Investigation of semicrystalline morphology in poly(ether ether ketone)/poly(ether imide) blends by dielectric relaxation spectroscopy

The semicrystalline morphology of a series of poly(ether ether ketone) [PEEK] poly(ether imide) [PEI] blends has been investigated as a function of blend composition and crystallization condition by dielectric relaxation spectroscopy. Dielectric scans of the crystallized blends revealed two glass-rubber relaxations for all specimens corresponding to the coexistence of a mixed amorphous interlamellar phase, and a pure PEI phase residing in interfibrillar interspherulitic regions: no (pure PEEK) crystal amorphous interphase was observed. Variations in the composition of the mixed interlamellar phase with crystallization temperature were consistent with kinetic control of the evolving morphology: lower crystallization temperatures led to an increase in the amount of PEI trapped between crystal lamellae. Comparison of the relaxation characteristics of the interfibrillar interspherulitic phase with those of pure PEI indicated a much broader spectrum of local relaxation environments for PEI in the blends, consistent with PEI segregation across a wide range of size scales.