(Invited) Polymer Simulations Under External Fields

Abstract

In order to design next generation functional polymers, not only the structure but the dynamics under external field should be understood. In this paper we report our simulation approach to investigate the structure and dynamics. Polymer brush is used for the model system of very low friction such as synovial joints. Recently, polymer brush is focused as a functional binder of sodium ion secondary battery. Since sodium ions are hard to make passive film, or SEI (solid electrolyte interphase) layer on the negative electrode, functional polymer binder help to stabilize the atmosphere around the electrode. We simulate the ionic conductivity of polyelectrolyte binder system under external electric field. The conductivity depend on the polymer structure, such as hardness and linear charge density of the polymer chain. The other important function of polymers are the fluid dynamics effect of polymers under external fluid field. As a model system of VII (viscosity index improver) polymers, we simulate the dynamics under shear filed. The dynamics of polymers are studied for bulk system and the confined system. We made simulation algorithm. The Brownian motion of polymer segments are treated by Langevin Dynamics, and the solvent flow is treated by Lattice Boltzmann Method, in order to obtain both high computational efficiency and precise dynamics. We succeed to reproduce the flow dynamics of polymers under shear. Moreover, the model is extended to include long-range interactions of functional groups. In low dielectric constant medium such as lubricant oils, the functional groups interact as ionic groups in high dielectric constant medium such as waters. The specific results shows that the colloidal science in oils have many problems to be solved.