High‐resolution dark‐field imaging in epoxy and polyimide systems

The feasibility of molecular imaging in polymers by electron microscopy is discussed. The tilted dark‐field method is specifically chosen for studying ultramicrotome thin sections. One system studied here is bisphenol‐A diglycidyl ether epoxide monomer (DGEBA) amine cured either by dicyandiamine or by diaminodiphenyl sulfone under various conditions. The second sample is a polyimide prepared from maleic anhydride and diaminophenyl methane. The distribution of the molecules is consistent with the random‐coil model when neither etching nor strains are applied. Bisphenol‐A groups distributed at random in the polymer are imaged in DGEBA as units 10 Å long and 5 Å wide, whereas larger isometric diffracting domains (10–15 Å) are imaged in polyimides.