bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, characterisation and properties of aramid copolymers prepared from AB and AB2 monomers
Authors: Monticelli Orietta , Fiori Stefano , Mariani Alberto , Russo Saverio , Komber Hartmut 
Published: August 2014

Abstract Aromatic polyamide (aramid) copolymers having a highly branched architecture were prepared by direct polycondensation of an AB2 monomer (5-(4-aminobenzoylamino) isophthalic acid) with an AB monomer (N-(4-aminophenyl)terephthalamic acid). Two synthetic routes have been followed for copolymer preparation, differing from each other in the overall monomer content and the type of salts added to the reaction medium (LiCl or LiCl + CaCl2). Otherwise, both methods used the same conditions and the same condensing agent (triphenyl phosphite). The feed ratio of the monomers affected the copolymer solubility in aprotic polar solvents such as N,N-dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide. Only high AB2/AB monomer ratios allowed obtaining completely soluble polymers in the above media. Also copolymer intrinsic viscosity was influenced by that ratio as well as by the polymerisation routes. IR measurements gave an indication of polymer structure evolution as a function of the monomer feed ratio, while 1H NMR experiments verified the actual monomer composition in the synthesized polymers. The monomer feed ratio turned out to influence polymer properties, such as degree of crystallinity, thermal degradation temperature and liquid crystalline behaviour. Some of the characterisation techniques we used (1H and 31P NMR, IR, SEM-EDS) revealed the presence of phosphorus derivatives in the copolymers, despite extensive sample purification. This presence is coming from derivatives of the condensing agent, and is directly related to the content of AB2-type structures present in the copolymers.
Optical and thermal properties of novel diazine-based oligo(phenylene vinylene)s
Authors: Mainil Michaël , Pascal Laurent , Vanden Eynde Jean-Jacques , Van Haverbeke Yves , Dubois Philippe 
Published: August 2014

Abstract New electro-conjugated diazine-based oligo(phenylene vinylene) derivatives with some interesting optical and thermal properties have been synthesised and characterised. These conjugated systems are built up on two benzenic cycles linked to a central diazine, either pyrimidine or pyrazine, through a carbon-carbon double bond. Both benzenic rings are substituted by one or two alkoxy chains. The length, the position and the number of alkoxy chains per benzenic ring have been varied and have proved to modulate both optical and thermal properties. Optical properties have been studied by UV-visible absorption spectroscopy as well as emission spectroscopy. Differential scanning calorimetry, wide-angle X-ray scattering and optical microscopy under crossed polarizers have been applied for characterising the thermal transitions and crystalline changes occurring in these conjugated systems.
On the kinetics of nematic ordering in solutions of semiflexible macromolecules: a Monte Carlo simulation
Authors: Stukan Mikhail R. , Ivanov Viktor A. , Müller Marcus , Paul Wolfgang , Binder Kurt 
Published: August 2014

Abstract The occurrence of nematic liquid-crystalline ordering in semidilute and concentrated solutions of semiflexible macromolecules has been studied by means of grand canonical Monte Carlo computer simulations using the bond fluctuation model and the configurational bias scheme. Chain length was equal to 20 monomer units, while the persistence length was about 5 monomer units. We used an intramolecular stiffness potential depending on the angle between successive bonds along the chain and on the bond length, and an attractive interaction between monomer units to model variable solvent quality. We have monitored the processes of appearance and destruction of monodomain and multidomain nematic configurations. Our findings are that the first stages of both the ordering and disordering processes occur upon sufficient oversaturation through the spinodal ordering scenario. Possible screening of nucleation processes and the applicability of our model to real kinetics are discussed. Results of our simulations are visualized in six movies.
Metallo-celluloses, 2 Synthesis of cellulose derivatives bearing lateral bis-terpyridine ruthenium(II) complexes
Authors: Laube Bettina , Schmelz Oliver , Rehahn Matthias , Wunderlich Winfried 
Published: August 2014

Abstract An efficient method is described for the simultaneous introduction of 4’-p-benzyl-2,2’:6’,2’’-terpyridine and benzyl side groups into cellulose. For this purpose, cellulose triacetate was treated in dimethyl sulfoxide/NaOH solution with mixtures of 4’-p-bromomethylphenyl-2,2’:6’,2’’-terpyridine and benzyl bromide. An almost quantitative conversion of the cellulose hydroxyl groups was reached when less than one terpyridine substituent was attached to the cellulose repeating units on average. At higher degrees of terpyridine substitution, some of the cellulose hydroxyl groups seem to remain unsubstituted. This conclusion has been drawn on the basis of NMR, IR and solubility measurements. We assume that steric hindrance of the bulky side groups is responsible for incomplete conversion. In a final step, the terpyridine substituents of the cellulose derivatives could be converted quantitatively into ruthenium(II) complexes via treatment with activated [Ru(tpy)Cl3] in N,N-dimethylacetamide/1-butanol (tpy: 2,2’:6’,2’’-terpyridine).
Reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in fluid CO2
Authors: Arita Toshihiko , Beuermann Sabine , Buback Michael , Vana Philipp 
Published: August 2014

Abstract Reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene in fluid CO2 have been carried out at 80°C and 300 bar using cumyl dithiobenzoate as the controlling agent in the concentration range of 3.5·10-3 to 2.1·10-2 mol/L. This is the first report on RAFT polymerization in fluid CO2. The polymerization rates were retarded depending on the employed RAFT agent concentration with no significant difference between the RAFT polymerization performed in fluid CO2 and in toluene. Full chain length distributions were analyzed with respect to peak molecular weights, indicating the successful control of radical polymerization in fluid CO2. A characterization of the peak widths may suggest a minor influence of fluid CO2 on the addition reaction of macroradicals on the dithiobenzoate group.
Determination of wear of surfaces by scratch testing
Authors: Brostow Witold , Darmarla Gowrisankar , Howe Juliet , Pietkiewicz Dorota 
Published: August 2014

Abstract We have formulated a quantitative definition of wear different from the current imprecise definitions. Wear is defined as the unwanted loss of solid material from solid surfaces due to mechanical interaction. The debris method currently used to quantify wear produces results strongly dependent on conditions. We have performed multiple scratch tests for a variety of polymer samples: polypropylene, polytetrafluoroethylene and a polyester. In each of the materials studied, the scratch penetration depths reach a constant value at a given force after 8 scratches or so. Similarly, the scratch recovery (final, healing) depths for a fixed force reach a plateau after a dozen or so scratch tests. Thus, strain hardening by repetitive scratching takes place. A likely explanation is formation of a more ordered phase - as seen before in mechanical tests by Siegmann, Aharoni, Faitelson et al. Given these results we define a measure of wear W(F) for a given indenter geometry and force F as W(F) = limn→∞ Rh(F) where n is the number of tests performed and Rh is the final (residual, healing) depth after viscoelastic recovery. The present results confirm also our earlier ones that scratch recovery is another useful way to characterize viscoelasticity.
Interfacial irregularity induced by hydrogen bonds at the interface in immiscible polymer blends
Authors: Kobori Yuka , Yasumitsu Rei , Akiba Isamu , Akiyama Saburo , Sano Hironari 
Published: August 2014

Abstract Effects of interactions at the interface on the morphologies of immiscible polymer blends were investigated using linear low-density polyethylene/poly(4- vinylphenol) (LLDPE/PVPh) and LLDPE/poly(methyl methacrylate) (LLDPE/PMMA) blends containing polyethylene-block-PMMA (PE-b-PMMA). In the case of LLDPE/ PMMA/PE-b-PMMA blends, in which there is no specific interaction at the interface, shapes of dispersed droplets were maintained and sizes were simply diminished with increasing PE-b-PMMA content. On the other hand, in the case of LLDPE/ PVPh/PE-b-PMMA, in which hydrogen bonds are formed between PVPh and PMMA blocks at the interface, we found irregularly undulated phase boundaries.
Hydrogels from chitosan crosslinked with poly(ethylene glycol) diacid as bone regeneration materials
Authors: Mincheva Rosica , Manolova Nevena , Sabov Rumen , Kjurkchiev Galen , Rashkov Iliya 
Published: August 2014

Abstract A simple method to covalently crosslink chitosan using poly(ethylene glycol) diacid as crosslinking agent is proposed. Networks net-chitosan-ι- PEG(COOH)2 were obtained by heating chitosan in aqueous PEG600(COOH)2 solutions at a temperature higher than 60°C. IR spectroscopy revealed the formation of amide bonds. It is shown that the obtained chemical networks are pH-sensitive hydrogels with enhanced hydrophilicity. The equilibrium degree of swelling of the hydrogels is determined by the conditions of their preparation - heating temperature and mole ratio between chitosan and the crosslinker. The ability of the polymer networks to facilitate bone regeneration processes was shown by in vivo implantation experiments.
Novel silicone-based capacitive pressure sensors with high sensitivity for biomedical applications
Authors: Arshak Khalil , Morris Deirdre , Korostynska Olga , Jafer Essa , Arshak Arousian , Harris John , Clifford Seamus , Lyons Gerard 
Published: August 2014

Abstract In this work, an investigation of the pressure-sensing properties of a silicone rubber was conducted. Small amounts of carbon black were added to the silicone during fabrication and the effect on the sensitivity was explored. A full investigation of the mechanical and electrical properties of each composition shows that adding carbon black to the material greatly increases its sensitivity to pressure. This increase in sensitivity appears to be related to improvements in the material’s permittivity, which increases with carbon loading.
Turbulent drag reduction characteristics of amylopectin and its derivative
Authors: Lim Sung Taek , Choi Hyoung Jin , Biswal Diptirani , Singh Ram Prakash 
Published: August 2014

Abstract Using amylopectin (AP) and a derivative, we systematically investigated their turbulent drag reduction characteristics and shear stability. The expected shear stability of polysaccharides as drag reducing and flocculating agents triggered our study on structural modification of AP. For this purpose, we prepared a derivative of AP, viz. AP grafted with polyacrylamide (GA), in which the granular form of AP powder (≈10 μm) changed into a mixture of larger fibrils and lumps. Using a rotating-disk apparatus, we measured the shaft torque and calculated the turbulent drag reduction (DR) efficiency under various experimental conditions, i.e., different polymer concentration, rotation speed, and temperature. Contrary to AP, GA showed relatively high DR efficiencies (27%) and very strong shear resistance.
Electrospun poly(vinyl alcohol)/poly(acrylic acid) fibres with excellent water-stability
Authors: Zeng Jun , Hou Haoqing , Wendorff Joachim H. , Greiner Andreas 
Published: August 2014

Abstract The water stability of electrospun poly(vinyl alcohol) (PVA) nanofibres was improved significantly by annealing with poly(acrylic acid) (PAA). Effects of annealing were tested on solution-cast PVA/PAA films by measurement of the swelling degree. The influence of PVA/PAA ratio, annealing temperature and period, molecular weight of PAA, and addition of esterification catalyst was investigated. The results were verified by a significant improvement of the water-stability of electrospun PVA/PAA composite nanofibres.
Wear of thermoplastics determined by multiple scratching
Authors: Bermúdez M. Dolores , Brostow Witold , Carrión-Vilches Francisco J. , Cervantes Juan J. , Pietkiewicz Dorota 
Published: August 2014

AbstractWe studied wear resistance in sliding by multiple scratching along the same groove for a variety of thermoplastics: polystyrene, styrene-acrylonitrile, polyamide 6 and polysulfone. Constant-load experiments were carried out with a micro scratch tester for several loads between 2.5 and 15 N; each time 15 scratches were performed. Except for polystyrene, all materials show an asymptotic residual depth as a function of the number of scratch tests performed. In contrast to other materials, polystyrene exhibits brittleness and debris formation. Scanning electron microscopy and scanning probe microscopy were used to characterize the deformation and wear mechanisms and were connected to the wear data obtained by multiple scratching. At 15 N we found a viscoelastic recovery for polystyrene of 27.8% while for polyamide 6 the corresponding value is 80.2%.
Carbon composite material and polysulfone modified by nano-hydroxyapatite
Authors: Szaraniec Barbara , Rosół Patrycja , Chłopek Jan 
Published: August 2014

AbstractThis paper reports on mechanical and biological properties of carboncarbon1 composites and polysulfone modified by hydroxyapatite (HAP), both natural (nano-particles) and synthetic (micro-particles) minerals. Results show that carbon-HAP composites have mechanical properties similar to carbon-carbon composites, while addition of HAP to polysulfone causes advantageous growth of Young’s modulus and limitation of creep, and disadvantageous decrease of tensile strength. Tests performed in simulated body fluid for carbon-HAP and polysulfone- HAP composites prove that the process of hydroxyapatite build-up becomes most intensive in the case of composites with nano-particles originating from natural hydroxyapatite.
Cyclodextrin in polymer chemistry: Kinetic studies on the free-radical polymerization of cyclodextrin-complexed styrene from homogeneous aqueous solution
Authors: Ritter Helmut , Steffens Christopher , Storsberg Joachim 
Published: August 2014

AbstractStyrene was encapsulated by an equimolar amount of randomly methylated β-cyclodextrin (CD) in water resulting in a water-soluble CD complex. Polymerization of this complex was carried out at 50°C using different amounts of the water-soluble azo-initiator 2,2’-azobis[N,N’-dimethyleneisobutyramidine] dihydrochloride. Unthreading of CD during polymerization led to water-insoluble polystyrene. Analysis of the polymers obtained showed that the polymerization from homogenous aqueous solution can be described by an equation similar to the classical polymerization in solution (number-average degree of polymerization vs. initiator concentration: Pn -1 ~ [I]0.5).
Self-ignition of polymerization fronts with convection: the ‘rainstorm effect’
Authors: Bidali Simone , Ducrot Arnaud , Mariani Alberto , Rustici Mauro 
Published: August 2014

AbstractThis work is devoted to an experimental and numerical study on the influence of natural convection on the ignition of polymerization reaction fronts. Numerical simulations confirm experimental findings. Indeed, it has been observed that under the same initial and boundary conditions the front ignition can occur either in the centre of the reactor or at the top. The difference between these two cases is determined by the viscosity of the medium and by other parameters that can influence the convective motion of a liquid monomer. If the viscosity is low, weak convective motion in the beginning of the development of the reaction will lead to the accumulation of the hotter monomer at the top of the reactor. In this case, front ignition occurs at the top and propagates downwards (rainstorm effect). If the viscosity is sufficiently high, the convective motion does not essentially change the position of the emerging hot spot; the front appears at the centre of the reactor and propagates almost spherically outwards.
A new approach to multiblock copolymers using atom transfer radical coupling
Authors: Nagelsdiek René , Keul Helmut , Höcker Hartwig 
Published: August 2014

AbstractAtom transfer radical coupling (ATRC) is a method for chain extension of styrene homopolymers prepared by atom transfer radical polymerization (ATRP). This concept is used to produce multiblock copolymers from block copolymers prepared via ATRP of styrene using various macroinitiators. ATRC comprises the reactivation of the dormant species at the chain ends. In the absence of monomer, the active radical species recombine to give chain extension (from polystyrene, PS) or multiblock copolymers (from block copolymers). The application of ATRC to PSblock- poly(bisphenol A carbonate)-block-PS (PS-b-PC-b-PS) was not successful because chain degradation of the PC block occurs. However, poly(phenylene oxide)-block-PS (PPO-b-PS) and PS-b-PPO-b-PS were successfully transformed into tri- and multiblock copolymers by ATRC, although the coupling efficiency is not as high as observed for PS oligomers under similar conditions.
Silica-coating of fluorescent polystyrene microspheres by a modified Stöber method and their stability against photobleaching
Authors: Kobayashi Yoshio , Misawa Kiyoto , Kobayashi Masaki , Takeda Motohiro , Konno Mikio , Satake Masanobu , Kawazoe Yoshiyuki , Ohuchi Noriaki , Kasuya Atsuo 
Published: August 2014

AbstractSubmicron-sized polystyrene spheres incorporating fluorescence dyes (fluorescent microspheres) were coated with silica by means of a seeded polymerization technique based on the Stöber method. Silica-coating of the fluorescent microspheres with a size of 100 nm was performed in the presence of 0 - 10 g/l polyvinylpyrrolidone (PVP), 1 - 13 mol/l water, 0 - 0.8 mol/l aq. ammonia and 0.00038 - 0.2 mol/l tetraethoxyorthosilicate (TEOS). The addition of PVP was found to suppress the generation of free silica particles and produced no shell-free fluorescent microspheres improving the uniformity of shell thickness of silicacoated fluorescent microspheres. Silica shell thickness increased from 11 to 63 nm with increasing TEOS concentration at 10 g/l PVP, 0.4 mol/l aq. ammonia and 11 mol/l water. Silica-coated fluorescent microspheres showed more stable fluorescence to laser-irradiation than uncoated fluorescent microspheres.
Plasma-bonding of poly(dimethylsiloxane) to glass
Authors: Katzenberg Frank 
Published: August 2014

AbstractFor the purpose of bonding poly(dimethylsiloxane) (PDMS) to glass, both components’ surfaces were treated with low-pressure oxygen plasma, indirect corona or simply with an oxygen-rich butane gas flame. In the case of low-pressure oxygen plasma treatment, the process parameters were varied and optimized with the consequence that the achieved adhesion between PDMS and the glass substrate was so strong that the PDMS could not be peeled off the glass slide without damaging the elastomer.
Hybrid Microgels Containing Gold Nanoparticles
Authors: Pich Andrij , Karak Arpita , Lu Yan , Ghosh Anup K. , Adler Hans-Juergen P. 
Published: August 2014

AbstractIn present paper we report on a preparation of hybrid microgels filled with gold nano-particles (AuNPs). Temperature-sensitive VCL/AAEM microgels have been used as containers for deposition of Au by in situ formation of gold nano-particles. Synthesis of AuNPs has been performed by two methods: a) reduction of chloroauric acid with sodium borhydride and b) reduction of chloroauric acid by sodium citrate under ultrasonic agitation. In both cases AuNPs were deposited directly into microgels leading to formation of composite particles which exhibit temperature-sensitive properties, tunable gold contents and high colloidal stability. The influence of Au load on microgel size, morphology, swellingdeswelling behaviour and stability is discussed.
Aggregation of Blends of Poly(N-vinyl pyrrolidone) and End-functional Polystyrene in Aqueous Solution
Authors: Masunaga Hiroyasu , Sasaki Kanako , Akiba Isamu 
Published: August 2014

AbstractAggregation behavior of blend of poly(N-vinyl pyrrolidone) (PVP) and polystyrene having a sulfonic acid group at one end (PSS) in aqueous solution was investigated by dynamic and static light scattering (DLS, SLS) measurements and scanning electron microscopy (SEM). The angular dependence of apparent diffusion coefficients suggested that the PVP-PSS aggregate shows an anisotropic structure. Comparison of an experimental SLS profile with theoretical calculations of particle scattering functions indicated that the PVP-PSS aggregate formed rodlike structure with 1200 nm height and 20 nm cross-sectional radius. Corresponding results were obtained by SEM observations.
Influence of Porosity on the Fragmentation of Ziegler-Natta Catalyst in the Early Stages of Propylene Polymerization
Authors: Zheng Xuejing , Pimplapure Makarand S. , Weickert Günter , Loos Joachim 
Published: August 2014

AbstractCatalyst fragmentation and polymer growth in the early stages of propylene polymerization has been investigated using different Ziegler-Natta catalysts. Polymerization was carried out in slurry under mild conditions and stopped at low yield. Scanning electron microscopy (SEM) has been used to characterize the surface and cross sectional morphology of polymer particles at different stages of particle growth. Different fragmentation behavior is observed, and it is found that the way that catalyst fragments in the early stages of polymerization is greatly influenced by the porosity of the catalyst. When a less porous catalyst was used, the resulting mass diffusion limitation causes layer-bylayer fragmentation, starting at the outer surface of the catalyst particle to the center. In contrast, for highly porous catalyst, monomer can easily penetrate into the pores of the catalyst / polymer particle. The polymer growing throughout the particle results in a coarse and instantaneous fragmentation.
Macroporous 4-Vinylpyridine-divinylbenzene – Estimation of Pore Volume, Surface Area, and Pore Size Distribution
Authors: Malik Muhammad Arif 
Published: August 2014

Abstract4-Vinylpyridine-divinylbenzene copolymer beads of ~0.3 mm in diameter were synthesized by suspension polymerization technique. The beads were made porous by dilution of the monomers with phthalate esters. The porosity was varied by changing the diluent, by varying the degree of dilution, and by varying the ratio of divinylbenzene in the monomers. Pore volume, surface area, and pore size distribution were determined by mercury penetration method, and densities of the dried copolymers were determined by a measuring cylinder and a balance. Statistical analysis of the data shows that the surface area and swelling coefficient in acetone can be estimated from the pore volume value with a reasonable good accuracy. Pore size distribution curves for the copolymers having pore volume in the range of 0.1 ml/g to 0.8 ml/g are shown. One can approximately estimate the pore size distribution if the pore volume is known. The pore volume can be estimated with a reasonable good accuracy from the density of the copolymers.
Optically active polymer: synthesis and characterization of new optically active poly (hydrazide-imide)s incorporating L- leucine
Authors: Hajipour Abdol Reza , Zahmatkesh Saeed , Ruoho Arnold E. 
Published: August 2014

AbstractThis paper deals with the polycondensation between a chiral diacyl chloride (N,N′-Pyromelliticdiimido-di-L-leucine chloride) and six different dihydrazides. The corresponding poly (hydrazide-imide)s which have been obtained in quantitative yields are moderately soluble in polar aprotic solvents, have good thermal stability and optical activity. The synthetic compounds have been characterized by IR, UV and 1H NMR spectroscopy, elemental analysis and specific rotation. The thermal properties of the polymers (10 and 15) have been studied by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC).