Molekülbewegung in Polymeren: III. Teil: Mikrostruktur und mechanische Eigenschaften
01 Nov 1970-Vol. 241, pp 955-976
TL;DR: In this article, a Molekulare Theorie der Relaxationserscheinungen (α, β, γ) is given and experimentally proved for linear polyethylene.
Abstract: ZusammenfassungAuf der Grundlage des Bündelmodells und mit streng molekularen Parametern wird im ersten Teil die Mikrostruktur von Polymerschmelzen und teilkristallinen Festkörpern behandelt. Die mäanderartige Anordnung der Bündel im amorphen Zustand läßt sich thermodynamisch begründen und führt zu einem Mäanderradius von 50 Å. Auf dieser Grundlage wird eine molekulare Theorie der Relaxationserscheinungen (α, β, γ) am Beispiel des linearen Polyäthylens vorgelegt und experimentall geprüft. Im letzten Teil werden die beiden Grenzfälle des Deformationsverhaltens molekular quantitativ beschrieben: die reine Plastizität am Beispiel der Streckgrenze (yield-stress) des linearen Polyäthylens und die reine Paraelastizität am Beispiel der Spannungs-Dehnungskurve des verstreckten Polyamidfadens.SummaryIn the first part the microstructure of polymer melts and semicrystalline bulk material is treated on the basis of the bundle model and with molecular parameters. The meander-shaped arrangement of the bundles in the amorphous phase can be founded thermodynamically and leads to a radius of the meander of 50 Å. Based on this model a molecular theory of the relaxation processes (α, β, γ) is given and experimentally proved for linear polyethylene. In the last part both limiting cases of the deformation behavior are quantitatively derived in a molecular picture: the ideal plasticity illustrated by the yield stress of linear polyethylene and the ideal paraelasticity illustrated by the stress-strain curve of the drawn polyamide fiber.
Citations
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TL;DR: In this paper, the structure and dynamics of alkylammonium-modified montmorillonites with different cation exchange capacity (CEC), ammonium head groups, and chain length are investigated by molecular dynamics simulation for a large set of structures and compared to a wide array of experimental data.
Abstract: The structure and dynamics of alkylammonium-modified montmorillonites with different cation exchange capacity (CEC), ammonium head groups, and chain length is investigated by molecular dynamics simulation for a large set of structures and compared to a wide array of experimental data. In the 44 systems, the relationship between computational (molecular dynamics) and experimental data (X-ray, IR, NMR, and DSC) was found to be very complementary. Much of the properties appear to be dictated through the inorganic−organic interface, which in addition to electrostatic interactions involves hydrogen bonds between primary ammonium head groups (NH3+−R) and oxygen on the silicate surface (O···H distance ∼150 pm) or flexibly attached quaternary ammonium head groups (NMe3+−R) of higher lateral mobility (O···H distance ∼290 pm). The gauche content is a function of the packing density of the head groups on the surface, the preferred orientation of the head groups, and the interlayer density of the alkyl chains. These ...
253 citations
TL;DR: In this paper, the structure of monomolecular and bimolecular films has been investigated in terms of reversible kink-block and gauche-block structures of lipid layers in membranes.
Abstract: Layer silicates and some other layer compounds can take up organic compounds such as long-chain alkanols and alkylammonium ions with formation of ordered bimolecular films This system enables new ideas to be developed concerning the structure of monomolecular and bimolecular films: the films form reversible kink-block and gauche-block structures Conclusions can be derived about the structure of the lipid layers in membranes
186 citations
TL;DR: In this article, the volume change at the crystalline-liquid crystalline phase transition was measured for the dipalmitoylphosphatidylcholine-water system containing lamellar bimolecular structures.
183 citations
01 Jan 1985
TL;DR: In this paper, a review of recent progress in our knowledge about the behaviour of synthethic and biological macromolecules and larger biological particles in dilute solution and in the liquid crystalline state, when exposed to strong magnetic fields is presented.
Abstract: This is a review of recent progress in our knowledge about the behaviour of synthethic and biological macromolecules and larger biological particles in dilute solution and in the liquid crystalline state, when exposed to strong magnetic fields. Emphasis is on the observation of magnetic orientation as resulting mostly from an anisotropic molecular diamagnetic susceptibility, and on its interpretation in terms of molecular structure, flexibility and intermolecular orientational correlation. Some biological applications of magnetic fields are briefly discussed, including the separation of macromolecules in inhomogeneous fields, the field-induced modification of cellular growth and the field sensitivity of animals.
107 citations
TL;DR: In this paper, an IR spectrum of a polymer sample provides the following qualitative and quantitative information about the polymer under consideration: Chemical nature of the polymer: type and degree of branching, nature of end groups, impurities, etc.
Abstract: Since 1945 inrared (IR) spectroscopy has become one of the most important methods for characterizing and studying the chemical and physical structure of compounds. Especially in the polymer field, IR spectroscopy and Raman spectroscopy have proved valuable for analytical and structural investigations. An IR spectrum of a polymer sample provides the following qualitative and quantitative information about the chemical and physical structure of the polymer under consideration: Chemical nature of the polymer: type and degree of branching, nature of end groups, impurities, etc. Steric order: cis-trans isomerism, stereoregularity, etc. Conformational order: physical arrangement of a polymer chain, planar zigzag conformation, helix conformation, etc. Crystallinity: number of chains per unit cell, intermolecular forces, etc.
91 citations
References
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01 Aug 1991
TL;DR: Menard et al. as mentioned in this paper discuss the use of dynamic mechanical analysis (DMA) as a tool for thermal analysis, rheology, and materials science in the analytical laboratory.
Abstract: Dynamic Mechanical Analysis-Kevin P. Menard 2002-01-01 Although dynamical mechanical analysis or spectroscopy has left the domain of the rheologist and has become a prevalent tool in the analytical laboratory, it is still common to hear, "What is DMA, and what will it tell me?" or "I think I could use a DMA, but I cannot justify its cost." Previously, the novice in the field had to sort through texts on thermal analysis, rheology, and materials science just to find basic information — until now.
2,756 citations
TL;DR: In this paper, the molecular motions in polyethylene terephthalate samples of different crystallinities have been investigated by dynamic mechanical measurements at a frequency of 1 cycle/sec. between −180° and +260°C.
287 citations
TL;DR: The Langperiode wachst in diesen Fallen nach dem gleichen Zeitgesetz wie bei verstreckten Folien as mentioned in this paper, das die Ketten bei den Einkristallen and im schmelzkristallisierten Material an den Grenzflachen der Kristallite gefaltet sind, im verstwreckten Polyathylen dagegen nicht.
Abstract: Die im Rontgenkleinwinkeldiagramm von verstrecktem Polyathylen auftretenden Meridian- Interferenzen werden durch eine nahezu periodische Anordnung von kristallinen und fehlgeordneten Bereichen hervorgerufen. Die durch den mittleren Abstand zweier aufeinanderfolgender Kristallite definierte Langperiode hangt von der Vorbehandlung ab. Zeit- und Temperaturabhangigkeit der Lage der Kleinwinkelreflexe wurde untersucht. Die beim Tempern stattfindende Umkristallisation, die zu einem Anwachsen der Langperiode fuhrt, wurde auch mit anderen Mesmethoden verfolgt. Vergleichende Untersuchungen wurden an unverstrecktem, massivem Polyathylen und an Polyathylen-Einkristallen durchgefuhrt. Die Langperiode wachst in diesen Fallen nach dem gleichen Zeitgesetz wie bei verstreckten Folien. Bezuglich des Zusammenhanges zwischen Dichte und Langperiode ergaben sich jedoch charakteristische Unterschiede. Sie werden darauf zuruckgefuhrt, das die Ketten bei den Einkristallen und im schmelzkristallisierten Material an den Grenzflachen der Kristallite gefaltet sind, im verstreckten Polyathylen dagegen nicht. Auf den Zusammenhang des Langperiodenwachstums mit anderen im gleichen Temperaturbereich beobachteten Vorgangen (partielles Schmelzen, Nachkristallisation wird hingewiesen).
247 citations
TL;DR: In this article, the dynamic tensile modulus of oriented specimens of polyethylene (PE), polypropylene (PP), polyoxymethylene, polyoxide (polyethylene oxide), and polytetrahydrofuran were measured in sheet form as a function of direction.
Abstract: Complex moduli of oriented specimens of polyethylene (PE), polypropylene (PP), polyoxymethylene, polyethylene oxide), and polytetrahydrofuran were measured in sheet form as a function of direction. The dynamic tensile modulus (E′) along the stretched direction (0° direction) was found to be lower than that perpendicular to the stretched direction (90° direction) above the temperature of primary dispersion (αa) for all polymers cited above. Below the temperature of an dispersion the E′ value of 0° direction is higher than that of 90° direction as expected from the anisotropy of modulus of the crystal. This fact leads us to the model that the crystalline region (C) and this amorphous region (A) are arranged mainly in series along the stretched direction and at the same time the C region should be more or less continuous along the 90° direction. The actual drawn sample is composed of many microfibrils as proved l y the x-ray small-angle scattering. Those conditions imposed on the model should be satisfied even when many microfibrils are bound together into a fiber. This picture agrees with the structural model of hot-drawn PE presented by Hosemann after its slight modification. Effects of cold drawing on the anisotropy of modulus were also surveyed.
211 citations