A Brownian Dynamics Study of Crossover Scaling in Semidilute Polymer Solutions

Understanding the dynamics of polymer solutions in the semidilute regime is important not only from the point of view of advancing fundamental knowledge in polymer science but also from the point of view of technological applications. The behavior of semidilute polymer solutions varies significantly with concentration and solvent quality, which are reflected in the concentration driven crossover from the dilute to the concentrated regime, and the solvent quality driven crossover from theta solvents to good solvents, respectively, in the phase diagram of polymer solutions. Here, we examine this double crossover using scaling (blob) theory and verify scaling predictions by carrying out Brownian dynamics simulations (BDS). The Brownian dynamics algorithm developed here is capable of simulating a large system of polymer chains interacting with each other through excluded-volume and hydrodynamic interactions, achieved through the implementation of a fast Ewald summation method. In this paper, we verify the scaling predictions for the static structure factor of a semidilute polymer solution. We also examine the effects of concentration and solvent quality on the static structure factor. Keyword: semidilute polymer solutions; double crossover; scaling theory; Brownian dynamics simulation; static structure factor