bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

A 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

Liquid 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

Quenched 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

We 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

Human 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

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

Semi-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

Polymeric 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

Cyclization 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

A 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

Synthesis 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

Potato 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

A 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

The 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.
Processing, rheology and structure of melt compounded PBTclay nanocomposites having different chemical composition.
Authors: Scatteia Luigi , Scarfato Paola , Acierno Domenico
Published: August 2014

In this study the melt flow behavior of poly(butylene terephthalate)-clay nanocomposites produced by melt compounding was investigated. Four commercial organo-modified montmorillonites, differing mainly by the organic treatment used in the modification, were employed as nanometric fillers and blended with the poly(butylene terephthalate) (PBT) at two weight percentages each (6 and 9wt%). The process was carried out using a laboratory-scale twin-screw extruder at two different extrusion rates, in order to evaluate the effect of the shear rate during the process on microstructure and flow properties. In this regard, the nanocomposite samples were submitted to morphological analyses and rheological measurements in the dynamic regime. The effect of temperature on the flow behavior of the hybrids with respect to the neat PBT matrix was also investigated. The obtained data were related to the hybrid compositions and then to the chemical affinity between polymer and clay type. All the reported results have shown a gradual transition from a pseudo-Newtonian trend towards a pseudo-solid-like flow behavior with the increase of the clay loading and the dispersion/exfoliation level of the clay particles, due to the corresponding increase of the polymer-silicate interactions that slow the relaxation times of the PBT chains. Moreover, it was also evident that for the fillers having the higher affinity towards the PBT the nano-scale dispersion benefit from higher residence times, and therefore slower extrusion rates; on the contrary, for the fillers having poor interaction with the polymer, higher shear stress, and therefore higher extrusion rates, are needed to disrupt the clay tactoids in smaller particles. In the last part of the work, in order to verify if a relationship between flow properties and degree of exfoliation does actually exist, the rheological data were also processed using a simple semi-quantitative empirical method proposed in literature. The method failed for our systems, thus underlining the insufficiency of the rheological response alone in quantifying the exfoliation degree of an organoclay in the matrix.
Synthesis and Homopolymerization of the Olefin- Derived Acrylic Monomer, 1-Methyl-1-Propyl-Hexyl Acrylate
Authors: Mange Siyabonga , Tonge Matthew P. , Sanderson Ronald D.
Published: August 2014

The synthesis of a new olefin-derived acrylate monomer, 1-methyl-1-propylhexyl acrylate (1-MPHA), starting from 1-pentene, is reported. 1-MPHA was found to be polymerizable to high conversion by conventional free radical means. Homopolymerization of the monomer in benzene and toluene progressed faster in toluene than in bulk. Kinetic studies show 1-MPHA to be a relatively slow reacting monomer. The homopolymer of 1-MPHA was found to be thermally stable to about 200 °C, and soft at room temperature, with a Tg of -43 °C.
Novel Thermally Stable Poly(sulfone ether ester amide)s with Improved Solubility
Authors: Mehdipour – Ataei Shahram , Babanzadeh Samal , Bahri-Laleh Naeemeh
Published: August 2014

A three-step method was used to prepare a novel sulfone ether ester diamine. In the first step, reaction of 1,5-dihydroxy naphthalene with 4- nitrobenzoyl chloride afforded 5-hydroxy-1-naphthyl-4-nitrobenzoate (HNNB). By reduction of nitro group, an amino compound named 5-hydroxyl-1-naphthyl- 4-aminobenzoate (HNAB) was obtained. Reaction of HNAB (two moles) with bis (4-chlorophenyl) sulfone resulted in preparation of a novel sulfone ether ester diamine (SEED). Polycondensation reactions of the diamine with aromatic and aliphatic diacid chlorides led to preparation of new poly(sulfone ether ester amide)s. Conventional methods were used to characterize the structure of the monomer and polymers. Physical properties of the polymers were also studied. The polyamides were thermally stable and they showed improved solubility in dipolar aprotic solvents.
Studies on the Preparation of Telechelic Polymers by Atom Transfer Radical Polymerization and Cross Coupling Processes
Authors: Durmaz Yasemin Yüksel , Cianga Ioan , Yagci Yusuf
Published: August 2014

Combination of Atom Transfer Radical Polymerization (ATRP) and Atom Transfer Radical Cross Coupling (ATRCC) processes as a route to prepare telechelic polymers was described. The concept is based on the activation of the dormant species at the chain ends of polystyrene (Br-PS-Br or PS-Br) prepared by ATRP and functional ATRP initiator (F-R-Br) in the absence of a monomer. Depending on the type of polystyrene used in the system, cross coupling of these active species gives α,ω-polystyrene and ω-polystyrene telechelics. Detailed investigations using a model system revealed that the efficiency of functionalization was not very high because of the self-coupling of the species derived from the polymer and functional initiator. However, the highest functionalization (Xf=0.85) was achieved by introducing a small amount of styrene in the ATRCC.
Comb-like copolymers of n-alkyl monoitaconates and styrene
Authors: Inciarte Helen , Orozco Margie , Fuenmayor Miladys , López-Carrasquero Francisco , Oliva Haydee
Published: August 2014

Random and block copolymers containing styrene and mono n-alkyl itaconates with n = 12, 14, 16, 18 and 22 have been prepared by free radical polymerization and nitroxide-mediated radical polymerization. The molar fraction of the mono n-alkyl itaconate in block copolymers increased with increasing size of the alkyl group in the ester substituent. A calorimetric study of all these copolymers was performed. No glass transition (Tg) was observed in the temperature range - 30ºC-120ºC for random copolymers. Melting process attributed to crystalline order in the long side chains was observed for some copolymers depending on their composition and of the monoitaconate chain side length.
Synthesis by oxidative polymerization of optically active, regioregular polythiophene from quinquethiophene monomer bearing chiral and n-dodecyl groups as substituents
Authors: Angiolini Luigi , Brazzi Alice , Grenci Valeria , Salatelli Elisabetta
Published: August 2014

The synthesis and characterization of an optically active quinquethiophene monomer 3,3””-didodecyl-4’,3”’-di[(S)-(+)-2-methylbutyl]- 2,2’:5’,2”:5”,2”’:5”’,2””-quinquethiophene [(S)-(+)-DDDMBQT], bearing at the C-β positions of thiophene rings both linear C12 alkyl chain and chiral, enantiomerically pure, alkyl group is described. The polymerization of [(S)-(+)-DDDMBQT] by oxidative mechanism has been optimized in terms of yield of soluble polymer with high molecular weight.

The obtained polymeric derivative displays enhanced conjugation extension with respect to similar poly(3-alkylthiophene)s reported in the literature and optical activity in the spectral region related to the chromophore absorptions when in the microaggregate state, indicative of the presence of supramolecular chiral conformations.
Infrared study of the photochemical behaviour of aromatic Poly (ether urethanes)
Authors: Mendikute G. , Irusta L. , Fernández-Berridi M.J.
Published: August 2014

Poly(ether urethanes) based on aromatic diisocyanates and poly(propylene glycol) of different molecular weight and different hard segment content have been synthesised. The extent of the photooxidation of UV exposed samples has been evaluated by FTIR spectroscopy. The results proved that both the isocyanate chemical nature and polyol molecular weight play an important role in the photooxidation behaviour of these systems.
Synthesis of azobenzene-centered (co)polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization
Authors: Liping Yu , Jian Zhu , Zhenping Cheng , Zhengbiao Zhang , Wei Zhang , Xiulin Zhu
Published: August 2014

An azobenzene-based dithiocarbamate, 4,4'-bis[2-(carbazole-N-dithio formatyl)-2-methyl-propionatyl]-azobenzene (CDMPA), was synthesized and used as the chain transfer agent (CTA) for reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in anisole solution. Well-defined azobenzene-centered and carbazole-ended polystyrene (PS) with well-controlled molecular weight (Mn) and narrow molecular weight distributions (Mw/Mn) was obtained. The good agreement between the theoretical molecular weight (Mn,th) and the 1H NMR determined molecular weight (Mn,NMR) indicated that most of the polymer chains contained an azo-functional center-group end-capped with the carbazole moieties, which were derived from the RAFT agent. The obtained polystyrene (PS) showed a strong ultraviolet absorption in tetrahydrofuran (THF) and emitted fluorescence after excited by UV-irradiation in N,N’-dimethyl formamide (DMF) solutions. The PS was used as the macro-RAFT agent to carry out the polymerization of methyl acrylate (MA) and N-isopropylacrylamide (NIPAAM). Triblock copolymers (PMA-b-PS-b-PMA), and pentablock copolymers (PNIPAAM-b-PMA-b-PS-b-PMA-b-PNIPAAM) were obtained, respectively. These copolymers were characterized by gel permeation chromatography (GPC), FT-IR spectroscopy and NMR spectroscopy.
The study on effective thermal conductivity of carbon foam based on fractal theory
Authors: Yong Wang , Qingqing An , Lingling Cao , Xiaojuan Si , Donghui Liu , Jianjun Chen , Yimin Wang , Kin Tak Lau
Published: August 2014

Novel carbon foam with high thermal conductivity is prepared by thermal treating of mesophase pitch under certain temperature and pressure condition. With fractal theory, the thermal conducting property of this novel porous material is discussed. Then we deduce the area fractal dimension of carbon foam. A thermal conductivity model of carbon foam is proposed. The relationship formula of effective thermal conductivity is presented by using thermal resistance method. Through computation, the effective thermal conductivity of carbon foam is acquired. The value of model forecast is consistent with that of the actual observed for carbon foam. This method has provided the theoretical basis for better using its fine heat conduction performance.
Microencapsulation of n-hexadecane as phase change material by suspension polymerization
Authors: Yafei Ai , Yong Jin , Jing Sun , Deqing Wei
Published: August 2014

In this study, suspension polymerization is described to fabricate microcapsules containing n-hexadecane as phase change material. In the suspension polymerization, casein is employed as emulsifier and stabilizer instead of synthetic surfactant. Microcapsules with polystyrene as shell and n-hexadecane as core have an average diameter of 3~15μm and the size distribution are narrow. Thermal properties are investigated by differential scanning calorimetry (DSC) showing that the microcapsules can store and release an amount of latent heat over a temperature range nearing the melting point of pure n-hexadecane. The latent heat of fusion of microencapsulated n-hexadecane decreases after microencapsulation. The melting point of microencapsulated n-hexadecane is near but higher than that of pure n-hexadecane, and the polymerization time has little effect on the melting point.
The effect of attapulgite on crystallization behavior of Poly(ethylene terephthalate) (PET)/Attapulgite (AT) nano composites
Authors: Xufen Fan , Dajun Chen
Published: August 2014

Poly (ethylene terephthalate) (PET)/Attapulgite (AT) nanocomposites were prepared via in-situ polymerization. According to the observation of transmission electron microscopy (TEM), attapulgite is well dispersed in the PET matrix in a nanometer scale. The influence of attapulgite content on the nonisothermal crystallization kinetics was studied using a classical Avrami equation with Jeziorny method. The crystalline structures of the pure PET and PET/AT nanocomposites with different amount of AT (0.2%, 0.5%, 1%, 2%) were characterized by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) methods. It was found that the crystallization temperature for PET/AT nanocomposites with 0.2% and 0.5% content of AT were higher than pure PET and the rate of crystallization of all PET/AT nanocomposite samples increased significantly which indicated that attapulgite could be used as an effective nucleating agent in PET. However, with the addition of AT, smaller crystalline size, more crystalline defects and lower degree of crystallization was demonstrated.
Comparison of the structure and thermal properties of a poly(aryl ether ketone ether ketone naphthyl ketone) with those of poly(aryl ether ketone ether ketone ketone)
Authors: Dosière Marcel , Villers Didier , Zolotukhin Mikhail G. , Koch Michel H.J.
Published: August 2014

Poly(oxy-1,4-phenylene carbonyl-1,4-phenylene oxy-1,4-phenylene carbonyl-2,6-naphthalene carbonyl-1,4-phenylene) or 2,6-PEKEKNK is a polymer of the poly(aryl ether ketone) family differing from PEKEKK by the presence of a naphthyl group linked at positions 2 and 6 to the two ketone groups. It is synthesized by electrophilic precipitation polycondensation of 2,6- naphthalenedicarboxylic acid chloride with 4,4’-bis-(4-phenoxy) benzophenone in the presence of aluminium chloride. The dimensions of the orthorhombic unit cell determined from an initially amorphous, stretched film are: a = 0.778 nm, b = 0.613 nm, c = 5.52 nm. In contrast with PEKEKK no signs of polymorphism were found for 2,6 PEKEKNK. Its glass transition and melting temperatures are 20 °C and 2 °C above those of PEKEKK, respectively.
RAFT Polymerization of Styrene Using Dithioester with Anthracene Z Group as Chain Transfer Agent
Authors: Nianchen Zhou , Jian Zhu , Zhengbiao Zhang , Xiulin Zhu
Published: August 2014

A novel dithioester, bearing anthracene as Z group, benzyl anthracene-10-carbodithioate (BAC) was successfully synthesized and used as the RAFT agent for the RAFT polymerizations of styrene (St). The results indicated that the polymerization presented the characteristics of “living”/controlled radical polymerization. 1H NMR characterization of obtained polystyrene confirmed that most of the polymer chains were end-capped by the anthracene moiety. The successful chain extension experiment further demonstrated the “living” character of the polymer. The fluorescence investigation of the polymers contained an anthrancene moiety of BAC in the chain end expressed enhanced fluorescence property than that of BAC in CHCl3 solution.
Structure and Mechanical Behavior of Isotactic Polypropylene Composites Filled with Silver Nanoparticles
Authors: Tjong Sie Chin , Bao Suping
Published: August 2014

Isotactic polypropylene (PP) nanocomposites containing 0.1, 0.3, 0.5 and 1.0 wt % silver (Ag) nanoparticles were prepared via melt compounding in a twin-screw extruder followed by injection molding The effects of the Ag nanoparticle additions on the structure and mechanical behavior of PP were studied using DSC, WXRD, optical microscopy, tensile and Izod impact techniques. DSC and WXRD measurements showed that the addition of only 0.1 wt% Ag nanoparticles promote the formation of β-form PP. Further increasing Ag content would not lead to additional increase of the β-PP phase content. The induced β- form PP phase is beneficial to enhance the impact strength and tensile ductility of the PP/Ag nanocomposites.
Effect of temperature and pH on swelling behavior of hydroxyethyl cellullose-acrylamide hydrogel
Authors: Alonso Gabriel J. , Rivera José Luis A. , Mendoza Ana María M. , Mendez Maria Leonor H.
Published: August 2014

The swelling behavior of hydroxyethyl cellulose-acrylamide hydrogels at different pH and temperatures was studied. The absorption increased for the first 12 hours and then decreased. Several hydroxyethyl cellulose-acrylamide ratios were studied. Increasing hydroxyethyl cellulose amount decreased swelling, indicating that swelling was affected by increase in crosslinking. Three different levels of crosslinking agent were studied. Hydrogels exhibited a thermal and pH sensitive behaviour. Highest swelling capacity was found at pH 7.0 and 30 °C. All samples were characterized by means of infrared spectroscopy (FTIR). Characteristic absorbance peaks for both materials were found, showing the presence of hydroxyethyl cellulose and acrylamide on hydrogel.
Thermoresponsive hydrogels of hydrophobically modified polyglycidol
Authors: Utrata-Wesołek Alicja , Trzebicka Barbara , Dworak Andrzej , Ivanova Sijka , Christova Darinka
Published: August 2014

Synthesis, swelling properties and thermoresponsive behavior of a new class of hydrogels based on high molar mass polyglycidol are presented. High molar mass polyglycidol was synthesized by coordination polymerization. Thermosensitive poly(glycidol-co-glycidyl ethyl carbamate)s were obtained via a simple chemical modification of the polyglycidol with ethyl isocyanate. Polyglycidol and poly(glycidol-co-glycidyl ethyl carbamate)s were chemically crosslinked in DMF solution using oligomeric poly(ethylene glycol)-bis-(carboxymethyl ether chloride) as crosslinking agent. The hydrogels of degree of swelling of over 1000% were obtained. Thermoresponsive properties of the networks and the swellingdeswelling behavior of hydrogels in response to cyclic changes of the temperature were studied.
Investigation of Poly(vinyl pyrrolidone) in methanol by dynamic light scattering and viscosity techniques
Authors: Aschi Adel , Jebari Mohamed Mondher , Gharbi Abdelhafidh
Published: August 2014

The behavior of poly(vinyl pyrrolidone) (PVP) in methanol was examined using several independent methods. The hydrodynamic radius (Rh) of individual samples, over a range of molecular weights (10,000-360,000), was determined using dynamic light scattering (DLS) measurements. Dynamic Light Scattering (DLS) techniques directly probe such dynamics by monitoring and analyzing the pattern of fluctuations of the light scattered from polymer molecules. Some viscosity measurements were also performed to complete the DLS measurements and to provide more information on the particle structure. The results obtained with PVP-methanol system showed that plotting the variation of intrinsic viscosity versus the logarithm of the molecular mass of this polymer, we observe one crossover point. This crossover point appears when we reach the Θ-solvent behavior and delimit two molecular mass regions. The second order least-squares regression was used as an approach and was in excellent agreement with viscometric experimental results.
Synthesis, Chemical Structure and Properties of Crosslinked Poly(esterurethanes) Based on Unsaturated Oligo(alkyleneester)diols
Authors: Jasinska Lidia , Balas Adolf , Haponiuk Jozef T.
Published: August 2014

The cross-linked poly(esterurethanes) (PEU) based on unsaturated oligo(alkyleneester)diol (OAE) are presented. OAE was prepared from adipic acid, maleic anhydride and ethylene glycol and then characterized by elemental analysis, FTIR, 1H NMR and 13C NMR spectroscopy in account of double bonds and -COOH end groups. The synthesis of PEU was conducted in two steps. In the first step the prepolymers, containing free NCO or OH groups, were obtained via the reaction of OAE with 4,4`-diphenylmethane diisocyanate (MDI) used in excess. The cross-linking was achieved in the next step, in which the prepolymers were dissolved in methyl methacrylate (MMA) of concentrations in the range of 30 to 50 wt% in the presence of 1 wt% of methyl ethyl peroxide and 0.003 wt% of cobalt (II) 2-ethylhexanoate. It is proved that both chemical structure and MDI content in prepolymer influence the static and dynamic mechanical properties and thermal stability of the poly(esterurethanes).
Synthesis and characterization of new macromolecule systems for colon-specific drug delivery
Authors: Galehassadi M. , Mahkam M. , Hosseinzadeh F.
Published: August 2014

Network polymers containing silyl groups were synthesized. Silyl derivatives of 2-hydroxyethylmethacrylate (HEMA), and methacrylic acid (MAA) were copolymerized with 1,2-bis(vinylphenyl)ethane (BVPE) and divinylbenzene (DVB) as cross-linking agents by radical polymerization using α,α′-azobis (isobutyronitrile) (AIBN) as initiator to produce network polymers. Then mesalasine (MZ) were loaded to these network polymers, and amount of drug entrapped was determined. In vitro release studies showed that drug delivery property was modified and showed considerable difference in swelling at pH 1 and 7.4. Incorporation of silyl groups in new macromolecule system modified network polymers for drug delivery. Monomers and polymers were characterized by spectroscopic methods.
Comparative studies of functional nanostructures sputtered on polypropylene nonwovens
Authors: Wei Qufu , Yu Liangyan , Hou Dayin , Wang Yingying
Published: August 2014

Functional nanocomposite nonwoven materials were prepared by surface coating with copper and silver using magnetron sputter coating. The composite nonwoven materials with metallic nanostructures were analyzed and compared by means of atomic force microscopy, energy dispersive X-ray analysis and electrical and optical tests. The observations by atomic force microscopy revealed the formation of functional nanostructures on the fibre surfaces. It was found that copper had more compact structures on the fiber surface than silver under the same sputtering conditions. The transmittance analysis showed that the nonwoven substrates deposited with nanostructural copper showed better ultraviolet and visible light absorption than those coated with silver. The functional nonwoven materials coated with silver had lower electrical resistance than those coated with copper.
Novel Polymerization of Myrcene in Aqueous Media via Cyclodextrin-Complexes
Authors: Choi SooWhan , Ritter Helmut
Published: August 2014

Free radical homopolymerization with methylated β-cyclodextrin (CD) complexed myrcene (1a) and co-polymerization of 1a with diethyl fumarate (2a) and styrene (3a) were carried out using redox initiator in aqueous media at room temperature. Control experiments showed that uncomplexed myrcene (1) does not polymerize under similar conditions in water. The polymers obtained were characterized by means of 1H/13C-NMR spectroscopy, differential scanning calorimetry (DSC) and gel-permeation chromatography (GPC). Additionally, Nisopropylacrylamide containing copolymer was synthesized in water using redox initiator and the lower critical solution temperature (LCST) behaviour was studied.
Application possibilities of preparative size exclusion chromatography to analytical problems in polymer science
Authors: Thijs Hanneke M. L. , Meier Michael A. R. , Schubert Ulrich S.
Published: August 2014

The application possibilities of preparative size exclusion chromatography for the detailed analysis of polymer analytes are discussed. Using the example of star-shaped polymer architecture, the possibilities of utilizing fractions obtained from preparative size exclusion chromatography and their subsequent off-line characterization with a variety of hyphenated analytic techniques are discussed and compared to one another. It was, for instance, possible to obtain an absolute SEC calibration for the investigated star-shaped polymers that showed very good agreement with theoretical expected values and values obtained by absolute molecular weight determination techniques by analyzing fractions of different molecular weights of this polymer architecture by MALDI-TOFMS in order obtain the Mp values required for SEC calibrations. Moreover, the star-shaped polymers were investigated by SEC-viscometry in order to obtain their absolute molecular weight. All analytical results are compared to each other and possibilities as well as limitations are discussed.
A novel hyperbranched polyester based on 2,2-bis(hydro xylmethyl)butyric acid: synthesis and characterization
Authors: Soccio Michelina , Finelli Lara , Lotti Nadia , Marchese Paola , Siracusa Valentina , Munari Andrea
Published: August 2014

A novel hyperbranched polyester was synthesized in bulk from 2,2- bis(hydroxymethyl)butyric acid and two different core molecules (1,1,1-tris- (hydroxylmethyl)propane and 1,3,5-tris(2-hydroxyethyl)cyanuric acid), using ptoluensolfonic acid, scandium trifluoromethanesulfonate, titanium tetrabutoxide and dibutyltin oxide as catalysts and varied reaction temperature and time. At room temperature the samples obtained appeared as glassy, slightly yellow solids, with Mn (calculated by 1H-NMR spectra) in the range 500 - 2000. The degree of branching of the polyesters was determined by 13C-NMR spectroscopy and was found in the range 0.32 - 0.53. The introduction of the monomer in various steps seems to influence slightly the degree of branching, but has no effect on the molecular weight of these polymers. The polyesters exhibited a good thermal stability, as revealed by TGA technique, and the glass transition temperature, determined by DSC, was found to depend on the molecular weight and the kind of catalyst employed.
Synthesis and photophysical properties of fluorescent polystyrene containing 1,8-naphthalimide via atom transfer polymerization
Authors: Zhengneng Jin , Jianmei Lu , Qingfeng Xu , Lihua Wang , Xuewei Xia
Published: August 2014

Fluorescent polystyrene was synthesized by Atom transfer polymerization with a novel 1,8-naphthalimide derivative as initiator. The optical characteristics of initiator and obtained polystyrene in DMF solution are discussed. Results indicate that both initiator and polystyrene can emit intensive green luminescence at 520 nm, but the polymer has a higher quantum yield and energy yield.
Performance Improvement of Nano-silica/Polypropylene Composites through in-situ Graft Modification of Nanoparticles during Melt Compounding
Authors: Zhou Tong Hui , Ruan Wen Hong , Wang Yue Lin , Mai Yu Liang , Rong Min Zhi , Zhang Ming Qiu
Published: August 2014

To prepare inorganic nanoparticles filled polymer composites, reactive monomer was added to the ingredients prior to manufacturing. The results showed that in-situ graft polymerization of butyl acrylate onto nano-silica occurred during melt compounding with polypropylene matrix. As a result, dispersion of the grafted nanoparticles in the polymer became much more homogeneous than in the case of untreated version, and filler/matrix interaction was enhanced due to the intimate adhesion among the components. Both tensile performance and impact toughness of the composites were improved at rather low filler loading. Compared to the twostep approach developed in our lab, by which nanoparticles are treated by graft polymerization firstly and then mixed with polymer melt, the current one-step method is simpler and able to provide the composites with much higher notched impact resistance.
Synthesis of cationic flocculants based on acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride copolymers by semicontinuous inverse microemulsion polymerization. Part III: influence of HLB and surfactant blend concentration on flocculating performance
Authors: Río Francisca , José R. , Ochoa G. , Sasia Pedro M. , Escudero Francisco J. , Díaz de Apodaca Elena , Nieto Javier , Katime Issa
Published: August 2014

The influence of HLB (hydrophilic-lipophilic balance) and surfactant blend concentration (SBC) on flocculating performance of latex particles of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride copolymers with a cationic charge density of 40%, obtained by inverse microemulsion copolymerization by using a surfactant blend of Arlacel 83 and Softanol 90 as emulsifier and Rolling M-245, a mixture of n-decane and n-tetradecane in about 40/60 weight ratio, as oil phase, has been studied for a total comonomer concentration of 32.5% (w/w). Comonomer inverse microemulsion copolymerizations were carried out in the semicontinuous mode by adding continuously an aqueous solution of sodium metabisulfite (SMB) as initiator into stirred inverse comonomer microemulsions. From 7.75 to 8.26, HLB has a strong influence on average molar mass (Mw) and flocculating performance (FP), the higher the HLB the higher the FP. A small decrease in SBC causes a dramatic increase in Mw and a decrease in FP although the influence on copolymer viscosity is small. Results are explained in terms of copolymer structuring degree and collapsed state of copolymer chains inside latex particles as well as in terms of the observed composition drift with conversion.
Bioactive cellulose fibres with silver nanoparticles
Authors: Kulpinski Piotr
Published: August 2014

Cellulose fibres were prepared from N-methylmorpholine-N-oxide (NMMO) as a direct solvent. The specific chemical properties of NMMO allow in-situ silver particles to be generated during the process of cellulose dissolution. The fibres obtained contained 0.005% (50 ppm) to 3% w/w of silver. The SEM images showed that the silver particles size is in the range between 30 and 330 nm. The antibacterial properties of the cellulose fibres obtained showed their high bioactivity against E. coli and S. aureus bacteria. The mechanical properties, the size of silver crystallites and SEM images of the fibres obtained were examined.
The study of synthesis of poly(ethylene oxide)-b-poly(N,Ndimethylacrylamide) by atom transfer radical polymerization and self-assembly in selective solvents
Authors: Runmiao Yang , Ronghua Shi , Dan Zhou , Yanmei Wang , Yanchun Han
Published: August 2014

Poly(ethylene oxide)-b-poly(N, N-dimethylacrylamide) (PEO-b-PDMA) was synthesized by successive atom transfer radical polymerization (ATRP) of N,N-dimethylacrylamide (DMA) monomer using PEO-Br macro initiators as initiator, CuBr and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazamacrocyclotetra decane (Me6[14]aneN4) as catalyst and ligand.PEO-Br macroinitiator was synthesized by esterification of PEO with 2-bromoisobutyryl bromide. GPC and 1H NMR studies show that the plot of ln([DMA]0/[DMA]) against the reaction time is linear, and the molecular weight of the resulting PDMA increased linearly with the conversion. Within 3 h, the polymerization can reach almost 60% of conversion. PEO-b-PDMA copolymer with low polydispersity index (Mw/Mn≈1.1) is obtained. Self-assembly of PEO-b-PDMA in selective solvents is also studied. It could self-assemble into micelles in methanol/acetone (1/10, v/v) solution. TEM analyses of the PEO-b- PDMA micelles with narrow size distribution revealed that their size and shape depend much on the copolymer composition.
Swelling of iota-carrageenan gels prepared with various CaCl2 content: A fluorescence study
Authors: Tarı Özlem , Pekcan Önder
Published: August 2014

Iota carrageenan gels prepared with various CaCl2 content were completely dried and then swelled in water vapor. Steady-state fluorescence (SSF) technique was used to monitor the swelling process of each iota carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. Apparent fluorescence intensity, I increased as swelling time increased for all gel samples. The increase in I was modelled using Li-Tanaka equation from which the swelling time constants, τ1 and cooperative diffusion coefficients, Dc were determined. It was observed that Dc increased as the swelling temperature was increased. On the other hand at each temperature, it was seen that Dc decreased as CaCl2 content was increased. Activation energies for swelling were obtained and found to be 60.5, 61.0, 61.5 and 62.8 kJmol-1 for the gels prepared with increasing amount of CaCl2 content.
Synthesis and characterization of some composites with bioactive properties on the basis of vinyl ester resins
Authors: Rosu Dan , Cascaval Constantin N. , Rosu Liliana
Published: August 2014

Vinyl ester resins are unsaturated polyesters, widely used as matrix for high performance composite materials. The paper presents the synthesis and characterization of some vinyl ester resin/hydroxyapatite bioactive compositions using an unsaturated copolyester based on turpentine oil as reactive diluent. The vinyl ester oligomer /unsaturated copolyester/hydroxyapatite structural complex was characterized from the morphological point of view, water absorbtion, density measurements and volume contraction. The water uptake is dependent on the concentration in vinyl ester resin. The increase of the vinyl ester resin content in the bioactive composite leads to the increase of the density, respectively to a significant decrease of the volume contraction