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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 48: Poster: Polymer Crystallization, Nucleation and Selfassembly

CPP 48.1: Poster

Mittwoch, 22. März 2017, 18:30–21:00, P2-OG1

On the controvercy close folds versus coils in polyethylene and the weight of evidence. — •Heinz H.W. Preuss — Hameln

The highest weight of evidence in the field of morphology belongs to direct visualization and photography. Results of direct visualization and photography of entangled and coiled or looped chains of polymeric molecules in melts and of close folds of chains in solid polymers are not yet found to be published. But separated lamellae of HDPE could be visualized and photographed by H. Preuss (1) with a TEM after tearing them off from the surface of a specimen solidified from melt by slow cooling. The thickness of the lamellae (120 nm) was estimated from the shadow length in the fracture surface after evaporation of carbon under a 30o angle, and the orientation of the chains perpendicular to the plane of the lamellae was confirmed by electron diffraction. Thus the fold model of A. Keller could be confirmed as sure as for polyethylene crystals from dilute solution. *When the lamellae are isolated single entities, as in solution crystallization then given that the chains are perpendicular, or at a large angle to the basal plane, folding is a straightforward necessity as the chains have nowhere else to go."(2) Entangled and coiled molecules remain a fiction until they would be observed directly. 1 - H.H.W.Preuss, physica status solidi, vol. 3, 1963, K 109 ff.; Plaste und Kautschuk, 22.Jg. Heft 12, 1975, 958-959 2 - A. Keller, Faraday Discussion 1979 p. 149