Structure Pinning During Phase-Separation of Polyamide/Ionomer Blends

ABSTRACTBlends of lightly sulfonated polystyrene and poly(N,N'-dimethylethylene sebacamide) (Li-SPS/mPA) are miscible as a result of strong ion-amide complexation. The blends exhibit LCST phase behavior and an increase of the sulfonation level from 4 to 9.5 mol% raises the critical temperature by 150°C. Phase separation may be thermally induced and isthermodynamically reversible. The phase separation kinetics that occur following a temperature-jump deep into the spinodal region of the phase diagram deviate from conventional Cahn-Hilliard theory and the phase separation process stalls after a couple of hours, essentially pinning the structure at that point. The extent of phase-separation that occurs before pinning is temperature-dependent.