Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 5: Polyelectrolytes
CPP 5.10: Vortrag
Montag, 27. März 2006, 17:00–17:15, ZEU 160
Structure and Dynamics of Bottle-brush Polymers — •S. Rathgeber1, T. Pakula 1, A. Wilk1, K. Matyjaszewski 2, K.L. Beers2, and P. Panine3 — 1Max Planck Institute for Polymer Research, Mainz, Germany. — 2Carnegie Mellon University, Pittsburgh, USA. — 3ESRF, Grenoble, France.
The talk will address the structure and dynamics of bottle-brush polymers (BB) in solution. Due to high branching densities the hybrid character of BB between a flexible polymer and compact colloid is reflected their structure and dynamics. We investigated the dilute solution properties with static scattering methods, Monte Carlo simulations and measured the internal dynamics with neutron-spin echo spectroscopy. Collective breathing modes of the side chains in the brush lead to a slowing down of the dynamics on length scales of the brush diameter D. Attachment of longer, more space demanding side chains does not induce higher persistence to the overall brush. The persistence length λ is independent of the side chain length Ns. Thus, the ratio λ/D is decreasing with increasing Ns and lyotropic behavior becomes unlikely. We also looked at the lyotropic behavior and the rheological response of highly concentrated BB solutions. Structural changes occurring in a disordered and in a, perpendicular to the shear field pre-aligned sample, in response to the external shear field were measured by time-resolved x-ray scattering. Above a threshold torque the BB start to align in flow direction inducing a shear thinning process lasting two hours accompanied by a reduction in viscosity by two orders of magnitude. Above a higher threshold torque the alignment of the BB spontaneously flips into the flow direction.