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  • 1
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It has been shown that the 15N nuclear reaction technique for hydrogen profiling can be used for the characterization of polymer films. With an optimized sample geometry, a depth resolution of 5 nm near the sample surface is achieved. A special γ-ray detector allows radiation damage in the sample to be minimized. Since the 15N technique discriminates between the hydrogen isotopes H and D, a suitable contrast between the different components of a polymer film is achieved by deuterating one component of the polymer. This has been utilized in the study of the surface-induced lamellar ordering within diblock copolymer films.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Die Konformation von Makromolekülen im teilkristallinen Zustand wurde von verschiedenen Autoren im Hinblick auf die Gültigkeit des adjacent re-entry- oder switchboard-Modells mit Hilfe der Neutronenkleinwinkelstreuung untersucht. Sowohl analytische Rechnungen als auch Monte-Carlo Rechnungen zeigen, dag die an schmelzkristallisiertem Polyäthylen und isotaktischem Polypropylen gefundenen experimentellen Ergebnisse auf der Basis des Erstarrungsmodells interpretiert werden können. In diesem Modell wird angenommen, daß sich Knäuelsequenzen wahrend der Kristallisation ausrichten, ohne dag weitreichende Diffusionsprozesse erfolgen.
    Notes: Summary The conformation of macromolecules in the semicrystalline state has been studied by various authors with respect to the validity of the adjacent re-entry — or switchboard model by application of small-angle neutron scattering. Analytical as well as Monte-Carlo calculations show that the experimental results for melt crystallized polyethylene and isotactic polypropylene can be interpreted on the basis of the solidification model. In this model it is assumed that crystallization occurs by straightening of coil sequences without a long range diffusion process.
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  • 3
    ISSN: 1435-1536
    Keywords: Thermoplastic elastomers ; deformation behavior ; x-ray scattering ; long spacing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The scattering behavior of pre-drawn and annealed bristles of a highly deformable poly(ether ester) themoplastic elastomer based on poly(butylene terephthalate) as hard segments and poly(ethylene glycol) as soft segments in a ratio of 57/43 wt.-% is studied. Small-angle x-ray seattering measurements with an area detector are carried out on bristles with and without application of stress up to 195% relative deformation. Two-dimensional scattering patterns are used for morphological characterization of the sample. At small deformations one morphology peak is found, corresponding to a periodicity that changes affinely with deformation. The morphology of the smaple represents assemblies of mutually parallel crystalline lamellae, positioned perpendicular to the stretching direction both under and without stress. When macrodeformation increases a second peak appears, and a four-point pattern is observed in the relaxed state. In this intermediate deformation range coexisting morphologies contribute to the scattering. Additional contributions arise from lamellae, which are inclined to the stretching direction, as well as from lamellae, which are again perpendicular to the stretching direction, as a result of microfibril relaxation and loss of interfibrillar contacts. At large deformations the latter morphology dominates and the 2D-scattering pattern again shows a two-point character. A morphological model for this behaviour is discussed, where the break of interfibrillar contacts during deformation and the inhomogeneous stress field in the sample play an important role.
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  • 4
    ISSN: 1435-1536
    Keywords: Polymer blends ; interfaces ; interdiffusion ; ellipsometry ; neutron reflectometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The techniques of neutron reflectometry and spectroscopic ellipsometry are compared as methods to measure the interface width between immiscible polymers. The interface thickness of the incompatible polymer system of polystyrene (PS) and polyn-butyl methacrylate) (PnBMA) is determined by neutron reflectrometry to (6.4±0.2) nm and (8.6±0.2) nm at temperatures of 120 and 156°C, respectively. Some emphasis is put on the measurement of those values also by spectroscopic ellipsometry using the same materials. A special sample geometry is chosen for ellipsometric measurements to compensate for thickness changes of films during annealing, and the dispersions of PS and PnBMA films are determined. With respect to the determination of the interface widths, however, it turns out that in the available wavelength range of 280 to 700 nm spectroscopic ellipsometry is not sensitive enough to measure the thin interface width between PS and PnBMA films. Neutron reflectivity results obtained for PS/PnBMA are discussed with respect to the Flory-Huggins segment interaction parameter χ calculated within the approximations of meanfield theory.
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  • 5
    ISSN: 1434-6036
    Keywords: PACS. 68.10.Gw Interface activity, spreading - 68.10.m Fluid surfaces and fluid-fluid interfaces - 68.55.a Thin film structure and morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The effect of the ratio of block lengths on the interfacial partitioning of poly(styrene-block-1,4 isoprene) diblock copolymers from their mixtures with polystyrene homopolymer melt is investigated utilizing a series of copolymers with almost constant molecular weight but different compositions. The concentration profile of the copolymer is measured directly using the nuclear reaction analysis technique; a segregation of the diblock is found at both the air/polymer surface, due to the lower surface energy of polyisoprene, and at the substrate/polymer interface. No significant effect of the block length ratio on the free-surface excess was observed. The block molecular weights have apparently led to dangling chain conformations in the non-overlapping mushroom and in the overlapping mushroom regimes whereas the brush regime was not accessible; no indications of a real border between the two former regimes was found.
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  • 6
    ISSN: 1435-1536
    Keywords: Key words Block copolymers ; Interaction parameter ; LCOT ; Phase diagram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The morphological phase diagram of poly(styrene-block-n-butyl methacrylate), P(S-b-n-BMA), has been investigated in detail using thermal analysis, microscopy, rheology and scattering techniques. The system shows an upper critical order transition as well as a lower critical order transition (LCOT). For the first time, morphologies of the ordered system at higher temperatures (LCOT) as well as of a block copolymer system frozen-in during the phase separation process are reported. The Flory–Huggins interaction parameter, χ depends not only on temperature, but also on the composition and the molecular weight of the block copolymers, resulting in an asymmetrical phase diagram. Furthermore, the deuteration of the PS block seems to increase the χ parameter of the P[(d 8)S-b-n-BMA] system, reflecting the influence of small changes in architecture on phase behavior. The phase behavior and morphology of PS-b-PBMA are summarized in a phase diagram which is, however, quite complex and therefore needs further discussion. The equilibrium morphologies displayed are influenced by the temperature-dependent-conformation term as well as by the composition term.
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  • 7
    ISSN: 1435-1536
    Keywords: Thermoplastic elastomers ; SAXS ; deformation ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The scattering behavior of undrawn and drawn annealed bristles of thermoplastic elastomers with conventional and higher molecular weight based on poly (butylene terephthalate) as hard segments and poly (ethylene glycol) as soft segments in a ratio of 49/51 wt.% is studied. Small-angle x-ray scattering (SAXS) measurements with an area detector are carried out on single bristies under or without applied stress and with deformations up to 300%. At low macrodeformations (ε≤30–40%) the morphology of the predrawn samples represents assemblies of parallel crystalline lamellae positioned perpendicular to the stretching direction. These morphological characteristics remain unchanged within the entire deformation range (up to ε=300%) for the predrawn samples of lower molecular weight. For the initially undrawn sample of larger molecular weight reversible orientation and disorientation of the crystallites (microdomains) is established in the same deformation range. Common morphological features are found for the predrawn and undrawn samples with increased molecular weight at medium (ε=50–150%) and high (ε=150–300%) deformation ranges. For both samples in an unloaded relaxed state the x-ray patterns can be explained by a zig-zag arrangement of crystalline lamellae, i.e., the microdomains are inclined to the stretching direction. After loading, the microdomains transform to a position perpendicular to the stretching direction. This observed morphological transition is found to be reversible and becomes more pronounced with progressing deformation. It is suspected to contribute to reversible macrodeformations of thermoplastic elastomers in many cases and may be related to the large amount of tie-molecules created during solid-state reactions in those materials.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 272 (1994), S. 1327-1327 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    ISSN: 1435-1536
    Keywords: Structure ; phase transitions ; x-ray scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The structure of a fully aromatic thermotropic liquid crystalline (LC) copolyester poly-[(phenyl-p-phenylene)-co-(terephthalate)-co-(p-hydroxybenzoate)] (PES) prepared from terephthalic acid, phenylhydroquinone, andp-hydroxybenzoic acid at a molar ratio of 45/45/10, respectively, was studied at ambient and elevated temperatures by means of x-ray diffraction and differential scanning calorimetry as a function of molecular weight. On heating of PES fibers with fixed ends an irreversible phase separation process takes place above the glass transition point and two different crystalline phases are formed. A model is proposed where the phases are assumed to contain the constituents of the statistical copolymer in different amounts. The relative volume fraction of the two crystalline modifications depends on the molecular weight of the investigated fibers. At higher temperatures the melting of the two crystalline phases and their transition to a LC nematic mesophase is observed.
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  • 10
    ISSN: 1435-1536
    Keywords: Polymer blends ; spinodal decomposition ; activation energy ; scaling analysis ; small-angle neutron scattering ; double crystal diffractometry ; light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The dynamics of spinodal decomposition (SD) after a temperature jump from a kinetically formed single phase state into the unstable part of the two-phase region has been studied with a blend of polystyrene and poly(cyclohexyl acrylate-statbutyl methacrylate). The time evolution of the structure factor has been examined by small-angle neutron and light-scattering techniques. The combination of the different techniques gave access to a wide wave vector and time range covering a large range of length scales. The activation energy of the diffusion process during spinodal decomposition was determined by a scaling analysis of the later stages of SD, because early stages of SD could not be resolved.
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