Regensburg 2007 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 2: Polymer Physics I
CPP 2.2: Vortrag
Montag, 26. März 2007, 10:15–10:30, H40
Bicontinuous AB-diblock-copolymer mesophases: geometric arguments in favour of an "alternating" Im3m phase based on the I-WP surface — •G.E. Schroeder-Turk1, S.T. Hyde2, and A. Fogden2 — 1Inst. für Theor. Physik I, Univ. Erlangen-Nürnberg, Staudtstraße 7, 91058 Erlangen — 2Applied Maths, Res. School of Phys. Sciences, Australian National University, 0200 ACT, Australia
Bicontinuous phases in AB-diblock-copolymers are well known. In the "coreshell" Gyroid phase, immiscibility of A and B blocks leads to two intertwined identical networks of block A separated by a matrix of block B. The Gyroid triply-periodic minimal surface (TPMS) lines the middle of the B domain. For AB diblock copolymers, an "alternating" phase (as found in linear ABC terpolymers) with one network consisting of A and the other of B blocks does not exist. Chain stretching frustration is crucial to the phase stability analysis of these systems. Variations of the domain thickness, i.e. of the length between the TPMS and the center of the network channels, is unavoidable and incurs an entropic penalty for stretching of the polymer chains. We present an analysis of these variations for various TPMS of cubic symmetry. We demonstrate that the Gyroid is the bicontinuous geometry with the smallest frustration. The I-WP geometry is another TPMS where the two networks are not identical. The domain thickness variations are small for one network and large for the other. We argue that the I-WP may be suitable for an AB-diblock alternating phase in an asymmetrically polydisperse polymer system where one moiety has a wide and one a narrow molecular weight distribution.