bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modified chitosan, 7 Graft copolymerization of methacrylonitrile onto chitosan using ammonium persulfate initiator
Authors: Pourjavadi Ali , Barzegar Shahram , Mahdavinia Gholam Reza 
Published: August 2014

Abstract Graft copolymerization of methacrylonitrile (MAN) onto chitosan using ammonium persulfate (APS) as an initiator was studied. The reactions were carried out under argon atmosphere in a homogenous aqueous phase containing a small portion of acetic acid (AcOH). Evidence of graft copolymerization was obtained by FTIR spectroscopy, e.g., the appearance of nitrile in the spectrum of chitosan-graftpolymethacrylonitrile. The synthetic conditions were systematically optimized through studying the influential factors including temperature, as well as concentrations of initiator, MAN, AcOH, sodium dodecyl sulfate surfactant (SDS) and chitosan. The effects of individual factors were investigated by calculating and monitoring the variation of the grafting parameters, i.e., grafting ratio, grafting efficiency, add-on value, homopolymer content, and total conversion. The optimum condition was achieved at APS 0.0108 mol/L, MAN 0.201 mol/L, 80°C, SDS 0.0016 mol/L, chitosan 0.5 g, AcOH 0.0086 mol/L. The overall activation energy for the graft copolymerization was determined to be 7.3 kJ/mol.
Surface modification of polyamides by direct fluorination
Authors: Solomun Tihomir , Schimanski Arnd , Sturm Heinz , Mix Renate , Illenberger Eugen 
Published: August 2014

Abstract Bulk samples and thin films of polyamides (PA6 and PA12) were exposed to fluorine (1 - 10 vol.-% F2 in N2) and analysed with photoelectron (XPS) and infrared spectroscopy. Fluorination affects both, the amide and the hydrocarbon parts of the polymers. However, only the carbon atom next to the carbonyl is readily fluorinated. Chemical modification of the amide group is apparent in a large binding energy shift (+5 eV) of the N1s level and the appearance of a νCO band at 1734 cm-1. It is concluded that the amide C-N bond is cleaved in the fluorination process and that COOH and NF2 end groups are formed. This conclusion is corroborated by the appearance of ester oxygen in the XPS and by the 19F NMR spectra of the volatile products that show fluorine signals chemically shifted about 200 ppm towards lower field as compared with the CHF environment.
Electrodeposition of mixed adherent thin films of poly(ethyl acrylate) and polyacrylonitrile onto nickel
Authors: Baute Noëlle , Geskin Victor M. , Lazzaroni Roberto , Brédas Jean-Luc , Arys Xavier , Jonas Alain M. , Legras Roger , Poleunis Claude , Bertrand Patrick , Jérôme Robert , Jérôme Christine 
Published: August 2014

Abstract Adherent thin polymer films have been prepared by sequential electrodeposition of ethyl acrylate (EA) and acrylonitrile (AN) onto nickel. Their composition has been studied by IR spectroscopy and time of flight - secondary ion mass spectrometry. Morphology and thickness have been analyzed by atomic force microscopy and ellipsometry, respectively, and compared to single component films of PEA and PAN. No microphase separation was detected in the mixed PEA/ PAN films. These show a granular morphology comparable to that of PAN films. The grains contain the two constitutive polymers, as confirmed by the selective thermal degradation of PEA.
Morphology and phase behaviour of poly(propylene oxide) containing copoly(ether ester)s
Authors: Lange Ronald F. M. , Gabrielse Wouter 
Published: August 2014

Abstract The morphology and phase behaviour of six different copoly(ether ester) elastomers, based on poly(butylene terephthalate) (PBT) hard blocks and poly- (ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b- PPO-b-PEO) soft blocks, differing in soft-block content and molecular weight of the soft block, have been investigated using various analytical techniques such as DSC, dynamic mechanical thermal analysis, dielectric spectroscopy, 13C CP-MAS NMR, AFM, TEM, and optical microscopy. The PBT blocks were found to crystallize in lamellar structures that form a continuous highly interconnected architecture. No crystalline regions for the PEO-b-PPO-b-PEO triblock could be observed, whereas no indications of a separate pure amorphous PBT phase were found. It is further shown that the amorphous phase is not a homogeneous mixture of amorphous PBT and soft segments. Based on the combined results of the analytical techniques used it is concluded that the PPO segments form an almost pure amorphous phase, whereas the PEO segments form a mixed phase with amorphous PBT. It is believed that the presence of this pure amorphous PPO phase provides the PEO-b-PPO-b-PEO containing copoly(ether ester)s with their excellent coldtemperature properties.
Fractionation and ammonolytic degradation of poly(hexamethylene carbonate) in (supercritical) ammonia
Authors: Mormann Werner , Spitzer David 
Published: August 2014

Abstract Solubility, fractionation by extraction as a function of temperature, and ammonolysis of α-hydro-ω-hydroxy-poly(oxycarbonyloxyhexane-1,6-diyl) in liquid and supercritical ammonia have been studied. Up to 120°C, the solubility of poly- (hexamethylene carbonate) increases with temperature without significant ammonolytic cleavage. Above the critical temperature of ammonia, solubility and molar mass of the solute decrease as ammonolysis becomes more and more important. The molar mass of the extracted and residual polymer decreases with temperature under supercritical conditions. Adjusting residence time and reactivity through temperature and flow rate enables controlled ammonolysis to constant molar mass. Kinetics of dihexyl carbonate and hexyl carbamate shows that ammonolysis of the carbamate is much faster than of dihexyl carbonate.
Influence of the structure of new poly(amide-imide)s on their optical properties
Authors: Sęk Danuta , Grabiec Eugenia , Sobolewska Anna , Miniewicz Andrzej 
Published: August 2014

Abstract Two classes of poly(amide-imide)s with mono- and bisazoaromatic chromophores in the side chain have been synthesized using one-step hightemperature polycondensation. The influence of the structures of the macromolecules on their properties was investigated. Preliminary results of the kinetics of holographic grating recording using 514.5 nm Ar+ laser light for chosen poly(amideimide) films are presented. The gratings were recorded using two linearly polarized beams with s-s or s-p configurations. For comparative purposes all experimental conditions (light intensity, two-beams intersection angle) were kept unchanged. It was found that time constants of grating build-up were significantly larger for polymers containing a chromophore with two azo groups when compared with the same polymers having a single azo group. On the other hand diffraction efficiencies were lower for polymers containing a chromophore with two azo groups than with a single azo group.
Scale-free power-law distribution of branched polymers formed in a continuously stirred tank reactor: Simple relationship for the exponent
Authors: Tobita Hidetaka 
Published: August 2014

Abstract The high-molecular-weight tail of the molecular weight distribution (MWD) of branched polymers formed via free-radical polymerization involving polymer transfer reactions conducted in a continuously stirred tank reactor (CSTR) follows a power-law distribution. The exponent, α, of the weight fraction distribution W(M) ~ M-α is determined by the Pb value, which represents the probability that the chain end is connected to a backbone chain, with the simple relationship, α = 1/Pb. Since α > 1, the number-average molecular weight will always reach a stationary-state value but the weight-average and higher-order averages of molecular weights may continue to increase without limit under ideal CSTR conditions. Because it takes an infinitely long time for the second or a higher moment of the MWD to go to infinity, the kinetic behaviour is significantly different from usual gelation phenomena. The i-th moment of the MWD goes to infinity for Pb ≥ 1/i.
Time-temperature and time-stress correspondence in nonlinear creep. Experimental behaviour of amorphous polymers and quantitative modelling approaches
Authors: André José R. S. , Pinto José J. C. Cruz 
Published: August 2014

Abstract Non-linear creep is described by a non-simulative, analytical, dynamic molecular modelling approach. Elementary, molecular-scale, process-relevant frequencies are derived by adequate kinetic formulation. They follow almost exactly an Arrhenius-like behaviour with a range of activation enthalpies. Their relative contribution to the overall macroscopic behaviour of the materials is quantified to account for the materials’ retardation time spectra and final non-Arrhenius behaviour. A new creep compliance equation is derived, yielding a fully coupled timetemperature- stress formulation, with long-term predictive capability. Experimental data for poly(methyl methacrylate) are analysed to identify the extent to which timetemperature and time-stress correspondence relationships may be valid, and it is shown that they are approximations (especially the latter), limited to narrow ranges of experimental variables, in contrast to the proposed model, which more reasonably fits the experimental behaviour.
Unsteady bi-directional heat transfer with heat generation by crystallization in high-density polyethylene
Authors: Baré Wadou , Albano Carmen , Papa José , León Luis 
Published: August 2014

AbstractA method of coupling the heat transfer during the cooling process of a molten sample of high-density polyethylene (HDPE) and the heat released by crystallization is presented. From the simulated temperature profiles it is possible to obtain the thermal diffusivity, which is one of the physico-chemical properties characterizing heat transfer under non-stationary conditions. Using suitable initial and boundary conditions, it was possible to solve the heat equation analytically. The results obtained for HDPE, using the diffusivity α = 0.00197 cm2/s, show an increase in the temperature profile when the term due to crystallization is taken into account, compared to the temperature profiles without heat generation between 140 - 110°C. This temperature range, where crystallization of HDPE occurs, was determined using differential scanning calorimetry. A cylindrical conductivity cell was constructed with a thermocouple placed at varying positions. Comparing the simulated temperature profiles including heat generation by crystallization with the experimental data, we find that in the latter case the increase in the temperature profile was less significant; this is probably due to the assumptions made in the development of the kinetic equation.
Fast HPLC analysis of poly(ethylene oxide)s for highthroughput experimentation
Authors: Pasch Harald , Brüll Adele , Cabrera Karin 
Published: August 2014

AbstractLiquid chromatography of polymers is traditionally a slow technique with analysis times of typically 30 min per sample. For the application of liquid chromatographic techniques in combinatorial materials research the analysis time per sample must be reduced considerably. For fast high performance liquid chromatography (HPLC) small columns and new stationary phases with improved separation efficiencies can be used. HPLC separations of poly(ethylene oxide)s with different end groups can be conducted in less than 4 min. Accordingly, with new column technology and optimized separation methods time savings of more than 90% can be achieved as compared to conventional technology.
Effects of photo-oxidation on tensile deformation behaviour in low-density polyethylene
Authors: Miyagawa Eiichi , Nitta Koh-hei , Tanaka Akira 
Published: August 2014

AbstractQuenched low-density polyethylene (LDPE) films were photo-oxidized with a xenon arc lamp at 63°C for 12 days. The effects of photo-oxidation on the deformation behaviour of LDPE films were investigated by a rheo-optical method in which IR dichroism was examined under uniaxial extension. The orientations of the oxidized segments introduced by photo-irradiation as well as of LDPE crystals were measured simultaneously with tensile deformation. The crystalline parts dominate the deformation before yielding but the orientation of oxidized segments gradually increases after yielding and has a maximum just before the break point.
Synthesis and characterization of poly(methyl methacrylate) obtained by ultrasonic irradiation
Authors: Parra Cristina , González Gema , Albano Carmen 
Published: August 2014

AbstractWe have studied the influence of surfactant nature and concentration, and monomer concentration on the synthesis of poly(methyl methacrylate) (PMMA) using high-frequency ultrasound. Polymerization was carried out via free radicals from aqueous solutions with several concentrations of an anionic (sodium lauryl sulfate, SLS) or a cationic surfactant (cetyltrimethylammonium bromide, CTAB) and different concentrations of the insoluble monomer methyl methacrylate (MMA) as the dispersed phase. The polymer particles obtained were characterized by FTIR, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The IR spectra show the presence of the characteristic absorption bands for PMMA when SLS was used. When CTAB was employed, for all surfactant concentrations and high monomer concentration (14% v/v), PMMA was obtained. However, bands of the surfactant were present for lower monomer concentrations. The glass transition temperature measured by DSC was in the range 106 - 126°C characteristic of PMMA. Maximum conversion was obtained when the anionic surfactant was employed. SEM studies show the formation of sub-micrometric PMMA latex spheres with average particle size from 65 to 100 nm when the anionic surfactant was used and 65 nm - 0.3 μm for the cationic surfactant.
Alginate hydrogel – candidate support for cell transplantation
Authors: Woźniak Piotr , Kozicki Marek , Rosiak Janusz M. , Przybylski Jacek , Lewandowska-Szumieł Malgorzata 
Published: August 2014

AbstractHuman cartilage derived cells were encapsulated in alginate hydrogel beads. Viability of the cells was determined using both qualitative (microscopy) and quantitative (MTT and NR assays) examination. Microscopy indicated that encapsulated cells remained viable during the 7-days experiment. The quantitative tests failed to give reliable results. Possible factors affecting the results of the quantitative study are discussed.
Sulfonated poly(arylene thioether ketone ketone sulfone)s for proton exchange membranes with high oxidative stability
Authors: Shen Liping , Xiao Guyu , Sun Guoming 
Published: August 2014

Abstract Sulfonated poly(arylene thioether ketone ketone sulfone)s (SPATKKS) were synthesized by nucleophilic polycondensation of various amounts of 1,3- bis(4-fluorobenzoyl)benzene, 1,3-bis(3-sodium sulfonate-4-fluorobenzoyl)benzene, and 4,4’-dichlorodiphenylsulfone with 4,4’-thiobisbenzenethiol. Sulfonated poly- (arylene ether ketone ketone sulfone)s were also prepared in order to compare their oxidation resistance to peroxides with that of SPATKKS. SPATKKS show high oxidation resistance to peroxides. The resulting ionomers with moderate ion exchange capacity present excellent thermal stability (the 5% weight loss temperature is about 500°C) and low water uptake and swelling ratio until 85°C. The materials hold promise for application as proton exchange membranes in fuel cells.
New supramolecular crystalline polymer structure of syndiotactic polystyrene
Authors: Heeringen Mark van , Vastenhout Bob , Koopmans Rudy , Aerts Ludo 
Published: August 2014

AbstractSemi-crystalline polymers such as polyethylene and isotactic polypropylene are known to yield lamellar meso-structures through macromolecular chain folding upon solidification from the molten state. The lamellae typically assemble to form microscopic spherulitic or ‘shish-kebab’ super structures depending on the cooling condition being either quiescent or induced during flow. Cooling experiments with concentrated solutions of syndiotactic polystyrene, however, unexpectedly yielded a novel microscopic superstructure resembling a ‘bird nest’. These super structures can be made reproducibly under specific conditions. They reflect the impact of a chiral centre on the molecular organisation on the meso and micro level during a solidification process.
Enhancement of sensitivity and selectivity in surface plasmon resonance detection of a DNA point mutation by polymeric microspheres
Authors: Kawaguchi Haruma , Sato Yasunobu , Okumura Aya , Kyo Motoki 
Published: August 2014

AbstractPolymeric microspheres were used to enhance sensitivity and selectivity in the detection of DNA point mutations with a surface plasmon resonance (SPR) biosensor. First, single-strand DNA probes were immobilized onto epoxy group derivatized gold surfaces and the hybridization of DNA targets was monitored. SPR response was small. The subsequent interaction with DNA-carrying microspheres enhanced the response due to a significant increase of mass bound to the targets. After this, the flow rate of the buffer solution was increased during dissociation. An increase in shear stress resulted in the detachment of DNA-carrying microspheres hybridized with mismatched pairs and so the increasing ability to discriminate the point mutation. The same effect was reached by an increasing viscosity of the buffer solution.
Macrocyclic oligomers of an aromatic polyetherketone based on bisphenol A and difluorobenzophenone
Authors: Blagodatskikh Inessa , Sakunts Artur , Shaposhnikova Vera , Salazkin Sergey , Ronova Inga 
Published: August 2014

AbstractCyclization reactions accompanying the nucleophilic displacement polymerization of bisphenol A and difluorobenzophenone (DFB) were studied. Size distribution and amounts of cyclic species were determined depending on the concentration and isomerism in DFB. Experimental cyclization constants were found to be consistent with the values calculated using Jacobson and Stockmayer’s theory for a freely rotating chain of virtual bonds in the case of 4,4’-DFB. For 2,4’-DFB, hindered rotation around some virtual bonds should be taken into account.
Magnetic poly(glycidyl methacrylate) microspheres for Campylobacter jejuni detection in food
Authors: Horák Daniel , Hochel Igor 
Published: August 2014

AbstractA sandwich enzyme labelled immunoassay (ELISA) has been developed for the detection of Campylobacter jejuni in food using magnetic poly(glycidyl methacrylate) (PGMA) microspheres as an alternative solid phase. The microspheres (c. 2.5 μm in diameter) were prepared by dispersion polymerization in the presence of carboxymethylcellulose-coated Fe3O4 - obtained by precipitation of Fe(II) and Fe(III) salts with aqueous ammonia - finely dispersed in ethanol/water solution using poly(vinylpyrrolidone) and 2,2’-azoisobutyronitrile as stabilizer and initiator, respectively. PGMA microspheres were ammonolyzed and the antibody against Campylobacter jejuni was immobilized via the 2,4,6-trichloro-1,3,5-triazine method. The optimal concentration of the second hen IgY was 50 μg/ml and the optimal concentration of the labelled antibody (rabbit anti-hen IgY immunoglobulin-horseradish peroxidase complex) reached 4 μg/ml. The detection limit of the assay was 4.8⋅106 cfu/ml. A limited number of artificially contaminated and uncontaminated food samples have been tested. Only one false-negative and one false-positive result (out of 18) were observed.
Determination of chemical composition and molar mass distribution of random styrene-ethyl acrylate copolymers by high-throughput liquid chromatography
Authors: Romero Iván García , Bashir Mubasher Ahmed , Pasch Harald 
Published: August 2014

AbstractSynthesis and characterization of random copolymers by spectroscopic and chromatographic techniques are normally slow and expensive because most measurements are conducted consecutively and no high-throughput techniques are used. In the present work parallel synthesis and high-throughput analytical techniques for random styrene-ethyl acrylate copolymers were developed. With combinatorial methods, high-throughput instruments and a better design of experiments, the molar mass and chemical composition analyses were carried out simultaneously with time savings of more than 90% as compared to conventional set-ups. The chemical heterogeneity of high-conversion styrene-ethyl acrylate copolymers was determined successfully by fast gradient HPLC. Determination of the average composition was carried out via selective UV detection in size exclusion chromatography. The results were verified by 1H NMR and calculations based on the copolymerisation parameters. Differential scanning calorimetry and optical microscopy techniques were used for determination of the phase separation behaviour of the copolymers and correlated with the chemical heterogeneity.
Facile synthesis of potato starch sulfate magnesium salts
Authors: Staroszczyk Hanna , Tomasik Piotr 
Published: August 2014

AbstractPotato starch blended with MgSO4 and conc. H2SO4 - Mg(HSO4)2 generated in situ - forms directly starch sulfate magnesium salts. Properties of the products depend, first of all, on whether convectional heating (60 - 70°C for 1 h) or microwave heating for either 30 min at 180 W or 5 min at 300 W is applied. Starch monoester and crosslinking diester are formed. The products are up to 95% watersoluble. They were characterized by means of thermal gravimetry and differential thermogravimetry, FTIR spectroscopy, and elemental analysis for Mg. Resulting products are potential plasticisers for cement, mortar, concrete, or other products containing hydraulic binders.
Characterization, structural transitions and properties of a tightly crosslinked polythiourethane network for optical applications
Authors: Jaffrennou Boris , Droger Nicolas , Méchin Françoise , Halary Jean-Louis , Pascault Jean-Pierre 
Published: August 2014

AbstractA new polythiourethane thermosetting system based on a diisocyanate and a trithiol was studied. After characterization of the reactive species, two critical temperatures, namely Tg∞ (maximum glass transition temperature of the thermosetting system) and gelTg (Tg of the material at the gel point), were determined. The conversion at gel point was also determined and compared to the theoretical prediction. Two different characteristics of the evolution of a reactive system, Tg and conversion x as a function of time, were related. This is of particular interest for understanding the curing process, especially when non-isothermal cure schedules are used. Viscoelastic and plastic properties were investigated, with the aim of establishing connections between the chemical structure and properties through detailed analysis of the polymer chain motions (β and α relaxations). Measurements of the storage modulus at the rubbery plateau and of the critical strain intensity factor KIc complete the study.
Stabilization of commercial polyacrylonitrile fibres for fabrication of low-cost medium-strength carbon fibres
Authors: Eslami Farsani Reza , Shokuhfar Ali , Sedghi Arman 
Published: August 2014

AbstractThe process of fabrication of carbon fibres from polyacrylonitrile (PAN) fibres is composed of two steps including oxidative stabilization at low temperature and carbonization at high temperature in an inert atmosphere. Due to the high price of the raw material (special PAN fibres), carbon fibres are still expensive. It is shown that it is possible to produce desirable carbon fibres from (cheaper) commercial PAN fibres. In order to achieve this, it is necessary to make some changes in the conventional stabilization procedure to reach complete stabilization.