Logo image
Back
Molecular dynamics study on effect of elongational flow on morphology of immiscible mixtures
Journal article   Peer reviewed

Molecular dynamics study on effect of elongational flow on morphology of immiscible mixtures

Chau Tran and Vibha Kalra
The Journal of chemical physics, v 140(13), pp 134902-134902
07 Apr 2014
DOI: https://doi.org/10.1063/1.4869404
PMID: 24712811

Abstract

We studied the effect of elongational flow on structure and kinetics of phase separation in immiscible blends using molecular dynamics simulations. Two different blend systems have been investigated-binary blend of polymers and binary mixture of molecular fluids. The interaction potential parameters in both material systems were chosen to ensure complete phase-separation in equilibrium. We found that elongational flow, beyond a certain rate, significantly alters the steady state morphology in such immiscible mixtures. For the case of polymer blends, perpendicular lamellar morphology was formed under elongation rates (ε̇) from 0.05 to 0.5 MD units possibly due to the interplay of two opposing phenomena-domain deformation/rupture under elongation and aggregation of like-domains due to favorable energetic interactions. The elongation timescale at the critical rate of transition from phase-separated to the lamellar structure (ε̇ = 0.05) was found to be comparable to the estimated polymer relaxation time, suggesting a cross-over to the elongation/rupture-dominant regime. Under strong elongational flow rate, ε̇ > 0.5, the formation of disordered morphology was seen in polymer blend systems. The kinetics of phase separation was monitored by calculating domain size as a function of time for various elongational flow rates. The domain growth along the vorticity-axis was shown to follow a power law, Rz(t) ∼ t( α). A growth exponent, α of 1/3 for the polymer blend and 0.5-0.6 for the fluid molecular mixture was found under elongation rates from 0.005 to 0.1. The higher growth exponent in the fluid mixture is a result of its faster diffusion time scale compared to that of polymer chains. The steady state end-to-end distance of polymer chains and viscosity of the polymer blend were examined and found to depend on the steady state morphology and elongation rate.

Metrics

6 Record Views
5 citations in Web of Science
5 citations in Scopus

Details

InCites Highlights

Data related to this publication, from InCites Benchmarking & Analytics tool:

Web of Science research areas
Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Logo image