Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Crystalline structure of atactic polyacrylonitrile (1993)
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 6903-6907 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00077a030
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Two-Dimensional Lattice Model of Disclinations in Liquid Crystals: Choice of Energy Function (1994)
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 3439-3441 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00090a047
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Geometric and rotational parameters for the conformational modeling of liquid-crystalline polyester (1989)
    s.l. : American Chemical Society
    Macromolecules 22 (1989), S. 1129-1136 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00193a022
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Hierarchical approach to modelling of liquid-crystalline polymers (1996)
    Springer
    Journal of computer-aided materials design 3 (1996), S. 359-368 
    Details
    ISSN: 1573-4900
    Keywords: Liquid-crystalline polymers ; Molecular modelling ; Microstructure ; Lattice model ; Shear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Liquid-crystalline polymers exhibit fascinating structure at many size scales. This paper describes how computer models at different size scales can be linked together by a hierarchical approach to give a better understanding of the properties and behaviour of these materials. The atomic scale is considered first, where semi-empirical molecular orbital techniques are used to calculate the torsional energy functions associated with rotating the backbone bonds of the polymer. Secondly, entire chains are simulated using a Monte Carlo technique based on the torsional energy functions to deduce the persistence length of the polymer of interest. A theoretical relationship enables the Frank elastic constants to be determined from the persistence length. The elastic constants may then be used as input parameters for models both to predict microstructure and to help understand the role of defects in the shear flow of these materials. The hierarchical approach provides a meaningful framework within which data obtained from small-scale models are used to parameterise models at a larger scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185674
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Preparation and Properties of Carbon Nanotube-Reinforced Hydroxyapatite (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 361-363 (Nov. 2007), p. 419-422 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Composites of hydroxyapatite (HA) and multiwalled carbon nanotubes (CNTs) have beenprepared and characterised for potential application in major load-bearing medical devices. We havestudied the effect of nanotube surface chemistry, composite preparation methods, and heat treatmentconditions on the microstructure of the composites, dispersion of CNTs, and interaction between theHA and CNTs. The samples were characterised using SEM, XRD, FTIR, and BET surface area. Itwas found that, compared with pure HA, the composites had lower densities and higher surfaceareas. Additionally, functionalisation improved the dispersion of CNTs in the HA matrix and theinteraction between the two phases
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/56/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.361-363.419.pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Lattice modelling of nematodynamics (1999)
    Springer
    Rheologica acta 38 (1999), S. 548-561 
    Details
    ISSN: 1435-1528
    Keywords: Key words Liquid crystal polymers ; Textured nematics ; Shear flow ; Dynamics simulation ; Ericksen number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The microstructures of textured nematics under shear are investigated by means of a director lattice model incorporating linear shear response as well as elastic interactions between neighbouring directors. The model can be understood as a lattice implementation of the so-called nematodynamics equation for a constant uniaxial order parameter. The dimensionless number governing the model is found to be a mesoscale Ericksen number, which scales with the square of the lattice cell size. It is shown that the predicted microstructure depends strongly on the scale of that number. In particular, disclination loops are found to grow for a range of mesoscale Ericksen numbers, while below or above that they disappear. We apply the model to investigate the director profiles of tumbling nematics. If the orientations are restricted to lying in the vorticity plane, we reproduce the director wind-up layers and distortion saturation predicted theoretically. In the full three-dimensional case an initially polydomain director field evolves to a vorticity-aligned state up to a critical Ericksen number, above which in-plane orientations with distortion saturation are found. The simulations hence reproduce the transition from log-rolling to flow aligning with increasing shear rate observed experimentally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003970050207
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Electron microscopy of non-periodic layer crystallites in thermotropic random copolymers (1990)
    Springer
    Journal of materials science 25 (1990), S. 2727-2736 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Transmission electron microscopy (TEM) has been used to characterize non-periodic layer crystallites in thermotropic random copolyesters composed of 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid. The crystallites are most clearly observed when imaged in the equatorial reflection, indicating that they are associated with intermolecular ordering. The crystallites appear to be platelets with their thin axis parallel to the molecular chain axis. Crystallite growth is highly dependent on thermal history and occurs to a significant extent during the early stages of annealing above the glass-transition temperature in the solid state. Long-term annealing of the copolymers results in an increase in the number of crystallites, as well as sharpening the diffraction pattern. The extent of lateral development of the ordered regions also depends on the degree of polymerization (DP), being greater for a copolymer of lower DP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584872
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Transformation of banded structures on annealing thin films of thermotropic liquid crystalline polymers (1984)
    Springer
    Journal of materials science 19 (1984), S. 2085-2097 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The structures of a range of thermotropic copolyesters based on hydroxybenzoic and hydroxynaphthalic acids are studied using transmission electron microscopy. Starting from the banded structure characteristic of as-sheared specimens, annealing of thin films either upon a rocksalt substrate or between two rocksalt crystals leads to a rapid microstructural reorganization. The bands, initially transverse to the shear direction, are replaced by domains of uniform molecular orientation elongated along the shear directio n. Simultaneously, a substantial our-of-plane tilt of the molecules occurs, which for any domain is coupled with the degree of in-plane misorientation about the shear axis. Such orientation coupling may be associated with the need for splay-splay compensation to minimize energy. For longer anneals on specimens of lower molecular weight, distinctive boundaries separate the domains of alternating tilt “up” and “down” (relative to the specimen plane). The boundaries which appear as dark “veins” in bright-field images, are narrow regions of highly developed molecular tilt in which homeotropy is approached. The tendency towards overall homeotropy can be linked to the presence of constraining surfaces, and is absent for specimens annealed without a substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01058085
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Crystallite morphology in thermotropic random copolymers: Application of transmission electron microscopy (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 61-69 
    Details
    ISSN: 0887-6266
    Keywords: crystallite morphology in thermotropic random copolymers, application of TEM to ; electron microscopy of thermotropic random copolymer morphology ; copolyesters, thermotropic, application of TEM to study of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The morphology of nonperiodic layer (NPL) crystallites appearing in three thermotropic random copolyesters composed of 30/70, 58/42, and 75/25 monomer ratios of p-oxybenzoate (B) and 2,6-oxynaphthoate (N) is investigated with transmission electron microscopy. Copolymer films, produced by shearing the materials above their melting points and subsequently annealing them above their glass transition temperature, exhibit ordered entities averaging no more than 20 nm thick and 40-60 nm long, as observed with dark-field imaging. Selected-area electron diffractograms exhibit sharp equatorial reflections, indicating ordered packing of random intramolecular sequences of the molecules. Microdensitometry of these diffraction patterns reveal that both the equatorial and first meridional reflections are radiation sensitive, decaying exponentially with dose. Saturation doses (v) for the crystallites depend on the copolymer composition and degree of polymerization (DP) and are estimated to be approximately 130-150C/m2 for the high-molecular-weight copolymers (DP ≈ 150), with the N-rich copolymer possessing greater radiation resistance, and about 430 C/m2 for a low-molecular-weight copolymer (DP ≈ 25).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090300106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Diffraction modelling of poly(vinyl chloride): An approach to the crystallinity enigma (1993)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 2 (1993), S. 257-262 
    Details
    ISSN: 1018-5054
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This paper demonstrates that changes which are seen to occur in experimental X-ray diffraction patterns of poly(vinyl chloride) (PVC) with varying sample tacticity are indicative of a crystal structure in which both isotactic and syndiotactic sequences are incorporated within the same lattice. The isotactic sequences are in a conformation first suggested by Juijn et al. which enables them to emulate the shape of the syndiotactic chain. We present a short summary of molecular and diffraction modelling results which show how the intensities of the 200 and 110 peaks change with crystallite tacticity. The results provide a rational explanation for the long standing enigma that the observed crystallinity of atactic PVC is too high to be accounted for in terms of crystallization of syndiotactic sequences only.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1993.040020207
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...