Critical polymer-polymer phase separation in ternary solutions

TL;DR

This study uses Monte Carlo simulations to analyze polymer-polymer phase separation in ternary solutions, revealing nonlinear scaling of critical temperature and chain-length dependent amplitudes consistent with renormalization-group predictions.

Contribution

It provides new insights into the critical behavior and chain-length dependence of phase separation in polymer solutions, validating renormalization-group scaling predictions.

Findings

Critical temperature scales nonlinearly with concentration.

Critical amplitudes depend on chain length as predicted by renormalization-group theory.

Average coil shape varies upon phase separation.

Abstract

We study polymer-polymer phase separation in a common good solvent by means of Monte Carlo simulations of the bond-fluctuation model. Below a critical, chain-length dependent concentration, no phase separation occurs. For higher concentrations, the critical demixing temperature scales nonlinearly with the total monomer concentration, with a power law relatively close to a renormalization-group prediction based on "blob" scaling arguments. We point out that earlier simulations and experiments have tested this power-law dependence at concentrations outside the validity regime of the scaling arguments. The critical amplitudes of the order parameter and the zero-angle scattering intensity also exhibit chain-length dependences that differ from the conventional predictions but are in excellent agreement with the renormalization-group results. In addition, we characterize the variation of the average coil shape upon phase separation.