bluuebunny/crossref_metadata_2025 huggingface dataset:
Macromolecular design of the network structure of copolymers of ethylene glycol dimethacrylate with methyl methacrylate using the catalytic chain transfer reaction
Authors: Kurmaz Svetlana V. , Bubnova Maria L. , Perepelitsina Evgenia O. , Estrina Genrietta A.
Published: August 2014

It has been shown that catalytic chain transfer reaction is an effective instrument for the macromolecular design of the network structure of copolymers of ethylene glycol dimethacrylate with methyl methacrylate. Copolymers of various macromolecular architectures - from networks to soluble branched low-molecularweight oligomers - have been produced using cobalt porphyrin as catalytic chain transfer agent. The influence of cobalt porphyrin on the kinetics of copolymerization, structure and properties of final copolymers has been studied.
A study of aging in dental composites using IR and Raman spectroscopy
Authors: Pallikari Fotini , Iosifidou Soultana
Published: August 2014

The application of dental restorative composites has opened wide possibilities in modern dentistry. The dental pastes studied in this work consist of a dimethacrylate-based matrix to which silica or ceramic fillers are added to improve their mechanical properties, colour stability and aesthetic appearance. The pastes were cured through free-radical polymerisation with visible light and were subjected to accelerated aging in the laboratory. The degree of monomer conversion with photo-curing, studied with FTIR and FT-Raman spectroscopy, was 42 ± 2% on average, which further advanced after aging to 56 ± 4%. The samples exhibited fluorescence at various intensities, which declined by the curing and aging procedures by a maximum of c. 20%, depending on the type of fillers present.
Microwave dielectric properties of glass-reinforced polymers
Authors: Costa Luís Cadillon , Devesa Susana , André Paulo
Published: August 2014

The well-balanced combination of properties of some polymers makes them good materials for industrial microwave applications, such as telecommunications or microwave ovens. Particular electrical properties are usually needed and can be controlled by additives. In this work, we present the results of complex dielectric permittivity measurements, ε* = ε’ - iε’’, in the microwave frequency region (2.7 and 12.8 GHz), at constant temperature 300 K, on different glass-reinforced and pigmented plastics (poly(butylene terephthalate), polypropylene and acrylonitrile- butadiene-styrene), using the resonant cavity method. We measured the shift in the resonant frequency of the cavity, Δf, caused by the insertion of the sample, which can be related to the real part of complex permittivity, ε’, while the change in the inverse of the quality factor of the cavity, Δ(1/Q), gives the imaginary part, ε’’.
Kinetic investigation of styrene emulsion polymerization with surface-active polyelectrolytes as emulsifier, 1 Kinetic study
Authors: Kato Satoshi , Suzuki Kiyoshi , Nomura Mamoru
Published: August 2014

A copolymer of methyl methacrylate and methacrylic acid to be used as a polymeric surfactant was synthesized by emulsifier-free semi-batch emulsion copolymerization. Emulsion polymerization of styrene was carried out at 50°C utilizing the ammonium salt of the copolymer as the polymeric emulsifier and potassium persulfate as the initiator, respectively. Both the number of polymer particles produced and the rate of polymerization were proportional to the 0.6 power of the initial emulsifier concentration, to the 0.4 power of the initial initiator concentration, and independent of the initial monomer concentration, respectively. These relationships are almost the same as those observed in the emulsion polymerization of styrene conducted using conventional surfactants like sodium dodecyl sulfate as the emulsifier and potassium persulfate as the initiator.
A facile method to prepare methylcellulose from annual plants and wood using iodomethane
Authors: Ye Daiyong , Farriol Xavier
Published: August 2014

A novel facile method was developed to prepare methylcellulose from miscanthus, cardoon and eucalyptus. Pulps were obtained by the impregnation rapid steam pulping process (IRSP). A total-chlorine-free (TCF) method was used to bleach the pulps with hydrogen peroxide. Bleached pulps were mercerized in 40% NaOH solution for one hour at ambient temperature. Mercerized cellulose reacted with iodomethane in 2-propanol slurry at 60°C for 22 h. Mercerization and methylation were repeated. Intrinsic viscosities of methylcellulose were measured in 4% NaOH solution. Super-molecular substitution patterns of methylcellulose were determined by 13C NMR. Molecular weights of methylcellulose were measured in dimethyl sulfoxide by gel permeation chromatography. Pulping severity is a key factor influencing the properties of the methylcellulose prepared.
Coagulation kinetics and the stability of surfactant-free emulsion-polymerised latexes
Authors: Sadiku E. Rotimi , Sanderson Ron D.
Published: August 2014

The stability factor of styrene/sulfopropyl methacrylate (styrene/SPM) and styrene/3-[N,N-dimethyl-N-(methacryloxyethyl)ammonium]propane sulfate (styrene/ SPE) latexes was studied using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and the critical coagulation concentration, CCC, was deduced for the latexes. Photon correlation spectroscopy was used to study ionic stabilities. The stability factor was determined as the ratio of the rate constant for rapid coagulation to that of slow coagulation, obtained from the coagulation kinetics data. The log-log plot of the stability factor, W, as a function of NaCl electrolyte concentration shows an asymptotic decrease in W of both latexes. DLVO theory was successfully employed, whereby the characteristic properties of the diffuse electric double layers or the Stern layers around latex particles in terms of their Hamaker constants and diffuse potentials were determined. The electric double layer thickness decreases with increasing NaCl concentration. Stability curves revealed a higher CCC value for the styrene/SPM latex than for the styrene/SPE latex, which is in accordance with the higher surface charge density and an indication of a better stability.
Extraction and characterization of polysaccharides from Mesembryanthemum crystallinum
Authors: M’sakni Nour H. , Zayane Hamouda , Majdoub Hatem , Morvan Claudine , Roudesli Sadok , Deratani André
Published: August 2014

Water-soluble polysaccharides were isolated from Mesembryanthemumcrystallinum. Two methods were applied, based (i) on the extraction in hot water (for fresh and dry plants, FP and DP) and (ii) on freeze-thawing of fresh plants (FT). Each fraction was purified by precipitation in ethanol followed by ultrafiltration of recovered solids dissolved in water through a membrane with a molecular weight cut off of 100 000. Elemental analysis demonstrated that the extracted products were polysaccharides exempt from proteins. The yield relative to the corresponding dry matter varied from 1.6 to 3% depending on the starting sample and the extraction process. Obtained products were characterised by their structural (sugar composition, degree of methylation (DM) and acetylation, molar mass of acid equivalent unit) and macromolecular characteristics (molar mass and intrinsic viscosity). A galacturonic-acid content larger than 65% and a DM value of c. 40% showed that the isolated polysaccharides belong to the fairly methylated pectin class. FP and FT structures consisted of the two blocks homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) with relative proportions of 62 - 68% and 29 - 34%, respectively. They showed very similar physicochemical behaviour. On the other hand, DP exhibited significant differences in the chemical structure (50% HG and 46% RG-I blocks) and physical properties, indicating that partial degradation of HG moieties occurred during plant drying.
Morphology of nanocomposites from ethylene-acrylic acid copolymers
Authors: Magagnini Pierluigi , Filippi Sara , Marazzato Cristina , La Mantia Francesco P. , Minkova Liliya I.
Published: August 2014

New nanocomposites have been prepared by melt-compounding from commercial ethylene-acrylic acid copolymers (EAA) of different molar mass, molecular structure (branched or linear) and AA concentration, and a Zn-ionomer, with three commercial clays containing different proportions of the same organic modifier (dimethyldi(hydrogenated tallow)ammonium ion). Their morphology has been preliminarily investigated by X-ray scattering and transmission electron microscopy. The nanocomposites showed disordered intercalated morphology, with an expansion of the average gallery height, which appears to depend quite strongly on the molecular architecture of the EAA, whereas the other investigated variables, including the excess of surfactant used to organically modify the silicate, have negligible effect.
Annealing effects on the electrical conductivity of polymerized liquid crystalline 3,4-ethylenedioxythiophene derivatives
Authors: Wrubbel Noelle , Ritter Helmut , Reuter Knud , Karbach Alexander , Drechsler Doris
Published: August 2014

3,4-Ethylenedioxythiophene derivatives with aromatic, in most cases mesogenic, side groups were synthesized and their liquid crystal behaviour was characterized. These monomers were polymerized oxidatively to charged, electrically conductive polythiophenes. X-ray and atomic force microscopy studies were performed. Films of theses polythiophenes achieved via in situ polymerization were prone to a significant increase of the conductivity by annealing.
Emulsion copolymerization of hydrophobic and hydrophilic monomers: an experimental study with styrene and 2- hydroxyethyl methacrylate
Authors: Ahmad Hasan , Islam A.H.M. T. , Hossain M. Amran , Miah M.A. Jalil , Tauer Klaus
Published: August 2014

Ab initio emulsion copolymerization of styrene with 2-hydroxyethyl methacrylate (HEMA) at weight ratios of the hydrophilic monomer of 1 and greater was investigated at various temperatures in dependence on the concentration of sodium dodecylsulfate (SDS) and potassium peroxodisulfate as emulsifier and initiator, respectively. Both the course of the polymerization and the latex properties are strongly influenced by the hydrophilic monomer. For instance, transparent or highly translucent latexes are obtained resembling the appearance of microemulsion latexes with polymer contents as high as 10 weight-% but at much lower surfactant concentration. Moreover, polymerization rate, average particle size, and particle morphology depend on the surfactant and initiator concentration, monomer feed composition, and polymerization temperature.
Use of new hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs): Influence of isocyanate and chain extender nature and their equivalent ratios on the mechanical and thermal properties of PUs
Authors: Kébir Nasreddine , Campistron Irène , Laguerre Albert , Pilard Jean-François , Bunel Claude , Couvercelle Jean-Pierre
Published: August 2014

New segmented polyurethanes (thermoplastic-elastomers) based on previously described hydroxytelechelic cis-1,4-polyisoprene (HTPI), miscellaneous isocyanates and chain extenders at various equivalent ratios were prepared by the classical one-shot method. The influence of the nature of isocyanate and chain extender, as well as their equivalent ratios, on the mechanical and thermal materials behavior was investigated. Thus, a comparative assessment of material properties was performed. Microphase separation of hard and soft segments was observed by DMTA, DSC and AFM. Moreover, according to Thermogravimetric Analysis (TGA), linear relationships depending on the isocyanate and chain extender nature were found between the weight loss (%) and the percentages of hard segments. A classification of thermal stability in terms of weight loss was established. With the aim of a thermo-mechanical comparative study, polyurethane elastomers based on HTPI and isocyanates without chain extender, were also synthesized.
Development and Characterization of Bismaleimides Containing Aliphatic Chain for Microelectronics Application
Authors: Feng J. L. , Yue C. Y. , Chian K. S.
Published: August 2014

A series of bismaleimide systems containing aliphatic backbone chain have been synthesized and investigated. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Thermomechanical analysis (TMA), rheometry and tensile test were used to characterize the thermal and mechanical properties. It was noted that backbone chain length and odd-even effect affected properties. As the chain length increases, the curing peak temperature, gel temperature of BMI all increase, but the melting point, glass transition and moisture absorption decrease. The melting points of BMI-3,5,7 reduced most significantly. The tensile properties were affected by odd even effect significantly. BMI-3,5,7 with odd number of carbons have less stress and strain than those of even ones.
DEA and DSC study of cubic silsesquioxane epoxy resin nanocomposites
Authors: Dias Filho Newton Luiz , Aquino Hermes Adolfo de
Published: August 2014

Non-isothermal dielectric analysis (DEA) and differential scanning calorimetry (DSC) techniques were used to study the epoxy nanocomposites prepared by reacting 1,3,5,7,9,11,13,15-octa[dimethylsiloxypropylglycidylether] pentaciclo [9.5.1.13,9.15,15 .17,13] octasilsesquioxane (ODPG) with methylenedianiline (MDA). Loss factor (ε”) and activation energy were calculated by DEA. The relationships between the loss factor, the activation energy, the structure of the network, and the mechanical properties were investigated. Activation energies determined by DEA and DSC, heat of polymerization, fracture toughness and tensile modulus show the same profile for mechanical properties with respect to ODPG content.
Synthesis and radical polymerizations of acrylamides having Gabapentin moieties
Authors: Akat Hakan , Balcan Mehmet
Published: August 2014

The synthesis and radical polymerizations of several acrylamides having Gabapentin(GBP) moieties were examined. The monomers were prepared by the reactions of 1-aminomethyl-1-cyclohexane acetic acid salts with acryloyl chloride in the presence of triethylamine in moderate yields. Radical polymerizations of the monomers were carried out in the presence of AIBN (3 mol%) in Dimethyl formamide (DMF) with moderate yield. The thermal behavior of the polymers was investigated by thermo gravimetric analysis (TGA) and differential scanning calorimeter (DSC) to determine the thermal degradation pattern and glass transition temperature (Tg). The resulting polymers showed a thermal stability up to 400 °C. The glass transition temperatures of the polymers were found not to depend on the substituents of the GBP moieties. Nearly the same TG’s were observed for polymers. We found the molecular weights of the polymers to be between 20700 and 2300 g/mol. We obtained poly(HFCHA) as a water-soluble polymer. Poly(MFCHA), poly(EFCHA) and poly(PFCHA) were soluble in common solvents.
Morphological and chromatographic characterization of molecularly imprinted monolithic columns.
Authors: Sirc Jakub , Bosakova Zuzana , Coufal Pavel , Michalek Jiri , Pradny Martin , Hobzova Radka , Hradil Jiri
Published: August 2014

The chromatographic stationary phases based on molecularly imprinted monoliths were prepared by free radical polymerization and subsequently characterized. The mixture of commonly used comonomers of ethylene dimethacrylate/methacrylic acid was polymerized in presence of various porogenic mixtures. Tosyl-L-phenylalanine was selected as a model template. Polymerization steps were carried out in the glass columns (i.d. of 3.3 mm) enabling UV initiation. Difficulties encountered with polymerization in situ, e.g. volume contraction and adhesion of polymer onto the glass inner wall, were successfully solved. The morphology of monoliths was investigated by electron microscopy, mercury porosimetry and surface area measurements. The influence of polymerization conditions on monolith morphology and subsequent chromatographic properties was evaluated. Polymers prepared by UV polymerization showed higher total porosity and the most frequent pore radius compared to the same polymers prepared thermally. The prepared monoliths by UV irradiation were also significantly more permeable for mobile phase during the chromatography tests. Morphology of monoliths prepared in dodecanol/toluene porogenic mixture markedly depended on the temperature of polymerization; the most frequent pore radius decreased with increasing temperature. From chromatographic point of view, monolithic columns were tested by separations of standard hydrophobic solutes. Height equivalent to a theoretical plate reached the values of approx. 25 μm, Walters indices of hydrophobicity laid slightly above 3. Prepared monoliths were compared to the conventional columns, filled with the particles prepared from the polymer of the same composition and preparation. In many cases the monolithic columns showed better chromatographic parameters.
On polyamide 6-montmorillonite nanocomposites obtained by in-situ polymerization
Authors: Monticelli Orietta , Musina Zenfira , Ghigliotti Francesca , Russo Saverio , Causin Valerio
Published: August 2014

Nanocomposites based on polyamide 6 (PA6) and montmorillonite-type (MMT) commercial clays, either unmodified or organically modified, were prepared by in-situ polymerization of ε-caprolactam (CL). The above materials were characterized in detail by a number of experimental techniques, including transmission electron microscopy (TEM), wide angle X-ray diffraction (WAXD), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The formation of nanostructured systems was checked not only for the commonly used ω-aminoacid-modified clay, but also for other types of organoclays. In general, a correlation was found between nanoscopic swelling of the clay in molten CL, measured by X-ray diffraction, and level of clay dispersion in PA6. Specifically, with the most swellable clays, completely exfoliated nanocomposites were obtained. However, also layered silicates modified by compatibilizers having carboxy groups, because of the active role of latter in CL polymerization, formed delaminated nanocomposites despite their low degree of swelling in CL monomer. Both molecular mass and crystallinity of the polyamide matrix were found to be strongly influenced by the presence of specific layered silicates. In particular, some characterization techniques (WAXD, FTIR) have evidenced a close relationship between the MMT used and PA6 crystal structure. Namely, PA6 γ-form is promoted by clay with compatibilizer bearing the carboxy group, which is able to induce the polymer to be tethered on the silicate layers, thus provoking conditions of restricted mobility to occur.
Construction of an arranged nano-fibrous structure by selforganization of a designed amphiphilic peptide based on β- strand
Authors: Hattori Makoto , Hayashi Shujiro , Yokoi Hidenori , Tanaka Masayoshi , Kinoshita Takatoshi
Published: August 2014

An amphiphilic peptide having alternate sequence of hydrophobic and charged amino acid residues, RFDF16 (CH3CO-RFDFRFDFRFDFRFDF-NH2), was designed to form a β-sheet monolayer at the air/water interface. The peptide monolayer was prepared by Langmuir-Blodgett (LB) method. The LB films were transferred onto mica substrates without the compressing process at various pH values in order to investigate a self-organized structure of peptide monolayer. Surface morphology of LB films showed arranged nano-fibers which have differences in interval between fibers and their orientation depending on pH of the subphase. On the other hand, the self-organized nano-fiber was also re-arranged by compressing process. The nano-fibers became elongated and aligned upon compression to higher surface pressures. The exploitation of an electrostatic interaction and compressing process will allow a larger two-dimensionally regulated nano-structure.
Reversible Addition-Fragmentation Chain Transfer (RAFT) Polymerization of Vinyl Monomers Initiated by Poly(methyl methacrylate) Peroxide
Authors: Zhang Zhengbiao , Zhu Xiulin , Zhu Jian , Cheng Zhenping
Published: August 2014

Poly(methyl methacrylate) peroxide (PMMAP) was synthesized and used as the initiator in the reversible addition-fragmentation chain transfer (RAFT) polymerization. Methyl methacrylate (MMA) as the monomer and 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the chain transfer agent was used in the polymerization system. The polymerization was successfully initiated by PMMAP while maintaining features of “living”/controlled radical polymerization such as the number-average molecular weights (Mn) increasing linearly with the monomer conversions and low polydispersity index (PDI) values. The results of 1H NMR and IR spectra confirmed that a small quantity of polymer chains were derived from the PMMAP moieties. The PMMAP can also initiate the RAFT polymerization of styrene (St) and methyl acrylate (MA), and the polymerization proceeded in a “living”/controlled fashion.
Effect of addition of organic solvents on properties of the chemically synthesized polyaniline in aqueous solutions
Authors: Xing Shuangxi , Jing Shengyu , Zhao Chun , Wang Zichen
Published: August 2014

In the process of polymerization of aniline in aqueous solution, different kinds or volumes of organic solvents were added. The effects of the organic solvents on the morphology, structure, conductivity and water-dispersity of the resulting polyaniline (PANI) were investigated with the aid of SEM, UV-Vis, FT-IR and Raman spectra and conductivity measurements. The results showed that the weak H-bond interactions between PANI and the solvents might play an important role in forming uniform nanofibers with relatively high conductivity and good waterdispersity. However, excessive addition of organic solvents led to the aggregation of the nanofibers and the corresponding PANI had a bad water-dispersity.
Synthesis and stimuli-responsive properties of Polyacrylic acid and Polyacrylamide Trapped with Polysodium-pstyrenesulfonate semi-IPN hydrogels
Authors: Wang Yansong , Wu Chengxun
Published: August 2014

A series of Polyacrylic acid (PAA)/Poly (Sodium-p-styrenesulfonate) (PSS) and Polyacrylamide (PAAm)/PSS semi-IPN hydrogel with different contents of PSS were prepared. The swelling behaviour of PAA hydrogel in alkaline environment was improved while the swelling ratio of PAAm hydrogel was decreased after PSS was added. With the increase of ionic strength in solution, the swelling ratios of PAA/PSS and PAAm/PSS showed a decreasing trend. Moreover the swelling ratio of PAAm/PSS decreased more quickly than that of PAA/PSS. The swelling speed of PAA and PAAm both decreased after adding PSS and a more rapid responsive speed was found in the former system. The experiment of in vitro drug release showed that the drug release speed from PAAM/PSS semi-IPN hydrogel was slower than that from PAA/PSS semi-IPN hydrogel. These results suggested that the polymer composition and the trapped polyelectrolyte made a great influence on the drug release behavior.
Adsorption Behaviour of Methylene Blue from Aqueous Solution on Poly(Ethylene Terephthalate)-g-4-Vinylpyridine/ 2-Hydroxyethylmethacrylate Fibers
Authors: Yiğitoğlu Mustafa , Arslan Metin
Published: August 2014

In this study, a novel fibrous adsorbent obtained by grafting 4-vinyl pyridine (4-VP)/2-hydroxyethylmethacrylate (HEMA) comonomers onto poly (ethylene terephthalate) (PET) fibers was used for removal of methylene blue (MB) from aqueous solutions through a batch equilibration technique. The Influence of treatment time, pH of the solution, dye concentration, reaction temperature and percent graft yield on adsorbed amount were investigated. 300 min. of adsorption time was found sufficient to reach adsorption equilibrium for MB. It was found that the adsorption isotherm of MB fitted to Langmuir type isotherm. The highest adsorption capacity was found to be 55.33 mg MB per gram adsorbent. The adsorbed amount of MB was much higher on the comonomers grafted PET fibers than on the ungrafted PET fibers. MB was removed by 98 % while the initial dye concentration was at 5 mg L-1 and by 88% at 300 mg L-1 by monomers mixture grafted PET fibers. It was found that the reactive fibers were stable and regenerable by acid without loosing their activity.
Fatigue Crack Growth Process in CPVC Pipe Couplings
Authors: Khan Z. , Merah N. , Saghi F.
Published: August 2014

An investigation of the influence of temperature and loading frequencies on the morphological features found on the fatigue fractured surface of chlorinated polyvinyl chloride (CPVC) has been conducted. Single edge notched rectangular coupons obtained by flattening schedule 80 CPVC pipe couplings were subjected to fatigue loading at different temperatures of 0, 23, 40, and 70 °C and frequencies of 0.1, 1, and 50 Hz. Crack growth in CPVC, involved a combination of shear yielding and crazing processes. At the test temperature of 0 °C and 23 °C, the fatigue crack growth was noted to occur predominantly by shear yielding while crazing played a secondary role. On the other hand at 40 °C and 70 °C, the fatigue crack growth process appeared to predominantly involve a crazing process while shear yielding played a less significant role. Filler material particles played a major role as brittle second phase stress-raiser particles and facilitated craze initiation. iDiscontinuous crack growth bands (DGBs) indicating repeated crack arrests were also noted on the fracture surface.
A novel low k thin film based on plasma-polymerized 1- cyano isoquinoline
Authors: Xiong-Yan Zhao , Ming-Zhu Wang , Zhi Wang
Published: August 2014

A novel low dielectric constant polymer, plasma-polymerized 1-cyano isoquinoline (PPCIQ) was prepared by plasma polymerization for the first time. The structure and surface compositions of the deposited PPCIQ thin films were investigated by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that a high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained when a low discharge power of 15 W was used during film formation. In the case of higher discharge power of 35 W, more severe monomer molecular fragmentation can be observed. The dielectric properties measurements show that a low dielctric constant of 2.62 can be obtained for PPCIQ thin film deposited at 15 W.
Use of chemically modified poly(ethylene terephthalate)-g- (acryl amide) fibers for α-amylase immobilization
Authors: Temoçin Zülfikar , Yiğitoğlu Mustafa
Published: August 2014

Acryl amide grafted Poly(ethylene terephthalate) (AAm-g-PET) fiber was used for covalent coupling of α-amylase. The amide groups of Poly(acryl amide) were converted to the amine groups by Hofmann degradation reaction. The amine groups were activated by glutaraldehyde, before coupling of the enzyme. The free α-amylase and immobilized α-amylase were characterized by determining the activity profile as function of pH, temperature, thermal stability and storage stability. For the immobilized α-amylase, operational stability was also determined. The immobilization of α-amylase on support caused the optimal reaction pH to shift from 5 to 6. The maximum activity of the free and immobilized enzymes occurred at 50 0C. Km for the immobilized system was higher than that for the free enzyme. The activity of the free enzyme ended in 30 days, whereas the activity of the immobilized enzyme lasted for 60 days at storage conditions. α-Amylase immobilized on matrix maintained 40% of its original activity after 30 times of repeated use.
Highly gas permselective polyetherketone hollow fibre membranes using aqueous sulfuric acid solution as coagulant
Authors: Yang Jiping , Brown Philip J
Published: August 2014

Hollow fibre membranes with more sponge-like morphology and improved gas permeation performance were spun from 20% polyetherketone (PEK) /sulfuric acid (H2SO4) dope solution with aqueous sulfuric acid solution as coagulant using dry-jet wet spinning process. The membrane morphology, mechanical properties and gas separation performance (hydrogen, methane and carbon dioxide) of as-spun PEK hollow fibres have been measured using SEM, Instron and gas test rig. Better cross section structures and mechanical properties in as-spun PEK hollow fibres were observed when aqueous sulfuric acid solution replaced water as coagulant (internal and external). The hydrogen/methane selectivity of up to 40 and hydrogen permeation rate of 3.65 GPU obtained in PEK hollow fibre membranes using 30% sulfuric acid solution as internal and external coagulant simultaneously at the bore fluid injection rate of 30 ml/h are higher than those reported in literatures. Furthermore the effects of bore fluid injection rate and various coagulants on the membrane morphology, mechanical properties and gas separation properties were investigated, as well.
Novel poly(fluorene-alt-squaraine) derivatives having large coverage with solar spectrum
Authors: Jiangyong Wu , Erfu Huo , Zhibing Wu , ZhiYun Lu , Minggui Xie , Qing Jiang
Published: August 2014

Novel main-chain-conjugated poly(fluorene-alt-squaraine) using vinyl as linkage group were synthesized through direct condensation of 9,9’-dioctylfluorene derivates and squaric acid. The resulting polyfluorenes were characterized by NMR and FT-IR. They have good solubility in common organic solvents, good thermal stability and electrochemical reversibility. The structure of donor-acceptor-donor interaction in the polymer backbone resulted in much more red-shifted absorption spectra of 500-1000 nm, and extremely low band gaps of ~1.2 eV have been obtained. Their absorption spectra have large coverage with solar spectrum, suggesting that they are potential materials that can be used in photovoltaic devices.
Surface Characterization of Absorbing Polymer Films Deposited on Transparent Glasses
Authors: Gonçalves Débora , Travain Silmar A. , Giacometti José A. , Irene Eugene A.
Published: August 2014

PANI films were deposited on glass substrates by in-situ polymerization and characterized by UV-VIS spectroscopy and atomic force microscopy. A method is developed to accurately analyze ellipsometric data obtained for transparent glass substrates before and after modification with absorbing polymer films. Surface modification was made with an overlayer such as polyaniline (PANI), which exhibits different optical properties by varying its oxidation state. First, the issue of using transparent substrates for ellipsometry studies was examined and then, spectroscopic ellipsometry was used to characterize absorbing overlayers on transparent glasses. The same methodologies of data analysis can be also applied to other absorbing films on transparent substrates, and deposited by different techniques
The structure and property of the electrospinning silk fibroin/gelatin blend nanofibers
Authors: Weiwei Bao , Youzhu Zhang , Guibo Yin , Jialin Wu
Published: August 2014

Nanofibers could provide benefits due to high surface area for biomaterial scaffolds. In order to improve both silk fibroin and gelatin performance for potential biomedical applications, in this article the electrospinning of silk fibroin (SF)/gelatin (GT) blends with different composition ratio and concentration was performed with formic acid as a spinning solvent. The nanofibers morphologies and diameters were observed by Scanning electron microscopy (SEM). Blending with GT could improve the viscosity and spinnability of spinning solution. As-spun SF/GT blend nanofibers were more homogeneous and non-beaded than pure SF nanofibers. The diameter decreased with higher voltage at same electric field intensity. On increasing the concentrations of spinning solution, the pore diameter of nanofibers decreased, and the porosity increased. In addition, FTIR and DTA analyses showed SF/GT nanofibers had more β-sheets than pure SF nanofibers, which may be caused by an intermolecular interaction between SF and GT. Blending with GT also led to substantial enhancement in mechanical properties of SF nanofibers.
Using eggshell as a filler in elastomeric compounds: effect of incubation period on its performance toward elastomers
Authors: Dakhel Hadi Ramezani
Published: August 2014

The effect of incubation period and the presence of organic membrane on eggshell activity toward elastomers (NBR, NR and SBR) has been investigated. After hatching eggshell (AHES) showed enhanced mechanical properties when compared to before hatching eggshell (BHES) and calcium carbonate. Compounds containing BHES powder also showed good mechanical properties. Both types of eggshells reduced optimum curing time of the compounds. This trend was more considerable in NBR compound. The improvement of mechanical properties of the compounds attributed to elemental composition and higher specific area of AHES. The results of this study showed both before hatching and after hatching eggshell can be used in elastomeric compound as a bio-filler
Polyhydroxyalkylation of urea with ethylene carbonate and application of obtained products as components of polyurethane foams
Authors: Zarzyka-Niemiec Iwona
Published: August 2014

The reaction between urea and ethylene carbonate occur with partial release of CO2 and partial incorporation of carbonate groups into products. The carbonate groups were found to be attached both to nitrogen of urea and to oxyethylene chain. The most effective catalyst of the synthesis was potassium carbonate. The hydroxyethyl and hydroxyethoxy groups of urea derivatives undergo partial dimerization to form carbamate groups in the products. The products of reaction between urea and ethylene carbonate have good thermal stability, they start to decompose at 200°C. The obtained products can be used as polyol components for polyurethane foams. Polyurethane foams obtained from hydroxyethoxy derivatives of urea (EC8) are rigid products of low water uptake, good stability of dimensions, low mass loss on 30 days heating at 150°C, enhanced thermal stability and good compressive strength.
MWNT Surface Self-Assembling in Fire Retardant Polyethylene-Carbon nanotubes nanocomposites
Authors: Bocchini Sergio , Annibale Emanuela , Frache Alberto , Camino Giovanni
Published: August 2014

Multiwall carbon nanotubes (MWNT) were melt blended at different concentration with linear low density polyethylene (LLDPE). The nanotubes impart the fire-retardant characteristics to the polymer by formation of a thin protective film of MWNT/carbon char generated on the surface of the nanocomposites. The film formation mechanism is discussed
Sisal, Sugarcane Bagasse and Microcrystalline Celluloses: Influence of the Composition of the Solvent System N,NDimethylacetamide /Lithium Chloride on the Solubility and Acetylation of these Polysaccharides
Authors: Ciacco Gabriela T. , Ramos Ludmila A. , Frollini Elisabete , Ass Beatriz A. P.
Published: August 2014

The present work describes an investigation concerning the acetylation of celluloses extracted from short-life-cycle plant sources (i.e. sugarcane bagasse and sisal fiber) as well as microcrystalline cellulose. The acetylation was carried out under homogeneous conditions using the solvent system N,Ndimethylacetamide/ lithium chloride. The celluloses were characterized, and the characterizations included an evaluation of the amount of hemicellulose present in the materials obtained from lignocellulosics sources (sugarcane and sisal). The amount of LiCl was varied and its influence on the degree of acetate substitution was analyzed. It was found that the solvent system composition and the nature of the cellulose influenced both the state of chain dissolution and the product characteristics. The obtained results demonstrated the importance of developing specific studies on the dissolution process as well as on the derivatization of celluloses from various sources.
Modeling the physical properties of a homologous series on the melting temperatures and densities of n-alkanes and their simple alkyl-derivatives
Authors: Rubčić Antun , Rubčić Jasna , Chickos James S.
Published: August 2014

Several aspects of the melting temperatures (MT) of linear chain homologs are discussed. It is shown that with some reasonable modifications of Einstein's model of simple solids, the MT of n-alkanes and their derivatives can be successfully modeled. Results are compared with those obtained by previous authors who have used numerical methods and thermodynamics. Results of investigation of quadratic recurrence relations of the second order and forms including exponential functions are reported. Finally, the correlation of MT with density at T = 298.15 K gives the limiting value, 0.86 gcm-3 , at the temperature of nearly 420 K. It is expected that proper correlations should use densities of liquids just at the MT, because some available data suggest a linear dependence of MT on density. All results obtained are mutually consistent
Proton irradiation of ultra high molecular weight polyethylene for space applications
Authors: Stephens C.P. , Benson R.S. , Ling X. , Song H. , Ham H.-J. , Buchanan R.A. , Chipara M.
Published: August 2014

The effect of low dose proton irradiation on the morphology of ultra high molecular weight polyethylene (UHMWPE) was studied. The integral proton dose was ranging from 900 Gy to 1200 Gy. The experimental data revealed that low dose proton irradiation in the presence of oxygen leads to the formation of intermolecular crosslinks in UHMWPE and that proton irradiation produces morphological changes that involve a reduction in the thickness of the interfacial region and increase in the thickness of the amorphous region. The observed morphological changes depend on the integral dose
Optically active poly(ester-imide): synthesis and characterization of new optically active poly(ester-imide) thermoplastic elastomers
Authors: Hajipour Abdol Reza , Zahmatkesh Saeed , Ruoho Arnold E.
Published: August 2014

This Paper deals with the polycondensation between a chiral diacyl chloride (2-(N,N’-pyromelliticdiimido)-bis-propanoic acid chloride (4)) and polyethyleneglycol-diol (PEG-200) and/or three synthetic aromatic diols. The corresponding new PEIs and Co-PEIs which have been obtained in quantitative yields are soluble in polar aprotic solvents, have good thermal stability and optical activity.
Aromatic-aliphatic copolyesters based on waste poly(ethylene terephthalate) and their biodegradability
Authors: Prokopová Irena , Vlčková Eva , Šašek Václav , Náhlík Josef , Soukupová–Chaloupková Veronika , Skolil Jan
Published: August 2014

The solvolysis of poly(ethylene terephthalate) from disposed beverage bottles by an aqueous solution of lactic acid, followed by the zinc acetate catalyzed polycondensation of the solvolytic product, yielded a series of aromatic-aliphatic copolyesters containing up to 55 mol.% of incorporated lactic acid structural units. Their molecular parameters were determined using SEC and viscometry. According to DSC, the copolyesters have amorphous structure. Selected copolyester samples were subjected to abiotic hydrolysis at pH 7 and 60 °C. After three days of hydrolysis, the mass of the samples decreased substantially and their molar mass was reduced. At 37 °C, strong degradation of copolyesters by action of the actinomycete Rhodococcuserythropolis was observed. Biodegradability of the copolyesters was confirmed by a composting test. In addition to the changes of the molecular structure of the composed samples, the physical degradation of the foils of the samples tested was also documented by SEM.
First application of electrosynthesized polyterthiophene to organic solar cells
Authors: del Valle M. Angélica , Soto Giovanny M. , Canales Luis I. , Canales Luis I. , Díaz Fernando R. , Bernède J. Christian
Published: August 2014

Polyterthiophene (PTT) thin films have been electrosynthesized using potentiodynamic and potentiostatic methods. The optimal experimental conditions to prepare organic solar cells were determined by deposition of films on platinum and then the process was adapted to an indium tin oxide substrate. Surface morphology of films deposited by potentiostatic methods proved to be more homogeneous than films obtained by potentiodynamic methods. When PTT is employed in photovoltaic cells, the best results are attained using the latter technique. In these solar cells, the polymer is used as electron donor while N,N'- diheptyl-3,4,9,10-perylene-bis-carboximide (PTCDI-C7), deposited by vacuum sublimation, was the electron acceptor. The short circuit current is systematically small, probably due to the roughness of the polymer which induces high series resistance. In any case, it was demonstrated that the electrochemical method is suitable to prepare polymeric layers of electronic devices.
New polyurethane materials from renewable resources: synthesis and characterization
Authors: Macocinschi Doina , Filip Daniela , Vlad Stelian
Published: August 2014

In the present study new types of polyurethane-cellulose derivative biomaterials based on urethane prepolymers functionalized with hydroxypropylcellulose are presented. The aim of the present study is to obtain materials with better haemocompatibility, biocompatibility and amphiphilic microphase-separated domain structures. The outcome of remarkable chemical versatility characteristic to polyurethane materials combined with polymers derived from nature like cellulose derivatives resulting in bulk and surface properties is evidenced by means of different techniques like DSC, TGA, FT-IR, AFM and mechanical tensile tests. The influence of various factors on the developed morphologies and the microstructural changes is investigated. Both polyester and polyether macrodiols have been used to prepare these polyurethanes. The aim of this study is to find also alternative methods for improving biostability while maintaining the excellent biocompatibility and other properties.
Synthesis and Characterization of Highly Soluble and Heat Stable New Poly(amide-ether)s Containing Pyridine Rings in the Main Chain
Authors: Banihashemi Ahmad , Vakili Mohammad Reza
Published: August 2014

A pyridine-based diacid containing ether linkage was synthesized via reaction of 2,6-dichloropyridine with 3-hydroxybenzoic acid in presence of potassium hydroxide in dimethyl sulfoxide (DMSO). The corresponding diacid chloride was synthesized by reaction of the diacid with oxalyl chloride. New poly (amide-ether)s were prepared by solution polycondensation reaction of the prepared diacid chloride with different commercial aromatic diamines. The synthesized polymers were characterized by elemental analysis, IR, and 1H NMR spectra, wide-angle X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC); inherent viscosity and solubility were studied. These polymers showed high thermal stability and good solubility.
Preparation and characterization of a novel spongy hydrogel from aqueous Bombyx mori sericin
Authors: Zhang Haiping , Yang Mingying , Min Sijia , Feng Qiang , Gao Xin , Zhu Liangjun
Published: August 2014

We attempted to obtain a novel spongy hydrogel from aqueous Bombyxmori (B. Mori) sericin by using a freeze-thaw method without any cross-linking reagent. The aqueous sericin solution utilized was extracted from silkworm cocoons by using boiling method, and showed continuous molecular weight distribution mainly from 43 kDa to 212 kDa and even higher. To optimize the conditions for hydrogel preparation, the efficiency of hydrogel transformation from sericin solution were investigated by changing sericin concentration, freezing time, freezing temperature and frozen-thawed repetition. The porous characteristics of sericin hydrogel including the porosity, density and maximal water absorbency were performed by changing freezingn conditions. The pore size and morphology of hydrogels prepared at different concentration and freezing temperatures were observed with SEM. FTIR, XRD and DSC curves indicate that the hydrogel prepared at -20 °C and -80 °C adopt mainly random coil conformation.
Synthesis, characterization, thermal stability, conductivity and band gaps of monomer and oligo-4-[(thien-2-ylmethylene) amino] phenol
Authors: Kaya İsmet , Aydın Aysel
Published: August 2014

In this study, the oxidative polycondensation reaction conditions of 4- [(thien-2-yl-methylene) amino] phenol (4-TMAP) by using oxidants such as air O2, H2O2 and NaOCl were studied in an aqueous alkaline medium between 313 and 363 °K. The structures of the synthesized monomer and oligomer were confirmed by FT-IR, UV-vis, NMR and elemental analysis. The characterization was made by TG-DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of oligo-4-[(thien-2-yl-methylene) amino] phenol (O-4- TMAP) was found to be 36% for air O2 oxidant, 40% for H2O2 oxidant and 47% for NaOCl oxidant. According to TG analysis, the weight losses of 4-TMAP and O-4- TMAP were found to be 58.11% and 51.38% at 1273°K, respectively. O-4-TMAP was shown higher stability against thermal decomposition. Also, electrical conductivity of the O-4-TMAP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and electrochemical energy gaps ( ' gE ) of 4- TMAP and O-4-TMAP were found to be -6.13, -6.02; -2.72, -2.69; 3.41 and 3.33 eV, respectively.
Transient nucleation in isothermal crystallization of poly(3- hydroxybutyrate)
Authors: Sajkiewicz Pawel , Di Lorenzo Maria Laura , Gradys Arkadiusz
Published: August 2014

The time dependence of nucleation rate in isothermal crystallization of poly(3-hydroxybutyrate) was experimentally shown, both in heterogeneous and homogeneous nucleation. The time dependence of nucleation rate is one of the important limitations for the applicability of the simplified form of Kolmogoroff- Avrami-Evans model with time independent kinetic characteristics. The presented results are interpreted in terms of non-steady-state cluster size distribution underlying transient nature of nucleation. The relaxation time needed for reaching a steady-state cluster size distribution and thus steady-state nucleation rate is relatively long, exceeding the time of exhaustion of heterogeneities. The relaxation time estimated from homogeneous process was tens of seconds in the temperature range between 83 and 120 oC. Application of Arrhenius law allows estimation of relaxation time in broader temperature range, showing an increase of relaxation time with decreasing temperature.
Radiopaque acrylic bone cement with bromine-containing acrylic monomer. II
Authors: Rusu Marius Ciprian , Ichim Ionut Cameliu , Popa Marcel , Rusu Daniela , Rusu Mihai
Published: August 2014

Bromine-containing methacrylate, 2-(2-bromoisobutyryloxy) ethyl methacrylate (BIEM), had been used in the formulation of acrylic radiopaque cements. The effect of this monomer incorporated into the liquid phase of acrylic bone cement (ABC), on the curing parameters, thermal properties, water absorption, density, compression tests and radiopacity was studied. A decrease of maximum temperature and an increase of the setting time were observed with the addition of the brominecontaining monomer in the radiolucent cement composition. Adding BIEM in radiolucent ABCs composition results in the decrease of glass transition temperature and increase in its thermal stability. The ABCs modified with bromine-containing comonomer are characterized by polymerization shrinkage lower than the radiolucent cement. Addition of bromine-containing comonomer in radiolucent ABC composition determines the increase of compressive strength. The ABCs modified with brominecontaining comonomer proved to be radiopaque.