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Spinodal Decomposition of a Polymer and Ionic Liquid Mixture: Effects of Electrostatic Interactions and Hydrogen Bonds on Phase Instability
journal contribution
posted on 2016-01-26, 00:00 authored by Issei NakamuraWe
studied the spinodal decomposition of a homopolymer and ionic
liquid mixture. Our theory accounts for the dielectric contrast and
hydrogen bond between the polymer and the ionic liquid and the effect
of fluctuations in the local density and electrostatic potential.
We attempted to rationalize the observed shift in the critical point
and the asymmetry of the observed spinodal curve by applying the self-consistent
field theory and Langmuir adsorption model. The dielectric contrast
between the polymer and the ionic liquid produces a shift in the critical
point toward polymer-rich regions. The fluctuation effect yields drastic
changes in the trend of the phase boundary. We show that both effects
are marked by the appearance of inflection points in the spinodal
curve. Although hydrogen bonding also yields similar effects, the
spinodal curve rather exhibits a double-well structure or relatively
flat structure when combined with the solvation energy of ions. Hydrogen
bonding, ion solvation, and the fluctuation have equal significance
on the magnitude and trend of the spinodal curve. Our theory provides
strategies to dissolve low-dielectric polymers in ionic liquids by
altering the dielectric constant of ionic liquids and employing hydrogen
bonding.