Near-surface structure of aromatic polyimides: The effect of precursor isomers

The near-surface structure of an aromatic polyimide has been investigated as a function of the isomeric form of the precursor alkyl ester. Using grazing-incidence X-ray scattering, enhanced ordering was observed within 10 nm of the air surface for films prepared from both the meta- and para-isomers of the precursor. However, the extent of ordering is much less for the polyimide prepared from the meta-alkyl ester. This is consistent with the extent of ordering observed in the bulk material. The results suggest a correlation between the extent of ordering near the surface and the persistence length of the polymer.