Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Poster - Glasses / Stat. Phys. Bio. / Networks (joint session DY/BP/CPP/SOE)

DY 13.13: Poster

Dienstag, 1. April 2014, 09:30–12:30, P1

Molecular Order and Dynamics of Nanometric Thin Layers of Poly(styrene-b-1,4-isoprene) Diblock Copolymers — •Wycliffe K. Kipnusu¹, Mahdy M. Elmahdy¹, Martin Tress¹, Emmanuel U. Mapesa¹, Detlef-M. Smilgies², Jianqi Zhang³, Christine M. Papadakis³, and Friedrich Kremer¹ — ¹Institute of Experimental physics I, Linnstr.5, 04103, Leipzig — ²CHESS, Wilson Laboratory, Cornell University, Ithaca, NY 14853, USA — ³Technische Universität München, Physik-Department, James-Franck-Straße 1, 85748 Garching, Germany

Order and dynamics of poly(styrene-block-1,4-isoprene), P(S-b-I) diblock copolymers in nanometer thin layers with different isoprene volume fraction (fPI) and identical molecular weight of the styrene blocks are studied by a combination of Grazing-Incidence Small-Angle X-ray Scattering (GISAXS), Atomic Force Microscopy (AFM) and Broadband Dielectric Spectroscopy (BDS). GISAXS and AFM reveal randomly oriented lamellar structures in the films and a parallel orientation at the top surface, respectively. Using BDS, three well separated relaxation processes are detected, (i) and (ii) the dynamic glass transitions (segmental mode) in the styrene and isoprene blocks respectively and (iii) the normal mode relaxation representing fluctuations of the isoprene chain as a whole or parts of it. While the two former do not show any thickness dependence in their spectral positions, the latter becomes faster with decreasing sample thickness. This reflects the difference in the length-scale on which the molecular fluctuations take place.