Order-disorder transition in a poly(styrene-b-isoprene) diblock copolymer at hypersonic frequencies
Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser - P.O. Box 1527, 711 10 Heraklion Crete, Greece
2 Max-Planck Institut fur Polymerforschung - Postfach 3148, D-55021 Mainz, Germany
3 Department of Chemistry, University of Athens - Zografou 15771, Athens, Greece
Accepted: 28 July 1998
The order-to-disorder transition (ODT) has been studied in a poly(styrene-b-isoprene) diblock copolymer with a polystyrene (PS) volume fraction fPS of 0.22 at hypersonic frequencies using a tandem Fabry-Perot interferometer. Because of the asymmetric composition we are effectively studying the sound dispersion in a composite material made of hard PS spheres embedded in a soft polyisoprene matrix. All measurements are made in the long-wavelength limit, qD<1, where q is the scattering wave vector and D is the sphere diameter. The transition temperature (TODT) was identified earlier with rheology and SAXS at . We have investigated the sound velocity and attenuation at temperatures below and above the transition. We find the signature of TODT from the broad hypersonic attenuation reflecting the enhanced segmental mobility due to mixing at temperatures near the .
PACS: 61.41.+e – Polymers, elastomers, and plastics / 78.35.+c – Brillouin and Rayleigh scattering; other light scattering / 64.60.Cn – Order-disorder transformations; statistical mechanics of model systems
© EDP Sciences, 1998