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  • 1
    Electronic Resource
    Electronic Resource
    Eigenvectors of the polyethylene chain with conformational defects calculated semianalytically by Green's function (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 364-374 
    Details
    ISSN: 1435-1536
    Keywords: Polyethylene ; eigenvector ; conformationaldefect ; Green's function ; resonance mode ; fold ; kink
    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 Eigenvectors of vibrating polyethylene chains with (200) and (110) folds have been calculated by solving the phonon-scattering problem exactly with the method of Green's function. The results are applied to analyze the resonance modes of the (200) fold (ggtgg: 1353, 1356, 1374 cm−1) and the (110) fold (approximately g′g′ggtg: 820, 1288, 1342, 1348, 1372, 1374 cm−1) in terms of the characteristic vibrations of smaller subunits of the (200) fold (gg, gtg) and the (110) fold (g′g′ggtg, g′g′gg, gtg) which can be identified spectroscopcally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654583
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  • 2
    Electronic Resource
    Electronic Resource
    Struktur- und Konformationsberechnung in Polymeren (1970)
    Springer
    Colloid & polymer science 241 (1970), S. 977-984 
    Details
    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: Summary In order to calculate perfect structures as well as structures, conformational and activation energies of a class of rotational isomers in aliphatic hydrocarbons (kinks, jogs, torsional defects, gauche- and kinkblocks) a potential is discussed which includes steric interaction of the atoms, the „intrinsic part” of the potential of the internal rotation, and valence angle deformation. The potential parameter set is fitted in such a way that it is suitable for the single molecule as well as for the crystal. The following results of the calculations are presented and — as far as possible — compared with experimental data: molecular structures and energies of ethane, propane, and butane; structure of the single planar polyethylene chain; structure of the isotactic polypropylene and the polyisobutene chain; structures and energies of special rotational isomers of the polyethylene chain.
    Notes: Zusammenfassung Zur quantitativen Erfassung der Idealstrukturen sowie der Strukturen, Konformations- und Aktivierungsenergien einer Klasse von Rotationsisomeren in aliphatischen Kohlenwasserstoffen (Kinken, Jogs, Torsionsfehler, gauche- und Jogblöcke) wird ein Potentialansatz diskutiert, der die sterische Wechselwirkung der Atome, den „inneren Anteil” des Rotationspotentials und Valenzwinkeldeformationen berücksichtigt. Der Potentialparametersatz wird so angepaßt, daß er sowohl für das Einzelmolekül als auch für den Kristall verwendbar ist. Folgende Ergebnisse der Rechnungen werden mitgeteilt und soweit möglich mit experimentellen Daten verglichen: Molekülstrukturen und Energien von Äthan, Propan, Butan; Struktur der gestreckten Polyäthylen-Einzelkette; Struktur der isotaktischen Polypropylen-und der Polyisobutylen-Kette; Strukturen und Energien von speziellen Rotationsisomeren der Polyäthylen-Einzelkette.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02137402
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  • 3
    Electronic Resource
    Electronic Resource
    Atomistic calculations of kink defects in the polyethylene crystal by means of semiempirical potentials (1974)
    Springer
    Colloid & polymer science 252 (1974), S. 871-879 
    Details
    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 Diese Arbeit gibt am Beispiel des Polyäthylens eine Methode an, mit der Defekte in Polymerkristallen berechnet werden können. Das Verfahren wurde am Idealkristall überprüft und dann zur Berechnung von Kinken im Kristall verwendet. Es ergaben sich zwei stabile Kinklagen an jedem Gitterplatz. Die Defektenergie für die Kinken beträgt ca. 8,5 kcal/mol. DieReneker-Kinke (Renekerdefekt) im Kristall führt mit 13,5 kcal/mol zu einer wesentlich höheren Defektenergie. Blockanordnungen von Kinken erniedrigen die Defektenergie beträchtlich. Die Energieabsenkung pro Kinke beträgt für einen flächenhaften Block ungefähr 4 kcal/mol, für lineare Blöcke etwa 2 kcal/mol.
    Notes: Summary A method to calculate defects in polymer crystals is introduced and applied to the polyethylene crystal. It is tested for the ideal crystal and is then used to investigate defects (kinks,Reneker defects, kink blocks). Two stable kink positions have been determined at a lattice point. The defect energy of the kinks is about 8.5 kcal/mole. TheReneker defect has been found to have a remarkably higher defect energy of about 13.5 kcal/mole in the crystal. It has been verified that block arrangements of kinks decrease the defect energy per kink. The amount of decrease is about 4 kcal/mole per kink for planar kink blocks and is about 2 kcal/mole per kink for linear kink blocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01554987
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  • 4
    Electronic Resource
    Electronic Resource
    Atomistic calculations of crystal structures of polyisobutylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 449-454 
    Details
    ISSN: 1435-1536
    Keywords: Polyisobutylene ; atomistic calculations ; conformational analysis ; crystal structure
    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 Semiempirical atomistic calculations are performed to investigate the crystalline structure of stretched poly(1,1-dimethylethylene), or polyisobutylene. The packing analysis was done without any lattice symmetry assumptions. The results are in good agreement with the x-ray analysis and favor Tanaka's model II. The calculations show several other crystalline structures with the chains in an all-gauche conformation. They have a somewhat higher density and may play a role in a hypothetical high-pressure phase of polyisobutylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655881
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  • 5
    Electronic Resource
    Electronic Resource
    Atomistic calculations on the high-temperature condis phase of poly(trans-1,4-butadiene) (PTBD) (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 999-1008 
    Details
    ISSN: 1435-1536
    Keywords: Poly(trans-1,4-butadiene) ; conformational analysis ; atomistic calculations ; packing analysis ; condis phase ; phase transition
    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 the low-temperature phase of poly(trans-1,4-butadiene) was calculated by means of semiempirical atomistic potentials. Without using any symmetry assumptions there is good agreement with experimental data. In order to understand the high-temperature phase, packing energy calculations were performed with different chain conformations. There are a great number of possible packing modes. They show an approximately linear relation between defect volume and defect energy. The results of these calculations are taken as a basis for a thermodynamic treatment (cooperative pair theory) of the phase transition. The experimental transition enthalpy can only partially be explained by intermolecular interactions, and the defect energy of the various intramolecular equilibrium conformations is not sufficient to explain the difference. A refined treatment with a simultaneous inter-and intramolecular minimization of the energy reveals that the chains are not in their intramolecular equilibrium state. This results in an additional intramolecular defect energy which seems to lead to an understanding of the experimental transition data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655969
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  • 6
    Electronic Resource
    Electronic Resource
    Semiempirical atomistic calculations of kink isomers in the isotactic polystyrene chain (1976)
    Springer
    Colloid & polymer science 254 (1976), S. 228-236 
    Details
    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 In dieser Arbeit wurden Ideal- und Defektstrukturen, sowie Aktivierungsenergien in hinreichend langen isotaktischen Polystyrol-Ketten berechnet. Es konnte die Anwendbarkeit eines für Polyäthylen entwickelten semiempirischen Potentialsatzes durch Berechnung der Gitterkonstanten und Kohäsionsenergie des Benzol-Idealkristalls gezeigt werden. Die Rechnungen ergeben 6 stabile Idealstrukturen. Die niedrigsten Energien haben tt- und tg- Sequenzen. Ausgehend von diesen Konformationen wurden mehrere Kinkdefekte niedriger Defektenergie, sowie Phenyl-Ring-Drehungen untersucht. Für die 3/1 Helix wurde das Rotationspotential einer achsenparallelen C-C-Bindung berechnet. Damit konnte die vonHäßler undBauer gegebene Deutung der Ultraschallrelaxation in Polystyrol-Lösungen bestätigt werden.
    Notes: Summary In this paper conformational energy calculations of ideal- and defective structures as well as activation energy calculations have been carried out on sufficiently long isotactic polystyrene chains. The accuracy of the used set of semiempirical potentials, formerly fitted to polyethylene, was shown by calculations on the benzene ideal crystal. Six stable ideal conformations have been found, with tt- and tg- sequences having lowest energies. Starting with these conformations several kink isomers with low defect energies, as well as phenyl-group rotations, have been investigated. The rotational potential of a C-C-bond in the 3/1-helix parallel to the helix axis has been calculated. Using this results, the interpretation fo ultrasonic relaxation in polystyrene solutions byHässler and Bauer could be supported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01517037
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  • 7
    Electronic Resource
    Electronic Resource
    Taylor expansion of polymer chain dispersion relations and spectral densities to calculate thermodynamic functions (1982)
    Springer
    Colloid & polymer science 260 (1982), S. 241-247 
    Details
    ISSN: 1435-1536
    Keywords: polymer chain ; dispersion relation ; spectral density ; density of states ; partition function
    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 It is shown how to calculate exactly the derivatives of the dispersion relation and the spectral density for arbitrary regular polymer chains in harmonic approximation. The theory is based on a generalization of the characteristic polynomial. In the vibrational part of the free energy and other thermodynamic functions, the integral over normal modes is done approximately by Taylor expanding the density of states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447960
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  • 8
    Electronic Resource
    Electronic Resource
    On the solid state phases of poly(trans-1,4-butadiene) (1981)
    Springer
    Colloid & polymer science 259 (1981), S. 714-723 
    Details
    ISSN: 1435-1536
    Keywords: Poly(trans-1,4-butadiene) ; conformational analysis ; phase transitions ; high pressure dilatometry ; calorimetry
    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 Methode der semiempirisch-atomistischen Rechnung wird auf ein Polydien angewendet. Dazu wird ein bei Polyolefinen bewährter Potentialsatz um einen Coulombterm erweitert. Berechnet werden alle stabilen 4 *p/q Helices des Poly-trans-1,4-butadiens, und es ergibt sich eine Konformation für die Tieftemperaturphase, die mit Röntgendaten in der Literatur übereinstimmt. Für die Hochtemperaturphase werden Kettenkonformationen vorgeschlagen, bei denen die in der Einzelkettennäherung bestimmte Energie und die Packung berücksichtigt wird. Die Enthalpie- und Entropieunterschiede zwischen beiden Phasen, die bisher nur intramolekular berechnet sind, werden experimentell mit den Methoden der Hochdruckdilatometrie und der Kalorimetrie bestimmt. Dabei wird im Hochdruckbereich bis 3 kbar ein handelsübliches Material gemessen, im Niederdruckbereich und kalorimetrisch aber ein reines trans-Polymeres, das anfangs gestrecktkettig vorliegt. Die experimentellen Werte werden mit den berechneten verglichen, und ihre Unterschiede werden diskutiert.
    Notes: Summary The method of semiempiric-atomistic calculations is applied to a polydiene. For this purpose a Coulomb term has to be added to a potential set used successfully for polyolefines. All stable 4 *p/q helices of poly(trans-1,4-butadiene) are calculated. This yields a conformation for the low temperature phase which is in agreement with X-ray data in the literature. Chain conformations are proposed for the high temperature phase carefully considering the energies (determined in the single chain approximation) and the packing properties. Experimentelly, the enthalpy and entropy differences between the phases, calculated only intramolecularly, are determined by high pressure dilatometry and calorimetry. A commercial material is investigated in the full pressure range up to 3 kbar; for low pressure dilatometry and calormetry a purely trans polymer, initially in extended chain conformation, is used. Experimental data are compared with calculated values and discrepancies are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01419315
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