Kinetics of phase separation in polymer mixtures: a molecular dynamics study

Area of Science:

• Polymer Physics
• Materials Science
• Computational Chemistry

Background:

• Phase separation is a critical process in polymer mixtures, influencing material properties.
• Understanding the kinetics of phase separation is essential for controlling polymer blend morphology.
• Hydrodynamic effects play a significant role in the dynamics of phase separation.

Purpose of the Study:

• To investigate the phase-separation kinetics in polymer mixtures using molecular dynamics simulations.
• To determine the universality class of polymeric phase separation.
• To analyze the influence of dimensionality and degree of polymerization on domain growth laws.

Main Methods:

• Detailed molecular dynamics (MD) simulations were employed to model polymer mixtures.
• Hydrodynamic effects were naturally incorporated within the MD framework.
• Domain growth laws were analyzed by tracking the evolution of separated domains over time.

Main Results:

• Polymeric phase separation belongs to the same universality class as simple fluid segregation.
• The degree of polymerization primarily affects the rate of segregation, not the universality class.
• In 2-D, domain growth shows crossovers from L(t) ~ t^(1/3) to t^(1/2) to t^(2/3).
• In 3-D, domain growth exhibits a crossover from L(t) ~ t^(1/3) to t^1.

Conclusions:

• Polymer mixture phase separation dynamics are fundamentally similar to those of simple fluids.
• Dimensionality significantly impacts the domain growth kinetics in polymer systems.
• Further simulations are needed to explore the inertial hydrodynamic regime in 3-D systems.