Improved model for mixtures of polymers and hard spheres

Extensive Monte Carlo simulations are used to investigate how model systems of mixtures of polymers and hard spheres approach the scaling limit. We represent polymers as lattice random walks of length L with an energy penalty w for each intersection (Domb-Joyce model), interacting with hard spheres of radius R-c via a hard-core pair potential of range R-mon + R-c, where R-mon is identified as the monomer radius. We show that the mixed polymer-colloid interaction gives rise to new confluent corrections. The leading ones scale as L-nu, where nu approximate to 0.588 is the usual Flory exponent. Finally, we determine optimal values of the model parameters w and Rmon that guarantee the absence of the two leading confluent corrections. This improved model shows a significantly faster convergence to the asymptotic limit L -> infinity and is amenable for extensive and accurate numerical simulations at finite density, with only a limited computational effort.