Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 19: Semiflexible Polymers and Networks

BP 19.4: Talk

Wednesday, February 27, 2008, 18:15–18:30, PC 203

Misfits never yield – A microscopic approach to the nonlinear rheology of biopolymer solutions — •Pablo Fernández¹ and Klaus Kroy^2,3 — ¹E22 Biophysik, Technische Universität München, James Franck Straße 1, D-85748 Garching, Germany — ²Institut für Theoretische Physik, Universität Leipzig, Postfach 100920, D-04009 Leipzig, Germany — ³Hahn-Meitner Institut, Glienicker Straße 100, D-14109 Berlin, Germany

We propose a nonlinear extension of the standard tube model for semidilute solutions of semiflexible polymers. Non-affine filament deformations at the entanglement scale, the renormalisation of direct interactions by thermal fluctuations, and the geometry of large deformations are systematically taken into account. The analysis of the shear response of a simplified unit cell sheds light onto fundamental issues in cytoskeletal mechanics. The strong geometric stiffening predicted for purely enthalpic networks is found to be thermally suppressed. Instead, we obtain a broad linear response regime covering typical physiological mesh sizes. Surprisingly, we discover a destabilizing effect of large strains (∼ 100%). The theory thus provides a novel perspective at the widely observed catastrophic collapse of in-vitro sheared biopolymer solutions, usually attributed to irreversible network damage. It moreover supports the interpretation of shear stiffening at finite frequencies as indicative of adhesive polymer interactions. In combination with such friction-type interactions, our analysis provides an analytically tractable framework to address the nonlinear viscoplasticity of biological tissue on a molecular basis.