Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 11: POSTER Disperse Polymer Systems
CPP 11.19: Poster
Dienstag, 28. März 2006, 17:00–19:00, P3
The diblock copolymer as an external field in A/B/A-B polymer mixtures — •Vitaliy Pipich, Dietmar Schwahn, and Lutz Willner — Forschungszentrum Jülich GmbH, Institut für Festkörperforschung, Jülich, Germany
Ordering transitions in an A/B/A-B polymer mixture have been examined by small angle neutron scattering. The homopolymer blend PB/PS of critical composition was mixed with an increasing amount of the symmetric diblock copolymer PB-PS [PB and PS being polybutadiene and polystyrene, respectively] [1]. By deuteration of individual components we got blends with two scattering contrasts: (i) “bulk” contrast by deuteration the PB homopolymer and the PB-block of the copolymer, and (ii) “block” contrast, when only the PS-block was protonated. In particular for case (ii) we observed large-scale density fluctuations of the copolymer following a Q−3 scaling behavior. These density fluctuations were independent of temperature within the 3D-Ising (ΦDB<0.05) and Brasovskii universality class (ΦDB>0.2). However, within the Lifshitz universality class, e.g. 0.05<ΦDB<0.3, the density fluctuations of the copolymer increased with decreasing temperature. Between 0.09<ΦDB<0.3 the ordering of the copolymer occurred prior to the ordering of the homopolymers. So in a limited copolymer range a pre-ordered copolymer structure seemingly served as a template for the polymeric microemulsion and lamellar phase.
[1] V. Pipich, D. Schwahn, J. Chem. Phys. 123, 124904 (2005).