Polymer Diffusion in Semicrystalline Polymers. 1. Poly (ether imide)/Poly(aryl ether ketone ketone)

The transport of poly(ether imide) (PEI) into amorphous and semicrystalline matrices of poly(aryl ether ketone ketone) (PEKK) has been characterized quantitatively. Diffusion measurements were performed by an infrared attenuated total reflectance technique and the semicrystalline morphology investigated both before and after transport via DSC, TEM, SEM, WAXS, SAXS, and microtomy/FTIR. Fickian interdiffusion occurs when these polymers are in contact as melts. Two distinct time scales of sorption kinetics are observed during PEI transport into PEKK with a stable semicrystalline morphology. The early time transport is Fickian mutual diffusion although the amount of PEI imbibed remains far below that expected for complete miscibility in the PEKK amorphous phase. The mutual diffusivity activation energy increases from 9 kcal/mol in amorphous PEKK to 30 kcal/mol for the early time regime in semicrystalline PEKK. The suppression of the PEKK matrix mobility significantly hinders transport. The existence of slower transport in a later-time, kinetics regime is identified with a time scale over which macromolecules explore bottlenecks between crystalline obstacles. The competitive evolution of PEKK spherulites during mutual diffusion both significantly retards the transport kinetics and diminishes the total sorption of PEI.