Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 15: POSTER: Polymers and Biomaterials

CPP 15.32: Poster

Tuesday, March 9, 2004, 17:00–19:00, B

Electric field induced structural fluctuations in lamellar block copolymers — •Xiuli Jiang¹, Thomas Thurn-Albrecht¹, Thomas Gutberlet², Mukul Gupta², and Daniel Clemens² — ¹Martin-Luther-Universitaet Halle-Wittenberg,Fachbereich Physik,D-06099 Halle — ²Paul Scherrer Institut,Lab. f. Neutron Scattering,5232 Villigen PSI,Switzerland

Lamellar microphase structures formed in symmetric diblock copolymers [1], as well as cylindrical microdomains formed in asymmetric diblock copolymers [2], can be oriented by an external electric field. Though the mechanism of the orientation is not fully understood yet, it is believed that the electric field induces an instability connected with structural fluctuations or undulations leading eventually to a disruption of the original structure which facilitates alignment to set in. Using neutron reflectometry the current study investigates these undulations in films of different thicknesses with and without application of an electric field. To map the intensity in the relevant range of reciprocal space we use the newly established time-of-flight (TOF) mode on the AMOR neutron reflectometer at the Paul-Scherrer-Institute. Our results show that thermally excited fluctuations always exist. The film thickness was shown to be an important parameter governing the length scale as well as the amplitude of the undulations. As expected the electric field leads to an amplification of undulations with smaller wavelengths. [1] K. Amundson, E. Helfand, D. D. Davis, X. Quan, S. S. Patel and S. D. Smith, Macromolecules 24, 6546 (1991). [2] T. Thurn-Albrecht, J. DeRouchey, T. P. Russell and R. Kolb, Macromolecules 35, 8106 (2002).