bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioactive Plasma‐Polymerized Bipolar Films for Enhanced Endothelial Cell Mobility
Authors: Yang Zhilu , Tu Qiufen , Wang Jin , Lei Xingjiang , He Tingting , Sun Hong , Huang Nan 
Published: March 2011

AbstractA facile approach to a highly bio‐active interface material is reported. XPS reveals that polar entities exist at the interface between PPAam and PPAac nanolayers. They induce strong dipolar orientation polarizability and cause the redistribution of charges, which results in a remarkable increase of polar surface energy and hydrophilicity of the multistack bipolar films. In particular bipolar films with amine groups on their outermost surface show strongly enhanced cellular mobility. The attachment, adhesion, proliferation, migration, and coverage of ECs are significantly enhanced on such films. They are therefore promising as vascular implant materials, and could have applications as coating materials for tissue engineering. magnified image
Interfacial interactions and the polymer/polyurethane bond
Authors: Tocheff E. , Schreiber H.P. , Deng Zhuo 
Published: March 2011

AbstractLap shear measurements of adhesion in joints of polymers bonded with polyurethane adhesives varied significantly with time at elevated temperature. The effect has been linked with the ability of polyurethane molecules to restructure in response to the orienting strength of substrate surfaces, as defined by their non‐dispersive surface energy component. Acid/base interactions at the polymer/adhesive interface further affect the bond strength, increasing this important property when acid/base pairs are located at the interface, and diminishing the variable when acid/base interactions are absent.
Structure and properties of polystyrene‐polyethylene interpenetrating polymer network (ipn)‐like systems
Authors: Borsig Eberhard , Fiedlerová Agnesa , Häusler Karl G. , Michler Goerg H. , Greco Roberto 
Published: March 2011

AbstractA series of samples of polystyrene (PS) –polyethylene (PE) interpenetrating polymer network (IPN)–like system was prepared by synthesis in situ. The measurement of uniaxial compression modulus of the IPN samples was used for the determination of mean molar mass of the polymer chain between two junction points of the polymer network – M̌C. The electron microscopic records gave an evidence about two phase structure of the IPN samples. Generally, the crystalline part of PE network in all IPN investigated samples is relatively low. The influence of the concentration of crosslinking agent on mechanical behaviour of the IPN samples was studied.
Effect of external donor in polymerization of propylene by a MgCl2 supported titanium catalyst
Authors: Makio Haruyuki , Kioka Mamoru , Kashiwa Norio 
Published: March 2011

AbstractPolypropylene (PP) prepared with a MgCl2/TiCl4‐Et3Al/Ph2Si(OMe)2 catalyst system was fractionated by temperature rising elution fractionation method in order to investigate the effect of Ph2Si(OMe)2 as an external donor (ED). This PP had a broad and continuous distribution of tacticity. In comparison to the system without donor, however, ED brought a decrease of lower isotactic portions and an increase of higher isotactic ones simultaneously to the resulting polymer. The latter portions were eluted at higher temperature than the corresponding component obtained without donor, showing that the higher isotactic PP was newly produced by ED.
Magnetism of spin polymers prepared by the oxidative polyrecombination of captodative compounds
Authors: Tanaka Hitoshi 
Published: March 2011

AbstractMagnetism of hydroanilino ladder polymer and indigo polymer which were prepared by the oxidative polyrecombination of captodative substituted methane and indoxyl, respectively, was studied by ESR spectroscopy and magnetic susceptibility measurement. It was found that both spin polymers contained domains with high spin state in their structures and their spins were much more ordered with decreasing temperature.
Ion‐pair structure in anionic polymerization. Effect of temperature and association on an allylic lithium compound in two polar solvents
Authors: Bywater Stanley , E. Black Paul 
Published: March 2011

Abstract13C NMR studies are reported on enriched samples of a one‐unit model of the active centres present in butadiene polymerization. Concentrations between 2 × 103 M and 1M, and temperatures between −120° and 50° were investigated. The effect of ion‐pair association on charge distributions in diethyl ether solutions is described. The effect of temperature on the overall structure in tetrahydrofuran solutions is discussed.
Synthesis of star‐branched oligomers by reaction of oligobutadienyllithium with diesters and epoxidized soyabean oil
Authors: Schuéa F. , couvé J. , Dobreva R. , Sledz J. , Nicol P. 
Published: March 2011

AbstractAnionic polymerization can produce branches with low molecular weight and narrow molecular weight distributions. Post polymerization linking involving the still active chain ends can then be done to produce branched oligomers with a predetermined number of arms. These species are then excellent model compounds for testing high molecular weight branches. Here we chose the reaction of oligobutadienyllithium with ethyl acetate, dimethyl adipatc, diethyl adipatc, dimethyl phthalatcand epoxidized soyabean oil. For the last linking agent, we compared the result obtained with a high molecular weight poly(styryl‐b‐butadienyl)lithium.
Solid state NMR investigation of antiplasticization of polystyrene by mineral oil
Authors: Smith P. B. , Delassus P. T. , Ellaboudy A. S. , Diedering D. E. , Landes B. G. , Anderson S. L. , Grulke E. A. 
Published: March 2011

AbstractThe effects of mineral oil plasticization of polystyrene were investigated as a function of polystyrene molecular weight and mineral oil concentration. Solid state NMR, thermo/mechanical methods and positron annihilation spectroscopy (PAS) were used to study the molecular dynamics and free volume effects of this blend. Antiplasticization was observed in the low (40,000) molecular weight polystyrene samples as an embrittlement of the system. In contrast, the flexural modulus was not affected by the presence of mineral oil in the higher (270,000) molecular weight polymers but a decrease in the flexural strength was observed with increasing mineral oil concentration. The NMR and PAS data indicated that the mineral oil was not dissolved in the polymer at ambient temperature, rather it phase separated even at very low concentrations. This caused antiplasticization in low molecular weight polymers because the small free volume holes were filled causing a densification of the system. With high molecular weight polystyrene, this phase separation was manifested as a decrease in the flexural strength.
An overview of the correlations between NMR cross polarization time constants and dynamic moduli
Authors: Marcinko Joseph J. , Parker Anthony A. 
Published: March 2011

AbstractThe development of correlations between storage modulus (E'), loss modulus (E”), and the mean cross polarization time constant <TCH> are reviewed for a series of polyurethanes and a series of diverse polymers. The apparent validity of the relationships as well as their limitations and applications are discussed.
Functional polysiloxanes as photoinitiators for UV‐curable compositions: Evidence for a polymer effect
Authors: Coqueret Xavier , Pouliquen Lydie 
Published: March 2011

AbstractFunctional silicone copolymers containing one or several types of pendant ester groups including a benzophenone or a thioxanthone chromophore, and/or a tertiary amine were used to prepare novel photo‐initiating systems based on the phenone ‐ amine photogeneration of radicals. The influence of the nature and relative amounts of the functional pendant units on the overall efficiency of the various initiating systems was evaluated by measuring the rate of polymerization of an acrylate based composition. By comparing the results obtained from different combinations of polymeric or low molecular weight reactants, a neat polymer effect inducing a greater initiation efficiency is evidenced, especially when a polysiloxane containing only aromatic carbonyl ester groups is associated with free 4‐dimethylaminobenzoic esters as hydrogen donors. Time‐resolved spectroscopy performed with thioxanthone functional systems indicates that the favourable effect on the apparent polymerization rate is not correlated with the rate of quenching of the triplet excited state by a tertiary amine. The polymer effect can rather be explained by the microheterogeneity of the distribution of the partners in the complex initiation process.
Supramolecular structures and conformational transitions in polyelectrolyte gels
Authors: Khokhlov Alexei R. , Makhaeva Elena E. , Philippova Olga E. , Starodubtzev Sergei G. 
Published: March 2011

AbstractThree actual problems connected with the collapse transition of polyelectrolyte gels in poor solvent are reviewed. (i) The first topic is the appearance of microstructures for polyelectrolyte gels in poor enough solvents. Three reasons for microsegregation are discussed: effect of polyelectrolyte – hydrophobic competition, effect of the formation of multiplets from ionic pairs in the ionomer regime and the effect of partial formation of glassy kinetically frozen polymer rich regions. (ii) Second we analyze the interaction of the gels with polymers which are capable to form complexes with the gel chains. Main experimental results are presented for poly(methacrylic acid) gels interacting with poly(ethylene oxide), (iii) Finally, we consider the problem of interaction of polyelectrolyte gels with the sufactants. The micelle formation of surfactants inside the gel and its consequences for the conformational properties of the gel are discussed in detail.
Dynamic scattering of ternary polymer mixtures in solutions: The χF interaction parameter and the single chain diffusion coefficient DS
Authors: Borsali Redouane 
Published: March 2011

AbstractThis work discusses the dynamic scattering properties of ternary polymer mixtures in solution and emphasizes on how can be extracted the value of the single chain diffusion coefficient DS and that of the interaction parameter χF when using Quasi Elastic Light Scattering (QELS) in any good solvent. This is the direct consequence of considerable efforts made during the past decade, in the understanding of dynamic properties of multicomponent systems from both theoretical and experimental points of view.
Dynamic heterogeneity in diblock copolymer systems
Authors: Fytas George 
Published: March 2011

AbstractDynamic light scattering from diblock copolymers in melt and solution in a non‐selective solvent reveals different mechanisms for relaxing the composition and orientation fluctuations near the order to disorder transition (ODT). For the former, internal relaxation and copolymer chain diffusion are the main relaxation processes whereas the latter relate to collective orientation of the copolymer chains near the ODT and induced form anisotropy of coherently ordered microstructures below ODT.
Recent developments in the design of functionalised polymeric microspheres
Authors: Pichot Christian , Charleux Bernadette , Charreyre Marie‐Thérèse , Revilla Javier 
Published: March 2011

AbstractThis paper is a brief survey on the preparation of latexes bearing covalently bonded functional groups using various routes. Recent methods are presented using water soluble functional (or surface active) initiators, monomers or macromonomers. For tailor synthesis, the copolymerisation approach of a basic monomer with a functional monomer under emulsifier‐free conditions is generally the more suitable and versatile one. More progress should be pursued in this field in order to design better adapted chemical structures which will improve their use in radical‐initiated heterogeneous conditions and favour surface incorporation.
Recent advances in propylene polymerization with MgCl2 supported catalysts
Authors: Albizzati Enrico , Giannini Umberto , Morini Gianpiero , Galimberti Maurizio , Barino Luisa , Scordamaglia Raimondo 
Published: March 2011

AbstractThe role of Lewis bases in MgCl2 supported catalysts for olefin polymerization is a subject of continuous interest and discussion in order to obtain more and more active and stereospecific catalysts and to explain their stereoregulating mechanism.Through molecular calculation and conformational analysis it was possible to identify chelating diethers that have the correct oxygen‐oxygen distance necessary to tightly coordinate with the Mg ions of the support, even in the presence of other strong Lewis acids, and unable to give secondary reactions with TiCl4, AlR3, Ti‐C and Ti‐H bonds. The use of these donors has allowed the synthesis of catalytic systems that are both highly active and stereospecific even in the absence of external donors. Kinetic data of propylene polymerization with these catalyst systems are reported.The importance of the distance between the donor atoms in bifunctional Lewis bases has been proved also in the case of new classes of internal donors.Molecular modelling studies have enabled us to formulate models of active sites, located on some corners of MgCl2 crystallites, whose chirality is induced by the presence of a donor molecule in their environment. These models could explain, at least in part, the exceptional increase of isotactic polymer productivity observed for stereospecific catalyst systems, containing only the internal donor, with respect to catalysts lacking the Lewis base and could account for the influence of the donor on the molecular properties of the obtained polymers.
Disorder in layered TiCl3. Symmetry of the coordination site
Authors: Allegra Giuseppe 
Published: March 2011

AbstractThe structural layers of TiCl3 consist of two monoatomic layers of chlorine atoms octahedrally coordinated to intercalating Ti atoms. Mechanical (grinding) and/or chemical treatment of the regular α‐ or γ‐forms may produce the disordered δ‐form, wherein shifts and rotations between neighboring layers give rise to the largest disorder compatible with close‐packing of the chlorine layers, accompanied by reduction of crystallite size both along the layers and across them. A Bernoullian statistical model fully describes the statistical structure of the polycrystalline samples in terms of 4 parameters, two of them relating with the stacking disorder, the other two with crystallite size distribution.The catalytic sites for isospecific α‐olefin polymerization lie on the side edges of the structural layers. It is shown that Ti atoms on these edges possess two isochiral free valencies, enabling them to exchange the roles of the (Ti‐coordinated olefin) and of the (Ti‐growing chain) bonds at each polymerization step with no change of the local chirality, in analogy with the metallocene‐based isospecific catalysts.
How coordinating are non‐coordinating anions?
Authors: Siedle A. R. , Hanggi Bonnie , Newmark Richard A. , Mann Kent R. , Wilson Timothy 
Published: March 2011

AbstractElectrochemistry of (p‐CH3PhNC)6Cr+3 and optical spectroscopy of [1,2‐(9‐fluorenyl)2C2H4]ZrMe+ have been used to craft scales of coordinating ability of various anions. Coordinating ability also influences the barriers to intramolecular rearrangement in (RCp)2ZrMe+ as well as activity of zirconocenium ions as polymerization catalysts.
Pd(II) ‐catalyzed addition polymerizations of strained polycyclic olefins
Authors: Melia Jennifer , Connor Eric , Rush Stephen , Breunig Stefan , Mehler Christof , Risse Wilhelm 
Published: March 2011

AbstractCationic Pd(II) ‐complexes with weakly coordinating ligands were used for the olefin addition polymerization of strained polycyclic olefins. The cyclic structure of the monomers remained intact during the reaction which contrasts with products obtained from the olefin metathesis polymerization. The Pd(II) ‐catalyzed polymerizations showed the features of a “living” polymerization, when norbornene and selected exo‐substituted norbornene derivatives were used as the monomers.Endo‐ andexo‐dicyclopentadiene,exo‐1,2‐dihydrodicyclopentadiene,endo, exo‐1,4,5,8‐dimethano‐1,2,3,4,4a,5,8,8a‐octahydronaphthalene andendo, exo‐1,4,5,8‐dimethano‐1,4,4,a,5,8,8a‐hexahydronaphthalene were converted into the corresponding rigid polymers. The exo‐substituted monomers were found to polymerize at a higher rate than the corresponding or similar endo‐substituted monomers. The polymerization of norbornadiene and the subsequent thermal elimination of cyclopentadiene resulted in the formation of polyacetylene.
Amorphous phase and interphase organization of syndiotactic polypropylene
Authors: Sozzani Piero , Simonutti Roberto , Comotti Angiolina 
Published: March 2011

AbstractMaterials prepared by syndiotactic polypropylene of different stereochemistry (62 ÷96% r pentads) undergo transitions in the crystal phase, which depend on the thermomechanical history. The interfaces and the amorphous phase may be affected by the crystallite organization and the stereoregularity of the material. MAS NMR techniques provided a tool for characterizing the arrangement and the mobility of the polymer chains in the inter‐crystallite region. Chemical shifts, line‐width and relaxation parameters were determined as a function of recording temperature and glass transition temperature of the material. The same parameters were followed in the presence of a plasticizer. The different degree of intimacy of the phases was established by following the diffusion of magnetization among the hydrogen atoms of the amorphous and the crystalline phase. Defective regions and boundary regions were also identified and showed a large amount of conformations in the trans arrangement; the relaxation times indicate the chains being rigid and intimately mixed with the crystalline phase.
Electroactive block copolymers
Authors: Li Jean , Khan Ishrat M. 
Published: March 2011

AbstractSynthesis, characterization and properties of microphase separated mixed (ionic and electronic) conducting or MIEC block copolymers are reported. Poly{[ω‐methoxyocta(oxyethylene) methacrylate]‐block‐(4‐vinylpyridine)}, abbreviated as P[MG8–4VP], and poly{(3‐methylthiophene)‐block‐[(ω‐methoxyocta(oxyethylene) methacrylate]}, abbreviated as P[3MT‐MG8], have been synthesized. Differential scanning calorimetry (DSC) studies indicate that the polymers form a microphase separated structure. P[3MT‐MG8] can be doped with I2 and LiClO4 to generate electronic and ionic conducting microdomains, respectively. For the P[3MT‐MG8] series, bulk electronic conductivity as high as 1×10−3 S cm−1 and bulk ionic conductivity as high as 6.6×10−7 S cm−1 is observed at 30°C. This work represents a new concept in the area of electroactive polymers and should impact the microelectrochemical device industry.
The science of polymer colloids: The state of the art
Authors: Fitch Robert M. 
Published: March 2011

AbstractA review of recent developments is given, with a focus on those which promise the greatest future advancements of the science and technology of polymer colloids. Only those which involve Radical Copolymers are discussed. The topics are (1) Particle Formation, (2) Phase‐separated Latex Particles, (3) New Techniques of Characterization and Analysis, and (4) Surface Chemistry.
Practical methods to control morphology of heterogeneous polymer particles
Authors: Rudin Alfred 
Published: March 2011

AbstractThis review focusses on processes in which emulsion polymerizations are carried out in stages so that previously formed particles are either overcoated in subsequent polymerization stages or engulf the second and later stage polymers. These products are often called “core‐shell” particles. Basically, the most stable state of the final system is the one with the lowest net interfacial energy. In the case of a two‐stage emulsion polymerization there can be three interfacial tensions to consider. Several mutually consistent, effective thermodynamic treatments have been published. At present, they serve primarily to predict when the morphology of multi‐stage polymerization products may not be a simple reflection of the synthesis sequences. It is possible, and frequently desirable, however to produce particle structures that appear at first glance to be thermodynamically forbidden. This is achieved either by changing the surface characteristics of a polymer from those of the bulk material or by employing kinetic factors to anchor energetically unprofitable morphologies. This paper summarizes methods of both types that have been reported to control the texture of structured latex particles in order to produce designed morphologies.
Morphologies of micron‐sized monodispersed composite polymer particles having crosslinked structures produced by seeded polymerizations
Authors: Okubo Masayoshi , Nakagawa Tomoaki , Yamashita Tsuyoshi , Tsuji Morio 
Published: March 2011

AbstractThree kinds of micron‐sized monodispersed polystyrene (PS)/ poly(styrene ‐ divinylbenzene) composite particles were produced by two kinds of seeded copolymerizations of styrene (S) and divinylbenzene (DVB) (PS seed/ (S+DVB)=2/1, wt. ratio; S/DVB=1/1, molar ratio) in the presence of about 2 μm‐sized monodispersed PS particles, and their morphologies were examined. One was produced by a seeded dispersion copolymerization where almost monomers and initiators exist in an ethanol/water (12.6/4.0, w/w) medium. The others two were produced by seeded copolymerizations with the dynamic swelling method where almost monomers exist in the monomer‐swollen particles using 2, 2'‐azobisisobutyronitrile in monomer‐swollen PS seed particles or using 4, 4'‐azobis (4‐cyanopentanoic acid) in an ethanol/water (7/43, w/w) medium. In the former polymerization, the produced composite particles had a high dense crosslinked shell, whereas in the latter two polymerizations, they did the comparatively homogeneous crosslinked structures.
Characterization of particle morphology by scattering techniques
Authors: Ottewill Ronald H. , Cole Sarah J. , Waters Julian A. 
Published: March 2011

AbstractA description is given of the application of small angle neutron scattering to examine structural aspects of copolymer particles. Analysis of recent data obtained using a “single shot” polymerisation to prepare polystyrene‐poly (methyl methacrylate) particles shows that these have a core‐shell morphology.
Recent developments in microemulsion copolymerization
Authors: Candau FrançOise 
Published: March 2011

AbstractRecent results obtained in microemulsion copolymerization are presented. The characteristic features of microemulsions ‐ large interfacial area and great variety of structures ‐ have been used with profit to yield novel materials with interesting morphologies and properties. The examples considered here include the synthesis of i) novel solid porous materials ii) functionalized microlatex particles iii) water‐soluble copolymers with specific properties iv) hydrophilic‐hydrophobic copolymers. The characteristics inherent to each of these syntheses are discussed.
Modelling nucleation and particle growth in emulsion copolymerization in continuous loop reactors
Authors: Abaé Carlos , De La Cal José C. , Asua José M. 
Published: March 2011

AbstractA mathematical model for emulsion copolymerization in continuous loop reactors is presented. The flow pattern of the loop reactor can be represented by a loop formed by two tubular reactors with axial dispersion. The mathematical model combines this flow model with the physico‐chemical characteristics of the emulsion copolymerization. The outputs of the model are monomer conversion, copolymer composition, particle size distribution and latex viscosity. The model was checked during the redox initiated emulsion copolymerization of vinyl acetate and veova 10 carried out in a completely automated continuous loop reactor.