NMR study of miscibility and morphology of polyimide/polyimide blends

Abstract The miscibility and morphology of polyimide/polyimide blends, PEI‐E/PTI‐E PEI‐E: poly(ether imide‐ether), PTI‐E: poly(thioetherimide‐ether), PBPI‐E: poly(biphthalimide‐ether); cf. exptl. part. and PBPI‐E/PTI‐E , have been studied by means of 13C CPMAS NMR technique. The results indicate that PEI‐E/PTI‐E blends are miscible on a molecular level, but molecular aggregation exists in pure PBPI‐E specimen as well as PBPI‐E/PTI‐E blends with high content of PBPI‐E, which vanishes in the blends with high content of PTI‐E. When the content of PBPI‐E is higher than that of PTI‐E, the addition of PTI‐E to PBPI‐E has almost no effect on the size of the PBPI‐E rigid domains, but has a large effect on the populations of the PBPI‐E rigid domains. It is the intermolecular charge‐transfer interaction that plays a critical role in the miscibility of PEI‐E/PTI‐E and PBPI‐E/PTI‐E blends.