Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 58: Polymer Dynamics II

CPP 58.1: Hauptvortrag

Freitag, 4. April 2014, 09:30–10:00, ZEU 114

Probe Rheology with Neutron Scattering — •Wim Pyckhout-Hintzen — Jülich Centre for Neutron Science (JCNS-1) and Institute for Complex Systems (ICS-1), Forschungszentrum Jülich, Germany

An improved understanding of the nonlinear rheology of complex mixtures of polymers with different architectures for e.g. processing applications is a formidable task and one of today's challenges in polymer science. Therefore, blends of model branched and linear polymers with strongly disperse time scales were investigated with time-dependent small angle neutron scattering after a fast uniaxial step strain and quenched after different relaxation times. A hyperbranched structure of second generation, dilutely dispersed in linear homopolymer matrices of different length acted thereby like sensitive probes for structurally, not yet firmly established features of the tube model for bi-disperse melts. We show that the equilibration time of the linear matrix determines the size of the fluctuations that the outer and inner arms of the branched probe experience. Within a random phase approximation treatment, accounting for different degrees of freedom inherent to the broad time scales and the hierarchical relaxation scheme, the observed loss of anisotropy with time is described in terms of two parameters only, namely the tube diameter and the fraction of relaxed arms of the minority component. The scattering data reveal the underlying mechanisms, which cannot be extracted from but determine the macroscopic flow properties. This information is a prerequisite to quantify the nonlinear viscoelasticity for the strategic blending of mixed architectural systems.