Regensburg 2002 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 1: Struktur und Dynamik in Polymersystemen I

CPP 1.4: Vortrag

Montag, 11. März 2002, 12:00–12:20, H38

Orientation of Isotactic Polystyrene Induced by Magnetic Fields during Isothermal Crystallisation — •Florian Ebert and Thomas Thurn-Albrecht — Universität Freiburg Fakultät für Physik

Semicrystalline polymers can interact with magnetic fields due to their anisotropy in diamagnetic susceptibility. Crystallization of isotactic polystyrene in high magnetic fields (7 or 11 Tesla) leads to the formation of oriented lamellar stacks with the lamellar normal, i.e. the chain direction, normal to the magnetic field. This was shown by small and wide angle x-ray scattering as well as electron microscopy. The degree of orientation is strongly temperature dependent: the orientation is almost perfect for high crystallization temperatures and disappears for low temperatures. Orientation does not occur prior to crystallization in the melt but only during the crystallization process. Since it is not possible to orient individual polymer chains in the melt because of their small size and persistence length, the experiments indicate the existence of preordered anisotropic aggregate structures during the crystallization, which are large enough to be oriented by the magnetic field.