Phase separation behavior in blends of poly(benzimidazole) and poly(ether imide)

A 50/50 blend of a poly(ether imide) (PEI) and a poly(bensimidasole) (PBI) has been studied by SAXS and solid-state NRM. This blend, cast from a DMAc is shown to be intimately blended on a scale of 2.5 nm. Phase separation is detectable upon annealing for 1 h at temperatures of 310 o C and above even though the DSC-determined T g for this blend composition is 344°C. The minimum domain dimensions (MMD) was estimated in those annealed blends exhibiting phase separation. In keeping with the expectations, relatively small MMD's are observed. The composition of the PBI -rich phase was found to move closer toward a pure PBI pxhase as the annealing temperature is raised