bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional segmented polymer networks based on polytetrahydrofuran and poly(vinylbenzyl chloride)
Authors: Jonckheere Laura , Goethals Eric J. , Du Prez Filip E. 
Published: August 2014

Abstract Functional segmented polymer networks (FSPNs) were synthesised via free radical initiated copolymerisation of polytetrahydrofuran (PTHF) bis-macromonomers with vinylbenzyl chloride (VBCl). The purpose of this work was to create FSPNs, providing supports with a functional group that can be substituted and may serve to immobilise other reagents such as catalysts. After the preparation and detailed characterisation of several PTHF bis-macromonomers, FSPNs were prepared with varying molecular weight of the PTHF chain and varying PTHF/ PVBCl ratio. Measurements of the soluble fraction and elemental analyses demonstrated that FSPNs with a wide composition range could be prepared. From dynamic-mechanical and thermal analyses, it could be concluded that most FSPNs showed some degree of compatibility and complete absence of crystallinity. The mechanical properties of the FSPNs are directly related to their composition. The degree of substitution of all networks is close to quantitative.
Synthesis and characterization of 4-chloromethylstyrene polymers containing bulky organosilicon groups
Authors: Safa Kazem Dindar , Babazadeh Mirzaagha 
Published: August 2014

Abstract The homopolymer of 4-chloromethylstyrene and its copolymers with styrene (in 1:3 and 1:1 mole ratio) were synthesized by bulk and solution freeradical polymerisations, respectively, at 70±1°C using α,α'-azoisobutyronitrile as an initiator. Highly sterically hindered tris(trimethylsilyl)methyl (Tsi) substituents were then covalently linked to the obtained homopolymer and copolymers. The polymers were characterized by IR, 1H NMR and 13C NMR, differential scanning calorimetry (DSC) and gel permeation chromatography. DSC showed that incorporation of Tsi substituents in the side chains of homopolymer and copolymers increases the rigidity of the polymers and, subsequently, their glass transition temperature.
Conformational properties of dendritic polymers with variable branching functionality in their generational shells
Authors: Roovers Jacques 
Published: August 2014

Abstract The shrinkage factors, g, of long-chain dendritic polymers with different branching functionalities in their generational shells are derived in the Gaussian approximation. The equations for generations zero (star) to 3 are given explicitly in a form that can be extrapolated easily to higher generation number. Examples of the evolution of the shrinkage factors with branching functionality are given. The form factors, P(x), of the same dendritic polymers are also derived. The equations can be extrapolated to higher generation number and easily incorporated into a simple calculation program. Comparisons are made with regular stars with the same number of arms as the peripheral subchains in the dendrimers. It is found that 3rd generation dendritic polymers with low branch functionality (= 3) are less sphere-like than the star with 24 arms, but the 3rd generation dendrimer with functionality 5 is more sphere-like than the star with 108 arms.
Synthesis and characterization of a pressure-sensitive adhesive based on an isobutyl acrylate / 2-ethylhexyl acrylate copolymer
Authors: López Betty L. , Murillo Edwin , Hess Michael 
Published: August 2014

Abstract A removable pressure-sensitive adhesive was obtained by free-radical emulsion polymerization. The product is a low-viscosity copolymer from different polar and apolar acrylic monomers consisting of microspheres of about 1 μm diameter. 2-Ethylhexyl acrylate and isobutyl acrylate were used as non-polar constituents while acrylic acid and acrylamide provided the more polar constituents to regulate the cohesive force of the adhesive. The amounts of initiator, water and emulsifier (nonylphenol) were varied to obtain the best adhesive properties at the given copolymer composition. The resulting adhesive showed the desired balance of low tack and good adhesive strength in combination with a wide variety of substrates, which made it useful as a removable adhesive for many applications. The product was characterised by viscometry, measurements of tack and peel strength, FTIR, DSC, and microscopy.
Electrorheology of conducting polyaniline composite particles
Authors: Choi Hyoung Jin , Cho Min Sung , Lee Young Hoon , Cho Yun Hyang , Jhon Myung S. 
Published: August 2014

Abstract Three different kinds of particles of semiconductive polyaniline (PANI), spherical poly(methyl methacrylate) with a PANI shell (PAPMMA), and conductive PANI encapsulated by insulating melamine-formaldehyde resin (MCPA) were synthesized and adopted as a dispersed phase for electrorheological (ER) fluids. ER fluids are suspensions of polarizable particles dispersed in non-conducting liquids. The rheological characteristics of ER fluids rapidly change in the presence of an applied electric field, which can be controlled by both the applied electric field strength and particle concentration with a fast response time on the order of milliseconds. MCPA-based ER fluids show the largest stress enhancement by an applied electric field compared with both PANI- and PAPMMA-based ER fluids, demonstrating that the conductive core with an insulating shell system is a better ER material than homogeneous, semiconductive materials or surface-semiconductive materials with insulating cores.
Pre-treatment of CaCO3 nanofiller by irradiation in the presence of vinyl monomers for the preparation of poly(vinyl acetate) composites
Authors: Leskovac Mirela , Kovačević Vera , Lučić Blagojević Sanja , Vrsaljko Domagoj , Volovšek Vesna 
Published: August 2014

AbstractPoly(vinyl acetate) (PVAc) composites were prepared by different approaches, namely (i) by mechanical mixing of untreated CaCO3 and PVAc, (ii) by mechanical mixing of CaCO3 pre-treated by irradiation polymerization in the presence of vinyl acetate, and (iii) by in situ emulsion polymerization of VAc in the presence of untreated CaCO3 nanofiller. The effects of nanoparticle pre-treatment and different approaches of preparation were correlated with changes in morphology and mechanical properties of PVAc composites using scanning electron microscopy and tensile tests. Untreated CaCO3 nanoparticles in the composite prepared by mechanical mixing provided strong interactions with the PVAc matrix. On the other hand, CaCO3 pre-treated nanoparticles decreased the interfacial interactions. For composites prepared by in situ polymerization a better dispersion of encapsulated nanoparticles was achieved and, as a result, a significant improvement of composite strength was observed. Interfacial interactions in nanocomposites can be changed by filler pre-treatment or by a suitable way of nanocomposite preparation.
Distribution of clay particles in the spherulitic texture of poly(L-lactide)/organo-modified montmorillonite hybrids
Authors: Ninomiya Naoya , Nam Pham Hoai , Fujimori Atsuhiro , Masuko Toru 
Published: August 2014

Abstract The distribution of clay particles in the spherulitic texture of poly(Llactide)/ clay hybrids crystallized isothermally at 140°C has been investigated by use of energy-dispersive X-ray microanalysis. After crystallization of the hybrids, the clay particles were found to distribute with almost constant concentration along the radial direction of the spherulites, i.e., they are still kept in stacked state inside the spherulites without any segregation during crystallization. The concentration distribution of the clay particles showed that these particles were incorporated into the spherulitic texture of the crystallized hybrids.
Interaction between sodium polystyrenesulfonate and Triton X-100 in aqueous solution
Authors: Salem Jamil K. J. , Melad Omar , Baraka Rajai 
Published: August 2014

Abstract The interaction between sodium polystyrenesulfonate (PSS) and Triton X-100 (α-(4-octylpenyl)-poly(oxyethylene), TX-100) has been investigated by viscosity and conductivity measurements. The results show that the reduced viscosity of PSS increases with increasing PSS concentration at low constant TX-100 concentrations (0.006 - 0.029 g/ml). On the other hand, at higher constant TX-100 concentrations, 0.048 and 0.062 g/ml, the reduced viscosity decreases with increasing PSS concentration. The behaviour of conductivity of PSS in pure water is quite different from that in the presence of TX-100.
Application of dynamic mechanical analysis techniques to bismuth telluride based thermoelectric materials
Authors: Brostow Witold , Menard Kevin P. , White John B. 
Published: August 2014

Abstract Dynamic mechanical analysis (DMA) techniques are commonly applied to characterize polymer-based materials - but little if at all to characterize semiconductor thermoelectric (TE) materials. TE materials may be coupled with polymeric materials in advanced thermoelectric devices, and the knowledge of TE material properties will be useful in the choice of materials for future applications. We have obtained DMA results for both n-type and p-type bismuth telluride based TE materials. We find that tan δ values, indicative of viscoelastic energy dissipation modes, approach the values for glassy or semi-crystalline polymers, and are larger by more than a whole order of magnitude than the tan δ of structural metals. DMA thermal scans show clear hysteresis-type effects and a correlation with differential scanning calorimetry thermal transitions. DMA properties as a function of frequency are briefly discussed. Our results show that DMA techniques are useful in the evaluation of thermophysical and thermomechanical properties of these TE materials and of assembled coolers. The viscoelastic effects we report may provide a damping mechanism for severe stresses inherent to service conditions of the TE coolers.
Small-angle neutron scattering study of shear-induced phase separation in aqueous poly(N-isopropylacrylamide) solutions
Authors: Stieger Markus , Lindner Peter , Richtering Walter 
Published: August 2014

Abstract The influence of shear flow on the structure of concentrated aqueous poly(N-isopropylacrylamide) solutions near the lower critical solution temperature was investigated by means of small-angle neutron scattering. Two samples, both in the semi-dilute regime above the overlap concentration, were studied. The scattering curve of the less concentrated sample was not influenced by shear flow, although high shear rates were reached. The more concentrated 4 wt.-% sample, however, displayed shear-induced demixing under strong shear flow conditions. Experiments at different shear stresses indicated the existence of a threshold shear stress and the phase separation process became faster with increasing stress. The two-dimensional scattering patterns remained isotropic even during the phase separation process and the correlation length as obtained from an Ornstein- Zernike plot increased. The influence of shear flow on the phase separation process is thus similar to a temperature increase. The results are in excellent agreement with data from recent rheo-optical experiments where shear-induced phase separation was also observed for the concentrated solution at high shear rates. Apparently, strong shear flow exerts an effect analogous to a temperature increase.
Formation of superlattices in blends of 3-miktoarm star terpolymers with diblock copolymers
Authors: Abetz Volker , Jiang Shimei 
Published: August 2014

Abstract In this contribution we report on the morphological structures formed in blends of microphase-separated 3-miktoarm star terpolymers of polystyrene-armpolybutadiene- arm-poly(2-vinylpyridine) (SBV*) and polystyrene-block-polybutadiene (SB), polystyrene-block-poly(2-vinylpyridine) (SV), poly(2-vinylpyridine)- block-poly(cyclohexyl methacrylate) (VC) diblock copolymers. The morphologies are characterized by transmission electron microscopy. Blends with similar morphologies as known from linear triblock terpolymers are found, like core-shell structures based on cylinders or gyroids. Other blends show very distorted morphologies, or morphologies similar to the ones found for pure 3-miktoarm star terpolymers. While attractive interactions between blocks of the two species enhance the formation of common superlattices, blends with too large diblock copolymers tend to macrophase-separate.
Molar mass characterization of hydrophilic copolymers, 1 Size exclusion chromatography of neutral and anionic (meth)acrylate copolymers
Authors: Adler Martina , Pasch Harald , Meier Christian , Senger Raimund , Koban Hans-Günter , Augenstein Michael , Reinhold Günter 
Published: August 2014

Abstract A robust and reproducible method for the molar mass analysis of neutral and anionic copolymers based on methacrylic acid and different (meth)acrylates has been developed. Size exclusion chromatography (SEC) using a novel polyester- based packing as the stationary phase and dimethylacetamide (DMAC) as the mobile phase yields highly accurate results for copolymers with a methacrylic acid content up to 50 wt.-%. To suppress the different polar and ionic interactions between the sample molecules, the stationary phase and the eluent, DMAC was modified with LiBr and acetic acid. Calibrating the SEC system with poly(methyl methacrylate) of narrow polydispersity, molar masses were obtained that are in good agreement with data obtained by SEC-MALLS (multi-angle laser light scattering) and SEC measurements of methylated samples. The reproducibility and the robustness of the novel method were proven by running similar samples in three different laboratories and for an extended period of two weeks.
Studies on flocculation of clay suspension by polyacrylamide
Authors: Prabhu T. Niranjana , Rao Y. Jagannadha , Prashantha K. 
Published: August 2014

Abstract The flocculation of dilute pottery clay suspension using polyacrylamide (PAM) was investigated. Different molecular weight PAMs were synthesized by free-radical polymerization initiated with the persulfate-bisulfate redox pair. The synthesized polyelectrolytes (PAM1, PAM2 and PAM3, from low to high molecular weight) and a commercial one (C-492) were used for flocculation studies. The flocculating performance of polyelectrolytes was measured on 3% w/v pottery clay suspension using settling tests and turbidity measurements. PAM2 at pH 5.0 showed the maximum settling rate, which is nearly three times that of C-492, and it also showed a better turbidity reduction. Molecular weight is the key factor in influencing settling and turbidity reduction. In the present study, increasing molecular weight enhanced settling rate and turbidity reduction to a certain level beyond which there is a decrease, suggesting an optimum molecular weight for the given application. PAM2, a medium molecular weight polyelectrolyte (2.0·105 g/mol) has shown better performance than PAM1 (1.3·105 g/mol), PAM3 (6.0·105 g/mol) and the commercial polyelectrolyte C-492 (molecular weight of order 106).
AB Block-copolymers poly(oxyethylene)-blockpoly( dicyclohexyl itaconate): temperature dependence of the morphology
Authors: Aleksieva Krasimira , Ancev Ane , Koseva Slobodanka , Cvetkovska Maja , Nedkov Emanuel 
Published: August 2014

Abstract The paper deals with AB block-copolymers poly(oxyethylene)-blockpoly( dicyclohexyl itaconate) (POE/PDCHI) containing 2000 and 5000 g/mol of the flexible POE. The study aims at revealing the thermal effect on the copolymer morphology in the 20 - 200°C range. Optical microscopy investigations were performed. The results confirm our previous X-ray studies. A liquid crystalline state is observed in the 90 - 180°C range. It is characterized by birefringence and is determined by the chair-chair conformation, a dominating structure of the cyclohexyl rings. A condis-crystal state is observed at cooling in the interval 90°C to room temperature. It is characterised by a variety of cyclohexyl conformations and, therefore, by a lack of birefringence. The PEO component in the copolymer starts crystallising into small local spherulites at about room temperature. The results obtained allow the conclusion that the presence of PDCHI is a determining factor for the mesomorphic state of the copolymers discussed.
Synthesis and characterization of 1,4-diazophenylenebridged Cu-phthalocyanine polymer
Authors: Alkan Cemil , Aras Leyla , Gündüz Güngör 
Published: August 2014

Abstract A novel type of phthalocyanine polymer, 1,4-diazophenylene-bridged Cuphthalocyanine, was prepared from the diazonium salt of diaminobenzene and Cu(II) 1,8,15,22-tetraaminophthalocyanine. The polymer is partially soluble in tetrahydrofuran, dichloromethane, and dimethylformamide. Characterization of the polymer was performed by IR and UV-visible spectroscopy, X-ray diffraction, ash analysis, viscometry, differential scanning calorimetry and thermogravimetric analysis. The molecular weight of the soluble part of the polymer was determined by ebullioscopy. Electrical conductivity of the polymer and its doped samples were determined by the 4-probe technique. It was found that the electrical conductivity increased up to 10-4 S/cm after doping. The redox behaviour of the polymer was investigated utilizing cyclic voltammetry.
Thermal stability of side-chain polymer liquid crystals
Authors: Mano João F. 
Published: August 2014

Abstract Five simple-comb polymer liquid crystals - four polyacrylates and one polysiloxane - were studied using thermogravimetric analysis. A simple kinetic model was used to access the activation energy of the weight loss events. For the polyacrylates one main degradation process was observed with activation energy around 165 kJ/mol, probably involving intramolecular transfer, which would include a coupled weight loss mechanism of both polymeric backbone and mesogenic side-groups. For the studied polysiloxane, two overlapped mechanisms are observed that suggest separate mechanisms for the degradation of side-groups and main chain.
Poling of β-poly(vinylidene fluoride): dielectric and IR spectroscopy studies
Authors: Sencadas Victor , Costa Carlos M. , Moreira Victor , Monteiro Jorge , Mendiratta Sushil K. , Mano João F. , Lanceros-Méndez Senentxu 
Published: August 2014

Abstractβ-Poly(vinylidene fluoride) (β-PVDF) exhibits ferroelectric properties due to the special arrangement of the chain units in the crystalline phase. The piezoelectric properties of the material can be optimised by poling the original stretched film. The main effect of the poling process is the alignment of the randomly organised dipolar moments against the applied field. In this work, poled and non-poled β- PVDF from the same batch are characterised by dielectric spectroscopy. The origin of the electrical and mechanical response of poled and non-poled β-PVDF were further explored by far IR spectroscopy and discussed on a molecular level. The main effect of the poling process on the dielectric response of the material is a small increase of the dielectric constant due to the preferential alignment of the main dipolar contribution and a slight decrease of the dielectric loss, due to the more organized amorphous structure. The conductivity is strongly increased by poling, especially the high-temperature conductivity, ascribed mainly to hopping conductivity due to free charges induced during poling. FTIR experiments indicate that the origin of these effects and also of the variations in the thermo-mechanical response of the material can be found in the reorientation of the crystalline dipoles along the poling field, together with a partial reduction of the amount of α phase and an increase of the amount of β phase. The α to β transformation, mainly due to the stretching process, seems to be optimized by the poling process.
Synthesis and characterization of highly branched polymethacrylates via self-condensing oxyanionic copolymerization
Authors: Jia Zhifeng , Huang Wei , Yan Deyue 
Published: August 2014

AbstractHighly branched polymethacrylates were successfully synthesized by the self-condensing vinyl copolymerization of 2-dimethylaminoethyl methacrylate (DMAEMA) and methacrylic inimer containing a vinyl group and an oxyanionic active site, which was formed via the in situ reaction of 2-hydroxyethyl methacrylate (HEMA) with potassium hydride. Depending on the comonomer ratio, γ = [DMAEMA]0/[HEMA]0, branched poly(DMAEMA)s with number-average molecular weights between 4800 and 22 000 and degree of branching between 0.09 and 0.38 were obtained, as evidenced by gel permeation chromatography and NMR analysis. Thermally reversible phase transitions were observed for the branched poly(DMAEMA)s produced at higher comonomer ratio (γ ≥ 5). Quaternization of the branched poly(DMAEMA)s with methyl iodide led to cationic polyelectrolytes with branched structure.
Atom transfer radical polymerization of styrene initiated by the novel initiator 2-bromo-2-nitropropane
Authors: Wang Gang , Zhu Xiulin , Zhengping Cheng , Zhu Jian 
Published: August 2014

AbstractHeterogeneous atom transfer radical polymerization (ATRP) of styrene initiated by 2-bromo-2-nitropropane in bulk was carried out with CuCl/2,2′-bipyridine as the catalyst. The kinetics was first order in monomer and the numberaverage molecular weight of the polymer increased linearly with monomer conversion, indicating the ‘living’/controlled nature of the polymerization. However, the number-average molecular weight was usually higher than the theoretical one. The nitro group might react with the Cu complex, resulting in insufficient initiation. The amount of catalyst has no effect on the controllability of this catalyst system for the ATRP of styrene. The presence of a halide end group in the obtained polymer was confirmed by both 1H NMR and chain-extension reaction.
SEC/MALDI-TOF Mass spectrometry study of hydroxy-, carboxy- and methyl ester-terminated aliphatic polyesters
Authors: Salhi Slim , Tessier Martine , Blais Jean-Claude , Gharbi Rachid El , Fradet Alain 
Published: August 2014

AbstractPoly(ethylene adipate) (PEA) and poly(ethylene dodecanedioate) (PED) with dicarboxy-, dihydroxy-, dimethyl ester- and hydroxy-carboxy end-groups were synthesized and characterized by 13C NMR and MALDI-TOF MS. Size-exclusion chromatography (SEC) fractions of these polyesters were analyzed by MALDI-TOF MS and used as standards to obtain SEC calibration curves leading to the absolute molar masses of the unfractionated polyesters. PEA and PED calibration curves were different from each other, but the same calibration curve was obtained for each type of polyester, irrespective of the nature of end-groups, showing the predominant role of the nature of repeating units on the hydrodynamic volume of oligoesters. The study also shows that the conventional SEC calibration method using polystyrene standards leads to a significant overestimation of polyester average molar masses.
‘Surfactant-free’ stable nanoparticles from biodegradable and amphiphilic poly(ε-caprolactone)-grafted dextran copolymers
Authors: Ydens Isabelle , Degée Philippe , Nouvel Cécile , Dellacherie Edith , Six Jean-Luc , Dubois Philippe 
Published: August 2014

AbstractA variety of poly(ε-caprolactone)-grafted dextran copolymers were synthesized with a controlled architecture through a three-step procedure: partial protection of the dextran hydroxyl groups by silylation, ring-opening polymerization of ε-caprolactone initiated from remaining free hydroxyl groups on partially silylated dextran, and silyl ether deprotection under mild conditions. The potential of these amphiphilic grafted copolymers as surfactants was investigated by water/toluene interfacial tension measurements. Since each copolymer showed noticeable surfactant properties, their ability to form ‘surfactant-free’ nanoparticles was evaluated using the nanoprecipitation method. It was found that remarkably stable core (polyester) - shell (polysaccharide) nanoparticles with a mean diameter around 200 nm were formed.