bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of heavy metal contamination and water quality in an urban river from Argentina
Authors: Magdaleno Anahí , De Cabo Laura , Arreghini Silvana , Salinas Cristian
Published: August 2014

In aquatic ecosystems, the potential effects of toxic compounds are greatly determined by their physicochemical forms and bioavailability. The aim of this work was the assessment of metal toxicity to the green alga Pseudokirchneriella subcapitata in contaminated water samples of an urban river (Matanza-Riachuelo, Argentina). A total of 30 samples were analyzed. Physicochemical parameters and total and dissolved metal (Cd, Cu, Cr, Pb, Ni and Zn) concentrations were measured. Toxicity was related as a function of size fractionation and chemical speciation (using the program Mineql+) in the dissolved fraction (<1.2Î¼m). Percentage inhibition of algal growth (%Iw) was estimated as the differences between cultures with and without EDTA additions in the filtered water samples. Concentrations of Cd (1-85Î¼g.L-1), Cr (3-164Î¼g.L-1), and Ni (10-99Î¼g.L-1) in river waters were always lower than the respective EC50 for P. subcapitata, whereas concentrations of Cu (5-306Î¼g.L-1), Pb (13-546Î¼g.L-1), and Zn (4-380Î¼g.L-1) in dissolved fractions resulted above the EC50 values in many samples. Only 10 samples showed algal growth inhibition (between 11.21% and 42.19%), which 8 of them also showed high concentrations of free ionic forms of Pd or Zn. Free ionic concentrations of Cu were always lower than the EC50 for the algae. Two samples resulted toxic to P. subcapitata in spite of the absence of toxic metal concentrations. Besides, 13 samples no inhibited the algal growth and high concentrations of Pd and Zn were obtained, producing expected %Iw values between 10.03% and 90.51%. The absence of toxicity in most samples with toxic metal concentrations could be related to the presence of organic ligands, colloidal organic matter, and antagonism effects among other metals, which reduce their bioavailability.
Features of eating behavior, emotional state and metabolic parameters in obese patients with insomnia
Authors: Strueva N V , Poluektov M G , Saveleva L V , Melnithenko G A , Katsya G V , Goncharov N P
Published: August 2014

Aim. The aim of this study was to investigate the influence of insomnia on eating behavior, anxiety, depression, metabolic and hormonal parameters in obese patients. Materials and Methods. The study involved 104 patients with primary obesity from 20 to 55 years old: 47 men and 57 women, mean age 39 years, mean body weight 118 kg, BMI 39.6. Patients were divided into 2 groups: the first group consisted of patients with complaints of insomnia (n=45), the second (control) group (n=59) were patients without sleep disorders. Results. Mean levels of anxiety and depression were significantly higher in the first group. The results of research showed a statistically significant association emotional eating and insomnia. Patients with chronic insomnia without obstructive sleep apnea had low levels of free cortisol in 24-hour urinary compared with patients without sleep disorders (169 [145, 194] vs. 324 [244, 330], respectively, p=0.001), positive correlation with total sleep time, sleep efficiency, and negative with wake time during sleep period time. Conclusions. Sleep disorders in obese patients are one of the factors contributing to the increase in food intake in response to changes in emotional state on the background of "hidden" anxiety and depressive disorders. It is possible that the data eating disorders and psychological status may have a negative impact on the dynamics of weight during the treatment of obesity.
Konfliktmanagement für Führungskräfte – von der täglichen Führungsarbeit zum System
Authors: Hennecke Joachim
Published: August 2014

Konfliktmanagement bietet mehr als Tools für die Schlichtung von Streitigkeiten im bibliothekarischen Alltag. Dies konnten die Teilnehmer eines von der dbv/vdb-Managementkommission veranstalteten Workshops anhand unterschiedlicher Konflikttypen, der Abwägung zwischen funktionalen und dysfunktionalen Konflikten, der verschiedenen Rollen von Führungskräften im Mediationsprozess sowie der systemkritischen Bedeutung von Konfliktmanagement im Rahmen der Gesamtorganisation mit Mediationsprofis der KPMG Deutschland diskutieren.
Fachwirtfortbildung für Bibliotheksbeschäftigte
Authors: Holste-Flinspach Karin
Published: August 2014

Im Jahr 2014 werden sowohl in Nordrhein-Westfalen als auch in Hessen Beschäftigten im Bereich Archiv-Bibliothek-Dokumentation Fortbildungsangebote zur Vorbereitung auf den Abschluss als Geprüfter Fachwirt für (Medien- und) Informationsdienste angeboten und bereits seit 2011 sind die ersten Fachwirte in unserem Berufsumfeld auf dem Arbeitsmarkt. Somit besteht für Fachangestellte für Medien- und Informationsdienste eine inzwischen auch in der Berufsöffentlichkeit anerkannte Möglichkeit, berufsbegleitend und ohne Hochschulzugangsberechtigung einen qualifizierten Weiterbildungsabschluss zu erwerben.
A multicenter nationwide reference intervals study for common biochemical analytes in Turkey using Abbott analyzers
Authors: Ozarda Yesim , Ichihara Kiyoshi , Aslan Diler , Aybek Hulya , Ari Zeki , Taneli Fatma , Coker Canan , Akan Pinar , Sisman Ali Riza , Bahceci Onur , Sezgin Nurzen , Demir Meltem , Yucel Gultekin , Akbas Halide , Ozdem Sebahat , Polat Gurbuz , Erbagci Ayse Binnur , Orkmez Mustafa , Mete Nuriye , Evliyaoglu Osman , Kiyici Aysel , Vatansev Husamettin , Ozturk Bahadir , Yucel Dogan , Kayaalp Damla , Dogan Kubra , Pinar Asli , Gurbilek Mehmet , Cetinkaya Cigdem Damla , Akin Okhan , Serdar Muhittin , Kurt Ismail , Erdinc Selda , Kadicesme Ozgur , Ilhan Necip , Atali Dilek Sadak , Bakan Ebubekir , Polat Harun , Noyan Tevfik , Can Murat , Bedir Abdulkerim , Okuyucu Ali , Deger Orhan , Agac Suret , Ademoglu Evin , Kaya Ayşem , Nogay Turkan , Eren Nezaket , Dirican Melahat , Tuncer GulOzlem , Aykus Mehmet , Gunes Yeliz , Ozmen Sevda Unalli , Kawano Reo , Tezcan Sehavet , Demirpence Ozlem , Degirmen Elif
Published: August 2014

A nationwide multicenter study was organized to establish reference intervals (RIs) in the Turkish population for 25 commonly tested biochemical analytes and to explore sources of variation in reference values, including regionality.

Blood samples were collected nationwide in 28 laboratories from the seven regions (≥400 samples/region, 3066 in all). The sera were collectively analyzed in Uludag University in Bursa using Abbott reagents and analyzer. Reference materials were used for standardization of test results. After secondary exclusion using the latent abnormal values exclusion method, RIs were derived by a parametric method employing the modified Box-Cox formula and compared with the RIs by the non-parametric method. Three-level nested ANOVA was used to evaluate variations among sexes, ages and regions. Associations between test results and age, body mass index (BMI) and region were determined by multiple regression analysis (MRA).

By ANOVA, differences of reference values among seven regions were significant in none of the 25 analytes. Significant sex-related and age-related differences were observed for 10 and seven analytes, respectively. MRA revealed BMI-related changes in results for uric acid, glucose, triglycerides, high-density lipoprotein (HDL)-cholesterol, alanine aminotransferase, and γ-glutamyltransferase. Their RIs were thus derived by applying stricter criteria excluding individuals with BMI >28 kg/m

With the lack of regional differences and the well-standardized status of test results, the RIs derived from this nationwide study can be used for the entire Turkish population.
Liquid crystalline elastomers as artificial muscles
Authors: Wermter Hendrik , Finkelmann Heino
Published: August 2014

New nematic co-elastomers were synthesized which consist of a combination of nematic side- and main-chain polymers and where the liquid crystalline main-chain polymer can be considered as a macromolecular crosslinking component. By applying a mechanical field during the crosslinking process, the director of the nematic phase becomes macroscopically uniformly aligned and liquid-single-crystal elastomers were obtained. Within a narrow temperature regime, these networks can change their shape in one dimension by a factor > 3 and considerably improve the ability of being used as artificial muscles or mechanical actuators compared to the well known nematic side-chain elastomers. Networks having a non-ordered polydomain structure exhibit “soft (or semi-soft) elasticity” which is not only determined by a director reorientation process. Obviously, hairpin conformations within the main-chain segments contribute to this effect.
Superlattices in block copolymer blends with attractive interactions
Authors: Markgraf Kirsten , Abetz Volker
Published: August 2014

Blends of microphase separated polystyrene-block-polybutadiene-blockpoly( methacrylic acid) triblock copolymers (SBA) with polystyrene-block-poly(2- vinylpyridine) (SV) or poly(2-vinylpyridine)-block-poly(cyclohexyl methacrylate) (VC) diblock copolymers were prepared and characterized. Attractive segmental interactions through hydrogen bonds between A and V could be monitored by infrared spectroscopy and dynamic mechanical analysis. Common superlattices were obtained by casting from a mixed solution of these block copolymers in tetrahydrofuran and were investigated by transmission electron microscopy. Varying the amount of hydrogen bonding donors via controlled saponification of an SBT triblock copolymer (T: poly(tert-butyl methacrylate)) lead to different superlattices in blends with a VC diblock copolymer.
Hydrolysis of the Nafion® precursor studied by X-ray scattering and in-situ atomic force microscopy
Authors: Elliott James A. , James Paul J. , McMaster Terence J. , Newton John M. , Elliott Alice M. S. , Hanna Simon , Miles Mervyn J.
Published: August 2014

The hydrolysis of Nafion® † precursor material to a perfluorosulfonate ion exchange membrane has been studied in situ at the surface of a sample using atomic force microscopy (AFM), and in the bulk using a combination of small and wide-angle X-ray scattering. The AFM results show that there is a rapid and significant change in the surface morphology of the sample during the first 12 min after the introduction of aqueous hydroxyl ions, provided that an appropriate swelling agent is used. After this point there is little change in surface morphology, although bulk swelling of the sample continues. The wide-angle X-ray scattering results indicate a significant drop in the degree of crystallinity of fluorocarbon matrix from 14±1% to 7±1% on hydrolysis, as a result of the bulk structural reordering necessary to accommodate the formation of ionic clusters. Ionic clustering is confirmed by the appearance of a characteristic small-angle X-ray peak. However, the peak forms towards the end of the hydrolysis process, and subsequently coarsens, suggesting that the formation of ionic clusters is a slow process compared to the rate of hydrolysis. It is confirmed that an appropriate water/solvent mixture is necessary to achieve an efficient conversion of precursor to membrane. AFM images of the precursor surface, when water alone is used, show no signs of structural change.
Review: Progress in liquid crystal displays by new developments in functional polymers
Authors: Broer Dirk J. , Haaren Jos A. M. M. van , Bastiaansen Cees W. M.
Published: August 2014

Functional polymers have become essential in the functioning and performance of many products for information and communication technologies. Special polymers have been constructed with an accurate control over their morphology to a size down to the wavelength of light. These polymers improve liquid crystal displays on eye-catching properties like brightness and viewing angle. The improved energy efficiency is crucial for the mobile communication equipment in today’s information society.
Photoinitiated cationic polymerization using allylsulfonium salts. Substituent effect on the initiator activity
Authors: Bayramoglu Fatma , Onen Aysen , Yagci Yusuf
Published: August 2014

Allylthiophenium salts with various substituents at the allylic moiety were synthesized, characterized and shown to be efficient coinitiators in radicallly promoted cationic photopolymerization of cyclohexene oxide. The relative efficiencies of these salts in combination with benzoin and benzophenone as free radical sources in the photopolymerizations are compared. Both additionfragmentation and electron transfer mechanisms are proposed and their relative merits discussed.
Effect of the dispersion of the chromophore on the optical performances of polarizers from polyethylene and 5”-thio- (3-butyl)nonyl-2,2’:5’,2”-terthiophene
Authors: Pucci Andrea , Moretto Letizia , Ruggeri Giacomo , Ciardelli Francesco
Published: August 2014

A new polyethylene-compatible terthiophene chromophore, 5”-thio-(3- butyl)nonyl-2,2’:5’,2”-terthiophene, with melting point lower than 0°C was prepared and used for linear polarizers based on ultra-high-molecular-weight polyethylene (UHMWPE). Differential scanning calorimetry and scanning electron microscopy indicate that the new chromophore is dispersed uniformly in films of UHMWPE obtained by casting from solution. The films show excellent dichroic properties (dichroic ratio 30) at rather low drawing ratio (≈ 20) . Moreover, qualitative agreement is observed with the Ward pseudo-affine deformation scheme.
Deprotective activity of nanosized globular partially quaternized poly(tertiary amine)s in peptide synthesis
Authors: Chapon Pascal , Coudane Jean , Garreau Henri , Vert Michel , Ferhentz Jean Alain , Martinez Jean
Published: August 2014

Bifunctional polybases of the partially quaternized poly[thio-1-(N,Ndiethylaminomethyl) ethylene] type (Q(PTDAE),X, with X = percentage of N-quaternization) are able to catalyze various reactions including lipophilic reagents temporarily entrapped in the hydrophobic core of the globules. In this contribution it is shown that benzyloxycarbonyl (Z) and fluoromethyloxycarbonyl (Fmoc) protecting groups of peptides are cleaved at room temperature in a few minutes in an aqueous medium at pH 7,4. Deprotection was also effective when peptides were attached to solid supports of the Merrifield type provided a hydrophilic spacer arm of the poly(ethylene glycol)-type was inserted between beads and the built up peptide moieties. However, unhooking was observed when the hydrophilic spacerpeptide bond was an ester but not when it was of the amide type. The work shows that Q(PTDAE),X globules exhibit enzyme-like activity in a homogeneous aqueous medium and in heterogeneous systems as well.
Sodium nitrite and ascorbic acid: a metal-free combination that controls the free-radical polymerization of tert-butyl methacrylate in water
Authors: Detrembleur Christophe , Mouithys-Mickalad Ange , Teyssié Philippe , Jérôme Robert
Published: August 2014

A mixture of sodium nitrite and ascorbic acid is able to control the radical polymerization of tert-butyl methacrylate (tBMA) in water at 80°C. Indeed, sodium nitrite is reduced by the ascorbic acid, and the nitric oxide (NO) which is formed insitu is nothing but a promoter of nitroxyl radicals. The radical polymerization of tBMA is thus basically controlled by a nitroxide-mediated process.
Cyclodextrins in polymer synthesis: Dimethyl-β-cyclodextrin as thermosensitive retardant for the radical polymerization of N-methacryloyl-L-tyrosine derivatives in water
Authors: Tabatabai Monir , Ritter Helmut , Schmelzer Monika
Published: August 2014

The synthesis and characterization of N-methacryloyl-L-tyrosine methyl ester (3a) and ethyl ester (3b), and their acetyl derivatives O-acetyl-N-methacryloyl- L-tyrosine methyl ester (4a) and ethyl ester (4b) are described. Monomers 3 and 4 were complexed with RAMEB (randomly methylated ß-cyclodextrin) yielding water soluble host-guest complexes 5a-d. The radical polymerization of monomers 3 and 4 was investigated in the presence as well as in the absence of RAMEB in aqueous medium at room temperature and also at 60°C. It is shown that the polymerization tendency of complexes 5a-d at room temperature is lower, leading to polymers of higher molecular weight, compared to the free monomers 3 and 4. Furthermore, the polymerization of monomers 3 and 4 was carried out in homogenous organic solution using 2,2’-azoisobutyronitrile as initiator, and the results are discussed.
Covalent immobilization of urease on polypyrrole microspheres for application as a urea biosensor
Authors: Gambhir Anamika , Kumar Arun , Malhotra Bansi D. , Miksa Beata , Slomkowski Stanislaw
Published: August 2014

Urease has been covalently immobilized on polypyrrole microspheres chemically linked to conducting polypyrrole-polyvinyl sulfonate (PPY-PVS) films. These films were electrochemically prepared during 5 - 7 min at a constant current of 2 mA using indium - tin oxide (ITO) glass plates as the working electrode, and a standard calomel electrode as the reference electrode. Urease covalently linked to polypyrrole microspheres (by reaction of protein amino groups with aldehyde groups on the surface of the microspheres) was entrapped/adsorbed onto electrochemically prepared conducting PPY-PVS films deposited on ITO. Potentiometric measurements undertaken on these conducting polymer electrodes using an ammonium ion analyzer reveal that they can be used for estimating the urea concentration in solutions from 5·10-3 mol/l to 6·10-2 mol/l.
Biomedical applications of polymers 2001 - 2002
Authors: Jagur-Grodzinski Joseph
Published: August 2014

Papers published during 2001 - 2002 on the synthesis and preparation of polymers and polymer-based devices and their applications are reviewed. Polymers for drug and gene delivery, gene therapy, controlled drug release, conjugation with peptides, proteins, and nucleotides, tissue engineering, bone repair and regeneration, coatings, wound dressing, artificial skin and other artificial organs are discussed.
The AA* + B*B2 approach A simple and convenient synthetic strategy towards hyperbranched polyurea-urethanes
Authors: Bruchmann Bernd , Schrepp Wolfgang
Published: August 2014

Synthesizing hyperbranched polyurethanes in a one step process using commercially available raw materials: these were the primary conditions for this work. By taking advantage of intramolecular reactivity differences of isocyanate groups in diisocyanates in combination with reactivity differences of OH and NH groups in alkanolamines, it is possible to generate in situ AB2 molecules by controlling reactions of specific functional groups towards each other. This AA* + B*B2 approach works without protecting groups and opens up a simple and versatile strategy towards hyperbranched aromatic as well as aliphatic polyureaurethanes. Preferential diisocyanates for this synthesis were 2,4-toluylene diisocyanate and isophorone diisocyanate, whereas diethanolamine and diisopropanolamine were used as isocyanate-reactive counterparts.
Novel soluble blue emitting PPV-like polymers: synthesis and characterization
Authors: Gruber Jonas , Li Rosamaria W. C. , Ponce Patricia , Benvenho Adriano R. V. , Mello Regina M. Q. , Hümmelgen Ivo A.
Published: August 2014

We report on the electrochemical synthesis of two novel soluble PPV-like polymers, poly(2-decyloxy-4,4'-biphenylenevinylene), DOPBV, and poly(2-decylsulfonyl- 4,4'-biphenylenevinylene), DSPBV, their spectroscopic and thermal characterization as well as their electrical properties. We also report on the use of sandwich devices Au/DOPBV/Al and Ni/DSPBV/Al to investigate the charge injection and transport characteristics, besides other important parameters such as the optical energy gap and the HOMO energy level, leading to an estimate of the ionization potential and electron affinity of these polymers.
On the entanglement density of differently N-substituted alternating styrene-maleimide copolymers
Authors: Teerenstra Marcel N. , Steeman Paul A. M. , Iwens Werner , Vandervelden Alexander , Suwier Davy R. , Van Mele Bruno , Koning Cor E.
Published: August 2014

Differently N-substituted maleimides were copolymerized with styrene to yield alternating styrene-maleimide copolymers (SMI-R) with different chain diameters. The polymers were obtained by free radical polymerization and characterized by NMR and size exclusion chromatography / differential viscometry. Glass transition temperatures were measured by differential scanning calorimetry. An increase in chain diameter and chain stiffness is accompanied by a decrease in the entanglement density, reflected in lower values of the plateau modulus, which were corrected for the low molecular weight portion using the Wasserman/Graessley model. Increasing the chain diameter by a factor of two results in a decrease of the entanglement density to one third. SMI-Me showed a much lower entanglement density than polystyrene (PS) although they have the same chain diameter. SMIMe however is more rigid than PS because of the maleimide five-membered ring structure in the main chain. SMI-Me and SMI-PhOPh show the same glass transition temperature. However, because of the larger chain diameter of SMIPhOPh, it has a much lower entanglement density. Thus, both the chain flexibility and the chain diameter, two parameters that are strongly related, affect the entanglement density.
Determination of acid and hydroxyl end-groups in endfunctionalized polystyrenes using 19F NMR
Authors: Rajan Merina , Cotiuga Irina , Ma Yunqian , Picchioni Francesco , Agarwal Uday S.
Published: August 2014

Carboxyl-terminated polystyrene was esterified with 2,2,2-trifluoroethanol using a carbodiimide-mediated room temperature reaction, and hydroxyl-terminated polystyrene was fluoro-derivatized with trifluoroacetic anhydride. The soformed fluorine-containing esters were then quantitatively determined with 19F NMR, using α,α,α-trifluorotoluene as secondary standard. This provides a technique for the reliable determination of carboxylic acid and hydroxyl groups in small samples of polymers.
In situ compatibilization of a polyetherimide and a thermotropic polyester using an epoxy resin
Authors: Turturro Antonio , Castellano Maila , Panzardi Gianluca , Valenti Barbara , Russo Saverio , Costa Giovanna , Falqui Luciano
Published: August 2014

This study examines the compatibilization of the polyetherimide Ultem 1000 with the thermotropic liquid crystalline polymer Vectra A 950 by using an epoxy resin (PKFE) as compatibilizer. IR spectroscopy and electron-microscopic morphological analysis indicate the grafting of PKFE molecules on fibrillar domains of Vectra during melt mixing. Moreover, morphological analysis shows that the addition of PKFE improves the dispersion and decreases the size of Vectra fibrils. Both Vectra and PKFE significantly reduce the glass transition temperature of Ultem in ternary blends. The tensile modulus and the ultimate strength of the blends are improved with respect to those of neat Ultem. However, the final materials are very fragile. The roles of Vectra and PKFE are discussed.
Memory effect in melting behaviour, crystallization kinetics and morphology of poly(propylene terephthalate)
Authors: Sisti Laura , Finelli Lara , Lotti Nadia , Berti Corrado , Munari Andrea
Published: August 2014

Crystallization kinetics and melting behaviour of poly(propylene terephthalate) (PPT) were investigated by means of differential scanning calorimetry and hot-stage optical microscopy. Isothermal crystallization kinetics was analysed according to the Avrami treatment. The effects of temperature and duration of melting on the overall rate of isothermal crystallization were studied: the rate was found to decrease with increasing melting temperature and melting time. This result was discussed on the basis of the gradual destruction of predetermined athermal nuclei. Values of the Avrami exponent close to 3 were obtained, regardless of the adopted thermal treatment and the crystallization temperature, Tc, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. As a matter of fact, spacefilling spherulites were observed by optical microscopy at all Tc’s, independent of the applied thermal treatments. For each of them, the rate of crystallization became lower as Tc increased, as usual at low undercooling where the crystallization process is controlled by nucleation. The observed multiple endotherms, which are commonly displayed by polyesters, were influenced by Tc and ascribed to melting and recrystallization processes. Linear and non-linear treatments were applied in order to estimate the equilibrium melting temperature for PPT, by using the corrected melting temperatures. The non-linear estimation yielded an about 33°C higher value with respect to the one obtained by means of the linear approach. Through the analysis of secondary nucleation theory, the classical II→III transition was found to occur at a temperature of 194°C. The average work of chain folding for nucleation was determined to be c. 5.2 kcal/mol. The heat of fusion was correlated to the specific heat increment for samples with different degree of crystallinity and the results were interpreted on the basis of the existence of an interphase, whose amount was found to depend on the thermal treatment the polymer was subjected to.
Two-dimensional chromatography of complex polymers, 5 Separation of blends of styrene-butadiene rubber and butyl rubber
Authors: Heinz Lars-Christian , Siewing Anja , Pasch Harald
Published: August 2014

Separation of blends of styrene-butadiene rubber and butyl rubber was accomplished by gradient HPLC. Using a polar stationary phase and chloroformcyclohexane as eluent, the blends were separated with regard to chemical composition, irrespective of the molar masses of the components. The exact chemical structure of the blend components was analysed by coupling the chromatographic separation to FTIR detection. FTIR spectra of the components reveal information on styrene and butadiene contents and the conformation of the butadiene units (1,2-, 1,4-cis and 1,4-trans units). Complete separation of the blends with respect to chemical composition and molar mass was achieved by two-dimensional liquid chromatography. Combining gradient HPLC and size exclusion chromatography in a fully automated 2D chromatography set-up, the complex distributions of chemical composition and molar mass were fingerprinted simultaneously.
Degradation of unstabilised polypropylene and a propene- 1-pentene copolymer
Authors: de Goede Stefan , Brüll Robert , Pasch Harald , Marshall Niall
Published: August 2014

The degradation of polypropylene (PP) and a propene-1-pentene copolymer (P2) have been monitored with regard to chemical composition, molar mass distribution and chemical composition distribution. The increase in the carbonyl index can be monitored by IR and a decrease in molar mass can be observed from size-exclusion chromatography (SEC). CRYSTAF shows that the chemical heterogeneity of the samples broadens with continuing degradation. SEC-FTIR reveals that the degraded species are mainly found in the low-molecular-weight end of the molar mass distribution. Spatial heterogeneity of the degradation process has been proven by the analysis of abrased layers. It was found that the P2 copolymer degrades at a higher rate compared to PP.
Solvation of poly(methyl acrylate) and poly(vinyl acetate) by CO2 studied via atomistic Monte Carlo simulation techniques
Authors: Beuermann Sabine , Buback Michael , Drache Marco , Nelke Dorit , Schmidt-Naake Gudrun
Published: August 2014

The differences in solubility of poly(vinyl acetate) (PVAc) and poly(methyl acrylate) (PMA) were addressed by applying atomistic Monte Carlo simulation techniques. Polymer segments consisting of nine monomer units serve as model compounds for polymer chains. As a measure of intermolecular interactions with the solvent environment, cohesion energies of the polymer segments embedded in either the corresponding monomer or in CO2 were calculated. Only in case of PMA segments in CO2 environment, specific interactions between polymer segments were identified. This finding is in agreement with experimental results on phase behaviour and propagation kinetics.
Poly(methyl methacrylate)-block-polystyrene and polystyrene-block-poly(n-butyl acrylate) as compatibilizers in PMMA/PnBA blends
Authors: Stenert Michael , Döring Andreas , Bandermann Friedhelm
Published: August 2014

The influence of the addition of poly(methyl methacrylate)-blockpolystyrene (PMMA-b-PS) and PS-b-poly(n-butyl acrylate) (PS-b-PnBA) diblock copolymers on the structure and the mechanical properties of PMMA/PnBA polymer blends was investigated. In binary polymer blends of PMMA and PS, and PS and PnBA, and in the ternary system the corresponding diblock copolymers caused a significantly higher distribution of the dispersed phase and an appreciable narrowing of the particle size distribution as shown by scanning force microscopy using the pulsed force mode technique. Transmission electron microscopy images proved that in the ternary system the two diblock copolymers formed no own separate phase but are arranged as a ring layer at the interface between the two homopolymers PMMA and PnBA. Charpy tests demonstrated that the impact strength of the ternary blends is increased by the two diblock copolymers even at low amounts of the latter. The influence on mechanical properties like Young’s modulus, yield stress, and tensile strength at break was less marked as strainstress measurements showed. The major effect seems to be exerted on the elongation at break.
Nafion-layered silicate nanocomposite membrane for fuel cell application
Authors: Thomassin Jean-Michel , Pagnoulle Christophe , Bizzari Didier , Caldarella Giuseppe , Germain Albert , Jérôme Robert
Published: August 2014

Direct methanol fuel cells (DMFCs) using a proton exchange membrane as electrolyte is an attractive option for electricity generation. The most widely used membrane in the DMFC system is based on a perfluorinated polymer bearing sulfonic acid functions like Nafion ®. The latter combines chemical, mechanical and thermal stability and high protonic conductivity but shows elevated methanol permeability. We propose the preparation of a novel type of hybrid membranes to tentatively solve this problem. This innovative material results from the homogeneous dispersion of a nano-scaled inorganic filler within Nafion. The filler consists of stacks of negatively charged alumino-silicate layers (Cloisite), with a positive counter-ion in the interlamellar space. The purpose of the addition of this filler is to decrease methanol diffusion through the polymer membrane without decreasing too much the ionic conductivity.
Plasticizing of isotactic polypropylene upon addition of hydrocarbon oils
Authors: Nitta Koh-hei , Ando Hidetaka , Asami Takuo
Published: August 2014

The effect of the addition of hydrocarbon oil on the mechanical behaviour of isotactic polypropylenes (iPPs) was examined. It was found that the oil molecules are completely dissolved in the amorphous region of iPP so that the blending lowers the glass transition temperature, Tg, of iPP. As a result, Young’s modulus of iPP/oil blends is dominated by the difference between the measurement temperature and Tg (ΔTg = T - Tg), independent of the oil content. The elongation at break is proportional to ΔTg, while the strength at break increases linearly with increasing tie-molecule fraction (which increases with decreasing oil content), being independent of ΔTg.
Kinetic considerations on the mechanical behaviour of polypropylene + wood flour and polypropylene + sisal fibre blends
Authors: Albano Carmen , Poleo Rebeca , Reyes Jacobo , Ichazo Miren , González Jeanette , Brito María
Published: August 2014

This work is aimed at analyzing by means of simple mathematical models the effect of different integral doses of γ-irradiation on the mechanical properties and concentration of radicals of the blends of polypropylene (PP) + wood flour and PP + sisal fibre. The analysis of the results permits inferring that the kinetic behaviour of the mechanical properties and the concentration of radicals at low integral doses (≤ 10 KGy) are indicative of a complex degradation process, implying the possibility of cross-linking and chain scission reactions both in the polymer as well as in the filler. Consequently, it can be concluded that cross-linking reactions are predominant. The behaviour observed at higher irradiation doses means that both reactions (cross-linking and chain scission) occur, the breaking reactions being the prevailing ones. This study of the kinetic analysis of the tensile properties is based on the behaviour detected for the melt-flow index.
Room temperature Monte Carlo study of the mechanical properties of thermoplastic polymers
Authors: Ospina Silvio A. , Hess Michael , López Betty L.
Published: August 2014

The effect of the tensile test rate upon the mechanical properties of semicrystalline high-density polyethylene (HDPE) is studied by the Monte Carlo method. A two-dimensional lattice model is used, which considers first and second neighbour’s interactions between CH2-CH2 groups. Metropolis dynamics is implemented as energy minimization tool. Results reveal the existence of two distinguishable regions in the stress-strain curves. One of them is characterized by an elastic and linear behaviour below 0.27% of deformation where the elastic modulus is practically insensitive to the number of Monte Carlo steps, whereas at higher deformation the system exhibits a non-linear behaviour ascribed to the viscoelastic character of the material endorsed by a clear dependence of the relaxation modulus as a function of the strain rate. The relaxation behaviour of HDPE obtained in our simulation shows an exponential decrease of the stress as time increases, which agrees with experimental data.
Investigation of the effects of the types of food waste utilized as carbon source on the molecular weight distributions and thermal properties of polyhydroxybutyrate produced by two strains of microorganisms
Authors: A. L. Wong Phoeby , Cheung Man Ken , Lo Wai-Hung , Chua Hong , Yu Peter Hoi Fu
Published: August 2014

The average molecular weight and molecular weight distribution of polyhydroxybutyrate can be affected by different bacterial strains, different cultivation time and also different carbon sources. Food waste was proven to have a high potential in the induction of biosynthesis of polyhydroxybutyrate with different production yields and physical properties. A specific culture of Alcaligenes latus DSM 1124 and Staphylococcus epidermidis, which was isolated from sesame oil, were selected to ferment several types of food wastes as nutrients, including malt waste, soy waste, confectionery waste, milk waste, vinegar waste and sesame oil, into polyhydroxybutyrate in this study. Average molecular weight and molecular weight distribution of polyhydroxybutyrate were measured by gel permeation chromatography. By comparing the results with those obtained using sucrose as a carbon source, the average molecular weight of polyhydroxybutyrate produced from food wastes was increased for Alcaligenes latus; however, it was decreased for S. epidermidis. Thermal analyses of the biopolymer produced by S. epidermidis indicated that the melting point of the polymer produced from sesame oil as carbon source was 188°C, the highest temperature among those polymers produced by using ice cream, malt, and soya wastes.
Silane pre-treatment of calcium carbonate nanofillers for polyurethane composites
Authors: Lučić Blagojević Sanja , Kovačević Vera , Leskovac Mirela , Vrsaljko Domagoj , Volovšek Vesna , Nover Christoph
Published: August 2014

In this work we have investigated the effects of CaCO3 nanofiller pretreatment on the properties of polyurethane (PU) composites prepared by a mixing procedure. The aim was to enhance interactions at the matrix/filler interface and to improve the distribution of the filler in the polyurethane matrix. CaCO3 nanofiller was treated with two different functional trialkoxysilanes, viz. γ-aminopropyltriethoxysilane (AMPTES) and γ-glycidoxypropyltrimethoxysilane (GPTMS). Fourier transform IR spectroscopy of the pre-treated CaCO3 surface indicates that AMPTES formed a high-molecular-weight ladder-type structure on the CaCO3 surface, while GPTMS was adsorbed in the form of a lower-molecular-weight oligomeric structure. Increased ultimate tensile strength and elongation were obtained for PU + CaCO3 nanocomposites with silane pre-treated filler. This can be explained as the consequence of better stress transfer through the composite, observed on scanning electron micrographs, due to an improved adhesion between PU matrix and silane-treated fillers. The reinforcement effect is more pronounced for PU composites with aminosilane-treated CaCO3 filler in comparison to filler treated with glycidoxysilane.
N-Alkylacrylamide copolymers with (meth)acrylamide derivatives of cholic acid: Solution properties and aggregation
Authors: Avoce Damien , Baille Wilms E. , Zhu X. X.
Published: August 2014

Solution properties of a series of thermosensitive copolymers based on acrylamide and methacrylamide derivatives of cholic acid and N-alkylacrylamides such as N,N-diethylacrylamide, N-ethylacrylamide, and N-isopropylacrylamide have been studied by various techniques including fluorescence and turbidimetry. These copolymers contained 1 - 5 mol-% of the (meth)acrylamide derivatives of cholic acid as determined by NMR spectroscopy. A two-stage aggregation process was observed for the copolymers of N-isopropylacrylamide when the number of cholic acid residues was sufficiently high. The presence of the copolymers lowered the critical micellar concentration of sodium dodecyl sulfate but had little effect on the micellization of sodium cholate. The critical micellar concentration of these copolymers decreased with increasing content of cholic acid residues in the polymers.
On the durability of low-density polyethylene nanocomposites
Authors: Pandey Jitendra K. , Singh Raj Pal
Published: August 2014

Low-density polyethylene (PE) containing nano-particulate clay was prepared after functionalization with maleic anhydride (MA) by reactive grafting in the presence of peroxide followed by blending of maleated PE with neat polymer in different concentrations. Four classes of composites were obtained: (i) exfoliated, (ii) intercalated, (iii) microcomposites, and (iv) intermediate of intercalated and microcomposites, as evidenced by wide-angle X-ray diffraction. All samples were kept for artificial UV irradiation (λ ≥ 290 nm) and for composting to study their photo- and bio-durability. Fourier-transform IR spectroscopy (FT-IR) and scanning electron microscopy were used to monitor the functional group and morphological changes, respectively, whereas biodurability was evaluated by measuring the weight loss. MA functionalization and nature of composites have detrimental effects on the overall durability of composites. Nanocomposites showed higher resistance than microcomposites during initial weathering and composting with a long induction period. The stability of nanocomposites decreases with time and overall durability was worse than of pristine polymer in both environments. It was concluded that the initial protection is due to the filler-generated long diffusion path, which decreases the oxygen diffusion through the matrix. The bio-durability of composites decreased with oxo-degradation. Biodegradation of PE nanocomposites during composting follows the mechanism described by Albertsson et al. as evidenced by FT-IR spectroscopy.
Magnetic hydrogel beads based on chitosan
Authors: Paneva Dilyana , Stoilova Olya , Manolova Nevena , Rashkov Iliya
Published: August 2014

A novel effective route for incorporating magnetic material in chitosan beads by capillary extrusion is proposed. Magnetic material (Fe3O4) with particle size 2 μm and 10 nm was used. The weight ratio chitosan : Fe3O4 was varied in the range from 4:1 to 1:1. The obtained magnetic beads were modified by physical crosslinking with CuSO4, chemical crosslinking with epichlorohydrin, or were coated with a polyelectrolyte complex chitosan/poly(2-acryloylamido-2-methylpropanesulfonic acid). The morphology and the magnetic properties of the beads were studied by optical and scanning electron microscopy, and magnetometry. The magnetisation values of the beads increased on increasing the proportion of Fe3O4. A magnetic field intensity of 6 kOe was completely enough to reach orientation of all dipole moments of the incorporated Fe3O4. The magnetic beads completely sorbed a model dye - reactive red - from its aqueous solution, thus implying that such materials might be used for wastewater treatment in textile industry.
Degradation of networks composed of chitosan and polyacrylamide by a crude enzyme complex from Bacillus subtilis
Authors: Bonina Petranka , Petrova Tsvetanka , Manolova Nevena , Rashkov Iliya
Published: August 2014

The degradation of semi-interpenetrating and interpenetrating networks of chitosan and polyacrylamide - net-PAAm-sipn-chitosan, net-chitosan-sipn- PAAm and net-chitosan-net-PAAm, by a crude enzyme complex produced by the beneficial soil microorganism Bacillus subtilis was studied. The effect of the degree of crosslinking was examined under otherwise invariable conditions (pH 6, ionic strength I = 0.1, and 35°C). It was found that the lower the degree of crosslinking, the faster the enzymatic hydrolysis. Degradation of the three types of networks proceeded faster under the action of the enzyme complex from B. subtilis than by the enzymes from T. viride.
Synthesis and characterization of novel polyamides based on tridecanedioic acid: Nylons 3 13, 5 13, 6 13, 7 13, 9 13, 10 13, 11 13
Authors: Cui Xiaowen , Yan Deyue , Xiao Dan
Published: August 2014

Linear polyamides with high aliphatic content were prepared through step-heating melt polycondensation of tridecanedioic acid with various diamines. The synthesized polyamides were characterized comprehensively by means of IR, NMR and Raman spectroscopy. In addition, thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis were used to investigate thermal properties of the obtained polyamides. It was found that melting and crystallization temperatures decrease as the aliphatic content increases. X-ray diffraction was applied to determine the crystal structures of the polyamides.
The role of flow-induced crystallisation in melt spinning
Authors: Ziabicki Andrzej , Jarecki Leszek , Sorrentino Andrea
Published: August 2014

Flow-induced crystallisation in the course of melt spinning changes properties of as-spun fibres and modifies dynamics of the process. Velocity, stress and temperature profiles depend on the speed of on-line crystallisation. Very important but little studied is coupling between crystallinity and rheological properties of the polymer melt. Effects of crystallisation on the dynamics of melt spinning and on the rheological behaviour have been discussed and compared with model calculations and available experimental data.
Dynamic mechanical study of thermoplastic polyurethane/ polypropylene blends
Authors: Bajsić Emi Govorčin , Rek Vesna
Published: August 2014

Thermoplastic polyurethanes (TPU) are an important class of elastomers that found many novel and specialized applications where high mechanical and chemical performances are prerequisites. They are known for their good mechanical strength, wear and tear resistance, and low-temperature elasticity. The aim of this work is to study the viscoelastic behaviour of TPU, polypropylene (PP) and their blends using dynamic mechanical analysis. Blends of TPU+PP as well as samples of pure TPU and PP were prepared using a laboratory twin-screw extruder. Primary and secondary viscoelastic functions were determined. Primary viscoelastic functions, viz. storage modulus, loss modulus and loss tangent, were evaluated in the temperature range -100 to 250°C. The secondary viscoelastic functions creep, recovery and creep modulus were investigated in the creepfatigue regime at 25 - 65°C. A master curve at the reference temperature 25°C for the creep modulus of TPU, PP and TPU+PP blends was created by applying the time-temperature correspondence principle. The obtained results are discussed.
Properties of epoxy nanocomposites filled with carbon nanomaterials
Authors: Song Young Seok , Youn Jae Ryoun
Published: August 2014

Rheological, mechanical, electrical, and thermal properties of epoxy nanocomposites containing carbon nanomaterials (CNMs) were investigated with different loading. Two kinds of CNMs - multiwalled carbon nanotubes (MWNTs) and carbon blacks (CBs) - were selected to examine the effect of their geometrical structure on various properties. Under sonication, MWNTs and CBs (0.5, 1.0, and 1.5 wt.-%) were mixed with the epoxy resin by using a solvent. Dispersion of the CNMs in the epoxy nanocomposites was characterized by means of transmission electron microscopy and field emission scanning electron microscopy. Carbon nanotubes (CNTs)/epoxy composites show significant differences from the CBs/ epoxy composites due to their high aspect ratio. It was found that the CNTs/epoxy composites exhibit non-Newtonian rheological behaviour, while the CBs/epoxy composites with the same weight content show Newtonian behaviour. The CNTs/ epoxy composites have better mechanical and thermal properties than the CBs/ epoxy composites. In the CNTs nanocomposites, the percolation threshold of electrical conductivity is found to be less than 0.5 wt.-%, which is too low to be obtained by using other carbon materials such as carbon fibre in polymer composites. Effects of CNM content on the various properties were also examined. As loading of the CNMs increased, improved results were obtained.
Porous polymeric scaffolds for bone regeneration
Authors: Filipczak Katarzyna , Janik Ireneusz , Kozicki Marek , Ulanski Piotr , Rosiak Janusz M. , Pajewski Leonardo A. , Olkowski Radoslaw , Wozniak Piotr , Chroscicka Anna , Lewandowska-Szumiel Malgorzata
Published: August 2014

Solvent casting/particulate leaching has been used to synthesize highly porous polymeric scaffolds of controlled pore size, based on poly(methyl methacrylate) (PMMA) and poly(ε-caprolactone) (PCL). Obtained structures have a total porosity of c. 60%, with good interconnections between the pores. Porous scaffolds prepared using the greatest size of NaCl particles have the best mechanical properties. Both PMMA- and PCL-based materials can be sterilized by ionizing radiation. In the case of PCL-based scaffolds, irradiation causes cross-linking of polymer chains, which leads to an improvement of the mechanical properties of the scaffold. The compressive elastic modulus for non-porous samples increases with irradiation dose from 1.5 MPa for 0 kGy to 1.9 MPa for 280 kGy. Preliminary in vitro studies indicate good biocompatibility of both materials.