplets were formed on decreasing the emulsifier concentration. Toward higher emulsifier concentration increasingly insoluble agglomerates were formed by reactions between microgels.
Accelerated thermal aging of NBR and other materials under air or oxygen pressures
Authors: Budrugeac Petru
Published: April 2003

Accelerated thermal degradation of nitrile‐butadiene rubber, ethylene‐propylene rubber, low density polyethylene and glass reinforced epoxy resin was studied (a) in air, at atmospheric pressure, and various temperatures and (b) in air or oxygen at various pressures (P > 1 atm) and temperatures. On the basis of the experimental results, a kinetic equation of thermal degradation of investigated materials has been derived.
Aspects of poly(p‐phenylene sulfide) degradation and stabilization. Part 1. Influence of polymer end groups on exposure induced coloration
Authors: Deslauriers P. J. , Geibel Jon F. , Das P. K.
Published: April 2003

In this paper we reviewed some of our work on the photo induced coloration of Poly(p‐phenylene sulfide) (PPS) and compared it to recent results obtained from the thermal treatment of resins that varied in molecular weight and ionic content. The results from this study suggest that coloration of amorphous PPS films after UV irradiation is caused by products different from those that cause coloration in semicrystalline PPS after thermoxidation. In addition, we found that polymer end group chemistry and resin molecular weights play important roles in the thermoxidative coloration of PPS, but only nominally influence the photooxidative coloration of the resin. PPS coloration may arise from the accumulation of specific, colored products (e.g., phenyl‐phenyl moieties) and the possible presence of intermolecular aggregates. The mechanism and extent by which these structures occur in UV irradiated or heated PPS are likely dependent upon the polymer morphology of the samples tested.
Oxidation kinetics of poly(4‐methylpentene)
Authors: Guarrotxena N. , Audouin L. , Verdu J.
Published: April 2003

The thermal oxidation (in air between 70 and 150°C) of unstabilised camples of poly(4‐methylpentene) (PMP) were studied by infrared spectrometry and by gravimetry. The behaviour was compared to PP exposed in the same conditions.

The thermal oxidation was found to exhibit two well differentiated kinetic regimes both for PP as for PMP. The first regime predominates at temperature higher than 90°C. It is characterized by an activation energy of the pseudo induction period of about 100 kJ mol−1. The induction period of mass gain is about 1,8 time shorter than the induction period of carbonyl gain. These characteristics, and the fact that induction periods are of the same order for both polymers, are consistent with a «close loop mechanistic» scheme with unimolecular POOH decomposition. The advantages of this hypothesis compared to other proposed hypothesis (bimolecular POOH decomposition, heterogeneous oxidation...) are discussed. The main theoretical difficulty is that of explaining why the unimolecular process predominates, whereas POOH are obviously hydrogen bonded, even at very low conversions of the oxidation process. This point remains to be explained.

The second kinetic regime predominates at temperature lower than 90°C. It is characterized by a considerably lower activation energy. We have examined many hypothesis to explain the existence of a transition at that temperature (where neither PMP nor PP display a physical transition). A first hypothesis is that unimolecular POOH decomposition is replaced by a bimolecular one, which can explain a decrease of the apparent activation energy of about 50%. The bimolecular initiation creates pairs of radicals (POO·+ PO·). It can be imagined that a part of them desactivate mutually by termination after rearrangement of PO· by β scission. In this case, the transition at 90°C could be also a result of the temperature induced change in molecular mobility. Above 90°C, the radicals would diffuse almost freely out of the cage. In contrast, below 90°C, termination would become competitive with diffusion. A supplementary research is needed to fully elucidate the cause of this transition at 90°C.

The eventuality of the existence of spatial heterogeneity of the oxidation process has been discussed. It is well known that oxidation is heterogeneous at the morphological scale, but there is no evidence of heterogeneity at smaller scale, where the chemical kinetic would not be applicable.
Mechanical and morphological properties of stabilized and non‐stabilized HDPE films versus exposure time
Authors: Hoekstra H. D. , Spoormaker J. L. , Breen J.
Published: April 2003

Non UV‐stabilized and UV‐stabilized (a UV‐absorber) HDPE films were photo‐oxidized in a Xenotest. The concentration of carbonyl and the UV‐stabilizer, the molecular weight, the crystallinity and the density were studied versus exposure time. Furthermore, the mechanical behaviour was studied at different strain rates by tensile testing.

The number of chain scissions was found equal to the number of carbonyl groups. The density of the film increased from 950 to 970 kg/m3 and the crystallinity from 70 to 82%. The increase in density is explained by the increase in crystallinity and by oxygen uptake.

The rate at which carbonyl groups are formed, was found to accelerate with exposure time. This acceleration finally resulted in profiles, which could be measured by FT‐IR and verified by computer simulations.

After 14 days of exposure the specimen failed in a brittle manner. An activation volume was calculated and found to decrease. It is thought that a change in molecular mobility is responsible for the lower strain at yield values. The change in molecular mobility can also explain the increase in Young's modulus with the strain rate and exposure time. The Takayanagi and the Halpin/Tsai models were used to describe the increase of modulus of elasticity.
Applicability and limitations of current lifetime prediction models for thermoplastics pipes under internal pressure
Authors: Lang R. W. , Stern A. , Doerner G.
Published: April 2003

Engineering thermoplastics, in particular polyolefins such as special grades of poly(ethylene), are gaining importance in pipe applications such as gas and water supply systems. To ensure proper performance of such pipes over the required lifetime, polymer physics and mechanics concepts are needed to adequately account for the effects of time, temperature, and environmental conditions as well as the occurrence of pipe defects and imperfections on relevant polymer properties and pipe performance. This article provides a critical overview of the scientific background of current methodologies to describe the long‐term behavior of thermoplastic pressure pipes. In particular, the merits and limitations of two different approaches‐namely, the standard extrapolation method (SEM) described in ISO/TR 9080 and the linear elastic fracture mechanics (LEFM) approach‐are compared. Special attention is given to effects associated with material ageing and degradation.
Controlled degradation in tailor‐made macromolecules elaboration. Controlled chain‐cleavages of polydienes by oxidation and by metathesis
Authors: Reyx Danièle , Campistron Irène
Published: April 2003

A chain cleavage reaction allowing the transformation of high molecular weight polymers in well‐defined oligomers can be considered as a step in a synthetic scheme. The control of oligomers with respect to their average molecular weights, their molecular weights distributions and their chain‐end microstructures implies the control of the cleavage reaction with respect to its yield, its regiospecificity and its chemiospecificity. Among several examples of efficient uses of this principle for the preparation of liquid oligomers from unsaturated polymers, attention is focused (I) on controlled oxidative degradation of rubber and (II) on metathetical controlled degradation of 1,4‐polydienes and polyakenamers. (I.a) The mechanism of the phenylhydrazine accelerated oxidation of rubber in the latex phase is described according to accurate structural studies on molecular model molecules. (I.b) The epoxidation of rubber and periodic acid cleavages of epoxides in the latex phase are interpretated referring to the influence of the biphasic medium. The results are in agreement with interfacial blocky epoxidation by the water‐soluble reagent and interfacial arrangement of the epoxidized block to be cleaved. Finally the metathetical degradations resulting from back‐bitting cyclisation and cross metathesis with acyclic alkenes are presented as preparative methods to get (II.a) well‐defined cyclic oligomers and (II.b) telechclic oligomers (i.e. terminally functionalized oligomers).