Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 29: POSTER: Polymer physics

CPP 29.45: Poster

Dienstag, 8. März 2005, 16:30–18:30, Poster TU D

Side Chain Crystallization in Microphase-Separated Poly(styrene-octadecylmethacrylate) Copolymers — •E. Hempel, H. Budde, S. Höring, and M. Beiner — FB Physik & FB Chemie, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany

The crystallization behavior of two microphase-separated poly(styrene-b-octadecylmethacrylate) block copolymers with lamellar and cylindrical morphology is studied by DSC. The findings are compared with results for a polyoctadecylmetharcylate (PODMA) homopolymer. The situation in the block copolymers is characterized by the occurrence of a confined side chain crystallization in small PODMA domains surrounded by a glassy polystyrene phase. The strength of confinement effects depends significantly on the block copolymer morphology. In cylindrical PODMA domains with a diameter of about 10nm strong confinement effects are observed: The degree of crystallinity is 50% reduced and the crystallization kinetics is slowed down. The crystallization behavior of PODMA lamellae with a thickness of about 10nm is less affected and similar to the situation in the homopolymer. There are experimental arguments supporting one-dimensional growth in PODMA cylinders: The Avrami coefficients change from n ≈ 3 for the homopolymer and PODMA lamellae to n ≈ 1 for PODMA cylinders. A change from heterogeneous to homogeneous nucleation having similar consequences seems to be unlikely since the undercooling for the PODMA cylinders is tiny (TmTc < 1K). This value is smaller than those for the PODMA homopolymer and homogenously nucluated alkanes. A speculative picture explaning the different crystallization behaviors of PODMA lamellae and cylinders is discussed.

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