Experimental study of phase separation in dynamically asymmetric unentangled polymer blend

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Dynamically asymmetric polymer blends exhibit complex phase separation behavior.
• Understanding component mobility is crucial for modeling phase separation dynamics.
• Polyisoprene (PI) is dielectrically active, while poly(4-ethylstyrene) (PC2St) is dielectrically inert.

Purpose of the Study:

• To precisely model the phase separation process in a PI/PC2St blend.
• To estimate the composition dependence of component mobility.
• To validate the time-dependent Ginzburg-Landau (TDGL) model with experimentally determined mobility.

Main Methods:

• Dielectric and rheological measurements to determine friction coefficients.
• Williams-Landel-Ferry equation to model temperature dependence of friction.
• Extrapolation to estimate friction coefficients at lower temperatures.
• Time-dependent Ginzburg-Landau (TDGL) simulations.

Main Results:

• Friction coefficients of PI and PC2St were determined and modeled using the Williams-Landel-Ferry equation.
• Component mobility (Λ) was estimated as a function of composition at the test temperature.
• TDGL simulations incorporating the estimated mobility accurately described phase separation dynamics.
• Simulations qualitatively reproduced the observed phase-separated structures and dielectric properties.

Conclusions:

• Accurate estimation of component mobility is key to modeling polymer blend phase separation.
• The TDGL model, with composition-dependent mobility, effectively captures the dynamics and morphology.
• This approach provides a robust method for studying phase separation in polymer systems.