A Monte Carlo simulation of water + oil + ABA triblock copolymer ternary system II. Rheology under shear flow field by Monte Carlo Brownian Dynamics method

• Published in: Chemical physics letters 2021-08, Vol.777, p.138382, Article 138382
• Main Authors: Sugimura, Natsuko, Ohno, Kaoru
• Format: Article
• Language: English
• Subjects: MC simulation; MCBD method; Micelles pattern; Shear stress; Shear viscosity; Ternary system
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2021.138382

Change of micelles patterns in each polymer concentration from thermal equilibrium state (left side) to the almost steady state in the shear flow field (right side). Polymer concentrations are 35%, 42% and 49% in order from the bottom. Water concentration is fixed to 10%. This result was got by Monte Carlo Brownian Dynamics (MCBD) simulation. The stress and viscosity were also evaluated using MCBD method for the region where the velocity gradient was almost constant. [Display omitted] •We performed a Monte Carlo Brownian Dynamics simulation under shear field.•The dynamic simulation was started from the thermal equilibrium states of micelles.•The shear viscosity exponentially increased as polymer concentration rose.•Our new finding was the shear stress also exponentially increases with increasing concentration.•We concretely discussed polymer Dynamics in the category of lattice model. A water/oil/amphiphilic polymer ternary system is analyzed by Monte Carlo (MC) method using a lattice model to determine the thermal equilibrium distribution by changing the component ratio. Particularly the rheological properties such as shear stress and viscosity are evaluated via Monte Carlo Brownian Dynamics (MCBD) simulation, in which the flexibility of polymer movement is considered by the bond fluctuation model and the shear force is expressed by the Kramers potential. Our analysis on the micelle pattern for each concentration ratio shows that, the increase of polymer concentration decreases the solute (water, polymer) mobility, and exponentially increases the viscosity. These results in our simulation reflect general phenomena in concentrated colloid system. By assuming that the polymer orientation dominates the stress of system by the elasticity between polymer bonds, we newly find that from the polymer placement under the shear field, the shear stress itself exponentially increases while raising the concentration. Even in the category of lattice model, our study indicates the possibility of acquiring new knowledge on Dynamics by using a polymer model with specific consideration on flexible mobility and MCBD method.