bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coils, globules and single chain glasses
Authors: Napper Donald H. 
Published: March 2011

AbstractThe cyclic coil‐globule‐coil transitions for poly(N‐isopropylacrylamide) tethered to an interface exhibit unexpected phenomena. Two, not the predicted single, coil‐to‐globule transitions can be observed: the one that is predicted occurs in worse than θ‐solvents whereas the other is observed in better than θ‐solvents. The latter phenomenon appears to be associated with the the formation of n‐clusters, first postulated by de Gennes. The chains in their globular form were found to undergo an entropy driven entanglement process that prevents reversible swelling in the globule‐to‐coil transition and leads to hysteresis in the layer thickness. Single chain glasses of polystyrene prepared by microemulsion polymerisation display physical properties different from those of multichain glasses including a higher conformational temperature, larger free volume and a predominantly exothermic rather than an endothermic DSC scan near Tg. These observations have been attributed to the occurrence of cohesional entanglements.
Scattering from polymer films and its application to optical properties of blends and display devices
Authors: Stein Richard S. , Srinivasarao Mohan , Müller Jörg 
Published: March 2011

AbstractThe application of the technique of observing the light scattering from solid polymers for the study of amorphous phase separation, spherulitic crystallization, phase separation in crystalline polymers, and coarsening of liquid crystal polymers is reviewed. The effect of shear and electrical and magnetic fields on liquid crystal orientation is discussed and its application for constructing light control and display devices is considered.
Two‐dimensional NMR studies of molecular dynamics in heterogeneous polymers
Authors: Spiess H. W. 
Published: March 2011

AbstractAdvanced two‐dimensional solid‐state NMR techniques making use of 1H spin diffusion and high resolution 13C detection are powerful tools for the non‐destructive investigation of polymer morphologies and domain sizes. The spin diffusion coefficients needed for quantitative analysis have been calibrated for both rigid and mobile polymers by combining NMR, X‐ray scattering and electron microscopic measurements on diblock copolymers of known morphologies. It turns out that NMR is particularly sensitive to detect small domains in the range of 2–10 nm, and to residual heterogeneities in larger domains, reflected in changes of chain mobility. Last, but not least, NMR is a sensitive tool for characterizing interfacial regions.The techniques will be introduced and demonstrated on various block copolymers including core shell systems, polymer blends and layered systems of rigid rods and flexible side chains. There, the side chain mobility is directly related to the chain conformation and density modulations within the layers.
Effect of local dynamics on model epoxy resins
Authors: Monnerie L. , Halary J. L. , Lauprêtre F. 
Published: March 2011

AbstractA series of epoxy resins has been prepared with different chain stiffness either in the diepoxide residue or in the diamine crosslinker (1). Furthermore, the crosslink density has been changed by incorporating either monoamine or secondary diamine as a chain extender, but in each system the stoichiometric ratio was maintained (1).Viscoelastic measurements were performed over a wide range of frequencies with the aim of determining the main characteristics associated with the Tg and β relaxation processes (2, 3). In a complementary way, high resolution solid state 13C NMR measurements were carried out to determine the mobilities of the different aliphatic carbons in the epoxy moieties (4).The effects of the chemical structure and of the crosslink density on the mobility of the different groups and the consequences on the Tg values, the amplitude of the β transition and the modulus of the resins are analyzed (5).
Effect of flow on polymer‐polymer miscibility
Authors: Fernandez Maria L. , Higgins Julia S. 
Published: March 2011

AbstractThe effect of shear flow on the phase behaviour of partially miscible blends exhibiting a lower critical solution temperature behaviour has been investigated. Miscibility limits were detected, with and without the application of flow, as changes from optical clarity to turbidity using light scattering and as the appearance of double glass transition temperatures. Light scattering data were collected on a rheo‐optical device that was designed to monitor phase changes in polymer blends undergoing shear flow between parallel glass plates in a temperature controlled environment. Glass transition temperatures of some quenched sheared blends were measured using a differential scanning calorimeter in order to confirm the conclusions from the light scattering data. It was found that shear induced demixing and shear induced mixing may be observed within the same blend depending on the magnitude of the applied flow. Miscibility gaps and closed miscibility loops may appear in the phase diagrams. At certain temperatures and shear rates unusual scattering patterns were observed and these were associated with a “ripple” morphology when directly viewed through the microscope.
Creep and yield behaviour of polyethylene
Authors: Ward Ian M. 
Published: March 2011

AbstractExtensive studies of the creep and recovery behaviour of oriented polyethylene have been undertaken because of the potential engineering applications of high modulus polyethylene fibres and large section oriented materials made by the Leeds die‐drawing process. Two primary requirements are a valid protocol for the practical assessment of the creep behaviour and an adequate formal representation which can provide the basis for a physical interpretation of the creep processes in terms of the structure of the oriented materials.The practical requirements of improved creep performance lead to examination of the effects of molecular weight and copolymerisation on creep and recovery, together with studies of the effects of radiation cross‐linking either before or after drawing. A particular new feature has been the development of a process for cross‐linking in acetylene, where it has been shown that diene bridge crosslinks are produced with very little chain scission.The protocol adopted for assessing creep behaviour is to construct creep strain rate/strain (Sherby‐Dorn) plots which, for highly oriented fibres, show constant strain rates after an initial period. These equilibrium strain rates can be modelled by two thermally activated processes acting in parallel.In recent research these studies have been extended to fibres of lower draw ratio and to isotropic polyethylene. It has been possible to establish links between creep and yield behaviour, and to show that slow crack propagation can be understood in terms of a combination of yield and creep to failure.
New polymer systems exhibiting microphase separation transition with the formation of nano‐microstructures
Authors: Khokhlov Alexei R. 
Published: March 2011

AbstractThe concept of microphase separation was up to now widely applied mainly to the conformational transitions in block‐copolymer solutions and melts. However, recently it became obvious that this concept has a much more general meaning. It was shown that microphase separation transition can be observed in random copolymers, interpenetrating polymer networks, polyelectrolyte mixtures, poor solvent polyelectrolyte solutions, ionomer solutions and melts, polymer blends and solutions with nonlocal entropy of mixing. In all these examples the emerging microdomain structures correspond to the nanometer scale, therefore the study of these effects can lead to the new ways of obtaining polymer materials with controlled nano‐microstructure.In this presentation the review of our recent findings on microphase separation in some of the above‐mentioned systems will be presented.1. The problem of microphase separation in the systems containing weakly charged polyelectrolytes (polyelectrolyte mixtures and poor solvent polyelectrolyte solutions) will be considered. From the methodic point of view, it will be shown that this problem can be solved by direct minimization of the free energy, without the use of “weak segregation” or “strong segregation” assumptions which are common in the theory of block‐copolymers. The final phase diagrams exhibit wide macroscopic phase separation regions, which is their main difference from the corresponding phase diagrams for block‐copolymer systems. The formation of microdomains is thus coupled with macroscopic phase separation: in most of the cases microdomain structure is formed in one of the coexisting phases after macroscopic phase separation takes place [1] ‐ [2].2. The formation of the multiplet structure in ionomer melts and solutions can be also considered as the microphase separation in the random copolymer system with the formation of the “micelles” (or clusters) of ionic links. The parallels with micelle formation in block‐copolymer systems can be established if one considers a new “superstrong segregation regime” for block‐copolymer microstructures. This regime can be indeed observed for diblock copolymers with one ionomeric and one neutral block [3].3. The microphase separation transition in ordinary polymer blends and solutions is also possible. The conditions for this effect are: (i) significant entropic contribution to polymer/polymer or polymer/solvent miscibility, (ii) the nonlocal character of this contribution with a high value of the nonlocality radius. It is argued that one can expect that the entropy nonlocality radius increases in the vicinity of the glass transition for the blend or polymer solutions (in the latter case solvent molecules act like “poor solvent plasticisers”). Computer simulation data supporting the theoretical prediction of microphase separation transition in these systems will be presented [4] ‐ [5].
Precursor method for polymeric LB films
Authors: Kakimoto Masa‐Aki , Imai Yoshio 
Published: March 2011

AbstractFirst, the general concept of the “Precursor Method” for the preparation of polymeric Langmuir‐Blodgett (LB) films that possess no long alkyl chain between film layers, and the preparation of polybenzothiazole 7 LB film are described. The preparation of 7 LB film was carried out by the same procedure as that used to make polyimide LB films via precursor LB films of polyamides that contain β‐carboxyethylthio alkylamine salts 6. Precursor 6 LB film had a Y type structure with monolayer thickness of 2.8 nm, while polybenzothiazole 7 LB film had 0.34 nm. The nonlinear susceptibility χ(3) of polybenzothiazole 7 LB film in parallel to the dipping direction was 3.8 × 10−11 esu, whereas the susceptibility in the perpendicular direction was about one fifth of that of the parallel direction.
Thermoreversible gelation of a polysaccharide with immunological activity: Rheology and dynamic light scattering
Authors: Fuchs Tania , Richtering Walter , Burchard Walther 
Published: March 2011

AbstractThe β — 1.3/1.6 glucan schizophyllan is known to suppress tumor growth. Two different schizophyllan samples have been characterized by static and dynamic light scattering in dilute solution of 0.01M NaOH and dimethyl sulfoxide (DMSO). A thermoreversible, optically transparent gel of schizophyllan was obtained on addition of sorbitol to aqueous solution, and the gelation process was followed by low amplitude oscillatory shear and dynamic light scattering (DLS). Power law behavior of storage modulus G'(ω) and loss modulus G”(ω) with the exponent n=0.5 was found at the gel temperature. In the same temperature range intensity time correlation functions (TCF) were measured and the electric field TCFs were calculated, taking into account the heterodyne contributions. The occurrence of two motions gave evidence for inhomogeneities in the gel. The results of the slow motion from DLS agreed surprisingly well with those, estimated by oscillatory rheology. The viscoelastic properties and the influence of sorbitol and schizophyllan concentrations were investigated regarding the pharmaceutical application in cancer therapy.
Acrylic thermoplastic elastomers and comb‐shaped poly(methyl methacrylate) via the macromonomer technique
Authors: Radke Wolfgang , Roos Sebastian , Stein Helga M. , Müller Axel H. E. 
Published: March 2011

AbstractComb‐shaped poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PnBuA) grafted with PMMA were prepared by radical copolymerization of ω‐methacryloyl‐PMMA with MMA and nBuA, respectively. The comb‐shaped PMMA is characterized with respect to radius of gyration by using gel permeation chromatography equipped with a multi‐angle laser light scattering detector. The radical copolymerization of the macromonomer with nBuA in toluene follows complex kinetics. The dependence of the relative reactivity of the macromonomer on absolute concentration and on the ratio of comonomers may be explained by preferential solvation of comonomers by segments of their own kind (“bootstrap effect”) or even micelle formation. However, there is no clear evidence for the formation of micelles in toluene. In contrast, NMR studies show micelle formation in the preferential solvent dimethyl sulfoxide. The graft copolymers are transparent thermoplastic elastomers. Phase separation is demonstrated by differential scanning calorimetry and morphological studies.
A new oral microsphere drug delivery system
Authors: Ottenbrite Raphael M. , Zhao Ruifeng , Milsteln Sam 
Published: March 2011

AbstractA new oral proteinoid microsphere drug delivery system is discussed with respect to its unique dependence on pH. Extensive evidence indicate that this technique not only can be used to deliver the protein and polar macromolecular drugs which are currently administered via injection, but also can be used to administer antigens and vaccines. Future work has been proposed to study the physical interaction of specific drugs with specifically designed oligopeptides structures.
Nonthrombogenic polymers ‐ designs and evaluation
Authors: Nakabayashi Nobuo , Ishihara Kazuhiko 
Published: March 2011

AbstractNew nonthrombogenic polymers were designed with attention to the surface of biological membranes, that is, the surface was completely covered with phospholipids adsorbed from plasma. The polymers with phospholipid polar group, 2‐methacryloyloxyethyl phosphorylcholine polymers, could interact with phospholipids in plasma selectively and strongly. The adsorbed phospholipids on the polymer surface were concentrated, organized each other and then formed a self‐assembled biomimetic membrane surface. The surface showed excellent resistance for both protein adsorption and blood cell adhesion.
Polymerization of lactams, 89 magnesium caprolactamates as initiators of ∈‐caprolactam polymerization
Authors: Nováková Václava , Šáchová Monika , Brožek Jiří , Bernat Petr , Roda Jan 
Published: March 2011

AbstractThe anionic polymerization of ∈‐caprolactam initiated with magnesium initiators was studied in the interval 180–250°C. ∈‐Caprolactam magnesium bromide was much more active than magnesium di(∈‐caprolactamate) and the activity of both depended on the way of their preparation. The polymerizations obey the zero order kinetics with respect to the monomer.
The influence of thermoplastic elastomers on structure and crystallisation behaviour of polyolefin blends
Authors: Plawky Udo , Wenig Werner 
Published: March 2011

AbstractThe influence of a styrene‐ethylene/butylene‐styrene triblock copolymer (SEBS) on an isotactic polypropylene / polyethylene blend was investigated. For comparison binary blends with polypropylene and SEBS alone were also prepared. The blends obtained by solution mixing were characterised by small‐angle x‐ray scattering, light microscopy and dynamic mechanical analysis. The role of SEBS as matrix reinforcer or interfacial agent is composition dependent. Experimental data also reveal a different influence of SEBS on the binary blends than on the ternary blends containing polyethylene.
Surface modification of expanded poly(tetrafluoroethylene) by means of microwave plasma treatment for improvement of adhesion and growth of human endothelial cells
Authors: Simon F. , Hermel G. , Lunkwitz D. , Werner C. , Eichhorn K. , Jacobasch H.‐J. 
Published: March 2011

AbstractSurface modification of expanded poly(tetrafluoroethylene) (ePTFE) vascular prostheses was carried out by means of low pressure microwave plasma treatment. Hydrogen/ water vapour mixtures (containing excess of hydrogen) were shown to be efficient with respect to functionalization of PTFE.The results of treatments in dependence on various gas pressures and treatment times were detected by physicochemical techniques (zeta potential, wetting measurements) and by surface spectroscopy (XPS, ATR‐FTIR).Furthermore, adhesion and proliferation of human endothelial cells from umbilical cord (HUVEC) onto modified ePTFE were observed in vitro in culture media. The results of this biological test of plasma treated materials correlate well with physicochemical surface parameters.
Effects of gamma and electron beam irradiation on polymer electrolytes
Authors: Okamoto Yoshiyuki , Cho Myung D. 
Published: March 2011

AbstractPolymer electrolytes based on poly(ethylene oxide) and lithium salts have been widely studied in recent years. In order to enhance the room temperature ionic conductivity of PEO‐LiX complexes, various techniques, such as addition of plasticizers and crown ether, and also irradiation by γ and electron beams have been investigated. The enhancement of the conductivity by irradiation has been accounted for the decreasing of the crystallinity of PEO‐LiX. We reviewed these results and have investigated the degradation processes of PEO using Tb3+ fluorescence probes. We have also studied on the effects of irradiation of polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA) and PEO using Tb+3 fluorescence probe. Various monomers containing SO3H and COOH have been grafted on poly(ethylene oxide) using irradiation technique. The structures and ionic conductivities of Li and Na salts of irradiated products were investigated in detail.
Esterification of α‐olefins catalyzed by homogeneous and polymer supported phosphine ‐ palladium ‐ tin chloride complexes
Authors: Pan Cai‐Yuan 
Published: March 2011

AbstractThe polymer phosphine ligand with various crosslinkage and phosphine contents was prepared by copolymerization of diphenylvinyl‐phosphine with divinylbenzene using 2,2′ ‐azobisisobutyronitrile (AIBN) as initiator. Linear methyl heptanoate in high yield was obtained from hexene‐l catalyzed by polymer‐supported and homogeneous phosphine‐palladium‐tin chloride complex. Comparison with the homogeneous catalyst, the polymer catalyst had higher activity and almost the same selectivity. The effects of the catalyst composition, the structure of the polymer ligand and other experimental variables on the catalytic activity and selectivity of the polymer catalyst have been examined, and are discussed in relation to the mode of this catalysis.
Polypyrrole: Synthesis and electronic device application
Authors: Satoh Masaharu , Hasegawa Etsuo 
Published: March 2011

AbstractA Ta solid electrolytic capacitor using conducting polypyrrole as a counter electrode has been developed by means of the direct film formation of electrochemical and chemical polymerization methods. Two‐step electrochemical polymerization at a rapid and gentle rate yields a polypyrrole film on the dielectric surface of the capacitor. On the other hand, the homogeneous mixture dissolving pyrrole and oxidant under −70 °C allows chemical polymerization at elevated temperature, which also produces polypyrrole film on the dielectric surface. The capacitors produced by these methods demonstrate the improved characteristics, i.e., a high capacitance, low inner resistance and small leakage current, that correspond to the high‐speed electronic devices.
Synthesis and mesomorphic properties of fishbonelike, liquid crystalline polysilsesquioxanes: 4. Pd‐coordinating, fishbone‐like imine‐based liquid crystalline polysilsesquioxane
Authors: Wan Youzhi , Huang Yaxuan , Xie Ping , Li Bo , Jin Shunzi , Cao Xinyu , Liu Dongsheng , Dai Daorong , Li Ze , Zhang Rongben 
Published: March 2011

AbstractA new type of Pd‐coordinating, imine‐based, fishbone‐like liquid crystalline polysilsesquioxanes (Pd‐FBI) including μ‐acetato‐bridged Pd‐FBI [Pd(μ‐oAc)‐FBI] and μ‐chloro‐bridged Pd‐FBI [Pd(μ‐Cl)‐FBI] has been synthesized first by a hydrosilylation reaction to form fishbone‐like, imine‐based liquid crystalline polysilsesquioxane (H‐FBI and MH‐FBI respectively,) and then by an ortho‐palladation reaction with palladium acetates to obtain Pd(μ‐oAc)‐FBI. The latter was further subjected to ligand substitution reaction with NaCl to form Pd(μ‐Cl)‐FBI. Their mesomorphic properties investigated by differential scanning calorimetry (DSC) and optical polarization microscopy (OPM). show that the Pd‐FBI is a thermotropic liquid crystalline polymer and its clearing temperatures and mesophase range are much higher than those of the corresponding comb‐like imine liquid crystalline polysiloxanes (IMLCP) by about 100 °C. In this paper the influence of the palladium content on mesogenic behavior is discussed.
Ionomer‐surfactant self‐assembly in low‐polarity solvents
Authors: Bakeev Kirill N. , Chugunov Sergey A. , Larina Tat'yana A. , Macknight William J. , Zezin Alexander B. , Kabanov Viktor A. 
Published: March 2011

AbstractA systematic study of complexation reactions of sulfonated polystyrene ionomers containing up to 5 molar percent of polar chain units with various oil‐soluble surfactants is carried out in low‐polarity organic solvents. Dipole‐dipole attractions of the components lead to the formation of complexes characterized by limiting compositions and an unusual polymer‐colloidal morphology of joint clusters and/or micelles. The limiting compositions (φ) for the complexes formed between ionomers and surfactant of the same charge (bis(2‐ethylhexyl)sulfosuccinate sodium salt), or nonionic surfactants (primarily aliphatic amines) are equal to 15–30 surfactant molecules per one ionomer salt/acid group on average, with φ depending on the hydrophilic‐lypophilic balance of the components, the initial aggregation state of surfactant and the nature of low‐polarity solvent. Ionomersurfactant complexation is accompanied by disruption of self‐contacts of ionomer salt/acid groups, leading to “unfastening” and expansion of the ionomer coils in dilute solution. The “driving force” of the ionomersurfactant complexation and the structure of the resultant complexes are discussed.
Self‐assembly in ω‐functionalized block copolymers of styrene and isoprene
Authors: Floudas G. , Fytas G. , Pispas S. , Hadjichristidis N. , Pakula T. , Khokhlov A. R. 
Published: March 2011

AbstractThe spatial organization of end‐functionalized diblock copolymers of styrene and isoprene revealed two separate levels of microphase separation: one between the two blocks forming the microdomain and another between the polar and non‐polar material. The association produced by the latter process has a pronounced effect on the dynamics as revealed in rheology and dielectric spectroscopy. The introduction of a polar group into the different chain‐ends has a dramatic effect on the phase behavior of the diblock copolymers and provides new ways of controlling their miscibility.