bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiblock silicones, 1 Vinyl functionalized polydimethylsiloxane a
Authors: Ivanenko Carine , Maitre Catherine , Ganachaud François , Hémery Patrick 
Published: August 2014

Abstract The first part of this series is devoted to the preparation of vinyl functionalized multiblock silicones by the process of anionic ring opening polymerization in miniemulsion. The advantage of working in dispersed media is that different scales of reactivities are found between one-chain reactions, taking place at the interface (propagation, backbiting), and two-chain reactions, located in the bulk of the particles (polycondensation and intermolecular redistribution). First, homopolymerizations of octamethylcyclotetrasiloxane (D4) and tetramethyltetravinylcyclotetrasiloxane (D4 V) were carried out and compared, focusing specifically on the rates of polymerization, backbiting and polycondensation processes. Copolymerization of D4 with D4 V then gave insight into the extent of mixed cycles’ formation and particularly how to avoid these. On this basis, recipes were carefully selected so that homopolymerization and scarce co-polycondensation and redistribution progress at the expense of backbiting reactions and thus multiblock copolymers are formed, the microstructure of which was confirmed with 29Si NMR.
Porous structure formation via phase separation of two polymers Blends of aromatic polyoxalates and poly(lactic acid)
Authors: Zorin Ivan , Ovcharenko Nadja , Batuto Yan , Bilibin Alexander 
Published: August 2014

Abstract A new method of porous polymer structure formation by means of phase separation of two polymers with different degradation rates is proposed. Aromatic polyesters of oxalic acid as fast degradable polymers were synthesized and their degradation properties under alkaline conditions were studied. Heterogeneous mixtures of poly(phenolphthalein oxalate) with poly(lactic acid) were prepared by solution phase separation and co-precipitation, and porous poly(lactic acid) samples were produced by polyoxalate leaching due to its fast degradation.
Grafting of methyl methacrylate onto natural keratin
Authors: Martínez-Hernández Ana Laura , Velasco-Santos Carlos , Icaza Miguel de , Castaño Victor M. 
Published: August 2014

Abstract Keratin fibers from chicken feathers were modified through graft copolymerization with methyl methacrylate in an aqueous medium, using a KMnO4 / malic acid redox system. Original and grafted fibers were characterized by IR and Raman spectroscopy and their thermal behavior was studied by both differential scanning calorimetry and thermogravimetric analysis. The grafted fiber surface was characterized by scanning electron microscopy. The characterization results show that grafting was effectively achieved and this was confirmed by a ninhydrin test after acidic hydrolysis of the grafted keratin.
Impact modification of polyamide-12 through blending with liquid polybutadiene, 2 a Compatibilization of blends of PA12 and liquid polybutadiene with pyromellitic anhydride
Authors: Talon Olivier , Couvercelle Jean-Pierre , Bunel Claude 
Published: August 2014

Abstract The compatibilizing effect of pyromellitic anhydride (APy) in blends of PA12 and liquid polybutadiene (HTPB) was investigated. Blends were prepared, with or without APy, and the efficiency of this route of compatibilization was evidenced by observation of their morphologies. The addition of APy led to a finer dispersion of HTPB in the PA12 matrix. The formation of a compatibilizing block copolymer was proven by the evolution of the torque, the amine functionality and the size of the particles during blending, and by extraction of the dispersed phase followed by FTIR analysis. The effect of the mixing procedure was also investigated, and it was shown that the best dispersions were obtained when APy was added to a pre-blend of PA12 and HTPB.
Distribution of molecular weight and composition in diblock copolymers
Authors: Tobita Hidetaka , Zhu Shiping 
Published: August 2014

Abstract The distribution of molecular weight (MW) and composition of diblock copolymers is considered theoretically. Assuming that the chain end of each block is coupled randomly, the weight-average MW of the block copolymers is given by Mw = w1 (Mw,1 + Mn,2) + w2 (Mw,2 + Mn,1), irrespective of the shape of the distribution of each block, where wi is the weight fraction, and Mn,i and Mw,i are the number- and weight-average MW of each block. In copolymer chains, the chemical compositions as well as the MWs cannot be identical for all polymers, and there exists a bivariate distribution of MW and composition. When the MW distribution (MWD) of both blocks follows the Schulz-Zimm distribution, the bivariate distribution can be obtained analytically. In addition to the bivariate distribution, the full MWD, the average composition as a function of MW, the composition distribution of copolymers having a specified MW, and the overall composition distribution are obtained. The composition distribution, as well as the average composition, becomes independent of MW under the condition σ1/Mn,1 = σ2/Mn,2, where σ i is a parameter indicating the narrowness of the Schulz-Zimm distribution. The present theoretical analysis provides new insight into the design of diblock copolymers.
Adsorption of monodisperse polybutadienes on carbon black, 1 Adsorption from dilute and semi-dilute solutions
Authors: Vuillaume Kathy , Haidar Bassel , Vidal Alain 
Published: August 2014

Abstract A series of polybutadienes (PBs) of different molecular weights (in the range of 3000 to 120 000) but of identical microstructure (1,2-PB content ≈ 80%) was synthesized via anionic polymerization. The adsorption in solution of the various monodisperse PBs on carbon black (CB) was studied for different polymer/ CB ratios as well as for polymer and CB concentrations in the range of 0.1 to 100 g/l. The amount of adsorbed polymer was followed and was found to be essentially governed by the polymer concentration, which determines also the conformation of the polymer chain on the filler surface. CB concentration didn’t prove to be a pertinent parameter, whereas the polymer/filler ratio was found to control the formation of the three-dimensional polymer-filler network on the basis of a percolation process. Results are discussed with respect to the available theories.
Phase inversion and co-continuity domain in immiscible polyethylene/polystyrene blends
Authors: Prochazka Frédéric , Dima Romulus , Majesté Jean-Charles , Carrot Christian 
Published: August 2014

Abstract Blends of polystyrene and high-density or linear low-density polyethylene have been prepared in an internal mixer and studied in a wide range of compositions. Phase inversion compositions have been determined using selective extraction and scanning electron microscopy. It appears that phase inversion can occur in a domain of compositions rather than at a single point. The existing models of phase inversion are not complete enough to explain the entire phenomenon, and percolation of each component may be considered to describe the formation of co-continuity.
Artificial muscles based on conducting polymers
Authors: Cortés María Teresa , Moreno Juan Carlos 
Published: August 2014

Abstract Natural muscles have mechanical properties that conventional actuators do not possess. These natural machines show large strain, moderate stress, high efficiency and stability, fast response time, high power/weight ratio, long lifetime, etc. In the last years a great interest has arisen to develop materials that mimic natural mechanisms. Conducting polymers have an array of potential applications as artificial muscles since they are capable to produce a moderate displacement when submitted to an electrochemical reaction. This property has been used to fabricate actuator devices that imitate and even improve the performance of natural muscles. For example, conducting polymers show stresses 15 times higher than those generated by mammalian muscles, a high power/weight ratio and a high degree of compliance. However, there are also several responses that need improvement in the actuators based on conducting polymers. Strains are still c. 50% lower than in natural muscles. Most of this kind of actuators only work in liquid media. It is necessary to increase the response time and obtain more durable actuators with longer lifetime and higher stability. In spite of these disadvantages, the first actuators based on conducting polymers are being commercialized. This paper presents a brief summary of some of the actuators based on these polymers, focusing on their design, performance and actuation mechanism.
Living free radical polymerization of styrene with 2-cyanoprop-2-yl dithionaphthalate as RAFT agent
Authors: Jian Zhu , Xiulin Zhu , Di Zhou , Jianying Chen 
Published: August 2014

Abstract The reversible addition-fragmentation chain transfer (RAFT) bulk polymerization of styrene was studied using 2-cyanoprop-2-yl dithionaphthalate (CPDN) as RAFT agent in the presence or absence of 2,2’-azoisobutyronitrile (AIBN). The results of both thermally and AIBN-initiated styrene (St) polymerizations show that St can be polymerized in a controlled way using CPDN as RAFT agent; i.e., the polymerization rate is first order with respect to monomer concentration, and molecular weight increases linearly with monomer conversion. The molecular weights obtained from gel permeation chromatography are close to the theoretical values and molecular weight distributions are relatively narrow (Mw/Mn < 1.2). It is confirmed by chain extension reaction that the polymer prepared via RAFT polymerization can be used as a macroRAFT agent. The effects of reaction temperature and mole ratios [St]0/[CPDN]0/[AIBN]0 on the polymerization were investigated. The results indicate that the reaction temperature has a positive effect on the polymerization rate, but little effect on molecular weight and molecular weight distribution, and the optimum mole ratios were found to be [CPDN]0/[AIBN]0 > 4/3 and [St]0/[CPDN]0 < 800.
Cholesteric copolymers and mixtures containing dithienylethene photochromic fragments
Authors: Semenova Dasha , Bobrovsky Alexey , Boiko Natalia , Shibaev Valery , Zavarzin Igor , Kalik Marina , Krayushkin Mikhail 
Published: August 2014

Abstract The phase behaviour and optical properties of mixtures based on cholesteric copolymers with 3 - 6 wt.-% of photochromic dithienylethene dopants as well as a cholesteric copolymer containing dithienylethene side groups were studied. It was shown that planar-oriented films of the mixtures and of the copolymer possess a selective light reflection in the visible or near IR regions of the spectrum. UV irradiation of the mixture films leads to the appearance of an intense absorbance peak in the spectral range coinciding with the selective reflection band (λmax ≈ 522 - 615 nm depending on the chemical structure of the photochromic fragment). This process is associated with the photocyclization of dopants and photochromic side groups and the ‘degeneration’ of the selective light reflection. The photoinduced coloured form of dopants and photochromic side groups is thermally stable at room temperature, but subsequent irradiation of the film by visible light (550 or 633 nm) induces a decoloration process. The influence of temperature on the rates of forward and back photoprocesses in such polymeric liquid crystalline films was studied. The potentialities of the use of such type of materials for reversible data recording and storage were demonstrated.
Combination of supramolecular cross-linking with covalent cross-linking through epoxide ring-opening including gel studies
Authors: Hofmeier Harald , El-ghayoury Abdelkrim , Schubert Ulrich S. 
Published: August 2014

Abstract Terpolymers based on poly(methyl methacrylate), containing terpyridinemoieties as well as epoxide groups, were synthesized via free-radical polymerization. The products were cross-linked non-covalently with iron(II) ions and covalently by treatment with AlCl3. Both steps could be combined in different order. The non-covalent cross-linking could be reversed by applying a strong competing ligand. The swelling behaviour of the polymers was investigated.
Relevance of purification procedures in the direct synthesis of poly(p-phenyleneterephthalamide) from its dimer
Authors: Mariani Alberto , Monticelli Orietta , Fiori Stefano , Russo Saverio 
Published: August 2014

Abstract The direct synthesis of poly(p-phenyleneterephthalamide) has been successfully performed by polymerizing its dimer, N-(4-aminophenyl)terephthalamic acid, instead of p-phenylenediamine and terephthaloyl chloride or terephthalic acid, as commonly carried out. An intrinsic viscosity much higher than those typical of the commercial fibres (Kevlar®) has been obtained. The procedure and the advantages of the method are highlighted.
Impact modification of polyamide-12 through blending with liquid polybutadiene, 1 Binary blends of PA 12 and liquid polybutadiene
Authors: Talon Olivier , Couvercelle Jean-Pierre , Bunel Claude 
Published: August 2014

Abstract Blends of polyamide 12 (PA12) with liquid polybutadiene (HTPB) were prepared by melt blending over a composition range varying from 0 to 20% of polybutadiene. A study of the potential reactions led to the conclusion that the system undergoes no chemical reaction under the processing conditions used. Scanning electron micrographs of the blends showed a good dispersibility of HTPB in the PA12 matrix. Charpy impact tests and tensile tests demonstrated that the dispersion of HTPB in PA12 provides a good impact toughness enhancement but leads to a decrease of Young's modulus.
Synthesis and characterization of alternating poly(amide urea)s and poly(amide urethane urethane)s from ε-caprolactam, diamines, and diphenyl carbonate or ethylene carbonate
Authors: Ubaghs Luc , Sharma Bhaskar , Keul Helmut , Höcker Hartwig , Loontjens Ton , Benthem Rolf van 
Published: August 2014

Abstract Alternating poly(amide urea)s from ε-caprolactam, diamines H2N-(CH2)x- NH2 (x = 2 - 4), and diphenyl carbonate were prepared in two steps. The microstructure of the poly(amide urea)s, as determined by means of 1H NMR spectroscopy, reveals a strictly alternating sequence of the building blocks. The molecular weights and polydispersities obtained were 7500 < Mn < 10 000 and 1.48 < Mw/Mn < 1.56, respectively. Thermal properties were determined by means of differential scanning calorimetry (DSC) (163.9°C < Tm < 197.2°C; 55.5°C < Tg (2nd heating) < 72.2°C), and thermogravimetric analysis (TGA). TGA shows a three-step decomposition at 200, 350, and 450°C, which was attributed to the cleavage of O-phenyl urethane end groups, as well as urea and amide linkages. These assignments were made by comparison with model compounds. Furthermore, alternating poly- (amide urethane urethane)s from ε-caprolactam, diamines, and ethylene carbonate were prepared in three steps. The microstructure of the poly(amide urethane urethane)s, as determined by means of 1H NMR spectroscopy, reveals imperfections. The molecular weights and polydispersities obtained were 5400 < Mn < 17 000 and 2.08 < Mw/Mn < 2.99, respectively. Thermal properties were determined by means of DSC (155.9°C < Tm < 159.0°C; 35.5°C < Tg (2nd heating) < 39.0°C) and TGA. TGA shows a complex decomposition due to the formation of ethylene carbonate by cleavage of the urethane groups (at approx. 230°C) and formation of poly(amide urea)s. The newly formed poly(amide urea)s decompose in a similar way as the poly(amide urea)s.
Characterization of an isophorone-based polyisocyanate
Authors: Burel Fabrice , Feldman Adeline , Loutelier-Bourhis Corinne , Bunel Claude 
Published: August 2014

Abstract After chemical modification with methanol, a polyisocyanate based on the isocyanurate of isophorone diisocyanate was analysed. MALDI-TOF MS and sizeexclusion chromatography were chosen and indirectly coupled to identify and quantify the different species. While, as expected, the isocyanate trimer and pentamer are the two main components, homologues until the tridecamer could be identified with MS. Moreover, the isocyanurate cycle occurs preferentially on the primary isocyanate group. According to the calculated composition, a numberaverage molecular weight of 775 and a number-average isocyanate functionality of 3,24 were determined.
Binary frontal polymerization: Velocity dependence on initial composition
Authors: Pojman John A. , Griffith Jerry , Nichols H. Archie 
Published: August 2014

Abstract Frontal polymerization is a mode of polymerization in which a localized zone of reaction propagates through the coupling of thermal diffusion and the Arrhenius dependence of the reaction rate. The dependence of the front propagation velocity on the initial composition has been determined in initially miscible binary systems of a free-radically cured diacrylate and an amine- or cationically cured epoxy resin. A minimum of the velocity as a function of the monomer mole fraction is observed if the two polymerizations occur independently. Excellent agreement with an analytical description was found with the diacrylate and an amine-cured epoxy but not for a diacrylate and a cationically cured one because of the effect of HCl impurities on the peroxide.
Synthesis of a novel poly(p-phenylene-vinylene) derivative and its application in chemiresistive sensors for electronic noses with an unusual response to organic vapours
Authors: Gruber Jonas , Yoshikawa Eduardo K. C. , Bao Ying , Geise Herman J. 
Published: August 2014

Abstract We report the synthesis of a novel poly(p-phenylene-vinylene) derivative bearing dodecanoylsulfanyl side-groups (12COS-PPV). Good solubility in organic solvents was achieved. The average molecular weight was around 30 000, the energy gap 2.8 eV and the thermal stability up to 130°C. Doping with iodine vapours rose conductivity to 2·10-6 S/cm. Gas sensors made from FeCl3-doped 12COS-PPV showed an unusual behaviour responding to only four of the eight different organic solvent vapours tested. Recoveries from the responses are not complete, but are reproducible and can be used to discriminate between the four solvents. Quantitative analyses are also possible since there is a good linear correlation between relative response and concentration.
Preparation and swelling behaviour of a novel anti-salt superabsorbent hydrogel based on kappa-carrageenan and sodium alginate grafted with polyacrylamide
Authors: Pourjavadi Ali , Ghasemzadeh Hossein , Hosseinzadeh Hossein 
Published: August 2014

Abstract A novel superabsorbent hydrogel was synthesized via crosslinking graft copolymerization of acrylamide (AAm) onto kappa-carrageenan (κC) and sodium alginate (Na-Alg) backbones in a homogeneous solution. Methylenebisacrylamide (MBA) and potassium persulfate (KPS) were applied as water-soluble crosslinker and initiator, respectively. FTIR spectroscopy was used for confirming the structure of the final product. A mechanism for superabsorbent hydrogel formation was also suggested. The parameters affecting the swelling capacity of the synthesized hydrogel, i.e., κC-Alg weight ratio, concentration of AAm, MBA and KPS, as well as reaction temperature were systematically optimized for obtaining maximum absorbency. The swelling capacity of hydrogels was also measured in various salt solutions (LiCl, NaCl, KCl, MgCl2, CaCl2, SrCl2, BaCl2, and AlCl3). Due to their high swelling ability in salt solutions, the hydrogels may be referred to as ‘anti-salt superabsorbent’ polymers. The overall activation energy for the graft copolymerization reaction was found to be 374 kJ/mol. The swelling kinetics of the hydrogels in distilled water and in saline solution (0.9 wt.-% NaCl) was investigated.
Characteristics of non-isothermal crystallization of polypropylene with and without talc
Authors: Albano Carmen , Papa José , Ichazo Miren , González Jeanette , Ustariz Carmen 
Published: August 2014

Abstract The non-isothermal behaviour of crystallization of polypropylene (PP) and its talc-filled composites was investigated by means of differential scanning calorimetry. Different analytical methods were used to describe the crystallization process. According to the behaviour of crystallization temperature, crystallization activation energy and crystallization parameters and coefficient, talc results in an increase in PP crystallization rate and in a decrease in total energy opposing to homogeneous crystallization. Velisaris-Seferis’ kinetic equation was found to describe reasonably well the non-isothermal behaviour of crystallization of PP and its filled composites.
Removal of copper-based catalyst in atom transfer radical polymerization using different extraction techniques
Authors: Ydens Isabelle , Moins Sébastien , Botteman François , Degée Philippe , Dubois Philippe 
Published: August 2014

Abstract Several methods allowing the removal of copper-based ATRP active complexes from crude amino-functionalized polymethacrylate chains are compared. Among them, precipitation in basic medium is one of the most efficient techniques since it allows high recovery yields (above 90%) with a residual metal content as low as 5 ppm. Extraction methods such as liquid-liquid phase separation and dialysis but also selective adsorption on acidic macroporous ion exchange resin constitute other attractive alternatives. As far as water-insoluble polymers are concerned, catalyst adsorption on alumina remains the most universal method and provides acceptable recovery efficiency. However, we want to stress the key-importance of the experimental adsorption conditions and above all the relative content of alumina used for catalyst extraction.
Molecular dynamics in polymeric systems
Authors: Dionísio Madalena , Alves Natália M. , Mano João F. 
Published: August 2014

Abstract It is well known that the properties of polymeric materials depend strongly upon their chemical structure. Other more specific factors that may be related to the chemical structure also determine the macroscopic behaviour of such materials, namely the relative position of the different segments of the polymeric chain, the molecular architecture (molecular weight distribution, branching, copolymer organisation, cross-linking extent, etc.), the crystalline environment and the pressure/temperature conditions. All these factors have a common impact in the material: they are strongly correlated to the mobility on the molecular level. That is why a huge amount of work has been devoted to the study of translational/rotational mobility that occurs within the polymeric chains. This review is intended to provide a brief survey on such kinds of mobilities, how they can be studied and what are their main characteristics. Examples on systems studied in our groups will be provided, obtained by dielectric and mechanical spectroscopies and differential scanning calorimetry. It will be mainly focused on molecular motions that occur in the solid phase (i.e., to temperatures up to the rubbery plateau). The dynamics in blends or copolymers will be avoided here, as they would deserve a special discussion in their own context. Special attention will be paid to the glass transition and the mobility that occurs below and above it. The dynamics that are observed in peculiar systems, such as semi-crystalline or liquid crystalline polymers, will be addressed.