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Meander model of amorphous polymers (1982)

Pechhold, W. R. ; Gross, T. ; Grossmann, H. P. ; [et al.]

Springer

Colloid & polymer science 260 (1982), S. 378-393

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ISSN: 1435-1536

Keywords: Amorphous polymers ; biopolymers ; fibrils ; meander model ; superstructur

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 Assuming bundles (of shortrange ordered macromolecules, folding back and forth statistically), their equilibrium superstructure and diameter are described on the basis of cluster-entropy-hypothesis (CEH). As primary blocks in the bulk polymer and in thin films coupled meander cubes are most probable, which are linked via their cube diagonals serving as axis of statistical rotation and aggregate to coarse grains. Magnetic birefringence, SANS and elctronmicroscopy are used as further methods to determine the cube side length. Applying the same concept to myosin-, collagen-, and elastin-aggregates, these can be interpreted as equilibrium meander fibrils, additionally stabilized by specific interactions and by the length of the molecules.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01448144

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Theoretical birefringence of ultraoriented polyethylene from model structure calculations (1982)

Pietralla, M. ; Grossmann, H.-P. ; Krüger, J. K.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1193-1205

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ISSN: 0098-1273

Keywords: Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: The birefringence of model structures of ultraoriented polyethylene has been calculated by using the point-dipole concept and the polarizability tensor of the methylene group derived recently by Pietralla. For well-oriented chains the birefringence is determined by the combination of a negative anisotropy of the polarizability tensor of the methylene group and a positive anisotropy of the Lorentz tensor, both with respect to the chain direction. As a consequence it decreases with increasing density. The results are in agreement with experimental values of Mead, Desper, and Porter. In the model the amorphous regions are regarded as a mixture of planar and helical segments arranged in nematiclike bundles which additionally may have a certain distribution of orientation. The birefringence is not much affected by defects which, on the other hand, strongly influence the ultimate mechanical properties.

Additional Material: 4 Ill.