Compatibilization of Polymer Blends by Complexation: 3. Structure Pinning During Phase Separation of Ionomer/Polyamide Blends
The effects of strong intermolecular interactions on the phase behavior and phase separation kinetics of an ionomer/polyamide blend were investigated by light scattering and optical microscopy. The lithium salt of lightly sulfonated polystyrene (Li-SPS) ionomers (4.0−9.5 mol % sulfonation) and poly(N,N‘-dimethylethylene sebacamide) (mPA) are miscible as a result of the formation of an ion−amide complex. The blends exhibit LCST-type phase behavior. Phase separation can be thermally induced and is thermodynamically reversible. The phase separation process stalls after a couple of hours due to structure pinning, which may be due to concentration of the ion−amide complexes in a ionomer-rich phase and/or the formation of microphase-separated ionic aggregates in the ionomer-rich phase.