Distortion and flow of nematics simulated by dissipative particle dynamics

Abstract

In this study, we simulated distortion and flow of nematics by dissipative particle dynamics (DPD). The nematics were modeled by a binary mixture that contained rigid rods composed of DPD particles as mesogenic units and normal DPD particles as solvent. Elastic distortions were investigated by monitoring director orientation in space under influences of boundary anchoring and external fields. Static distortion demonstrated by the simulation is consistent with the prediction of Frank elastic theory. Spatial distortion profile of the director was examined to obtain static elastic constants. Rotational motions of the director under influence of the external field were simulated to understand the dynamic process. The rules revealed by the simulation are in a good agreement with those obtained from dynamical experiments and classical theories for nematics. Three Miesowicz viscosities were obtained by using external fields to hold the orientation of the rods in shear flows. The simulation showed that the Miesowicz viscosities have the order of ηc > ηa > ηb and the rotational viscosity γ1 is about two orders larger than the Miesowicz viscosity ηb. The DPD simulation correctly reproduced the non-monotonic concentration dependence of viscosity, which is a unique property of lyotropic nematic fluids. By comparing simulation results with classical theories for nematics and experiments, the DPD nematic fluids are proved to be a valid model to investigate the distortion and flow of lyotropic nematics.

Mesoscale Simulations of pH-Responsive Amphiphilic Polymeric Micelles for Oral Drug Delivery

“…Dissipative particle dynamics (DPD), which is a coarse-grained simulation method proposed by Hoogerbrugge and Koelman, can reveal mesoscopic-level information in the formation of PMs [30][31][32][33][34][35][36][37][38]. In the present work, DPD simulation was employed to investigate the self-assembly process, structure-property and stimuli-responsive behavior of multifunctional block copolymers based on copolymer poly(MMA-co-MAA)-b-PAEMA which was used for oral delivery of insulin in our previous work [29].…”