Osmotic pressure of solutions containing flexible polymers subject to an annealed molecular weight distribution

¹ Institute for Physical Chemistry, Bulgarian Academy of Sciences 1113 Sofia, Bulgaria
² Département de Physique des Matériaux, Université Claude Bernard and CNRS 69622 Villeurbanne Cedex, France
³ Department of Applied Physics, Technische Universiteit Eindhoven Postbus 513, 5600 MB Eindhoven, The Netherlands
⁴ Department of Physics & Astronomy, University of Georgia Athens, GA 30602, USA

Corresponding author: jwittmer@dpm.univ-lyon1.fr

Received: 22 August 2000
Accepted: 29 January 2001

Abstract

The osmotic pressure P of equilibrium polymers (EP) in a good solvent is investigated by means of an off-lattice Monte Carlo simulation. Our results compare well with conformation space renormalisation group theory and the osmotic compressibility K as obtained by recent light scattering measurements of long worm-like micelles. The present study allows for the first time the mapping of the relevant energy scale of a standard coarse-grained model on data from real experiments. We also confirm the scaling predictions for EP in the dilute and semidilute limit. In particular, we find for the scaling of the pressure with the volume fraction ϕ and, hence, in the semidilute regime -in agreement with both theory and laboratory experiment. At higher concentrations where the semidilute blobs become too small and hard-core interactions and packing effects become dominant, a much stronger increase is evidenced and, consequently, a compressibility that decreases much more rapidly with ϕ than predicted from semidilute polymer theory, but again in agreement with experiment. Our results apply both to EP systems with and without rings.