Osmotic Pressure of Solutions Containing Flexible Poly - mers Subject to an Annealed Molecular Weight Distribu - tion

– The osmotic pressure P in equilibrium polymers (EP) in good solvent is investigated by means of a three dimensional off-lattice Monte Carlo simulation. Our results compare well with real space renormalisation group theory and the osmotic compressibility K ∝ φdφ/dP from recent light scattering study of systems of long worm-like micelles. We confirm the scaling predictions for EP based on traditional physics of quenched monodisperse polymers in the dilute and semidilute limit. Specifically, we find P ∝ φ 2.3 and, hence, K ∝ φ −0.3 in the semidilute regime — in agreement with both theory and 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, the compressibility decreases much more rapidly with φ than predicted from semidilute polymer theory, but again in agreement with experiment. Introduction. Superficially, it would seem that the colligative properties of quenched and annealed polymers must differ vastly, because the former have a fixed molecular weight distribution , whilst the latter are in equilibrium with each other, and continually exchange material [1]. In this paper, where we study by means of computer simulations the osmotic pressure of " equilibrium polymers " (EP) in a good solvent, we demonstrate that systems of EP, as widely varying as giant polymer-like surfactant micelles, and supramolecular aggregates of dyes, dipolar colloids and proteins [2], behave in essence like conventional polymers. The work presented here complements earlier simulation studies, focusing on the density distribution of sizes in dilute, semidilute and concentrated solution, covering both cases with [3] and without ring closure [4, 5]. Our motivation for studying the osmotic pressure is that it is a