Electron energy-loss chemical imaging of polymer phases

Transmission electron energy-loss spectrum-imaging investigations of a low-density polyethylene blend with polystyrene show that chemical imaging is possible with high spatial resolution for polymers in a dedicated scanning transmission electron microscope. Spectrum-imaging provides highly accurate phase identifications without staining. This polymer blend also contains a small amount of styrene-hydrogenated polyisoprene diblock copolymer (Kraton G 1701) as a compatibilizer. Detection of this compatibilizer at interfaces was expected to be difficult because of its chemical similarity to the pure components. We were unable to detect the copolymer with EELS imaging unambiguously, but were able to accurately map regions rich in either polyethylene or polystyrene. Chemical imaging techniques that we develop here are of use for polymer mixtures that exhibit variations in either carbon bonding or distribution of heteroatoms.