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CPP: Chemische Physik und Polymerphysik

CPP 6: Polymer Networks

CPP 6.3: Vortrag

Dienstag, 3. April 2001, 16:25–16:45, 112

Are there nonergodic states in biopolymer networks? — •Michael Schulz and Peter Reineker — Abteilung Theoretische Physik, University Ulm, 89069 Ulm

Polymer networks hold a remarkable intermediate position between liquids and solids. Homopolymer networks can be described in terms of a closed field theory. A special result was the discovery that homogeneous networks are ergodic. Investigations on proteins show that they tend to collapse. There exist various theories describing the collapsed state as a nonergodic one. A large class of networks is formed by crosslinked biopolymers. We investigate the question whether a theoretical description of a biopolymer network unifies both contradictory results. We find that the physically relevant ground states of biopolymer networks depend strongly on the coupling parameters for interaction, topology and compositional disorder. Three possible states are predicted for random copolymer networks using replica field theory. For two regimes the saddle point shows a rotational symmetry after elimination of translation effects. Here the network behaves similar to a homogeneous network. The third regime corresponds to a ground state with broken replica symmetry. Here, the behavior of the random copolymer network shows similarities to the thermodynamical properties of spin glasses. This state is comparable to diluted proteins and suggests the existence of nonergodic states due to the stochastic interaction between the monomers. Finally, the properties of the network are compared with diluted and dense systems of biopolymer chains.