Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 38: Focus: Rheology II (joint focus with DRG)
CPP 38.7: Vortrag
Freitag, 30. März 2012, 11:15–11:30, C 130
Microscopic relaxation processes in branched/linear polymer blends by Rheo-Sans — •Nino Ruocco1, Wim Pyckhout Hintzen1, Aurel Radulescu1, Dieter Richter1, Peter Lindner2, and Daniel Read3 — 1Forschungszentrum Jülich, JCNS-1, Jülich, Germany — 2Institut Laue-Langevin, Grenoble, France — 3Department of Applied Mathematics, University of Leeds, UK
The present study focuses on the hierarchical relaxation processes in a cayley-tree polymer, dispersed in linear polyisoprene (PI) using a Rheo-SANS combination. The introduction of branching points, which join different generations, and the dynamics of the embedding linear matrix have a huge impact in the dynamic relaxation spectrum. Molecular variables that are relaxed on the time scale of experiment and those, which are frozen or quenched, can be distinguished. Within a RPA treatment, taking into account the different degrees of freedom, the observed loss of anisotropy after a fast step strain can be correlated with the fast relaxation of the outer arms and a slow one for the inner section: a hierarchical relaxation from the tips inwards to the branching point leads to isotropization of the chain ends with loss of orientation in a diluted tube. Microscopic access to relaxation processes and the corresponding structural parameters is enabled through uniaxial step strain experiments at strain rates faster than their inverse relaxation time. The parameter space is scanned by appropriate SANS experiments in the respective time domains, which uniquely resolve the difficulties in extracting dynamics of the minority component from macroscopic rheology, which is dominated by the matrix.