Regensburg 2004 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 15: POSTER: Polymers and Biomaterials
CPP 15.30: Poster
Tuesday, March 9, 2004, 17:00–19:00, B
Orientation of the Microdomains in Concentrated Block Copolymer Solutions using Electric Fields: Confinement Effects and Mechanisms — •Kristin Schmidt1, Helmut Hänsel1, Frank Schubert1, Heiko Zettl1, Thomas Weiss2, Franz Fischer3, Volker Abetz4, Alexander Böker1,5, and Georg Krausch1 — 1Physikalische Chemie II, Universität Bayreuth, Bayreuth, Germany — 2ESRF, Grenoble, France — 3Kristallographie, Universität Bayreuth, Bayreuth, Germany — 4Makromolekulare Chemie II, Universität Bayreuth, Bayreuth, Germany — 5Department of Polymer Science & Engineering, University of Massachusetts, Amherst, USA
We investigate the microdomain orientation of concentrated block copolymer solutions exposed to a DC electric field by time-resolved synchrotron SAXS. As a model system, we use a lamellar polystyrene-b-polyisoprene block copolymer dissolved in toluene. Depending on the polymer concentration we can identify two different microscopic mechanisms which dominate the orientation process, i.e. nucleation and growth of domains and grain rotation. The former dominates close to the ODT, while the latter prevails under more strongly segregated conditions.
Reduction of the electrode spacing from 2mm to 200µm leads to a dramatic increase in the time constant of the orientation process, i.e. it is slowed down significantly. This finding is attributed to a confinement effect which finally results in complete trapping of the process. Furthermore, in the case of highly segregated samples we observe that increasing confinement suppresses the grain rotation mechanism, favoring nucleation and growth for highly confined systems.