(180al) Influence of Excluded Volume Interactions On Dynamical Behavior of Flexible Macromolecules: A Brownian Dynamics Simulation Study

Flexible macromolecules establish an important category that encompasses biomacromolecules such as ss-DNA in addition to most of commercial polymers. Chain flexibility enables macromolecule segments to interact amply even at slightly extended conformations. Single molecule experiments have recently revealed and measured significant effect of intramolecular interactions on properties of flexible chains such as nonlinear force-extension behavior. Since these interactions will influence single chain dynamics as well, it's important to correctly understand these effects and be able to include them in polymer flow simulations accordingly.

In this work Brownian Dynamics (BD) simulation is used to incorporate effect of excluded volume (as the major intramolecular interaction) to investigate macromolecular dynamics in two stages. In step one it’s shown that careful incorporation of excluded volume (EV) constraint on a large enough chain suffices for reaching the universal force-extension behavior which conforms perfectly to theoretical prediction and experimental results. Moreover probability distribution of end to end distance under shear flow widens for chains with many statistical segments and EV, which suggests a different coil to stretch transition behavior.

A novel high fidelity force law was extracted from the aforementioned bead-rod mesoscale model in order to construct a new bead-spring model to investigate dynamical behavior of flexible macromolecules in presence of hydrodynamic interactions in shear flow. The effect of EV on rheological properties (such as viscosity), extensional behavior under shear flow and tumbling frequencies at various Weissenberg numbers (We) are discussed in detail. Results of the model with new spring force law are also compared with the FENE chain to pinpoint the effect of EV on chain dynamics.