Three-dimensional conformations of entangled ring polymers in solution
Seminar Room 1, Newton Institute
The physical properties of semi-dilute and dense polymer solutions are dominated by the topological, mutual constraints (the so-called "entanglements") between the chains. For linear chains, entanglements effects are captured by the Edwards-DeGennes reptation model [Doi & Edwards, "The Theory of Polymer Dynamics"; DeGennes, J. Chem. Phys. (1971)]. Within this model, single-chain diffusive behavior proceeds as it was effectively constrained to an almost one-dimensional path along its contour length. The model received experimental validation and it is nowadays accepted. Conversely, a consistent physical picture for unlinked, circular (ring) polymers is still lacking. One obvious way of tackling the problem is by resorting to computer simulations (Monte-Carlo or Molecular Dynamics) of coarse-grained polymer models, which however present the major difficulty of waiting over very long equilibration times when dealing with very long chains. Here, we present preliminary results concerning an alternative, possible way of attacking the problem: we construct "by hand" putative, equilibrated states for entangled ring polymers, by using a restricted ensemble of physical parameters which are calibrated on solutions of small ring polymers which equilibrate fast. Then, we use this model to "predict" chain behavior for much larger ring polymers.