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PO: Polymerphysik
PO 5: Poster: Molekulare Dynamik
PO 5.1: Poster
Tuesday, March 2, 1999, 14:00–16:00, Foyer
Dynamical behavior of polystryrene - polyisoprene tetrablock copolymers studied by dielectric spectroscopy — •Andreas Schoenhals1, Andreas Fritz1, and Timothy Lodge2 — 1Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, 12205 Berlin, Germany — 2University of Minnesota, Department of Chemistry, Minneapolis, MN 55455, USA
The dynamical behavior of four (styrene-b-isoprene-b-styrene-b-isoprene) terablock copolymers have been studied by dielectric spectroscopy in the frequency range from 0.01 Hz to 100 kHz and in a temperature range from 173 to 430 K. The copolymers have a styrene composition of 23, 42, 60 and 80 volume percent. Neutron scattering experiments indicates that the block copolymers are in the disordered state above 230 K. The dielectric spectra show two relaxation regions. The process at higher frequencies or lower temperatures is due to the dynamical glass transition whereas the process at lower frequencies or higher temperature is assigned to the chain dynamics. The chain dynamics can be measured by dielectrics because polyisoprene has a dipole component in parallel to the chain backbone. The dependence of both relaxation processes on composition and temperature is analyzed and discussed.