SPINODAL DECOMPOSITION WITH SURFACE TENSION DRIVEN FLOWS

Abstract

The Cahn-Hilliard theory of phase separation by spinodal decomposition has been extended to include hydrodynamics caused by surface tension. Numerical solutions for phase separation in binary polymer mixtures in two spatial dimension are presented. The surface tension influences the growth rate of the average domain size and the morphology for near critical quenches that would otherwise form cocontinuous networks. The growth rate exponent depends on the value of dimensionless surface tension, γ = [(ρ₀ m ^3/2)/(Dμ)][(κυ _s )/(R_gT)]^½, and ranges from 0.30 ±0.03, for γ = 0 (no hydrodynamics) to 0.69 ±0.04 for γ = 1 for a critical quench. For an off-critical quench in which a dispersed phase would be formed by diffusion alone, the scaling exponent shows little effect of surface tension and ranges from 0.28 ±0.02 for γ = 0 to 0.32 ±0.02 for γ = l. While not conclusive, the results suggest that it is infeasible to prepare bulk samples of cocontinuous polymer phases by the process known as compositional quenching.

KEYWORDS:

• Spinodal decomposition
• Cocontinuity
• Surface tension
• Phase Separation
• Hydrodynamics.

Notes

†Present address: Department of Equipment Design for Process Industries, Czech Technical University, Suchbatarova 4, 166 07 Prague, Czechoslovakia.